Comparative Risk Assessment 

for Intact (Non-Tenderized) 

and 

 Non-Intact (Tenderized)Beef: 

Executive Summary

Prepared by: 

Risk Assessment Division 

Office of Public Health Science 

Food Safety and Inspection Service 

United States Department of Agriculture 

March, 2002 
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

1. RISK MANAGEMENT REQUESTS AND OBJECTIVES 

In October 2001, the Office of Policy, Program Evaluation and Development (OPPDE) 

requested the following types of risk assessments to support policy decision-making 

regarding E. coli O157:H7 in non-intact beef: 

(1) a farm-to-table risk assessment to evaluate the effectiveness of interventions in reducing 

the occurrence and extent of E. coli O157:H7 contamination on carcasses and reduce the 

subsequent risk of illness; and 

(2) a comparative risk assessment to evaluate the risk of illness per serving from intact versus 

non-intact (e.g., tenderized) beef steaks and roasts prepared using traditional cooking 

practices (grilling, broiling, and frying). 

The requested farm-to-table risk assessment for non-intact (tenderized) beef could not be 

developed because of the lack of sufficient data on the prevalence and level of E. coli 

O157:H7 on specific locations of the carcass (see the Risk Assessment Plan for Non-Intact 

Beef; FSIS 2001). There was, however, sufficient data to assess the risk of illness from nonintact (tenderized) beef compared to intact (non-tenderized) beef. 

The comparative risk assessment, including modeling approach, data inputs and underlying 

assumptions, as well as the resulting risk estimates are summarized below. For additional 

technical detail, see the Technical Report: Comparative Risk Assessment for Intact (NonTenderized) and Non-Intact (Tenderized) Beef (FSIS, March 2002). 

2. PUBLIC HEALTH REGULATORY CONTEXT 

2.1. Public Health Background 

E. coli O157:H7 was first recognized as a foodborne pathogen with major public health 

consequences in 1982, when it was associated with two outbreaks of bloody diarrhea in 

Oregon and Michigan. An estimated 62,000 cases of symptomatic E. coli O157:H7 

infections occur annually in the United States due to foodborne exposures, resulting in 

approximately 1,800 hospitalizations and 52 deaths. As many as 3,000 cases may develop 

hemolytic uremic syndrome annually. Surveillance data indicate that the highest incidence 

of illness from E. coli O157:H7 occurs in children under 5 years of age (Mead 1999). 

While epidemiological evidence indicates that ground beef is the primary foodborne source 

of exposure to E. coli O157:H7, a recent study of the survival of E. coli O157:H7 in 

tenderized beef under customary cooking practices suggests that these sources of non-intact 

beef may also pose a public health risk (Sporing 1999, KSU 2001). Non-intact beef has also 

been implicated as the source of E. coli O157:H7-related illnesses in recent foodborne 

outbreaks in the U.S. and Canada (Michigan Department of Community Health 2000, 

Wisconsin Department of Health and Family Services 2000, and Health Canada 2002).1

 In 

two of these outbreaks, undercooked non-intact beef (e.g., beef tournedos and beef roasts) 

 

1

 These E. coli O157:H7 outbreaks did not provide sufficient quantitative data for use in this risk assessment. 

2
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

was implicated as the most likely vehicle for E. coli O157:H7 (Michigan Department of 

Community Health 2000, Health Canada 2002). In the third outbreak, illnesses may have 

resulted from the consumption of food that was cross-contaminated with E. coli O157:H7 

from non-intact beef (Wisconsin Department of Health and Family Services 2000). 

2.2. Regulatory Background 

To protect public health, FSIS declared raw non-intact beef, including ground beef, 

adulterated if it contains E. coli O157:H7. This policy is based on the premise that E. coli 

O157:H7, an extremely virulent organism, may survive after cooking non-intact beef 

products and cause serious illness in consumers. In contrast, FSIS does not consider intact 

beef containing E. coli O157:H7 to be adulterated because it is assumed that any E. coli 

O157:H7 on the surface of these products would be destroyed during cooking. 

The regulatory history for E. coli O157:H7 in beef is provided below: 

Ground beef. In 1994, FSIS notified the public that raw ground beef contaminated with E. 

coli O157:H7 is adulterated under the Federal Meat Inspection Act (FMIA) unless the ground 

beef is further processed to destroy this pathogen. Also in 1994, FSIS began sampling and 

testing ground beef for E. coli O157:H7. 

Non-intact beef. On January 19, 1999, FSIS published a Federal Register notice explaining 

that all raw non-intact beef products (e.g., those that have been mechanically tenderized by 

needling or cubing), in addition to ground beef, that are found to be contaminated with E. 

coli O157:H7 must be processed into ready-to-eat product, or they would be deemed to be 

adulterated. 

Intact beef. The January 1999 notice also explained that if intact cuts of beef that are to be 

further processed into non-intact product prior to distribution for consumption (e.g., 

manufacturing trimmings) are found to be contaminated with E. coli O157:H7, they must be 

processed into ready-to-eat product, or they would be deemed to be adulterated. FSIS would 

also consider it acceptable to irradiate these products prior to distribution for consumption, if 

they are found contaminated with E. coli O57:H7. 

Justification of the 1999 policy. FSIS explained that: (1) E. coli O157:H7 is an extremely 

virulent organism; and (2) E. coli O157:H7 may survive cooking in non-intact beef and cause 

illness among consumers. FSIS explained that pathogens, including E. coli O157:H7, may 

be introduced below the surfaces of non-intact products (e.g., tenderized beef) as the result of 

the processes by which they are made. As a result, customary cooking of these products may 

not be adequate to kill the pathogens.2

 In contrast, the meat interior of intact products 

remains essentially protected from pathogens migrating below the exterior. Consequently, 

customary cooking of intact products will destroy any E. coli O157:H7. 

3. SCIENTIFIC GUIDANCE 

 

2

 FSIS believes that there is ample anecdotal evidence that consumers frequently eat blade tenderized meat, 

particularly steaks, cooked “rare” or medium.” The Agency thought that this method of preparation would be 

insufficient to destroy E. coli O157:H7 in the interior of the meat and, as a result, may render the product injurious 

to health. 

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Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

A subcommittee of the National Advisory Committee on Microbiological Criteria for Foods 

(NACMCF) was asked to answer several questions with regard to the potential public health 

risk posed by E. coli O157:H7 in blade-tenderized, non-intact beef (e.g., steaks and roasts) 

(NACMCF 2002). The following questions were addressed: 

Q1: Do non-intact, blade tenderized beef steaks present a greater risk to the consumer 

from E. coli O157:H7 compared to intact beef steaks if prepared similarly to intact 

beef steaks? 

Q2: Do non-intact, blade tenderized beef roasts present a greater risk to the consumer 

from E. coli O157:H7 compared to intact beef roasts if prepared similarly to intact 

beef roasts? 

Q3: Is the available information on non-intact products adequate to answer questions 2 

and 3? If not, are there other reasons to conclude that the translocation of E. coli

O157:H7 that occurs with the blade tenderization or similar processes renders 

traditional cooking (consider the traditional cooking process for these products to be 

very rare or rare) of these products inadequate to kill the pathogen? 

Q4: Does the available scientific evidence support the need for a labeling requirement to 

distinguish between intact and non-intact products in order to enhance public health 

protection? 

NACMCF considered several sources of information in addressing these questions, including 

epidemiologic data, FSIS microbiological baseline data, the Kansas State University study 

(Sporing 1999), data on the predictive microbiology of E. coli O157:H7 under various 

cooking conditions, consumer cooking behavior data for steaks and roasts, and data on the 

processing of non-intact steaks and roasts. There were several data gaps identified by 

NACMCF in addressing its charge (see Research Needs). 

In January 2002, based on the available data, NACMCF concluded that “non-intact, blade 

tenderized beef steaks do not present a greater risk to consumers if the meat is oven broiled

and cooked to an internal temperature of 140 o

F or above” (question #1). NACMCF also 

concluded that “blade tenderized beef steaks would present a greater risk when compared to 

intact beef steaks if they are cooked to an internal temperature below 140 oF.” (question #1).3 

A primary resource for these conclusions was the Kansas State University study (Sporing 

1999). Since the KSU study considered only beef steaks and not beef roasts, NACMCF 

concluded that there was insufficient data to determine if non-intact beef roasts presented a 

greater risk than intact beef roasts (question #2). In addition, NACMCF concluded that there 

was insufficient consumer behavior data to determine if traditional cooking methods are 

adequate to destroy E. coli O157:H7 translocated to the interior of blade tenderized beef 

 

3

 These NACMCF statements are based primarily on data published by Kansas State University (Sporing 1999). 

Following inoculation of the surface of intact beef steaks (1/2”, 3⁄4” or 1 1⁄4” in thickness) with a five-strain cocktail 

of E. coli O157:H7 to approximately 107

 cfu/cm2, single-pass blade tenderization resulted in internalization of 

approximately 3 x 103

 cfu/gm or approximately 3-4% of the initial inoculum. It was assumed that the surface of 

intact beef (subprimals) steaks would typically harbor less than 103 coliforms /cm2 when produced under good 

manufacturing practices. A worst case scenario is that all of the coliforms may be E. coli O157:H7 and that their 

total numbers may exceed 103

/cm2. 

4
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

steaks and roasts (question #3). There was also insufficient data for the subcommittee to 

respond to the issue of labeling non-intact beef products (question #4).

4. RISK ASSESSMENT 

2.1. Problem Statement 

The majority of steaks and roasts destined for hotel, restaurant, and institutional use in the 

United States may be subjected to “mechanical tenderization.” This is a process in which 

large pieces of meat are penetrated, usually in several directions, by sets of needles, or 

double-edged blades, and then cut into steaks and roasts. Sometimes the needles used are 

hollow, allowing meat to be injected with solution containing flavorings and/or digestive 

agents such as papain. The purpose of the process is to make lower grade cuts of beef more 

tender. 

During tenderization, transfer of E. coli O157:H7 may occur in two ways: (1) from the 

surface to the interior of contaminated meat; and (2) from contaminated meat to previously 

non-contaminated pieces of meat (e.g., cross-contamination via blade tenderization needles 

and/or recycling of injection fluid). Subsequently, E. coli O157:H7 in these non-intact 

servings may survive cooking and cause illness among consumers. 

Taking these issues into consideration and using currently available data, the comparative 

risk of illness from non-intact (tenderized) beef relative to intact (non-tenderized) beef was 

quantitatively assessed. 

2.2. Methodology 

This risk assessment begins with an estimation of the occurrence and extent of E. coli 

O157:H7 contamination in raw intact beef steaks prior to tenderization, models the 

transfer of E. coli O157:H7 during tenderization, the growth and decline in the number of 

E. coli O157:H7 on beef steaks due to storage and handling conditions prior to cooking, 

the survival of E. coli O157:H7 contamination on intact and non-intact beef steals during 

cooking, and the subsequent probability of illness (Figure 1).4

 Each of these steps (1-5) 

along with the data inputs and underlying assumptions are discussed in more detail 

below. 

 

4

 It was assumed that the risk estimates apply to roasts as well as steaks. This assumption was made because data 

was available only for steaks (e.g., Sporing 1999). In general, roasts are thicker than steaks. Kansas State 

University found that the longer cooking time required to achieve the same internal temperature in thicker cuts of 

meat resulted in a greater reduction in the number of E. coli O157:H7 (Sporing 1999). As a result, it may be 

expected that roasts are cooked longer than steaks and there would be a greater reduction in the number of E. coli 

O157:H7. Further research is needed to evaluate the effectiveness of cooking in reducing E. coli O157:H7 in roasts 

compared to steaks. 

5
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

Cattle

Carcasses

Steaks/Roasts

Tenderize Consumed

Broiling

Grilling

Frying

Other

C1

C2

C3

C4

Consumed

Broiling

Grilling

Frying

Other

C5

C6

C7

C8



Not Tenderized

 Ill ?



 

 

 Ill ?

Figure 1. Conceptual process for the production, preparation and consumption of intact 

(non-tenderized) and non-intact beef (tenderized). 

Step 1. Estimation of the Level of E. coli O157:H7 Contamination in Raw Steaks. 

Currently, there is no sampling data available on the prevalence and levels of E. coli 

O157:H7 on, or in, steaks. As a result, the occurrence and extent of E. coli O157:H7 

contamination on servings of steak had to be estimated based on: (1) the proportion of 

the carcass that becomes intact or non-intact cuts of beef versus ground beef; and (2) the 

predicted prevalence and levels of E. coli O157:H7 in ground beef servings (Table 1).5

 

Table 1 indicates that of the approximately 0.3% contaminated ground beef servings 

produced annually, most contain about one E. coli O157:H7 organism. 

 

5

 The risk assessment for ground beef (FSIS August 2001) estimated the levels of E. coli O157:H7 in ground beef 

based on data from the FSIS (1994) national baseline survey of slaughter plants. In the 1994 FSIS survey, a 60-cm2

surface area was sampled from each of 2,081 chilled carcasses originating from feedlots. Four (0.2%) carcasses were 

E. coli O157:H7-positive, and enumerated densities were reported (50% were <0.030 cfu/cm2

 and 50% were 

between 0.301 and 3.000 cfu/cm2

). Based on a study using more sensitive detection methods, the actual prevalence 

of carcasses contaminated with at least 0.03 cfu/cm2

 would be about 5% (Elder 2000). Modeling was used to 

estimate the fraction of contaminated ground beef servings with various levels of E. coli O157:H7 (FSIS August 

2001). 

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Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

Table 1. E. coli O157:H7 levels predicted in ground beef servings (FSIS August 2001). 

E. coli O157:H7 Fraction of servings 

per serving June-September October-May 

0 99.5% 99.8% 

1 0.46% 0.19% 

3 0.038% 0.011% 

10 0.0035% 0.00040% 

31 0.0000027% 0.0000000002%

100 0% 0% 

See: The Public Health Impact of Escherichia coli O157:H7 in Ground Beef (FSIS August 2001).

The ground beef risk assessment (FSIS, August 2001) also estimated the proportion of 

beef processed into prime cuts versus ground beef as follows: 

• 75% of a steer/heifer carcasses’ original surface area becomes beef trim 

used to make ground beef, 

• 25% of the original surface area’s E. coli O157:H7 remain to 

contaminate primal cuts of beef (e.g., steaks and roasts),

• the remaining surface E. coli O157:H7 on primal cuts are distributed 

across about 82% of the weight of the original carcass (i.e., 500 lbs. of 

beef per carcass and about 18% is trim).

Adjusting the prevalence of E. coli O157:H7 in ground beef based on the proportion of 

carcass that become primary cuts of meat (e.g., steaks and roasts) rather than trim, an 

estimated 0.02% of steaks produced annually contain E. coli O157:H7. Assuming that 

the E. coli O157:H7 organisms are evenly distributed on the surface of carcasses, 

servings of steaks are estimated to have the same distribution of E. coli O157:H7 

organisms as in Table 1.6 To simplify the modeling, it was assumed that steak/roast 

servings contain either: 

• no E. coli O157:H7 organisms. (99.98% of the time); or 

• one E. coli O157:H7 organism (0.02% of the time).7

Step 2. Transfer of E. coli O157:H7 During Tenderization. Mechanical tenderization is 

performed using a series of stainless steel, double-edged blades or needles. The needles 

or blades penetrate the meat by cutting through muscle tissues and fibers, rather than 

 

6

 Such an assumption is necessary to derive the estimates from the ground beef risk assessment since both mapped 

carcasses contamination data or the availability of E. coli O157:H7 contamination data for steaks and roasts are 

lacking. A serving of ground beef is a mixture of trim from many carcasses, while a single serving of steak or roast 

is from a single carcass. As a result, E. coli O157:H7 in ground beef may not be a reasonable surrogate to estimate 

E. coli O157:H7 contamination in steaks. The National Cattleman’s Beef Association has conducted additional 

research on E. coli O157:H7 contamination in steaks and plans to make this data available to the FSIS Risk 

Assessment Division (Bo Regan, personal communication, February 2002). 

7

 This assumption did not have much effect on the risk estimates for steak/roast servings since there are > 10 times 

as many servings with only 1 E. coli O157:H7 organism. 

7
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

tearing the tissue or punching holes. It is estimated that large pieces of meat are pierced 

three times with about 0.8 needles per cm2 of meat surface each time the needle head 

strikes. During this process, E. coli O157:H7 can be transferred from the surface to the 

interior of contaminated meat and/or to meat previously not contaminated (e.g., crosscontamination). 

The Kansas State University study indicated that about 3-4% of E. coli O157:H7 on the 

surface of intact steaks is transferred to the interior during single-pass blade tenderization 

(Sporing 1999). The risk assessment assumed that this data (e.g., 3-4% translocation of 

surface E. coli O157:H7) is reasonably indicative of the results of commercial 

tenderization. The Kansas State University data also suggests that multiple-pass 

tenderization may not result in significantly more E. coli O157:H7 being translocated 

from the surface to the interior of meat (see below). 

The Kansas State University study also indicated that the amount of E. coli O157:H7 

translocated into the interior of steaks decreased with increasing depth of penetration. 

This suggests that most E. coli O157:H7 is deposited near the surface of a meat during 

single-pass blade tenderization and that there are few organisms remaining on a blade to 

be transferred to greater depths of contaminated meat or to meat that was previously not 

contaminated. Also, given the very low prevalence and levels of E. coli O157:H7 

contamination (e.g., 0.02% of steaks with most having only 1 E. coli O157:H7 organism), 

cross-contamination may not be a significant factor in the risk of illness from E. coli 

O157:H7 in non-intact beef when compared to steaks contaminated internally through 

translocation of E. coli O157:H7 during tenderization. As a result, cross-contamination 

was not modeled in this risk assessment and only single-pass tenderization was 

considered. 

Step 3. Estimation of growth and decline of E. coli O157:H7 during distribution, 

storage and handling prior to cooking. Large pieces of meat (subprimals), either 

tenderized or left intact, are then cut into standard pieces (e.g., steaks and roasts) and sold 

to retail for consumption. Consideration was given to the amount of growth and decline 

in the level of E. coli O157:H7 in intact and non-intact beef products during distribution 

and storage prior to cooking. Assuming that the growth of E. coli O157:H7 is the same 

in steaks as in ground beef (FSIS August 2001), the risk assessment estimated the 

following:

• about 50% of steaks have no change in the number of E. coli 

O157:H7 during storage and handling; 

• about 49% (range: 20-80%) of steaks have a reduction in the levels 

of E. coli O157:H7 resulting from freezing the product; and

• about 1% of steaks have some growth of E. coli O157:H7 during 

storage and handling.

To simplify the modeling, it was assumed that freezing eliminates E. coli O157:H7. Since 

all contaminated steaks (only 0.02% of all steaks) are modeled as having only 1 E. coli 

O157:H7 organism, freezing would leave, at most, 0.1 E. coli O157:H7 organism. This 

8
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

assumption does not significantly change the risk estimates for non-intact and intact 

steaks. The fraction of steaks estimated with various levels of E. coli O157:H7 

contamination (e.g., “bugs per serving” (BPS)) are shown in Figure 1. 

0.0000001

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 1 10 100 1000 10000 100000

BPSBC

Fraction of servings exceeding

Figure 1. Fraction of steaks contaminated with various levels of E. coli O157:H7 

organisms prior to cooking (“BPS” = “bugs per serving”). 

It is assumed that levels of E. coli O157:H7 are the same for non-intact (tenderized) and 

intact (not tenderized) beef prior to cooking. Figure 1 shows that 99.99% (range: 99.8% 

to 99.998%) of steaks are not contaminated with E. coli O157:H7 after taking into 

consideration the potential for growth and decline in the number of organisms as a result 

of storage and handling of these products. Only about 0.01% (range: 0.2% to 0.002%) of 

steaks contain E. coli O157:H7 and most of these contaminated servings contain only 1 

E. coli O157:H7 organism. 

Step 4. Estimation of the Level of E. coli O157:H7 Contamination After Cooking. 

After storage, steaks are prepared by a variety of cooking methods (e.g., broiling, grilling, 

and frying) prior to consumption. A recent analysis of the USDA Continuing Survey of 

Food Intakes by Individuals indicates that about 40% of consumers fry steaks, and an 

equal percent (30%) grill or broil these products (Bogen 2001). This information along 

with data from the FDA/Audits International Home Cooking Interactive Database8

 was 

used to estimate the temperatures to which steaks are cooked in the U.S. (FDA 2000) 

(Figure 3). 

 

8

 The data from the FDA/Audits International Home Cooking Temperature Database do not differentiate between 

observations for beef, pork or lamb. The lower temperatures in the database were used to represent cooking 

temperatures for beef since it is likely that pork and lamb are more thoroughly cooked. This more conservative 

estimate can be adjusted with consumer and retail behavior data as it becomes available. 

9
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

0.0

0.2

0.4

0.6

0.8

1.0

40.0 50.0 60.0 70.0 80.0 90.0

Temperature (C)

Cumulative frequency

Lower Most Likely Upper

Figure 3: Internal temperature (oC) to which steaks are cooked in the U.S. based on data 

from the FDA/Audits International Home Cooking Interactive Database. 

The Kansas State University study also provided data on the effects of cooking in 

reducing E. coli O157:H7 in non-intact (tenderized) and intact (tenderized) steaks as a 

function of cooking method (broiling, grilling, and frying), internal temperature, and 

steak/roast thickness (Sporing 1999). The Kansas State University data indicated 

significant uncontrolled variability in the experiment and a noticeable leveling out, or 

“plateauing,” effect at the higher temperatures, which is probably due to the limitation in 

the experiment of inoculating steaks to about 106 E. coli O157:H7. The best fit to this 

data was drawn taking into consideration the fact that at some temperature all E. coli 

O157:H7 would be destroyed (Figure 4). 

function of cooking method (broiling, grilling, and frying), internal temperature, and 

steak/roast thickness (Sporing 1999). The Kansas State University data indicated 

significant uncontrolled variability in the experiment and a noticeable leveling out, or 

“plateauing,” effect at the higher temperatures, which is probably due to the limitation in 

the experiment of inoculating steaks to about 106 E. coli O157:H7. The best fit to this 

data was drawn taking into consideration the fact that at some temperature all E. coli 

O157:H7 would be destroyed (Figure 4). 

The differences in best fit curves for the cooking methods (Figure 4) suggests that the 

same “internal cooking temperature” in the three cooking methods does not correspond to 

the same killing conditions in/on the meat. This suggests that there may be another 

confounding factor not controlled in the Kansas State University study. The movement 

of curves to the right suggest that E. coli O157:H7 is slightly shielded from the effects of 

cooking in non-intact (tenderized) steaks compared to intact (tenderized) steaks. 

The differences in best fit curves for the cooking methods (Figure 4) suggests that the 

same “internal cooking temperature” in the three cooking methods does not correspond to 

the same killing conditions in/on the meat. This suggests that there may be another 

confounding factor not controlled in the Kansas State University study. The movement 

of curves to the right suggest that E. coli O157:H7 is slightly shielded from the effects of 

cooking in non-intact (tenderized) steaks compared to intact (tenderized) steaks. 

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Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

Not-tenderized, 3.2 cm thick

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

45 50 55 60 65 70 75 80

Cooking Temperature (C)

Attenuation factor

Tenderized, 3.2 cm thick

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

45 50 55 60 65 70 75 80

Cooking Temperature (C)

Attenuation factor

Broiling Grilling Frying Broiling Grilling Frying

FitBroiling FitGrilling FitFrying FitBroiling FitGrilling FitFrying

Figure 4: Best fit curves to Sporing (1999) data for broiling, grilling, and frying 3.2 cm 

thick intact (not tenderized) and non-intact (tenderized steaks). Not shown: data for 1.3 

and 1.9 cm thick steaks. 

Combining this information, the risk assessment estimates that 0.000026% (i.e., 2.6 of 

every 10 million servings) of intact steaks contain one or more E. coli O157:H7. For 

non-intact (tenderized) steaks, 0.000037% (i.e., 3.7 of every 10 million servings) contain 

one or more E. coli O157:H7. See Figure 6 for a full range of exposure doses of E. coli 

O157:H7 in intact and non-intact beef. 

Step 5. Dose-Response. The E. coli O157:H7 dose-response relationship shown in 

Figure 5 was adapted from the ground beef risk assessment (FSIS August 2001) using 

data from five Japanese foodborne outbreaks (Nauta 2001, Shingawa 1997, Uchimura 

19979

). The dashed curve is intended to apply to the general population. A doseresponse curve for susceptible individuals (e.g., children < 5 years old) would be shifted 

to the left of this curve (i.e., closer to the Japan 2 young children data point). 

This dose-response relationship suggests, for example, that if 100 individuals from the 

general population each consumed servings containing, say, 10,000 E. coli O157:H7 (i.e., 

4 logs), about 60 would become ill. 

 

9

 Translated by Dr. Fumiko Kasuga, National Institute of Infectious Diseases, Japan. 

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Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8 9 10 11

Log (Dose)

Fraction ill

Japan 1 children Japan 1 adults

Japan 2 young children Japan 2 adults

U.S. outbreak ECRA Upper bound

ECRA Most likely ECRA Lower bound

Figure 5. Expected E. coli O157:H7 dose-response curve for the general population. 

 

2.2. Risk Assessment Results 

The probability of E. coli O157:H7 surviving typical cooking practices in either tenderized or 

not-tenderized steaks, is minuscule. As can be seen in Figure 6, 0.000026 percent (i.e., 2.6 of 

every 10 million servings) of steaks that are intact (not tenderized) contain one or more E. coli

O157:H7. For non-intact (tenderized) steaks, 0.000037 percent (i.e., 3.7 of every 10 million 

servings) contain one or more E. coli O157:H7. There is almost no difference in exposure to E. 

coli O157:H7 in cooked intact (not tenderized) versus non-intact (tenderized) steaks (see almost 

overlapping lines in Figure 6). 

Figure 6 suggests that illness seldom occurs at doses less than 10 E. coli O157:H7 per serving of 

intact or non-intact beef. At a dose of 100 E. coli O157:H7, approximately 16 percent of those 

exposed will become ill. The fraction of intact (not tenderized) steaks with exposure doses of 

100 or more E. coli O157:H7 is about 1.4 in 10 million, while the fraction of non-intact 

(tenderized) servings with exposure doses >100 E .coli O157:H7 is about 1.5 in 10 million. 

12
Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

0.00000001

0.0000001

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

1

10

100

1000

10000

100000

BPSAC (i.e., Dose)

Fraction of servings exceeding 

dose

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Fraction ill

Not-tenderized Tenderized Dose Response

Figure 6. Model output showing predicted bacteria per serving after cooking (exposure dose) 

and corresponding frequency of illness (response). 

Moreover, there is almost no difference in the risk of illness from intact (not tenderized) versus 

non-intact (tenderized) steaks10: 

• 1 illness per 15.9 million servings of intact steaks; 

• 1 illness per 14.2 million serving of non-intact (tenderized) steaks. 

This implies that there would be about seven additional illnesses due to tenderization for every 

billion steak servings. 

3. Comparison of Risk Assessment Results to NACMCF Findings

The risk assessment and NACMCF found had somewhat similar findings: 

• NACMCF found that non-intact (tenderized) beef does not pose a greater risk of illness than 

intact beef it is oven broiled and cooked to an internal temperature of 140oF (45.8oC) or 

more.

• The risk assessment found almost no difference in the risk of illness from intact versus nonintact (tenderized) steaks regardless of cooking temperature [1 illness out of 15.9 for intact 

steaks compared to 1 illness out of 14.2 millions non-intact steaks].

 

10 The risk assessment indicates 80% confidence that the predicted probability of illness from E. coli O157:H7 for 

both intact and non-intact (tenderized) steaks is between 4.5 x 10-8 and 1.0 x 10-7. 

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Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

4. Research Needs 

The following research needs have been identified in order to obtain more information about the 

microbiological profile, cooking practices, industry practices for blade tenderizing, and the 

proportion of blade tenderized beef marketed in the U.S.. Data is also needed regarding the 

exposure dose of E. coli O157:H7 likely to cause illness in susceptible populations. 

1. A lack of quantitative (variable) baseline data for E. coli O157:H7, or appropriate 

indicator organisms such as E. coli biotype 1, coliforms, and/or Salmonella, on primal 

and subprimal cuts of beef immediately prior to blade tenderization was identified. 

Ideally, mapped carcass prevalence and level of E. coli O157:H7 data should be 

collected. 

2. Data on the type of tenderization, processing conditions, and establishment production 

volume should be gathered along with baseline data as risk factors useful in as a profile to 

target Agency inspection resources for HACCP verification activities. 

3. Survival of E. coli O157:H7 in core beef samples following cooking to specified 

temperatures, including data on the survival of E. coli O157:H7 in beef roasts compared 

to beef steaks. 

4. Industry and consumer practices for cooking various cooking methods (e.g., grill vs. 

broil). 

5. Industry practices for blade tenderization; such as the type of machine, number of passes 

through the tenderizer, sanitation of equipment, through put, temperature of the 

processing room, and the temperature of the primal cuts. 

6. Proportion and quantity of blade-tenderized beef distributed to retail and food service 

establishments. 

7. Better understanding of the heat and mass transfer characteristics of blade-tenderized 

meats cooked by various means. 

8. Quantify the heat resistance (e.g., D and z values) of the individual strains of E. coli

O157:H7 used in the Sporing (1999) study. Individual strains should be identified and 

characterized. 

9. Dose-response relationship for susceptible populations (e.g., children < 5 years old). 

Exposure dose data could be collected during outbreak investigations. 

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Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

5. References 

Bogen KT and Keating GA (2001). U.S. dietary exposure to heterocyclic amines. J Exposure 

Analysis and Environmental Epidemiology 11(3):155-168. 

Elder RO, Keen, JE, Siragusa, GR, Barkocy-Gallagher GA, Koomaraie, and Laegreid WW 

(2000). Correlation of enterohemorrhagic E. coli O157 prevalence in feces, hides, and carcasses 

of beef cattle during processing. Proc Natl Acad Sci 97(7):2999-3003. 

Food and Drug Administration (2000). Audits International/FDA home Cooking Temperature 

Database. See: http:www.foodriskclearinghouse.umd.edu/ColdFusion/ Cooking/ 

Food Safety and Inspection Service (1994). Nationwide Beef Microbiological Baseline Data 

Collection Program: Steers and Heifers – October 1992-September 1993 

Food Safety and Inspection Service (2001a). Risk Assessment Plan for Non-Intact Beef. Janell 

Kause, Hazard Analysis and Regulatory Affairs Staff, Office of Public Health and Science. 

December 18, 2001. 

Food Safety and Inspection Service (2002). Technical Report: Comparative Risk Assessment for 

Intact (Non-Tenderized) and Non-Intact (Tenderized) Beef. Stan Kaplan, Eric Ebel, and Wayne 

Schlosser, Modeling and Exposure Assessment Staff, Office of Public Health and Science. 

March 2002. 

Food Safety and Inspection Service (August 2001). Draft Risk Assessment of the Public Health 

Impact of Escherichia coli O157:H7 in Ground Beef. Risk Assessment Division, Office of 

Public Health and Science. [Currently under review by the National Academy of Science]. See: 

http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/00-023NReport.pdf and 

http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/00-023N/InterpretiveSummary.pdf. 

Health Canada (March 2002). Reported cases of illness associated with tenderized beef. One 

page of summary information from the Quebec Center of Food Inspection and Animal Health 

provided by Dr. Anna Lammberding. 

Kansas State University. (August 3, 2001). Presentation: "Evaluation of Pathogen Risks 

Associated with Blade Tenderized Beef Cooked to Varying Degrees of Doneness." National 

Advisory Committee for Microbiological Criteria for Foods (NACMCF) meeting, Washington, 

DC. 

Mead PS, Slutsker L, Dietz V, McCaig LF, Bresee JS, Shapiro C, Griffin PM, and Tauxe RB 

(1999). Food-related illness and death in the United States. Emerg Infect Dis 5(5):607-625. 

Michigan Department of Community Health/Communicable Disease and Immunization Division 

(August 2000). Report: Foodborne Illness Investigation: E. coli O157. 

National Advisory Committee for Microbiological Criteria for Foods (January 25, 2002). Final 

Report: E. coli O157:H7 in Blade Tenderized Beef. See: 

http://www.fsis.usda.gov/OPHS/NACMCF/2002/rep_blade1.htm. 

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Executive Summary:Comparative Risk Assessment For Intact And Non-Intact (Tenderized) Beef March 18, 2002

Nauta, M.J., E.G. Evers, K. Takumi and A.H. Havelaar. 2001. Risk assessment of Shiga-toxin 

producing E. coli O157:H7 in steak tartare in the Netherlands. RIVM report 257851003. 

Shinagawa, K. et al. Correspondence and problem for Enterohemorrhagic E. coli O157 outbreak 

in Morioka city, Iwate. Bulletin of National Institute of Public Health, Vol. 46, No. 2, 104-112, 

1997. (Japanese publication translated and interpreted by Dr. Fumiko Kasuga). 

Sporing, Sarah B (1999). E. coli O157:H7 Risk Assessment for Production and Cooking of 

Blade Tenderized Beef Steaks. Kansas Statue University Master of Science thesis. Professor: 

Randall K. Phebus. 

Uchimura, M. et al. An outbreak of Enterhemorrhagic E. coli O157 in a daycare – Chiba 

Prefecture. Infectious Agents Surveillance Report, Vol. 18, No. 12, 309-310, 1997. (Japanese 

publication translated and interpreted by Dr. Fumiko Kasuga). 

Wisconsin Department of Health and Family Services/Wisconsin Division of Public Health 

(October 2000). Report: Investigation of an Outbreak of E. coli O157:H7 Infection at the 

Layton Avenue Sizzler Restaurant, Milwaukee, WI; July-August 2000. 

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