Food Protection Trends - November 2008 - (Page 796)

Ivan Parkin Lecture Utility of Microbiological Testing for Food Safety Assurance Presented by: Russell S. Flowers, Ph.D. Silliker Group Corporation Homewood, Illinois M icrobiological testing is an important component in assuring food safety. It is used to establish baseline information for microorganisms in ingredients, in-process samples, the process environment, and validate the efficacy of lethal and preservation processes. Microbiological testing also is useful for verification of critical ingredients, the processing environment, critical control points (CCPs), and the overall HACCP plan. Microbiological testing may be required as part of trade agreements between countries, or part of purchase specifications between buyer and supplier. In addition, regulatory programs have incorporated microbiological guidelines, requiring routine process control testing. Some food producers perform routine finished product testing as due diligence to minimize liability in the event of litigation. These different applications of microbiological testing require varying levels of accuracy, precision, sensitivity, specificity, time, and cost constraints. The confidence or uncertainty associated with microbiological data can be affected by various steps in the process, including the sampling plan, sampling procedure, method of analysis, and laboratory performance. Methodological considerations Over the past 25 years, tremendous innovations in microbiological food testing have occurred. For example, methods for the detection and identification of microorganisms, especially pathogens, that utilize enzyme immunoassays, immuno-capture, genetic hybridization, and gene amplification have been developed and commercialized. These techniques can also be used for quantification and identification of spoilage and indicator organisms. However, even with theses new technologies, the basic principles of microbiological testing of foods remains essentially the same as it has been for almost 100 years. A sample must be collected from the food, homogenized and analyzed for the presence of the organism(s) of interest. With few exceptions, e.g., direct microscopic techniques, detection and quantification of microorganisms in foods requires that the organism(s) of interest be cultivated in growth media, solid or liquid, to a level that can be observed visually or detected by various secondary screening methods. Historically, evidence of growth resulted from turbidity in liquid media or visible colonies on agar plates. Quantification was facilitated by serial dilution of the homogenates before cultivation. The basic principles were made more specific by the inclusion of selective and differential agents in the growth media to suppress the growth of competitive (non-target organisms) and provide visible changes in the media to differentiate the target organisms(s) from competitors. In order to observe visible changes in the media, high numbers of cells are required. Therefore, the methods generally required days to complete. Today, sampling, homogenization, and incubation is still required, but technological advancements have facilitated the detection of the target organism in the growth medium, leading to improvements in sensitivity, specificity, and the time required for specific detection; 8–24 hours. Quantitative methods have theoretical limits of detection of 1–10 cells per gram for MPN procedures, and 10–100 cells per gram for plate count procedures. Even direct enrichment methods are limited to the detection of 1 organism per amount of food tested, assuming that the one organism is able to grow and reach a detectable level, as described above. The limits of detection can be improved by analyzing larger samples and multiple sub-samples. However, even if 100 samples of a lot of food are tested, lots with 2% contaminated samples would be accepted ~18% of the time (1). Furthermore, the accuracy and precision of microbiological methods are often not considered. For a sample containing 100 cells/g of a specific or group of organism(s), the 95% confidence limits for a plate count and an MPN method would be +/- 20% and 30–300%, respectively (2). An enrichment method utilizing sixty 25 g samples, a total of 1500 g, would provide 95% confidence that there is <1 cell/500 g 796 FOOD PROTECTION TRENDS | NOVEMBER 2008

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Food Protection Trends - November 2008 Contents Sustaining Members Perspectives from Your President Commentary from the Executive Director Biofilm Formation of Listeria monocytogenes on Various Conveyor Belt Surfaces Third-Party Certification of Agro-Products in China:�A Study of Agro-Product Producers in Guangzhou, Shenzhen, Hangzhou and Qingdao IAFP 2008 in Review Award Winners 3M Microbiology - Black Pearl Award Winner Ivan Parkin Lecture - Russell S. Flowers John H. Silliker Lecture - Michael P. Doyle Student Travel Scholarships Session Summaries Highlights of the Executive Board Meeting Minutes of the 95th Annual Business Meeting Committee Minutes Executive Board Response to Committee Recommendations Exhibitors of IAFP 2008 Special Contributors and Sponsors Call for Awards - IAFP 2009 New Members What's Happening in Food Safety Industry Products Coming Events Advertising Index Journal of Food Protection Table of Contents Audiovisual Library Order Form Booklet Order Form Membership Application

Food Protection Trends - November 2008

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