# Presentation: 334317

## Pathogen Reduction Dialogue Panel 3 Microbial Testing for Control Verification

**Robert L. Buchanan**
**U.S. Food and Drug Administration**
**Center for Food Safety and Applied Nutrition**
**May 7, 2002**

## Microbiological Testing

**Microbiological testing important food safety tool**
**Technologically-based, statistically-based tool **
**Right tool for the right job**

## Microbiological Testing

**One of the most apparent, but poorly understood parts of food microbiology**
**Different types of microbiological testing**
**Safety of “batches” *******
**Process control *******
**Investigational sampling**
**Surveillance**

## Microbiological Testing

**Effective use requires a clear understanding of the goals, assumptions, and characteristics of testing programs **

## Microbiological Testing

**“****Within batch testing” vs. “Between batch testing”**
**Different goals, assumptions, and techniques**

## Microbiological Testing

**“****Within Batch Testing”:**** ****Demonstrate the safety of a single lot of food**

## Microbiological Testing

**Within-batch testing**
**detailed “snapshot” of an operation**
**assumes no prior knowledge of the process**
**focus on establishing safety (or quality) of the batch**
**provides only limited capability to do trend analysis of performance over time**
**can be used nationally to acquire “state of industry”**

## Microbiological Testing

**Effective within certain ranges of contamination frequency or levels of contamination**
**Above or below those ranges, becomes increasingly ineffective**
**When acceptable defect rate is less than 1%, the number of samples needed becomes a limiting factor**

## Microbiological Testing

**“****Between Batch Testing”: ****Demonstrate that a food safety system/process is continuing to  function as intended**

## Microbiological Testing

**“****Between-batch testing”**
_**not**_** designed to assure batch safety which is assumed to be safe if validated process is “in control”**
**assumes intimate knowledge of process**
**requires prior analysis for performance and variation**
**requires sampling over time**
**can also be used nationally to assess “state of industry”**

## Microbiological Testing

**“****Between-batch testing”**
**Much easier to demonstrate that a process is not functioning within a specification than to prove that something (e.g., a pathogen) is not present**

## Sampling for Process Verification

**Microbiological contamination typically flows with a process**
**A microbiological sample taken within a process provides a measure that integrates all the preceding steps in a process**

## Sampling for Process Verification

**The status of a multiple step process is the summation the initial level of contamination and all the steps that increase or decrease the level of contamination**
**	****Microbial Status = Ho + ********I + ********R**

## Sampling for Process Verification

**Sampling of end products integrates the effects of the entire food safety system**
**For investigations of cause, benefits to taking samples at multiple locations**

## Process Control Statistics

**The basis for process control evaluations is the collection of microbiological data over time**
**Typically arrayed graphically as a ****control chart**

## Process Control Statistics

**First step is to conduct a**** ****process control study ****(baseline study)**
**An “under control” process is run for a period of time to access its “capabilities” and establish:**
**Central tendency (mean or median performance)**
**Variance**
**Also used to establish limits (****control values****) **
**Often use 3******

## Process Control Statistics

**Loss of process control is then assessed by determining if “defect rate” has become greater than what would be expected by “chance alone” **
**Approach can be used with either ****“variables”**** (quantitative data) or ****“attribute”**** (+/- or binned quantitative data) sampling plans**

## Example: Moving Window Sum

**One of simplest for attribute sampling plans**

## Moving Window Sum

_**Example: Making red marbles**_

**Receive**
**Blue **
**Marbles**

**Paint **
**Marbles**
**Red*******

**Package **
**Marbles**

***Defect rate = 10%**

## Moving Window Sum

**Based on the probability of finding more than an expected number of “defective” responses within a specified window of samples**

## Moving Window Sum

**Is this process under control?**
**(Sampling rate = 1 per 1000)**

## Moving Window Sum

**When is control of this process lost?**
**(Sampling rate = 1 per 1000)**

## Impact of Stringency

**Impact of Stringency**

## JuiceHACCP 

## Juice HACCP

**Key feature:**
**5-D (99.999%) performance standard**
**Restricted to juice after it has been expressed**
**Verification of this requirement is via process validation and review of process records**
**Goal: Limit risk to >10****-5****/year**

## Juice HACCP

**Microbiological testing not required based on**
**ineffectiveness of testing at low defect rates**
**treatment affects all juice**
**processes are validated and reliable**

## Microbiological Testing

**Simplified example**
**Assume 1 enteric bacteria per ml**
**5-D treatment reduces to 1 per 10,000 mL**
**To detect survivor, need**
**1 10-L sample**
**10 1-L samples**
**100 100-mL samples**
**1000 10-mL samples  **
**10,000 1-mL samples**

## Juice HACCP

**Key exemption:  Citrus Juices**
**Processors of citrus juices may count surface treatments of the fruit as partially or totally fulfilling 5-D treatment**
**Based on the underlying assumption that the nature of citrus fruit is such that contamination is restricted to the fruit’s surface **

## Juice HACCP

**These citrus juice processors have an additional HACCP verification requirement of periodic testing for *****E. coli***
**Two 10-ml juice samples/1000 gal/day**
**Once per week if produce <1000 gal**

## Juice HACCP

**Data evaluated using process control statistics using a 7-sample window**
**One positive sample requires process review**
**Two positive samples require diversion to 5-D after extraction until cause identified**

## Juice HACCP

**Designed to verify that the original assumption is still valid, i.e. pathogens are restricted to the surface of the fruit**
**Internalized pathogens will not be treated**
**Potential for growth at least in some fruit**
**Within range for effective detection**
**Requirement takes into account potential for chance contamination  **

## Microbiological Testing

**Microbiological testing can be an integral part of any integrated program for verifying the effectiveness of food safety control measures**