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Hazard Analysis and Risk-Based 

Preventive Controls for Human Food: 

Draft Guidance for Industry1

This draft guidance, when finalized, will represent the current thinking of the Food and Drug 

Administration (FDA or we) on this topic. It does not establish any rights for any person and is 

not binding on FDA or the public. You can use an alternative approach if it satisfies the 

requirements of the applicable statutes and regulations. To discuss an alternative approach, 

contact FDA’s Technical Assistance Network by submitting your question

at https://www.fda.gov/Food/GuidanceRegulation/FSMA/ucm459719.htm.

Chapter 4: Preventive Controls

Table of Contents

4.1 Purpose of this Chapter

4.2 Overview of Preventive Controls

4.3 Process Controls

4.3.1 Treatments lethal to biological hazards

4.3.1.1 Use of Heat Treatment (Thermal Processing) as a Lethality Process 

Control

4.3.1.2 Use of High Pressure Processing (HPP) as a Lethality Process Control

4.3.1.3 Use of Irradiation as a Lethality Process Control

4.3.1.4 Use of Antimicrobial Fumigation as a Lethality Process Control

4.3.2 Use of Time-Temperature as a Process Control

4.3.2.1 Use of Refrigeration as a Time-Temperature Process Control

4.3.2.2 Use of Freezing as a Time-Temperature Process Control

4.3.3 Use of Product Formulation as a Process Control

 1 This guidance has been prepared by the Office of Food Safety in the Center for Food Safety and 

Applied Nutrition at the U.S. Food and Drug Administration. Underlined text in yellow highlights 

represents a correction from the draft Chapter 4 that we issued for public comment in August 2016.
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4.3.3.1 Use of Water activity (aw) as a Formulation Process Control

4.3.3.2 Use of Acidity (pH) as a Formulation Process Control

4.3.3.3 Use of Preservatives as a Formulation Process Control

4.3.4 Use of Dehydration/Drying as a Process Control

4.3.5 Use of Recipe Management as a Process Control for Food Ingredients

4.3.6 Use of Storage Conditions as a Process Control for Mycotoxins

4.3.7 Use of Physical Sorting as a Process Control for Mycotoxins

4.3.8 Use of Exclusion Strategies as a Process Control for Physical Hazards

4.3.8.1 Exclusion Strategies as a Process Control for Metal Hazards

4.3.8.2 Exclusion Strategies as a Process Control for Glass Hazards

4.4 Sanitation Controls

4.4.1 Use of Sanitation Controls for the Cleanliness of Food-Contact Surfaces

4.4.2 Use of Sanitation Controls to Prevent Allergen Cross-contact and Crosscontamination

4.5 Food Allergen Controls

4.6 Supply-chain Controls

4.6.1 Supply-chain Controls for Pesticides

4.6.2 Supply-chain Controls for Drug Residues

4.6.3 Heavy Metals

4.6.4 Supply-chain Controls for Mycotoxins

4.7 Recall Plan

4.8 References

4.1 Purpose of this Chapter

The guidance provided in this chapter is intended to help you identify and implement preventive 

controls. The PCHF requirements specify that you must identify and implement preventive 

controls to provide assurances that any hazards requiring a preventive control will be 

significantly minimized or prevented and the food manufactured, processed, packed, or held by 

your facility will not be adulterated under section 402 of the Federal Food, Drug, and Cosmetic 

Act (FD&C Act) (21 U.S.C 342) or misbranded under section 403(w) of the FD&C Act (21 U.S.C. 

343(w)). (See 21 CFR 117.135(a)(1)). This chapter provides an overview of common

preventive controls that you could use to significantly minimize or prevent the occurrence of 

biological, chemical, and physical hazards in food products and the food production 

environment when the outcome of your hazard analysis is that one or more of these hazards 

requires a preventive control. 
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The guidance in this chapter also is intended to help you monitor the preventive controls that 

you identify and implement. As appropriate to the nature of the preventive control and its role in 

the facility’s food safety system, the PCHF requirements specify that you must establish and 

implement written procedures, including the frequency with which they are to be performed, for 

monitoring the preventive control, and to monitor the preventive controls with adequate 

frequency to provide assurance that they are consistently performed. (See 21 CFR 117.145.)

This chapter does not provide all the details needed for identifying and implementing preventive 

controls. You have the flexibility to identify and implement preventive controls from among all 

procedures, practices, and processes that are available to you and that would provide 

assurances that the hazard is controlled (i.e., significantly minimized or prevented).

4.2 Overview of Preventive Controls 

Part 117 defines “preventive controls” as those risk-based, reasonably appropriate procedures, 

practices, and processes that a person knowledgeable about the safe manufacturing, 

processing, packing, or holding of food would employ to significantly minimize or prevent the 

hazards identified by the hazard analysis that are consistent with the current scientific 

understanding of safe food manufacturing, processing, packing, or holding at the time of the 

analysis. (See 21 CFR 117.3.) Preventive controls include: (1) Controls at critical control points 

(CCPs), if there are any CCPs; and (2) controls, other than those at CCPs, that are also 

appropriate for food safety (See 21 CFR 117.135(a)(2)). The PCHF requirements specify that 

preventive controls must be written. (See 21 CFR 117.135(b)).The PCHF requirements also 

specify that preventive controls must include, as appropriate to the facility and the food: (1) 

Process controls; (2) Food allergen controls; (3) Sanitation controls; (4) Supply-chain controls; 

(5) Recall plan; and (6) Other controls. (See 21 CFR 117.135(c)). 

Table 4-1 lists the sections in this chapter in which we address process controls, sanitation 

controls, food allergen controls, supply-chain controls, and recall plans. Although Table 4-1 

includes supply-chain controls, we intend to provide more information in our forthcoming 

“Chapter 15 - Supply-Chain Program for Human Food Products.” See Chapters 6 through 14 of 

this guidance for more detailed discussion of applicable preventive controls.

Table 4-1. Preventive Controls Addressed in this Chapter

Preventive Control Chapter Section

Process Controls 4.3

Sanitation Controls 4.4

Food Allergen Controls 4.5

Supply-chain Controls 4.6

Recall Plans 4.7

Table 4-2 lists the chapters in this guidance in which we provide additional details regarding 

certain preventive controls.

Table 4-2. Other Chapters in the Guidance With Additional Information About Specific 

Preventive Controls 

Preventive Control Chapter 
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Preventive Control Chapter 

Heat Treatment Process Control 6

Time/Temperature Control Process Control 7

Formulation Process Control (e.g., water 

activity, pH, and chemical preservatives)

8

Dehydration/Drying Process Control 9

Sanitation Controls 10

Food Allergen Controls 11

Preventive Controls for Chemical Hazards 12

Preventive Controls for Physical Hazards 13

Recall Plan 14

The PCHF requirements specify that you must validate that the preventive controls that you 

identify and implement are adequate to control the hazard as appropriate to the nature of the 

preventive control and its role in the facility’s food safety system. (See 21 CFR 117.160(a)).

The PCHF requirements also specify that validation of the preventive controls must be 

performed (or overseen) by a preventive controls qualified individual. (See 21 CFR 117.160(b) 

and the definition of a preventive controls qualified individual in 21 CFR 117.3.) You do not 

need to validate: (1) Food allergen controls; (2) sanitation controls; (3) the recall plan; and (4) 

the supply-chain program. You also do not need to validate other preventive controls, if the 

preventive controls qualified individual prepares (or oversees the preparation of) a written 

justification that validation of the other control is not applicable based on factors such as the 

nature of the hazard, and the nature of the preventive control and its role in the facility’s food 

safety system. (See 21 CFR 117.160(c).) We intend to discuss validation in “Chapter 16: 

Validation of a Process Control.”

4.3 Process Controls

Process controls include procedures, practices, and processes to ensure the control of 

parameters during operations such as heat processing, acidifying, irradiating, and refrigerating 

foods. Process controls must include, as appropriate to the nature of the applicable control and 

its role in the facility’s food safety system: (1) Parameters associated with the control of the 

hazard; and (2) the maximum or minimum value, or combination of values, to which any 

biological, chemical, or physical parameter must be controlled to significantly minimize or 

prevent a hazard requiring a process control. (See 21 CFR 117.135(c)(1).) Process controls do 

not include those procedures, practices, and processes that are not applied to the food itself, 

e.g., controls of personnel or the environment that may be used to significantly minimize or 

prevent hazards.
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Examples of processing parameters that can have a minimum or maximum value (or

combination of values) include time, temperature, flow rate, line speed, product bed depth, 

weight, product thickness or size, viscosity, moisture level, water activity, salt concentration, pH 

and others, depending upon the process. If a process parameter does not meet a minimum or 

maximum value (or critical limit), the process is not in control (i.e., a deviation has occurred) and 

the potential for producing a product that presents a consumer-health risk exists.

Many process controls, such as the application of heat to a food to adequately reduce 

pathogens, are applied in the same manner and for the same purpose as control measures 

established within HACCP plans and applied at CCPs as recommended by the National 

Advisory Committee on Microbiological Criteria for Foods (NACMCF, 1998) and the Codex 

Alimentarius Commission (CAC, 2003). When a process control is applied to a CCP in a 

HACCP plan, the maximum or minimum values (or combination of values) for the parameters 

associated with the control of the hazard are called “critical limits.” Critical limits have been 

defined by the NACMCF as a maximum and/or minimum value to which a biological, chemical 

or physical parameter must be controlled at a CCP to prevent, eliminate or reduce to an 

acceptable level the occurrence of a food safety hazard (NACMCF, 1998). 

In addition to this guidance, a number of sources of scientific and technical information can be 

useful in establishing process parameters or critical limits. Our guidance documents entitled 

“Fish and Fishery Products Hazards and Controls Guidance” and “Juice HACCP Hazards and 

Controls Guidance” each have information that can be broadly applied to food products. Other 

government agencies may also provide information through technical staff, regulations, 

guidelines, directives, performance standards, tolerances, and action levels. For example, the 

guidance documents entitled “Meat and Poultry Hazards and Controls Guide” (FSIS, 2005) and 

FSIS Compliance Guideline HACCP Systems Validation (FSIS, 2015), provided by the Food 

Safety and Inspection Service (FSIS) of the U.S. Department of Agriculture, has information that 

can broadly be applied to food products, not just meat and poultry products subject to FSIS’ 

jurisdiction. As another example, EPA lists maximum pesticide residues limits (MRLs) and

tolerances in 40 CFR Part 180. (EPA, 2015) and provides Indexes to Part 180 Tolerance 

Information for Pesticide Chemicals in Food and Feed Commodities on its website (EPA, 2016). 

Trade associations, process authorities, industry scientists, university and extension scientists, 

and consultants can provide expertise and guidance. For example, the Grocery Manufacturer’s 

Association (GMA) has provided guidance on Control of Salmonella in Low-Moisture Foods 

(GMA, 2009). Information can also be obtained from peer reviewed scientific literature. For a 

more comprehensive list of resources, see the training materials provided by the Food Safety 

Preventive Controls Alliance (FSPCA, 2016) In addition to (or in place of) information from such 

resources, you also can conduct scientific studies for specific products in-house, at a contract 

laboratory, or at a university to establish appropriate process parameters and associated 

values.

You should use care when applying information from any of these sources to processing 

parameters for a specific product and process. Among other reasons, there may be important 

differences between the application of processing parameters as discussed in these sources 

how you would apply the processing parameters to your specific product and process. The 

processing parameters and/or minimum or maximum values may need to be adjusted to 

account for those differences. For example, the temperature (and time at that temperature) 

necessary to kill microorganisms in a food product can depend on the fat level in that food 

product. 
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Table 4-3 lists examples of the application of process controls to significantly minimize or 

prevent ingredient-related and process-related biological, chemical, and physical hazards and 

the section in this chapter that addresses each listed example. 

Table 4-3 Common Process Controls 

Process Control 

Subcategory

Hazard 

Category

Examples Chapter 

Section

Lethal Treatments Biological • Heat treatments (also called thermal 

treatments) (e.g., cooking, roasting, 

baking)

• High Pressure Processing (HPP)

• Irradiation 

• Antimicrobial fumigation (e.g., with 

polypropylene oxide (PPO))

4.3.1

Time/Temperature 

of Holding

Biological • Refrigeration 

• Freezing 

4.3.2

Formulation Biological • Reducing the water activity

• Reducing the pH

• Adding preservatives

4.3.3

Dehydration/Drying Biological • Air-drying (forced air and heating) 

• Freeze drying 

• Spray drying 

4.3.4

Recipe 

Management

Chemical • Controlling the maximum level of food 

ingredients

4.3.5

Storage Conditions Chemical • Controlling moisture during storage of 

raw agricultural commodities 

4.3.6

Physical Sorting Chemical • Reducing mycotoxin content through 

sorting by color and physical damage in 

raw agricultural commodities

4.3.7

Exclusion of Metal 

and Glass

Physical • Using magnets

• Using metal detectors

• Using sieves, screens

• Using X-ray systems

4.3.8

4.3.1 Treatments lethal to biological hazards

We use the term “lethality treatment” when referring to a treatment that is used to kill/destroy or 

inactivate microorganisms. In general, when discussing bacterial pathogens in this document 

we use the terms “kill” or “destroy” when discussing treatments lethal to vegetative cells and we 

use the term “inactivate” when discussing treatments lethal to spores. Common lethality 

treatments include: (1) Heat treatments (e.g., cooking, boiling, pasteurizing, baking, frying); (2) 
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HPP; (3) irradiation; and (4) antimicrobial fumigation. We discuss each of these in the following 

sections of this chapter.

4.3.1.1 Use of Heat Treatment (Thermal Processing) as a Lethality 

Process Control 

Heat treatment is a common lethality process control. Heat treatments generally fall into into the 

following two categories:

• Heat treatment that leads to commercial sterility: heat processing at high temperatures (> 212oF

(100°C)) under presssure with the objective of killing all forms of microorganisms, including the 

spores of bacteria. The treated products are shelf-stable without refrigeration. (Lower temperatures 

can lead to products that are shelf-stable in some cases, e.g., when the pH is low enough to prevent 

growth of surviving sporeformers.)

• Heat treatment that reduces microbial pathogens but does not lead to commercial sterility: heat 

processing at lower temperatures (e.g., 158°F (70°C) to 212°F (100°C)), with the processes designed 

to kill the vegetative forms of microorganisms with little to no effect on the spores of bacteria. The 

treated products are not shelf-stable and require controls such as refrigeration to control spores of 

bacterial pathogens.

This chapter does not address heat treatments that lead to commercial sterility of “low-acid 

canned foods.” Such treatments are subject to the requirements of 21 CFR part 113 (Thermally 

Processed Low-Acid Foods Packaged in Hermetically Sealed Containers; commonly called 

“Low-Acid Canned Foods (LACF)) because the microbial hazards in LACF are not subject to the 

requirements for hazard analysis and risk-based preventive controls. Note that although some 

hermetically sealed containers (e.g., pouches and glass bottles) used to package thermally 

processed low-acid foods generally would not be viewed as “cans,” the term “low-acid canned 

foods” has been used for decades as a shorthand description for “thermally processed low-acid 

foods packaged in hermetically sealed containers,” and we continue to use that term (and its 

abbreviation, LACF) for the purposes of this guidance.

Pasteurization is an example of a lethal heat treatment that reduces microbial pathogens but 

does not lead to a shelf stable product. Pasteurization typically is applied to foods to kill nonsporeforming pathogens such as Salmonella, Listeria monocytogenes, and pathogenic strains 

of E. coli. One example is the pasteurization of grade “A” milk and milk products that is covered 

by the 2015 Pasteurized Milk Ordinance (PMO) (FDA, 2015a). This chapter does not address 

pasteurization of milk; if you pasteurize milk, you should refer to 21 CFR 1240.61 and the 

specific requirements in your jurisdiction.

Thermal Destruction of Microorganisms

To design a lethal heat treatment for use as a preventive control, you should have a basic 

understanding of thermobacteriology (i.e., the relationship between bacteria and heat), including 

two key types of data and information: 

• The kinetics of thermal inactivation or destruction of microorganisms, known as thermal death time 

data and;

• The rate at which heating occurs within the food material, also known as heat transfer or heat 

penetration.

Immediately below, we describe basic concepts associated with thermal death time data and 

heat transfer/heat penetration. For a more extensive review of thermobacteriology, including 
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graphical representations of the relationship of D values and z values to Thermal Death Time, 

refer to Stumbo, Chapter 7 (1973). 

Some terms and concepts used to describe the thermal destruction of microorganisms include:

• TDT (Thermal Death Time) is the time necessary to kill a given number of microorganisms at a 

specified temperature. The TDT is obtained by keeping temperature constant and measuring the time 

necessary to kill the amount of cells specified. 

• D Value (the decimal reduction time) is the time required to kill 90% of the microorganisms. Another 

way of expressing this is the time required at a specific temperature and under specified conditions to 

reduce a microbial population by one decimal (see discussion below).

• z Value refers to the degrees in Farhenheit required for the thermal destruction curve to cross one log 

cycle (i.e., for reducing the D value by a factor of 10).

Food processing experts evaluate treatments intended to kill or inactivate pathogens in food in 

terms of “logs” of kill, where the term “log” is a shorthand expression of the mathematical term 

logarithm. A logarithm is the exponent of the power to which a base number must be raised to 

equal a given number. In thermobacteriology, the base number is usually 10. As an example, 

the number 100 = 102 where the base number is 10 and the exponent is 2. Because the 

exponent is 2, the number 100 = log 2. Likewise, the number 1000 = 103 = log 3. The important 

thing to understand is that each “log” of kill is capable of causing a tenfold reduction in the 

number of microorganisms that the treatment is designed to kill, i.e., the most resistant 

microorganism of public health significance. 

The decimal reduction time (D) is used synonymously with “log” in the context of 

thermobacteriology. A 1-log or 1D process would be one that is capable of reducing the level of 

the most resistant pathogen of concern in the food by 10 fold, e.g., from 10,000 cells of the 

microorganism per gram of food to 1,000 cells of the microorganism per gram of food. 

Importantly, it is not possible to technically achieve a level of reduction to zero, or “no 

microorganisms”; instead, as a technical matter the probability of finding the organism becomes 

less likely as the magnitude of reduction increases. Thus, a 5-log reduction process would be 

one that is capable of reducing the level of the most resistant pathogen of concern in the food 

by 100,000 fold, e.g., from 10,000 cells of the microorganism per gram of food to a probability of 

1 cell in 10 g of food. 

Table 4-4 provides examples of how food processing experts would describe the effect of lethal 

heat treatments on microorganisms in foods using terms commonly associated with 

thermobacteriology.

Table 4-4. The concept of log reductions of microorganisms in foods

Initial number of the 

most resistant 

microorganism of 

public health 

significance per 

gram of food

Log 

reduction 

(also 

known as 

D)

Decrease in most resistant 

microorganism of public 

health significance per gram 

of food

Percent 

of change

Final number of 

bacteria per 

gram of food

10,000 or log 41 1 10-fold 90% 1,000 or log 3

10,000 or log 4 2 10 X 10 = 100 fold 99% 100 or log 2

10,000 or log 4 3 10 X 10 X 10 = 1000-fold 99.9% 10 or log 1

10,000 or log 4 4 10 X 10 X 10 X 10 = 10,000-fold 99.99% 1 or log 0
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Initial number of the 

most resistant 

microorganism of 

public health 

significance per 

gram of food

Log 

reduction 

(also 

known as 

D)

Decrease in most resistant 

microorganism of public 

health significance per gram 

of food

Percent 

of change

Final number of 

bacteria per 

gram of food

10,000 or log 4 5 10 X 10 X 10 X 10 X 10 = 

100,000-fold

99.999% 0.1 or log -12

10,000 or log 4 6 10 X 10 X 10 X 10 X 10 = 

1,000,000-fold

99.9999% 0.01 or log -2

1 Additional equivalent ways to express 10,000 include 104

, 10^4, and 10E4 

2 Additional equivalent ways to express 0.1 include 10-1 or 1 in 10.

Relative Heat Resistance of Microorganisms

Some microorganisms are more resistant to heat than other microorganisms and, thus, the 

require more stringent heating conditions to kill or inactivate them. Table 4-5 shows the relative 

heat resistance of common types of microorganisms.

Table 4-5. Relative Heat Resistance of Microbial Forms

Resistance to Heat Microbial Form

Highest Bacterial Spores

Moderate • Some Vegetative bacterial cells

• Cysts of Parasites

• Fungi, including fungal spores

Least • Some vegetative bacterial cells

• Viruses

As already noted, this chapter addresses relatively mild heat treatments that reduce microbial 

pathogens but do not lead to commercial sterility. These relatively mild heat treatments are 

used to reduce the number of vegetative cells of bacterial pathogens such as Listeria 

monocytogenes (L. monocytogenes), Salmonella, and enteropathogenic E. coli, and the spores 

of non-proteolytic strains of Clostridium botulinum (C. botulinum) and Bacillus cereus (B. 

cereus). These processes are designed to ensure product safety by achieving a 6-log reduction 

(6D). For a more detailed review of the relative heat resistance of food pathogens in mildly heat 

processed foods, see Jay (1996), FDA (2000), and Farkas (2007).

Factors Affecting the Heat Resistance of Microorganisms

In addition to the inherent heat resistance of specific microorganisms (or life stages of 

microorganisms, such as the spore stage), other factors associated with foods (such as water 

activity, pH, salt content, fat, and protein) can affect the heat resistance of microorganisms. 

Table 4-6 lists the most common factors that you should consider when designing a heat 

treatment as a process preventive control.

Table 4-6. Factors That Influence the Heat Resistance of Microorganisms in Foods

Factor Effect on Microbial Heat Resistance
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Factor Effect on Microbial Heat Resistance

Water As the humidity or moisture goes down, in general the heat 

resistance increases

Fat As the fat content increases, there is a general increase in heat 

resistance of some microorganisms

Salts The effect of salt varies and depends on the kind of salt and 

concentration. Some salts that decease water activity appear to 

increase heat resistance of microorganisms while other salts that may 

increase water activity (e.g., Ca2+ and Mg2+) appear to decrease heat 

resistance.

Carbohydrates The presence of sugars can increase the heat resistance of 

microorganisms due in part to the decrease in water activity. 

However, the impact can be variable, particularly among sugars and 

sugar alcohols.

pH Most microorganisms are more heat resistant near their optimum pH 

for growth. Generally, as the pH increases or decreases relative to 

this optimum pH, the microorganisms become more sensitive to heat.

Proteins Proteins have a protective effect and, thus, increase the heat 

resistance of microorganisms.

Other factors that can influence the heat resistance of microorganisms include the numbers of 

organisms, the age of the microorganisms, the temperatures at which microbial growth occurs, 

the presence of inhibitory compounds, and the time-temperature combination utilized. For a 

comprehensive compilation of data and research on the effect of food factors on the heat 

resistance of food pathogens of public health concern, see ICMSF (1996).

Lethal Heat Treatments 

Cooking:

Baking, boiling, roasting, steaming, and frying are conventional heating methods used for 

cooking a wide variety of foods (e.g., cereal-grain products, vegetables, soups, sauces, 

legumes, and assembled multi-component meals). Cooking is performed for two primary 

reasons: to make food palatable and to make it safe by eliminating vegetative pathogens such 

as Salmonella, L. monocytogenes, and enteropathogenic E. coli. This discussion focuses on the 

food safety aspects of the cooking methods.

You should design a cooking process to target heat resistant vegetative pathogens, such as L. 

monocytogenes. Typically, we recommend a thermal process that achieves a 5D to 7D 

reduction for most cooking treatments. However, if the expected initial microbial load is low, a 

less severe thermal process may be adequate. For cooking processes that target pathogenic 

sporeformers such as C. botulinum type E and non-proteolytic types B and F (i.e., 194°F (90o

C)) 

for 10 min), generally a 6D reduction in the level of contamination is suitable. 

Table 3-D in Appendix 3 of this document provides 6D process times for a range of cooking 

temperatures, with L. monocytogenes as the target pathogen. It is possible that higher levels of 

destruction may be necessary in some foods, e.g., if you expect especially high initial levels of 

the target pathogen.

Table 3-E in Appendix 3 of this document provides 6D process times for a range of heating 

temperatures, with non-proteolytic C. botulinum type B (the most heat-resistant form of nonproteolytic C. botulinum) as the target pathogen. 
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There are a variety of ways to control the application of these cooking processes depending 

upon the type of food and the method of delivery (e.g., boiling, steaming). For example, for 

liquid and semi-liquid food products that are batch-cooked in a cooking vessel such as a kettle 

agitated during the thermal process, the simplest way to control the process is to check the 

internal temperature of the product at the end of the designated cooking time (i.e., check the 

time-temperature parameters of the treatment). A dial thermometer with a long probe works 

quite well. If the temperature is taken at or near the center of the cooking vessel, it is reasonable 

to assume that all product in the cooking vessel is at or above that temperature, because foods 

processed in this manner generally heat by convection or forced convection. You can monitor a 

simple boiling heat process by visually observing and timing the boil. Usually, a temperature 

distribution study is performed to ensure that no point in the cooking vessel is at a lower 

temperature than the minimum value (or critical limit) for temperature required during the 

process. 

Heating food with large particles, like vegetables in stews and some soups, occurs primarily by

conduction, rather than by convection. Particle size and consistency can greatly affect the rate 

of heating at the center of the particle. You cannot control cooking processes for products with 

large particles by periodically checking the internal temperature of some of the product particles

as they leave the cooker because you cannot verify that each particle reached the appropriate 

temperature for adequate time. Therefore, you should establish the process scientifically and 

validate it through a scientific study demonstrating that if the minimum/maximum values are met 

for all the critical factors (e.g., cooking temperature, time, particle size) all particles will receive 

an adequate heat treatment.

Normally, a study to validate a cooking process is performed by a person or group 

knowledgeable in the design of thermal processes to determine the critical parameters required 

for the heat process being applied to ensure that it delivers the desired reduction level (logs of 

kill, as described in section 4.3.1.1 of this chapter). A preventive controls qualified individual 

must conduct (or oversee) such a study. See 21 CFR 117.180(a). (Because it is common 

practice for these studies to be conducted by entities with special expertise in the area, the 

preventive controls qualified individual likely will oversee, rather than conduct, the study.) Once 

that study has been completed, the person conducting the study will provide a time and 

temperature for the processor to monitor during processing, as well as any other parameters 

that are critical to delivery of an adequate heat treatment, such as maximum particle size). You 

can then monitor the time and temperature of the heat process to effectively ensure that all 

product particles have achieved the desired internal temperature. It may also be necessary to 

monitor other factors of the product or the process, such as the internal temperature of the 

product before the start of the process--called the initial temperature (IT), particle size, or 

relative humidity, where they affect the rate of heating. These factors, and their limits, will be 

determined by the process design study.

For some products, such as soups or sauces, you may be able to monitor End-Point Internal 

Product Temperature (EPIPT), a measurement of the internal temperature of the product at the 

end of the heat process, instead of performing continuous time and temperature monitoring. 

This approach is suitable if you have conducted a scientific study to validate that the EPIPT that 

you have selected will provide an appropriate reduction (e.g., 6D) in the numbers of the target 

pathogen in the slowest heating unit or portion of product under the worst set of heating 

conditions covered by the scientific study. If you want to monitor EPIPT, you should:

• Conduct a temperature distribution study within the heating system to identify any cold spots; 
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• Conduct a heat penetration study that accounts for the slowest heating product under the worst case 

heating conditions covered by the scientific study; and 

• Identify other critical factors of processing and/or packaging that affect the rate of product heating 

when scientifically establishing a heat process. 

You should use the EPIPT as a monitoring technique only under those conditions that were 

evaluated by the scientific study, with those conditions identified as process parameters with 

minimum/maximum values (or critical limits) that are monitored as part of your process controls.

See “Chapter 6 – Use of Heat Treatments as a Process Control” in this guidance for additional 

information about the EPIPT monitoring technique.

Other common forms of cooking that are used to produce commercially manufactured foods are 

baking and roasting. These are essentially the same unit operation because they both use 

heated air to alter the eating quality of foods. However, the term “baking” is usually used when 

heated air is applied to flour-based foods or fruits, and the term “roasting” is usually used when 

heated air is applied to meats, nuts, or vegetables. Baking and roasting operations use dry heat 

in gas-fired or electric ovens. For some products such as bakery products, the effectiveness of 

the dry heat in ovens is increased by the addition of steam for various cooking purposes.

Cooking equipment may be batch-type or continuous. In a continuous system the food is moved 

through the cooking equipment by conveyor or auger systems. The methods of controlling and 

monitoring the time-temperature parameters of these types of cooking processes will vary 

depending upon whether it is batch-type or continuous process. See “Chapter 6 – Use of Heat 

Treatments as a Process Control” for an example using baking as a preventive control. 

Emerging Technologies Based on Thermal Effects

Microwave, radio frequency, ohmic heating, and inductive heating are heat-based processes 

that can kill microorganisms by thermal effects. Microwave and radio frequency heating are 

based on the use of electromagnetic waves of certain frequencies to generate heat in a material 

through two mechanisms - dielectric and ionic. Ohmic heating is the process of passing electric 

currents (primarily alternating) through foods or other materials to heat them. The heating 

occurs in the form of internal energy generation within the material. Ohmic heating is 

distinguished from other electrical heating methods either by the presence of electrodes 

contacting the food (as opposed to microwave heating, where electrodes are absent), and 

depends on frequency of the current and waveform (typically sinusoidal). Inductive heating is a 

process of inducing electric currents within the food due to oscillating electromagnetic fields 

generated by electric coils. 

For any of these heat-based processes, the magnitude of time/temperature history and the 

location of the cold points will determine the effect on microorganisms. The effectiveness of 

these processes also depends on water activity and pH of the product. Although the shape of 

the destruction or inactivation curves is expected to be similar to those in conventional heating, 

the intricacies of each of the technologies need special attention if you plan to use them for 

microbial destruction or inactivation. For instance, in microwave heating a number of factors 

influence the location of the cold points, such as the composition, shape, and size of the food, 

the microwave frequency, and the applicator design. The location of the coldest-point and 

time/temperature history can be predicted through simulation software, and we expect that food 

processors may be able to use these emerging technologies in the future. 

For a detailed overview of these processing technologies, as well as alternative thermal 

processing techniques, see Sun (2005).
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4.3.1.2 Use of High Pressure Processing (HPP) as a Lethality Process 

Control

The pressure processing of foods for preservation was studied as early as the end of the 19th 

century and the beginning of the 20th century in the United States by people like Hite (1899) 

and Bridgman (1912). However the potential microbiological effects of HPP were not recognized 

by the food industry until around 1985. HPP has recently received a great deal of attention in 

the food, pharmaceutical, and biotechnology industries. Japan has been a leader in this 

technology, producing products such as jams, jellies, fruit juices, and yogurt.

Microorganisms vary in their sensitivity to high pressure. If you plan to use HPP, you should 

consider the organism of concern, product characteristics and, whether the process is to result 

in product that is to be refrigerated or that will be shelf stable. Destruction of the microorganism 

is primarily caused by changes in the structure and permeability of the cell wall which causes 

fluids to be forced into the cell. 

Bacterial spores are well established as the most pressure-resistant biological forms known. 

Spores resist inactivation by high pressure alone and most require the addition of heat or some 

other mechanism to achieve appropriate levels of destruction. C. botulinum is one of the most 

pressure-resistant and hazardous microorganisms, which is a challenge in the design of highpressure processes. Because of this, the best candidates for HPP continue to be acid foods and 

foods that will be refrigerated following processing (which provide control of sporeformers). 

High pressure processing of foods requires pressures of 400 to 700 MPa, or 4000 - 7000 bars 

(58,000 - 101,000 psig). The unit of measure frequently used for HPP in the food industry is the 

pascal (Pa) or megapascal (MPa, 1,000,000 Pa). Most commercial food industry applications 

use pressures in the range of 600 to 700 MPa. 

High pressure processing requires very specialized and costly equipment. Currently foods using 

HPP are being processed by batch systems. For batch processing, the food is packaged in a 

flexible or semi-flexible package, prior to placing the product in the HPP system, where the 

product is placed into a chamber and immersed in water or some other pressurizing fluid, then

subjected to the high pressure for a time of 1 - 20 minutes, depending on the temperature and 

pressure. The chamber would then be depressurized and the product removed. Applications 

and the feasibility for commercialization for other HPP systems such as semi-continuous, 

continuous, and pulsed HPP have been described elsewhere (FDA, 2000; Indrawati et al. 2003; 

Z. Berk, 2009).

For a detailed review of the application and use of HPP as a process control, see FDA (2000

and 2001) and Hogan et al. (2005).

4.3.1.3 Use of Irradiation as a Lethality Process Control

The application of radiation treatments to food for the purpose of improving safety (e.g. by 

reducing or eliminating pathogenic bacteria) or extending shelf life by (e.g. by reducing or 

eliminating spoilage microorganisms and insects) can use sources that have high enough 

energy levels to cause ionization (the creation of ions by expulsion of orbital electrons from 

atoms) or have lower energy levels that will not cause ionization. These are known as ionizing 

and non-ionizing radiation, respectively. The most commonly used form of radiation to treat 

foods as a lethality process control is ionizing radiation and the discussion in this section of this 

chapter focuses on ionizing radiation. Non-ionizing radiation in the form of lower energy 
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electromagnetic waves such as UV light and infrared heating can be used to treat foods similar 

to that described for microwaves, radio frequency, and ohmic heating in the section of this 

chapter entitled “Emerging Technologies Based on Thermal Effects” and will not be addressed 

here. For more information on the application of infrared (IR) radiation in food processing 

operations, see the review by Krishnamurthy et al. (2008). For more information on the 

application and use of UV light in food processing, see the discussion by FDA (2000, 2001). 

FDA is responsible for regulating the sources of radiation that are used to irradiate food (21 

CFR Part 179 Subpart B). Irradiation is considered a food additive in the United States and, as

such, its use in foods requires premarket approval by FDA (21 CFR Part 179). There are three 

sources of ionizing radiation approved for use on foods (21 CFR 179.26):

• Gamma rays – emitted from radioactive forms of the element cobalt (Cobalt 60) or the element 

cesium (Cesium 137). Gamma radiation is also used routinely in medicine to sterilize medical and

dental products and for the radiation treatment of cancer.

• X-rays – produced by reflecting a high-energy stream of electrons into food off a target substance 

(usually one of the heavy metals) using electron accelerators. X-rays are also widely used in 

medicine and industry to produce images of internal structures.

• Electron beam – (or e-beam) is similar to X-rays and is a stream of high-energy electrons propelled 

from an electron accelerator into food.

Some common terms that are used when describing the application of ionizing radiation in the 

treatment of foods are:

• Dose (absorbed) – The amount of energy absorbed per unit mass of irradiated material.

• D10 value – Amount of radiation required to reduce the population of a specific microorganism by 90% 

(one log10 cycle) under the stated conditions.

• Gray (Gy) - A unit of absorbed dose of ionizing radiation, equal to 1 joule/kg of absorbed energy. 

• Electron volt (eV) – A unit of energy. One electron volt is the kinetic energy acquired by an electron in 

passing through a potential difference of one volt in a vacuum.

The primary reason food irradiation is used as a lethal process control is to inactivate pathogens

and microorganisms that cause food spoilage (Farkas et al., 2014). The application of ionizing 

radiation damages DNA and very effectively inhibits DNA synthesis and further cell division in 

microorganisms that are exposed to these forms and levels of energy. The amount of radiation 

energy used to bring about the control of microorganisms varies according to the radiation 

resistance of the particular organism, which is often specific to the species level and the number 

or load of the microorganisms present. 

Radiation treatment at doses of 2–7 kiloGray (kGy), depending on the source of radiation and 

the food, have been reported to effectively eliminate potentially pathogenic non-sporeforming 

bacteria, including both long-time recognized pathogens such as Salmonella and S. aureus, as 

well as more recently emerged pathogens such as Campylobacter, L. monocytogenes or E. coli 

O157:H7, from suspected food products (Farkas, 1998). As an example, Table 4-7 provides a 

summary of compiled data on the ranges of decimal reduction doses (D10 values) for the most 

important non-sporeforming pathogenic bacteria determined in various foods under various 

conditions.
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Table 4-7. D10 Values (kGy) for Some Foodborne Non-sporeforming Pathogenic Bacteria

Bacteria Non-frozen food Frozen food

Vibrio spp. 0.02-0.14 0.04-0.44

Yersinia enterocolitica 0.04-0.21 0.20-0.39

Campylobacter jejuni 0.08-0.20 0.18-0.32

Aeromonas hydrophila 0.11-0.19 0.21-0.34

Shigella spp. 0.22-0.40 0.22-0.41

Escherichia coli O157:H7 0.24-0.43 0.30-0.98

Staphylococcus aureus 0.26-0.57 0.29-0.45

Salmonella spp. 0.18-0.92 0.37-1.28

Listeria monocytogenes 0.20-1.0 0.52-1.4

Adapted from Farkas et al., 2014

Bacterial spores are more resistant to irradiation than non-sporeforming bacteria. The spores of 

C. botulinum types A and B are particularly resistant.

For illustrative purposes, Table 4-8 lists the approved uses of ionizing radiation for application 

as a process control in food processing as of April, 2016. We adapted Table 4-8 from 21 CFR 

179.26(b), which specifies the limitations on the approved uses of ionizing radiation for the 

treatment of food and includes uses for purposes other than as a process control. For example, 

21 CFR 179.26(b) also specifies limitations on the use of ionizing radiation for use in 

disinfestation of arthropod pests in food. You should refer to 21 CFR 179.26 for the most 

current limitations on the approved uses for the treatment of food using ionizing radiation. 

Table 4-8. Approved Uses for the Treatment of Food Using Ionizing Radiation

Use Limitations

For control of Trichinella spiralis in pork carcasses or fresh, 

non-heat-processed cuts of pork carcasses

Minimum dose 0.3 kiloGray (kGy) (30 

kilorad (krad)); maximum dose not to 

exceed 1 kGy (100 krad).

For microbial disinfection of dry or dehydrated enzyme 

preparations (including immobilized enzymes)

Not to exceed 10 kGy (1 megarad 

(Mrad)).

For microbial disinfection of the following dry or dehydrated 

aromatic vegetable substances when used as ingredients in 

small amounts solely for flavoring or aroma: culinary herbs, 

seeds, spices, vegetable seasonings that are used to impart 

flavor but that are not either represented as, or appear to be, a 

vegetable that is eaten for its own sake, and blends of these 

aromatic vegetable substances. Turmeric and paprika may also 

be irradiated when they are to be used as color additives. The 

blends may contain sodium chloride and minor amounts of dry 

food ingredients ordinarily used in such blends

Not to exceed 30 kGy (3 Mrad).
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Use Limitations

For control of food-borne pathogens in fresh (refrigerated or 

unrefrigerated) or frozen, uncooked poultry products that are: 

(1) Whole carcasses or disjointed portions (or other parts) of 

such carcasses that are “ready-to-cook poultry” within the 

meaning of 9 CFR 381.l(b) (with or without non-fluid seasoning; 

includes, e.g., ground poultry), or (2) mechanically separated 

poultry product (a finely comminuted ingredient produced by the 

mechanical deboning of poultry carcasses or parts of 

carcasses)

Not to exceed 4.5 kGy for non-frozen 

products; not to exceed 7.0 kGy for 

frozen products.

For the sterilization of frozen, packaged meats used solely in 

the National Aeronautics and Space Administration space flight 

programs

Minimum dose 44 kGy (4.4 Mrad). 

Packaging materials used need not 

comply with §179.25(c) provided that 

their use is otherwise permitted by 

applicable regulations in 21 CFR parts 

174 through 186.

For control of foodborne pathogens in, and extension of the 

shelf-life of, refrigerated or frozen, uncooked products that are 

meat within the meaning of 9 CFR 301.2(rr), meat byproducts 

within the meaning of 9 CFR 301.2(tt), or meat food products 

within the meaning of 9 CFR 301.2(uu), with or without non-fluid 

seasoning, that are otherwise composed solely of intact or 

ground meat, meat byproducts, or both meat and meat 

byproducts

Not to exceed 4.5 kGy maximum for 

refrigerated products; not to exceed 7.0 

kGy maximum for frozen products.

For control of Salmonella in fresh shell eggs. Not to exceed 3.0 kGy.

For control of microbial pathogens on seeds for sprouting. Not to exceed 8.0 kGy.

For the control of Vibrio bacteria and other foodborne 

microorganisms in or on fresh or frozen molluscan shellfish.

Not to exceed 5.5 kGy.

For control of food-borne pathogens and extension of shelf-life 

in fresh iceberg lettuce and fresh spinach.

Not to exceed 4.0 kGy.

For control of foodborne pathogens, and extension of shelf-life, 

in unrefrigerated (as well as refrigerated) uncooked meat, meat 

byproducts, and certain meat food products

Not to exceed 4.5 kGy.

For control of food-borne pathogens in, and extension of the 

shelf-life of, chilled or frozen raw, cooked, or partially cooked 

crustaceans or dried crustaceans (water activity less than 0.85), 

with or without spices, minerals, inorganic salts, citrates, citric 

acid, and/or calcium disodium EDTA

Not to exceed 6.0 kGy.

Adapted from 21 CFR Part 179.26(b)

For additional information on processes, application, and equipment used in the ionizing 

radiation treatment of foods see FDA (2004), Lacroix (2005), Fellows (2009a), Farkas and 

Mohacsi-Farkas (2011) and FDA (2015b).

4.3.1.4 Use of Antimicrobial Fumigation as a Lethality Process Control

In California, treatment processes for almonds must use technologies that have been 

determined to achieve a minimum 4-log reduction of Salmonella in almonds (see 7 CFR part 

981, Almonds Grown in California). The Almond Board of California (ABC) has processes in 

place to review treatment processes for scientific adequacy. ABC has funded research projects 

demonstrating that fumigation with propylene oxide (PPO) (a registered fumigant in the United

States for the reduction of bacteria, yeasts, and mold on raw nut meats) is an effective 

treatment for achieving a minimum 4-log reduction of Salmonella in almonds (ABC, 2008). 
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4.3.2 Use of Time-Temperature as a Process Control

Temperature is an essential factor that affects the growth of bacteria. Bacterial growth can occur 

over a wide range of temperatures from about 23°F (-5°C) to 194°F (90° C). Table 4-9 lists four 

types of bacteria based on their temperature growth ranges.

Table 4-9. Temperature Ranges for the Growth of Microorganisms

Group Minimum Temperature 

°C (°F)

Optimum Temperature 

°C (°F)

Maximum Temperature 

°C (°F)

Thermophiles 40 - 45 (104 - 113) 55 - 75 (131 - 167) 60 - 90 (140 - 194)

Mesophiles 5 - 15 (41 - 59) 30 - 45 (86 - 113) 35 - 47 (95 - 117)

Psychrophiles -5 - +5 (23 - 41) 12 - 15 (54 - 59) 15 - 20 (59 - 68)

Psychrotrophs -5 - +5 (23 – 41) 25 - 30 (77 - 86) 30 - 35 (86 - 95)

Thermophiles grow at hot temperatures above 131°F (55°C). Mesophiles grow at or near room 

temperatures. Psychrophiles grow at or near refrigeration temperatures. Psychrotrophs are 

capable of growth at refrigeration temperatures, but their optimal growth temperature is in the 

mesophilic range.

Most pathogenic bacteria are mesophiles and their optimum growth temperature corresponds to 

human body temperature (see Table 3-A of Appendix 3 of this guidance). Typically, the higher 

the temperature (within the normal growth range), the more rapid the growth of the

microorganism.

It is not only the temperature that is of concern; it is the total time of exposure at temperatures

that allow growth that needs to be controlled. The most general recommendation is to hold cold 

foods below 41°F (5°C) and to keep hot foods above 135°F (57°C). However, in some situations 

it may not be possible to completely avoid product exposure to mesophilic temperatures.

4.3.2.1 Use of Refrigeration as a Time-Temperature Process Control

Refrigeration works well for controlling the growth of most pathogenic bacteria. However, some 

pathogens, like L. monocytogenes and Yersinia enterocolitica, can grow at temperatures close 

to freezing. Refrigeration has the added advantage of slowing down biological and chemical 

processes that result in spoilage, oxidative rancidity, and other quality defects. 

Control of temperature during storage can be accomplished in several ways, such as ice, 

chemical coolant gel packs, and mechanical dry refrigeration (e.g., in a cooler). 

Controlling temperature with ice or gel packs can be effective if there is an adequate amount of 

ice or gel packs. Therefore, you should monitor the control by checking whether an adequate 

amount of coolant is present on the product at all times, including when it is shipped and when it 

is received and checking the temperature of the food with a thermometer or temperature 

recording device. 

For mechanical dry refrigerated storage in a cooler, if the ambient temperature can be related to 

the product temperature, monitoring the temperature of the storage area will ensure that the 

product temperature is under control. Ordinarily monitoring of the cooler requires use of 

continuous monitoring instruments such as recorder thermometer charts, maximum-indicating 

thermometers, and high temperature alarms.
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Time/Temperature

When food is removed from refrigeration, the temperature of the food gradually increases and 

can reach the temperature associated with the growth range specific to particular pathogens. 

Bacterial pathogens go through a lag phase, where little or no growth occurs as the 

microorganisms adjust to their new environment. Depending upon the ambient temperature, it is 

possible that food can stay out of refrigeration for at least a couple of hours with no risk of 

significant pathogen growth. As the product temperature approaches the growth range, 

pathogens enter what is called the “log phase” (because they grow logarithmically). The object 

is to prevent that from happening, ideally keeping pathogens in their lag phase. We call the 

temperature range of concern (41°F (5°C) to 135°F (57°C)) the “danger zone.”

Traditionally, the rule of thumb for foods that will support microbial growth has been no more 

than 4 hours in the danger zone (41°F (5°C) to 135°F (57°C)). Different pathogens have 

different rates of growth at different temperatures, and the rate of growth will be affected by the 

type of food and its inherent properties. Therefore, the actual maximum time that a product may 

be safely held in the danger zone depends on a number of factors, including the type of 

pathogens that are present and the ability of the food to support their growth. Guidance on this 

issue is available in the US Food Code2 (FDA, 2013) and in Table 3-B in Appendix 3 of this 

document. You may set limits based on these factors or based on studies done on your own 

specific food products, rather than relying on the 4-hour rule of thumb. Food inspectors should 

also use these factors when they evaluate the significance of time - temperature abuse.

Control of time and temperature during processing may be more complicated than during

storage, because it involves information about the time and temperature exposure of the

product during production. You can obtain this information in a variety of ways, such as marking 

units of product and tracking how long they remain at unrefrigerated temperatures; monitoring

the ambient temperature in a chill room operation; or monitoring product temperatures during

different phases of production. See “Chapter 7 – Use of Time/Temperature Control as a 

Process Control” of this guidance for additional information about the application of timetemperature holding conditions.

Cooling after Cooking

Cooling after cooking can be a critical function influencing the safety of a food (FDA, 2013). 

Depending upon the food and ingredients, cooked foods can still have viable pathogenic 

bacteria present. For example, the spores of sporeforming pathogens such as C. botulinum can 

survive cooking processes. For non-sporeforming pathogens that are particularly heat tolerant 

(such as L. monocytogenes), vegetative cells can sometimes survive the cooking process; 

however, this should not be the case if you selected the appropriate target pathogen for control 

by the applied process and you validated the control. More often, it is the spores of 

 2 The U.S. Food Code (FDA, 2013) is a model that assists food control jurisdictions at all levels of 

government by providing them with a scientifically sound technical and legal basis for regulating the retail 

and food service segment of the industry (restaurants and grocery stores and institutions such as nursing 

homes). Local, state, tribal, and federal regulators use the FDA Food Code as a model to develop or 

update their own food safety rules and to be consistent with national food regulatory policy. Although the 

target audience for the U.S. Food Code does not include most food processing facilities, the U.S. Food 

Code nonetheless contains scientifically-based information that you can use as a resource where 

appropriate in establishing some preventive controls particularly regarding use of refrigeration to control 

the growth of microbial pathogens.
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sporeforming pathogens (such as C. botulinum) that survive the cooking process if they are 

present because temperatures that can only be achieved under pressure are usually needed to 

inactivate spores. These spores will begin to germinate when the product temperature drops to 

a temperature at which they can grow (usually below 135°F (57°C)) and will be present in the 

food during storage. Some spores, such as those from non-proteolytic C. botulinum and some 

strains of B. cereus, have the ability to germinate and grow at refrigeration temperatures, 

although long times are required. Other spores that may be present in the food remain dormant 

until the product is temperature-abused (i.e., held in the temperature range at which these 

pathogens can grow). In such an event, pathogenic spores are able to germinate, grow, and 

the resulting cells can possibly produce toxin due to the fact that most spoilage bacteria (which 

may otherwise compete for growth) have been eliminated by the cooking process. For further 

discussion on the importance of cooling food after cooking see Factors that Influence Microbial 

Growth (Chapter 3 in the Evaluation and Definition of Potentially Hazardous Foods) (FDA, 

2001).

If the cooking process is adequate to inactivate spores and the product is protected from 

recontamination during cooling, the cooling step will not be critical. Situations where these 

conditions exist are probably limited to certain pressurized steam processes.

Simply putting food in a refrigerator is not adequate to prevent microbiological growth. When 

large volumes of hot food are cooled, it can take a long time, sometimes as long as 36 hours, to 

chill the food to a point where pathogen growth is inhibited. The U.S. Food Code specifies the 

application of a two part cooling protocol In order to cool foods safely and keep bacteria in the 

lag phase. First, drop the temperature from 135°F (57°C) to 70°F (21°C) within two hours. The

temperature must be lowered through this range quickly because foodborne pathogens multiply 

most rapidly between these temperatures. Second, after dropping the initial temperature to 70°F 

(21°C), you can take up to additional 4 hours to get the product down to 41°F (5°C). FSIS also 

recommends a two part cooling for meat and poultry, but uses slightly different temperatures: 

“temperature should not remain between 130°F (54°C) and 80°F (27°C) for more than 1.5 hours 

nor between 80°F (27°C) and 40°F (4°C) for more than 5 hours” (FSIS, 1999). Both these 

protocols are adequate to minimize the potential for growth of foodborne pathogens.

A blast freezer is one of the best cooling methods. High velocity cold air can drop the

temperature of large volumes of hot food in less than an hour. The containers of food that have 

been chilled can then be shifted to a holding cooler. 

Cooling tunnels and spiral freezers are similar to blast freezers but are more compatible with 

moving production lines. They use high velocity cold air, or liquid carbon dioxide or nitrogen for

rapid cooling. Products may be frozen before or after packaging depending upon the product 

and package size.

Heat exchangers are used for cooling liquids like milk and juice after pasteurization. Lines 

containing a coolant such as water or cold, raw product run adjacent to lines of hot, pasteurized 

product. No actual exchange or co-mingling of coolant or raw product with heat-treated product 

occurs. However, the cold raw liquid, for example, picks up heat from the hot, pasteurized juice. 

This helps preheat the raw product and also helps precool the heat-treated liquid. See “Chapter 

6 – Use of Heat Treatments as a Process Control” in this guidance for additional information 

about heat exchangers.

Cook-chill operations are typically used in large institutional settings such as prisons, hospitals,

and schools as well as in food processing plants. Food is cooked in nylon reinforced plastic 
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bags or is cooked and then pumped into these bags. The bags are chilled in a tumble chiller that 

tumbles the bags in ice water. This drops the temperature of large volumes of hot food quickly. 

Typically, an ice tank where coils of refrigerant are run through the tank of water provides the 

large volume of cold water needed. 

Be advised that food can be recontaminated during the cooling process as a result of hand

contact, condensate drip, or contact with other foods. See “Chapter 10 – Sanitation Controls” in 

this guidance for additional information about controlling the risk of recontamination.

4.3.2.2 Use of Freezing as a Time-Temperature Process Control

Foods are microbiologically stable when held at temperatures below 17.6oF (-8oC). During 

frozen storage, populations of viable microorganisms in most foods will decrease; however, 

some microorganisms remain viable for long periods of time during frozen storage. Most

viruses, bacterial spores, and some bacterial vegetative cells survive freezing unchanged.

Some of the other microorganisms are sensitive to the freezing and thawing process (i.e.,

freezing, frozen storage, or thawing). Since multi-celled organisms (such as such as parasitic 

protozoa, nematodes, and trematodes) are generally more sensitive to low temperatures than 

are bacteria; freezing and frozen storage are good methods for killing these organisms in 

various foods. This is especially important if consumers are likely to eat the foods raw or

undercooked. See Kennedy (2003) and Fellows (2009b) for a detailed review on the use of 

freezing technologies in the preservation of foods.

4.3.3 Use of Product Formulation as a Process Control

Most food preservation techniques used by processors employ knowledge of factors (such as 

water activity, pH, temperature, nutrients, chemical inhibitors, competitive microflora, and 

atmosphere) that affect the growth of bacteria. For more information on how these factors affect 

microbial growth, see International Commission on Microbiological Specifications for Foods 

(ICMSF) (1996, 2002), Jay (1996), and Zeuthen and Bogh-Sorensen (2003).

In this section of this chapter, we discuss two key factors that are frequently used as a 

formulation process control – i.e., water activity and pH. We also discuss the use of 

preservatives as a formulation process control. 

4.3.3.1 Use of Water activity (aw) as a Formulation Process Control

Microorganisms need water to survive as well as to grow. Water activity (aw) refers to the 

availability of water to the organism. In general, microorganisms survive and grow better when 

the water activity is high than when the water activity is low. 

If you have a closed container of water, the air over the water becomes saturated with water. 

The relative humidity is 100%, which equals a water activity of 1.0. Thus, water has a water 

activity of 1.0. Foods are more complex systems than water, and the water can bind to 

components of the food so not all the water in the food is available to microorganisms; thus, the 

water activity of most food products is less than 1.0. 

Water activity is directly related to the vapor pressure of the water in a solution. You can 

determine water activity by measuring the equilibrium relative humidity of the air over the 

solution in a closed container. Relative humidity divided by 100 equals the water activity:
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(aw) = RH/100

or

aw = p/po

Foods vary in their water activity as shown in Table 4-10. Although you can measure the water 

activity of your specific food if you have the appropriate equipment, for many purposes you can 

rely on the water activity values shown in Table 4-10.
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Table 4-10. Principal Groups of Foods Based on Water Activity (aw) (ICMSF, 1980)

Water Activity Food Groups

0.98 and above • Fresh meats and fish

• Fresh fruits and vegetables 

• Milk and other beverages

• Canned vegetables in brine

• Canned fruit in light syrup

Below 0.98 to 0.93 • Evaporated milk

• Tomato paste

• Lightly salted pork and beef products

• Canned cured meats

• Fermented sausages (not dried)

• Cooked sausages

• Processed cheese

• Gouda cheese

• Canned fruits in heavy syrup

• Bread

Below 0.93 to 0.85 • Dry or fermented sausage

• Dried venison

• Cheddar cheese

• Sweetened condensed milk

Below 0.85 to 0.60 • Intermediate moisture foods

• Dried fruits

• Flour

• Cereals

• Jam and jellies

• Molasses

• Heavily salted fish

• Meat extract

• Nuts

Below 0.60 • Confectionery

• Chocolate

• Honey

• Dried Noodles

• Crackers

• Potato Chips

• Dried egg, milk and vegetables

Table 4-10 organizes the foods into five categories, based on their water activity. Table 4-11 

further classifies these five categories into three categories – i.e., moist foods, intermediatemoisture foods (often included in the low-moisture foods category), and low-moisture foods. 

Moist foods (i.e., foods with water activity above 0.85) require refrigeration or another barrier to 

control the growth of pathogens (see Table 4-11). Intermediate-moisture foods (i.e., foods with 

water activities between 0.60 and 0.85) do not require refrigeration to control pathogens, but

they may have a limited shelf life because of spoilage, primarily by yeast and mold. The 

microbiological stability of intermediate-moisture foods may depend on factors other than water 

activity, such as reduced pH, chemical preservatives, heat treatments, or combinations of these, 

even though the reduced water activity is of major importance. Low-moisture foods (i.e., foods 

with a water activity below 0.60) have an extended shelf life, even without refrigeration.
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Table 4-11. Classification of Foods and Control Requirements Based on Water 

Activity

Water Activity Classification Requirements for Control

Above 0.85 Moist Foods Require refrigeration or another barrier to control the

growth of pathogens

0.60 and 0.85

IntermediateMoisture Foods

• Do not require refrigeration to control pathogens 

• Limited shelf life because of spoilage, primarily by

yeast & mold

Below 0.60 Low-Moisture

Foods

Extended shelf life, even without refrigeration

See Table 4-12 for some examples of moist foods (water activities above 0.85). Most fresh 

meats, fruits, and vegetables, and many dairy products, fall into this category. The big surprise 

here is probably the bread. Most of us tend to think it is a dry, shelf-stable product. Actually, the 

“crumb” (interior) has a relatively high water activity. It is safe because of the multiple barriers of 

pH, water activity (the crust has a low water activity), and preferential growth by mold rather 

than pathogens. In other words, the bread spoils before it becomes hazardous.

Table 4-12. Examples of High Moisture (High Water Activity (aw)) Foods

Moist Foods Water Activity (aw)

Lettuce 0.99

Apples 0.99

Milk 0.98

Bread 0.95

See Table 4-13 for some examples of intermediate-moisture foods (water activity between 0.60 

and 0.85). Some unique products like soy sauce appear to be a high moisture product, but 

actually are in the intermediate-moisture category because salt, sugars or other ingredients bind 

the moisture. Because jams and jellies have a water activity that will support the growth of yeast 

and mold, they are mildly heat-treated immediately before packaging to prevent spoilage.

Table 4-13. Examples of Intermediate Moisture Foods

Intermediate Moisture Foods Water Activity (aw)

Soy sauce 0.80

Jams 0.80

Molasses 0.76

Honey 0.75

Flour 0.70

Dried fruit 0.70

Candies 0.65

See Table 4-14 for some examples of low-moisture foods (water activity below 0.60).
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Table 4-14. Examples of Low-Moisture Foods

Low-Moisture Foods Water Activity (aw)

Dried noodles 0.50

Cookies 0.30

RTE Cereals 0.20

Crackers 0.10

Some of the intermediate and low water activity foods have naturally low water activity (e.g.,

molasses and flour). We do not discuss those foods because water activity does not have to be 

controlled during processing.

Other intermediate and low water activity foods, like dried fruit, strawberry jam, crackers, soy 

sauce, and dried noodles, start with a high water activity and, through processing, end up with a 

reduced water activity. This section of this chapter focuses on these types of foods.

Control of Water Activity

Some products require careful control of water activity for food safety, while others do not. For 

example, the production of jam does not need careful control of water activity for food safety 

because the food would not thicken (and, thus, become jam) unless the water activity was 

reduced through the addition of the necessary amount of sugar. On the other hand, dried fruit 

products need careful control of water activity for food safety, because fruit products with a 

variety of moisture levels could still appear to be “dried fruit.”

There are two primary ways of reducing water activity in foods: (1) product formulation (such as 

by adding salt or sugar); and (2) dehydration (drying). In this section of this chapter, we discuss 

reducing water activity by product formulation. In section 4.3.4 of this document, we discuss 

reducing water activity by dehydration. 

Every organism has a minimum, optimum, and maximum water activity for growth (see Table 3-

A in Appendix 3 of this document). Yeasts and molds can grow at low water activity; however 

0.85 is considered the safe cutoff level for pathogen growth. Water activity of 0.85 is based on 

the minimum water activity for S. aureus growth. For a detailed discussion and listing of the 

minimal water activities for microorganisms of public health concern, see ICMSF (1996).

There are two basic ways for how you can approach product formulation that uses control of

water activity for food safety. One approach is to closely follow a scientifically established 

process for formulation that ensures a water activity of 0.85 or below. The other approach is to 

develop your own process for formulation and to validate it by taking finished product samples 

and testing them for water activity.

4.3.3.2 Use of Acidity (pH) as a Formulation Process Control

The term “pH” refers to a numeric scale used to describe acidity and alkalinity. The pH reflects 

the concentration of hydrogen ions and is expressed mathematically as the negative logarithm 

of the hydrogen ion concentration. The pH scale ranges from 0 to 14, with 7 being neutral.

pH = (-log of the [H+])
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Microorganisms can only grow at certain pH levels (Table 4-15). Table 4-15 shows that mold 

and yeast can grow over a broad range of pH, including very low pH. Table 4-15 also shows 

that the pH range where bacteria can grow is more restricted in that bacteria don’t grow at very 

low pH.

Table 4-15. Growth Limiting pH Ranges for Microorganisms

Type of Microorganism pH Range for Growth

Bacteria (Gram+) 4.0 to 8.5

Bacteria (Gram -) 4.5 to 9.0

Molds 1.5 to 9.0

Yeast 2.0 to 8.5

Table 4-15 classifies bacteria as “Gram positive” and “Gram negative.” In general, “Gram 

positive” and “Gram negative” are designations associated with the cell walls of bacteria, and 

how the bacterial cell walls appear under a microscope when a stain is used to see them. Gram 

positive bacteria appear blue, and gram negative bacteria appear red.

Lowering the pH is considered primarily a method of inhibiting the growth of bacteria rather than

a method for killing bacteria. Although many microorganisms held at low pH for an extended

time will be killed, keep in mind that some pathogenic bacteria, and in particular E. coli 

O157:H7, can survive acidic conditions for extended periods of time, even if their growth is 

inhibited. For details on the minimum and maximum pH limits for bacterial pathogens, see Table 

3-A of Appendix 3 of this document.

Foods with a natural pH of 4.6 and below are considered acid foods. Some foods are naturally 

acidic, including most fruits (e.g., many peaches, pH 4.0; apples, pH 3.5). However, some 

tropical fruits, including some pineapple, may fall in the pH range above 4.6, depending in part 

on variety and growing conditions. Foods with a pH above 4.6 are said to be low-acid foods. 

Examples of low-acid foods include protein foods (such as milk and eggs), most vegetables, 

and starch based foods (such as bread and crackers).

Acidification

Because an acid pH can inhibit the growth of many bacteria, acidification of foods is a common 

formulation process control. Acidification is the direct addition of acid to a low-acid food. 

Examples of foods that are acidified as a process control include pickled beets and peppers. 

There are a variety of acids (such as acetic acid, lactic acid, and citric acid) that can be used to 

acidify foods, depending on the desired attributes of the finished product. 

We have established specific CGMP requirements for thermally processed low-acid foods 

packaged in hermetically sealed containers (commonly called “low-acid canned foods” or LACF 

(21 CFR part 113). We also have established requirements for acidified foods (21 CFR part 

114). At the time when we established these regulations, the focus of these CGMP 

requirements was the control of C. botulinum; when the pH of a food is 4.6 or below, spores of 

C. botulinum will not germinate and grow. As a result, the pH of 4.6 is a dividing line for the 

purpose of determining whether a food other than an acid food is subject to part 113 as an 

LACF or part 114 as an acidified food. See 21 CFR 114.3. 
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An acid food, such as tomatoes with a pH of 4.2, is not subject to either the LACF regulations or 

the acidified foods regulations. Under the acidified foods regulations, “acidified foods” are lowacid foods to which acid(s) or acid food(s) are added; they have a water activity greater than 

0.85 and have a finished equilibrium pH of 4.6 or below (21 CFR 114.3(b)). The definition of 

acidified foods provides that carbonated beverages, foods that are stored, distributed, and 

retailed under refrigeration, and certain other foods are excluded from the coverage of 21 CFR 

part 114 (21 CFR 114.3(b)).

Processors of acidified foods must register with FDA to obtain a Food Canning Establishment 

number (21 CFR 108.25(c)(1)). Processors of acidified foods also must file a scheduled process 

with FDA (21 CFR 108.25(c)(2)); the scheduled process is the process selected by a processor 

as adequate for use under the conditions of manufacture for a food in achieving and maintaining 

a food that will not permit the growth of pathogens. The scheduled process includes control of 

pH and other critical factors equivalent to the process established by a competent processing 

authority (21 CFR 114.3). Acidified foods must be so manufactured, processed, and packaged 

that a finished equilibrium pH value of 4.6 or lower is achieved within the time designated in the 

scheduled process and maintained in all finished foods; manufacturing must be in accordance 

with the scheduled process (21 CFR 114.80(a)(1)). Sufficient control, including frequent testing 

and recording of results, must be exercised so that the finished equilibrium pH values for 

acidified foods are not higher than 4.6 (21 CFR 114.80(a)(2)). An equilibrium pH is achieved 

when a natural pH balance has been reached by all ingredients - which can take several days in 

foods with very large particulates (National Canners Association, 1968). You should refrigerate 

products that require several days to reach equilibrium pH to prevent the growth of C. botulinum 

or other pathogens.

There are several different methods of adding the acid to the product. One method is called 

direct acidification, where predetermined amounts of acid and the low-acid foods are added to 

individual finished product containers during production. With this method, it is important that the 

processor control the acid-to-food ratio. This is probably the most common method used for 

acidified vegetables. Another method of acidification is batch acidification. As the name implies, 

acid and food are combined in large batches and allowed to equilibrate. The acidified food is 

then packaged.

Acidified foods must be treated sufficiently to control spoilage microorganisms in addition to 

vegetative pathogens. Although one reason is to prevent spoilage triggering economic loss, the 

food safety reason is that the action of the spoilage organisms can raise the pH, compromising 

the safety of the product because any spores of C. botulinum that are in the food can germinate, 

grow, and produce botulinum toxin. The acidified foods regulation requires that you thermally 

process the food to an extent that is sufficient to destroy the vegetative cells of pathogenic and 

non-pathogenic microorganisms capable of reproducing in the food under the conditions in 

which the food is stored, distributed, retailed and held by the user. However, you may use 

permitted preservatives to inhibit reproduction of non-pathogenic microorganisms in lieu of 

thermal processing. (21 CFR 114.80(a)(1))

For further information on the use of acidification of foods as a process control, see 21 CFR part 

114. The regulation provides detailed information on appropriate procedures to measure pH for 

foods.
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Fermentation

During bacterial fermentation, acid-producing bacteria produce lactic acid, which reduces the 

pH. Because the reduced pH can inhibit the growth of many bacteria, bacterial fermentation of 

foods is a common formulation process control. Examples of low-acid foods fermented by 

bacterial fermentation to a pH below 4.6 include fermented olives, fermented cucumber pickles, 

cheeses, and sauerkraut. Molds are used to ferment some foods such as soy sauce, tamari 

sauce, and other oriental foods, mainly for taste and other characteristics.

In practice, fermentation is an art. You need to encourage growth of favorable organisms and 

discourage the growth of organisms that can cause spoilage. This is usually accomplished by 

adding salt or a starter culture to the food, or in some cases slightly acidifying it. A starter culture 

can be either yeast or bacteria.

In many fermented products, there is no process to eliminate the acid-producing bacteria. These 

fermented products are kept refrigerated so that the culture bacteria and bacteria not killed 

during the fermentation process do not spoil the product.

4.3.3.3 Use of Preservatives as a Formulation Process Control

Preservatives can be used to prevent the growth of microorganisms – e.g., if a food product is 

not thermally processed (or not thermally processed to an extent that is sufficient to kill the 

vegetative cells of non-pathogenic microorganisms (such as spoilage microorganisms) that are 

capable of reproducing in the food under the conditions in which the food is stored, distributed, 

retailed and held by the user). Preservatives work by denaturing protein, inhibiting enzymes, or

altering or destroying the cell walls or cell membranes of microorganisms. Examples of products 

that use preservatives as a formulation process control include acidified foods that are either not 

thermally processed or only minimally thermally processed, hummus (which uses sodium 

benzoate to inhibit yeast and mold), and many breads (which use calcium propionate to inhibit 

mold). 

Some of the more commonly used preservatives are:

• Acetic acid and its salts (e.g., sodium acetate, sodium diacetate), which is added to reduce bacterial 

growth. 

• Benzoates, which include benzoic acid, sodium benzoate and potassium benzoate. Benzoates are 

used primarily to inhibit yeast or mold. Also can inhibit bacterial pathogens (e.g., S. aureus, L. 

monocytogenes).

• Natamycin is applied on cheese to inhibit the growth of fungi. 

• Nisin is used as an antimicrobial agent to inhibit the outgrowth of C. botulinum spores and toxin 

formation in a variety of pasteurized process cheese spreads. 

• Propionates, which include propionic acid, and sodium, potassium and calcium propionates, are

used in breads, cakes, and cheeses to inhibit mold. Also can inhibit bacterial pathogens (e.g., S. 

aureus, Salmonella).

• Sorbates, which include sorbic acid, and sodium and potassium sorbates. Sorbates are primarily 

used to inhibit yeast and mold. Also can inhibit bacterial pathogens (e.g., E. coli O157:H7, L. 

monocytogenes).
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• Sulfites, such as sulfur dioxide, are used in a variety of products including lemon juice, seafood, 

vegetables, molasses, wines, dried fruit, and fruit juices. Sulfites are used primarily as an antioxidant 

but also have antimicrobial properties.

Table 4-16 provides examples of how some of these commonly used preservatives are used. 

Table 4-16. Preservatives Commonly Used in Conjunction with Main Groups of Foods in 

the United States

Foodstuff Acetic 

Acid

Benzoates Natamycin Nisin Propionates Sorbates Sulfites

Fat Emulsions + + - - - ++ -

Cheese - (+) + + + ++ -

Vegetable 

Products

++ ++ - - - ++ +

Fruit products + ++ - - - ++ ++

Beverages - ++ - - - ++ (+)

Baked goods + - - - ++ ++ -

Confectionery - (+) - - - ++ -

Source: Adapted from Davidson and Branen 1993; Table 11 in Lück and Jager 1997, p 61

++ used frequently

+ used occasionally

(+) used in exceptional cases only

 - not used

A food category that may benefit from the use of preservatives as a formulation process control 

is fresh, refrigerated, RTE deli salads. This category of food, which is typically formulated with 

multiple components, including spices and fresh vegetables, may experience a high bio-load at 

the time of preparation if treated ingredients are not used. Maintaining quality (e.g., by 

preventing spoilage by yeasts and molds) and ensuring product safety cannot always be 

achieved by reducing pH (e.g., by using an acidified food as a salad dressing (such as 

mayonnaise) or an acid food as a salad dressing (such as vinegar)). Antimicrobial substances 

such as potassium sorbate and propionic acid are commonly used for a variety of RTE deli 

salads to inhibit bacteria, yeast, and mold, extending the product shelf-life. 

For further regulatory guidance on the use of antimicrobial substances, see FDA (1999). For a 

comprehensive review on the application of antimicrobials, see Davidson, et al. (2005).

4.3.4 Use of Dehydration/Drying as a Process Control

Dehydration (which reduces water activity) is one of the oldest methods of food preservation. In 

the United States, there are three primary methods of dehydration as a process control. 

• Freeze-drying - used for a variety of products

• Forced air drying - used for solid foods like vegetables and fruit 

• Spray drying - used for liquids and semi-liquids like milk
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Dehydrated/dried products are usually considered shelf stable due to their low water activity 

(aw) and, therefore, are often stored and distributed unrefrigerated. Examples of shelf-stable 

dehydrated/dried food products include milk powders, powdered beverages, pasta, and dried 

peas and beans. 

If you use dehydration/drying as a process control, you should select a packaging material that 

will prevent rehydration of the product under the expected conditions of storage and distribution. 

Additionally, finished product package closures should be free of gross defects that could 

expose the product to moisture during storage and distribution. 

See “Chapter 9 – Use of Dehydration/Drying as a Process Control” of this guidance for 

additional information on the use of dehydration/drying as a process control. For a detailed 

overview of dehydration/drying technologies commonly used in the United States (including 

freeze drying, forced air drying, and spray drying), as well as other dehydration technologies 

such as drum drying and fluid bed drying, see Greensmith (1998) and Heldman and Lund 

(2007). For a discussion on the effects of drying on microorganisms, see Jay (1996).

4.3.5 Use of Recipe Management as a Process Control for Food Ingredients 

A food ingredient (such as a food additive, color additive, or GRAS substance) can be a 

chemical hazard if it is added in excess of a maximum use level, regardless of whether the 

maximum use level is established due to food intolerance (such as for sulfites) or is otherwise a 

condition of safe use of a food additive, color additive, or GRAS substance. Control strategies to 

prevent misformulation of food ingredients generally include recipe management to ensure that 

excessive amounts are not added. 

4.3.6 Use of Storage Conditions as a Process Control for Mycotoxins

Mycotoxins are toxic metabolites produced by certain fungi (i.e., molds) that can infect and 

proliferate on raw agricultural commodities (e.g., grains such as wheat and corn, peanuts, fruits,

and tree nuts) in the field and during storage. Contamination by toxigenic fungi during storage 

and transportation is caused by improper drying or re-wetting of the crop from rain or 

condensation. Thus, effective process controls involve correct drying and storage.

By far the most critical environmental factors determining whether a raw agricultural commodity 

will support mold growth are temperature, moisture content, and time, and each of these 

parameters can be manipulated and controlled to manage the prevention of mold growth in a 

raw agricultural commodity. The principal process control for prevention of mold growth in 

storage conditions is the control of moisture. Although low-temperature storage can help control 

mold growth in some conditions, large-scale storage of raw agricultural commodities generally 

takes place in structures that do not provide for low-temperature and, thus, low-temperature 

storage generally is not a control measure for mold during the storage of raw agricultural 

commodities.

4.3.7 Use of Physical Sorting as a Process Control for Mycotoxins

In most cases, mycotoxins in raw agricultural commodities are present in a very small proportion 

of individual seeds or kernels. As a result, removing the contaminated seeds or kernels 

mechanically is a practical and effective process control to reduce the mycotoxin content of the 

bulk raw agricultural commodity (West and Bullerman, 1991). Various techniques have been 

devised, based on color and visual appearance of decay or damage, to separate out 
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contaminated seeds during inspection processes. This may be manual or by more advanced 

electronic instrumental selection.

4.3.8 Use of Exclusion Strategies as a Process Control for Physical Hazards

 4.3.8.1 Exclusion Strategies as a Process Control for Metal Hazards

Metal-to-metal contact during processing can introduce metal fragments into products. For 

example, metal fragments can break off during mechanical cutting and blending operations, and 

some metal equipment has parts that can break or fall off, such as wire-mesh belts. You can 

control metal hazards by using physical separation techniques (such as magnets, sieves, 

screens, or flotation tanks), by using electronic or X-ray metal detection devices, and by 

regularly inspecting at-risk equipment for signs of damage.

The effectiveness of physical separation techniques depends on the nature of the product. 

These measures are more likely to be effective in liquids, powders, and similar products in 

which the metal fragment will not become imbedded.

The use of electronic metal detectors is complex, especially with regard to stainless steel, which 

is difficult to detect. The orientation of the metal object in the food affects the ability of the 

equipment to detect it. For example, if a detector is not properly calibrated and is set to detect a 

sphere 0.08 inch (2 mm) in diameter, it may fail to detect a stainless steel wire that is smaller in 

diameter but up to 0.9 inch (24 mm) long, depending on the orientation of the wire as it travels 

through the detector. Processing factors, such as ambient humidity or product acidity, may 

affect the conductivity of the product and create an interference signal that may mask metal 

inclusion unless the detector is properly calibrated. You should consider these factors when 

calibrating and using this equipment.

X-ray devices can also be used for metal detection. One advantage in using such a device is 

that X-rays can detect non-metal foreign objects that may also be hazardous, such as glass 

fragments. 

Preventive maintenance of equipment and periodically examining your processing equipment 

for damage that can contribute metal fragments can be a useful control measure, particularly 

when you have a piece of equipment that is prone to break, such as saw blades, or equipment 

that has metal-to-metal contact. The success of this strategy depends in large part on the nature 

of the equipment inspected and the frequency of the inspection. However, this approach will not 

necessarily prevent metal fragments from being incorporated into the product in all cases, but 

may enable you to separate products that may have been exposed to metal fragments. Visually 

inspecting equipment for damaged or missing parts may only be feasible with relatively simple 

equipment, such as band saws, small orbital blenders, and wire mesh belts. More complex 

equipment that contains many parts, some of which may not be readily visible, may not be 

suitable for visual inspection and may require controls such as metal detection or physical 

separation techniques.

See “Chapter 13-- Preventive Controls for Physical Hazards” of this guidance for additional 

information on the control of metal hazards.
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 4.3.8.2 Exclusion Strategies as a Process Control for Glass Hazards

Glass fragments can be introduced into food whenever processing involves the use of glass 

containers. Normal handling and packaging methods, especially mechanized methods, can 

result in breakage. Ingesting glass fragments can cause injury to the consumer. Most products 

packed in glass containers are intended to be a ready-to-eat (RTE) commodity that requires 

minimal handling on the part of the consumer before eating, so that consumers have little 

opportunity to detect glass inclusion. 

This chapter addresses the hazard of glass fragments that may occur from the use of glass 

containers. You should address the hazard of glass fragments originating from sources such as 

overhead light fixtures through CGMPs. 

You can help prevent glass from getting into your food products by periodically checking the 

processing areas and equipment for glass breakage. In addition, the line operator can listen for 

breakage and can look for broken glass on the floor. (You can enhance the utility of these 

controls by painting the floor under the processing line in a color that highlights the container 

glass.) These types of controls will not necessarily prevent glass fragments from being 

incorporated into your product, but they can enable you to separate products that may have 

been exposed to glass fragments from those that have not. 

You also can help prevent glass fragments from getting into your food products by cleaning 

empty containers before filling into the product package. You can do so by using water or 

compressed air and inverting the container during or after cleaning. You should be mindful that 

container cleaning may not fully control glass hazards in some processes that use automated 

filling systems because this equipment can result in glass breakage during the filling and

capping process. 

See “Chapter 13--Preventive Controls for Physical Hazards” of this guidance for additional 

information on the control of glass hazards.

4.4 Sanitation Controls 

CGMPs require sanitary operations (21 CFR 117.35) and sanitary facilities and controls (21 

CFR 117.37). There are requirements applicable to the cleanliness of equipment and utensils, 

including food-contact surfaces (21 CFR 117.40), and plant construction and design (21 CFR 

117.20(b)). To comply with these CGMP requirements, sanitation procedures, practices, and 

processes should take place every day in your facility. 

Sanitation controls include procedures, practices, and processes to ensure that the facility is 

maintained in a sanitary condition adequate to significantly minimize or prevent hazards such as 

environmental pathogens, biological hazards due to employee handling, and food allergen 

hazards. Sanitation controls must include, as appropriate to the facility and the food, 

procedures, practices, and processes for the: (1) Cleanliness of food-contact surfaces, including 

food-contact surfaces of utensils and equipment; and (2) prevention of allergen cross-contact 

and cross-contamination from insanitary objects and from personnel to food, food packaging 

material, and other food-contact surfaces and from raw product to processed product. (See 21 

CFR 117.135(c)(3).) 

You determine which hazards require a sanitation control, rather than CGMPs, through your

hazard analysis. Thus, some – but not all - of your sanitation procedures, practices, and 
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processes will be “sanitation controls”; other sanitation procedures, practices, and processes 

will be CGMPs. For your sanitation controls to be effective, you should first assess the 

sanitation procedures, practices, and processes that you will have in place to comply with the 

CGMP requirements. For example, equipment design that ensures that all surfaces can be 

accessed and cleaned is essential for the effective application of sanitation controls. Effective 

sanitary design should consider factors such as whether equipment includes hollow bodies or 

poorly developed welds and seams, as well as whether ease of disassembly allows adequate 

access to all food-contact surfaces to ensure thorough cleaning and sanitation. Sanitary design 

also applies to food facility structures (e.g., floors, walls, piping, and ceilings) to ensure effective 

cleaning and sanitation practices. The required elements for cleaning – time, temperature, 

mechanical force and chemical concentration – simply cannot be reliably applied if the 

equipment and facility structural design does not allow adequate access (Marriott and Gravani, 

2010). Due to this link between your CGMP procedures, practices, and processes and your 

sanitation controls, your CGMP procedures, practices, and processes are sometimes called 

“prerequisite programs.”

The nature of the processing conditions (i.e., wet or dry) required for the manufacture of a 

particular product (such as a dry processing environment for spray dried milk powder, and a wet 

processing environment for soft cheese) impacts the selection of the appropriate CGMP 

sanitation procedures, practices, and processes or the appropriate sanitation control. For 

example, moisture control is critically important in preventing contamination by an environmental 

pathogen, such as Salmonella, in low-moisture products. Water in a dry processing 

environment is one of the most significant risk factors for Salmonella contamination, because 

the presence of water allows for pathogen growth leading to product contamination from the 

environment or from insanitary food contact surfaces. Therefore, dry cleaning or controlled wet 

cleaning practices should be considered for use as sanitation control measures in a dry 

processing environment. Any time water is used for cleaning, the equipment should be 

thoroughly dried before use. Wet processing operations are subject to wet cleaning. However, 

water, in particular standing water, should be minimized even if facilities are wet cleaned. This 

is particularly true for facilities that need to control L. monocytogenes because they are 

producing RTE products exposed to the environment.

The nature of a bacterial pathogen (e.g., whether it is a transient or a resident strain of an 

environmental pathogen) also impacts the selection of the appropriate CGMP sanitation 

procedures, practices, and processes, or the appropriate sanitation control. (See section 

3.2.5.2 (Transient vs. resident facility-related environmental pathogens) in “Chapter 3-- Potential 

Hazards Associated with the Manufacturing, Processing, Packing, and Holding of Human Food” 

in this guidance for additional information about transient and resident strains of environmental 

pathogens. 

Table 4-17 lists examples of the application of sanitation controls to significantly minimize or 

prevent biological and chemical hazards and the section in this chapter that addresses each 

listed example. 
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Table 4-17. Examples of Sanitation Controls 

Sanitation Control 

Subcategory

Examples Chapter Section

Cleaning food-contact 

surfaces

• Applying a full wet clean with detergents 

and sanitizers for Clean in Place and Clean 

out of Place (CIP/COP)

• Applying controlled wet clean with minimum 

water usage and wipe down (COP)

• Dry cleaning with vacuums, brushes, wipes

4.4.1

Control cross-contact / crosscontamination

• Using hygienic zoning for separation of 

process operations such as raw vs. Workin-Process (WIP) vs. finished product; wet 

vs. dry; personnel and materials flow; air 

balance

• Using dedicated cleaning / sanitation 

practices in designated hygiene zones (see 

cleaning food-contact surfaces)

• Cleaning between different products 

containing different allergens

4.4.2

See “Chapter 10 – Sanitation Controls” of this guidance for additional information about 

sanitation controls. In addition to this guidance, a number of sources of scientific and technical 

information can be useful in establishing sanitation controls. See Holah, 2014 and Marriott and 

Gravani, 2010. 

4.4.1 Use of Sanitation Controls for the Cleanliness of Food-Contact Surfaces

The CGMP requirements for sanitary operations include specific requirements for cleaning foodcontact surfaces. See 21 CFR 117.35(d). All food-contact surfaces, including utensils and 

food-contact surfaces of equipment, must be cleaned as frequently as necessary to protect 

against allergen cross-contact and against contamination of food (21 CFR 117.35(d)). Foodcontact surfaces used for manufacturing/processing, packing, or holding low-moisture food must 

be in a clean, dry, sanitary condition before use (21 CFR 117.35(d)(1)). When the surfaces are 

wet-cleaned, they must, when necessary, be sanitized and thoroughly dried before subsequent 

use (21 CFR 117.35(d)(1)). In wet processing, when cleaning is necessary to protect against 

allergen cross-contact or the introduction of microorganisms into food, all food-contact surfaces 

must be cleaned and sanitized before use and after any interruption during which the foodcontact surfaces may have become contaminated (21 CFR 117.35(d)(2)). Where equipment 

and utensils are used in a continuous production operation, the utensils and food-contact 

surfaces of the equipment must be cleaned and sanitized as necessary (21 CFR 117.35(d)(2). 

Part 117 does not define the term “cleaning.” In this guidance, we use the term “cleaning” to 

mean removing the “soil”– i.e., bacteriological nutrients, such as fats, carbohydrates, proteins,
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and minerals”– that can build up on food-contact surfaces in the plant and processing 

equipment. Part 117 defines “sanitize” to mean to adequately treat cleaned surfaces by a 

process that is effective in destroying vegetative cells of pathogens, and in substantially 

reducing numbers of other undesirable microorganisms, but without adversely affecting the 

product or its safety for the consumer. (21 CFR 117.3) Although cleaning operations and 

sanitizing operations often are conducted separately – and sequentially – some systems (such 

as steam systems) both clean and sanitize the surfaces; we consider that such systems satisfy 

the definition of ‘‘sanitize.’’ (See 80 FR 55908 at 55956.)

Table 4-16 describes three types of cleaning strategies that you can use to remove soil, 

depending upon the processing conditions (wet or dry). Table 4-16 includes our 

recommendations for using these cleaning strategies. See Appendix 4 of this guidance for more 

details about these cleaning strategies.

Table 4-18. Types of Cleaning Strategies

Cleaning Strategy Description and Recommendations

Wet Cleaning Uses water-based and/or wet chemical cleaning solutions. When using 

wet cleaning, you should avoid certain practices, e.g., excessive use of 

water (e.g., floor is flooded with water), high pressure hoses. Instead, 

you should use water on an as-needed basis. You also should

minimize and isolate your use of water to specific areas where possible. 

Drying after wet cleaning helps to minimize growth of remaining 

microorganisms. 

Dry Cleaning Does not use any water. Dry cleaning is the physical removal of 

residues (e.g., food particles and dust) without water. You should 

remove food residues by actions such as sweeping, brushing, scraping, 

or vacuuming the residues from equipment surfaces and the facility 

environment. Be careful to not distribute food particles to other 

equipment or areas during removal. 

Controlled Wet 

Cleaning

Uses a limited amount of water, generally for dry operations. Complete 

drying should follow immediately after the controlled wet cleaning. You 

can move specific pieces of equipment out of the area to be wet 

cleaned, sanitized, and dried and then return the equipment after the 

area is cleaned.

After the surfaces are cleaned and rinsed you should sanitize food contact surfaces and other 

areas as appropriate. You should use all sanitizers in accordance with the EPA-registered (or 

similar registration in other countries) label use instructions, including approval for use in food 

establishments. 

As noted in section 4.4, sanitation controls must include, as appropriate to the facility and the 

food, procedures, practices, and processes for the cleanliness of food-contact surfaces, 

including food-contact surfaces of utensils and equipment. (See 21 CFR 117.135(c)(3).)

Examples of sanitation controls related to the cleanliness of food-contact surfaces include 

cleaning and sanitizing procedures, practices, and processes (including appropriate frequencies 

for these procedures, concentrations of cleaning and sanitizing compounds, method of 

application, and contact time) (Holah, 2014). See “Chapter 10 – Sanitation Controls” of this 

guidance for a practical example of the application of cleaning and sanitizing of food-contact 

surfaces as a preventive control for bacterial contamination.
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4.4.2 Use of Sanitation Controls to Prevent Allergen Cross-contact and 

Cross-contamination

As noted in section 4.4, sanitation controls must include, as appropriate to the facility and the 

food, procedures, practices, and processes for the prevention of allergen cross-contact and 

cross-contamination from insanitary objects and from personnel to food, food packaging 

material, and other food-contact surfaces and from raw product to processed product. (See 21 

CFR 117.135(c)(3).) 

Table 4-19 describes three common practices that you can use to prevent allergen crosscontact and to prevent cross-contamination of foods from insanitary objects, poor hygienic 

practices, different processing operations, and environmental pathogens. 

Table 4-19. Common Practices to Prevent Allergen Cross-contact and Crosscontamination 

Practice Description

Hygienic Zoning Hygienic zoning for separation and segregation of process operations such 

as raw vs. work-in-process vs. finished product; wet vs. dry; personnel and 

materials traffic flow; air balance

Hygienic Zone 

Specific Cleaning

Dedicated cleaning / sanitation practices within hygiene zones 

Allergen Specific 

Cleaning

Cleaning between different products containing different allergens

The objective of hygienic zoning is to reduce the potential for transient pathogens to enter 

sensitive areas in the facility, such as packing areas where an RTE product is exposed to the 

processing environment. Typically, this type of sanitation control is applied in facilities that 

make RTE products. 

You should determine the need for, and scope of, a hygienic zoning program based on your 

facility, the products you make, and the outcome of your hazard analysis. For example, the 

need for, and scope of, a hygienic zoning program are likely to be very different for a flour mill, 

a facility that makes RTE refrigerated food, and a facility that makes canned acidified foods. In 

determining the need for, and scope of, a hygienic zoning program, you should take into 

account the structure of your plant, packaging, personnel and ingredient traffic flows, and any 

cross over areas. You also should consider potential contaminants from raw materials, air flow, 

support areas, and other activities taking place in the facility. 

Some facilities implement hygienic zoning for quality reasons (e.g., to control mold 

contamination); however, the sanitation controls that are the subject of this guidance need only 

address food safety. See “Chapter 10 – Sanitation Controls” of this guidance for a practical 

example for the application of hygienic zoning to prevent recontamination by environmental 

pathogens.

4.5 Food Allergen Controls

Food allergen controls include procedures, practices, and processes to control food allergens. 

Food allergen controls must include those procedures, practices, and processes employed for: 

(1) Ensuring protection of food from allergen cross-contact, including during storage, handling, 
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and use; and (2) labeling the finished food, including ensuring that the finished food is not 

misbranded under section 403(w) of the FD&C Act (21 U.S.C. 343(w)). See 21 CFR 

117.135(c)(2).

Examples of procedures, practices, and processes to ensure protection of food from allergen 

cross-contact are:

• Identifying and marking allergen-containing ingredients at receiving;

• Segregating and storing allergen-containing materials at receiving and warehousing;

• Scheduling production of products based on allergen-containing recipes;

• Physical separation of processes for non-allergen-containing and allergen-containing products;

• Sanitation and cleaning practices;

• Using full wet cleaning to remove allergenic materials prior to producing a non-allergen-containing 

product on the same line;

• Using dedicated cleaning utensils and equipment for removing allergenic materials from food 

processing equipment. 

Examples of procedures, practices, and processes to label the finished food are:

• Performing label review for each new batch of labels received at the facility;

• Implementing procedures for application of correct label to product.

See “Chapter 11 - Food Allergen Controls” of this guidance for in-depth guidance on preventive 

control strategies for food allergen hazards.

4.6 Supply-chain Controls

Supply-chain controls include the supply-chain program required by 21 CFR part 117, subpart G

(21 CFR 117.135(c)(4)). Subpart G specifies:

• The requirement to establish and implement a supply-chain program (21 CFR 117.405); 

• General requirements applicable to a supply-chain program (21 CFR 117.410); 

• Responsibilities of the receiving facility (21 CFR 117.415); 

• Requirements for using approved suppliers (21 CFR 117.420); 

• Requirements for determining appropriate supplier verification activities (including determining the 

frequency of conducting the activity) (21 CFR 117.425); 

• Requirements for conducting supplier verification activities for raw materials and other ingredients (21 

CFR 117.430); 

• Requirements for an onsite audit (21 CFR 117.435); and 

• Requirements for records documenting the supply-chain program (21 CFR 117.475). 

In this section of this guidance, we discuss the use of ingredient specifications as a supply-chain 

control for several chemical hazards – i.e., pesticides, drug residues, heavy metals, and 

mycotoxins. See our forthcoming “Chapter 15: Supply-Chain Program for Human Food 

Products” for in-depth guidance on supply-chain controls.
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4.6.1 Supply-chain Controls for Pesticides

Pesticides used in the growing of vegetables fruits, and grain crops include fungicides, 

insecticides, and rodenticides that control pests found in growing environments. These may also 

be used in manufacturing environments. If you determine through your hazard analysis that a 

pesticide hazard requires a preventive control (e.g., due to residual pesticide level violations in a 

particular raw agricultural commodity), and that control is applied by your supplier, you would 

have a supply-chain program in which you would verify that your supplier controls pesticides. 

You could have specifications for your supplier that pesticide levels in raw materials and other 

ingredients must be within permitted levels and you could ask to review your supplier’s pesticide 

control program. Your program could have verification activities such as periodic testing by you 

or your supplier for pesticide residues.

4.6.2 Supply-chain Controls for Drug Residues

Drug residues due to the use of antibiotics or related drugs in livestock are principally a potential 

concern for milk-based products. If you determine through your hazard analysis that a drug 

residue hazard requires a preventive control, and that control is applied by your supplier, you 

would have a supply-chain program in which you would verify that your supplier controls drug 

residues to ensure that drug residues in raw materials and other ingredients are within permitted 

levels.

4.6.3 Heavy Metals

Heavy metals are principally a concern in raw agricultural commodities grown in soils that are

contaminated either naturally or through industrial activity. If you determine through your hazard 

analysis that a heavy metal hazard requires a preventive control, and that control is applied by 

your supplier, you would have a supply-chain program in which you would verify that suppliers 

source raw agricultural commodities from regions that do not have high levels of heavy metal 

contamination in soil, and specifications that heavy metals in raw materials and other 

ingredients will be within permitted levels.

4.6.4 Supply-chain Controls for Mycotoxins

Mycotoxins are toxic metabolites produced by certain fungi (i.e., molds) that can infect and 

proliferate on raw agricultural commodities (e.g., grains such as wheat and corn, peanuts, fruits,

and tree nuts) in the field and during storage. Critical environmental factors determining whether 

a raw agricultural commodity will support mold growth are temperature, moisture content, and 

time, and each of these parameters can be manipulated and controlled to manage the 

prevention of mold growth in a raw agricultural commodity. As noted in section 4.3.7 of this 

chapter, effective process controls for mycotoxins involve correct drying and storage as well as 

physical sorting techniques to remove damaged or moldy raw agricultural commodities. 

If you determine through your hazard analysis that a mycotoxin hazard requires a preventive 

control, and that control is applied by your supplier, you would have a supply-chain program in 

which you would verify that your supplier controls mycotoxins. You could have specifications

that mycotoxins in raw materials and other ingredients will be within permitted levels. 
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4.7 Recall Plan

For food with a hazard requiring a preventive control, you must establish a written recall plan for 

the food. The written recall plan must include procedures that describe the steps to be taken, 

and assign responsibility for taking those steps, to perform the following actions as appropriate 

to the facility: (1) Directly notify the direct consignees of the food being recalled, including how 

to return or dispose of the affected food; (2) Notify the public about any hazard presented by the 

food when appropriate to protect public health; (3) Conduct effectiveness checks to verify that 

the recall is carried out; and (4) Appropriately dispose of recalled food—e.g., through 

reprocessing, reworking, diverting to a use that does not present a safety concern, or destroying 

the food. See 21 CFR 117.139.

We recommend that you consult our general guidance on policy, procedures, and industry 

responsibilities regarding recalls in 21 CFR part 7, subpart C (§§ 7.40 through 7.59) and FDA’s 

Guidance for Industry: Product Recalls, Including Removals and Corrections (FDA, 2015c).

A recall can be disruptive to your operation and business, but there are several steps you can 

take in advance to minimize this disruptive effect:

• Adequately code products to make possible positive lot identification and to facilitate effective recall of 

all violative lots.

• Maintain such product distribution records as are necessary to facilitate location of products that are 

being recalled. You should maintain such records for a period of time that exceeds the shelf life and 

expected use of the product.

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