Food Protection Trends - July 2008 - (Page 475)

FIGURE 1. Listeria Diagram. Listeria control is achievable when all factors are controlled. This paper describes factors that must be controlled to prevent post-pasteurization contamination, especially: • plant layout, • plant construction, equipment construction and design, • effective cleaning & sanitation, • personal hygiene, • Hazard Analysis Critical Control Point (HACCP), • environmental and product testing All of these are required components of a successful LM prevention strategy, and deficiencies in just one can significantly increase the risk of LM contamination (Fig. 1). Most of these parameters are part of the Current Good Manufacturing Practices (cGMPs), which are regulations published by the FDA that outline minimum requirements for maintaining a safe and wholesome processing environment (21CFR110) (9). Plant layout. LM prevention must be considered prior to construction of the cheese plant, because the plant layout determines the flow of people as well as products. The concept of hygienic zones focuses on restricting the access of people to sensitive areas of the plant. People will have access only to pre-determined hygienic zones at the plant, and only the cheese maker and assistants would be allowed in the production area. On a farmstead dairy, it would be essential to prevent those who have been in the dairy barn/ milking parlor from entering the processing plant unless they have showered and changed clothes and foot-wear. Besides restricting the movement of people, the product flow must be controlled. It is common practice in all food processing that, to prevent cross contamination, a product can move only forward in the manufacturing chain. Larger food plants separate the raw and the processed sides of the manufacturing chain. This is rarely possible in smaller cheese plants, where the vat pasteurizer is often located in the cheese-making room, and in some situations the vat pasteurizer doubles as the cheese vat. Extreme care must be taken to prevent any possible recontamination of product in process by material from the raw milk side. For example, it is unacceptable to have spills/drips of raw milk onto plant floors. Plant construction. Construction of the cheese plant must involve close consulting with state regulatory agencies. such cheeses in the United States if they are made from raw milk. Even though LM is destroyed by pasteurization, it is important to keep LM levels in raw milk as low as possible, because this practice lowers the risk of environmental contamination. LM is a psychrotrophic type of bacterial pathogen that will grow at refrigeration temperatures (below 40°F). Because other flora are suppressed by refrigeration, the environment becomes less competitive and Listeria can be more viable; thus the time duration between milking and pasteurization/cheese making should be kept to a minimum. In the case of raw milk cheeses, it is advisable to utilize only raw milk free of LM. While this is difficult to ensure from a practical point of view, it is at least possible to lower the risk of LM by frequent testing of raw milk sources, with subsequent exclusion of LM positive suppliers. Certain dairy management deficiencies can be directly linked to high LM levels in raw milk. These production practices include: inadequate frequency of cleaning the exercise area; poor cow cleanliness; insufficient lighting of milking barns and parlors; active milking machines lying on the parlor floor sucking up manure-contaminated water, and either non-use of single service paper towels or incorrect disinfection of towels between individual cows (20, 42). Farmstead dairy plants have direct control over their raw milk quality; in contrast, when milk is purchased from outside sources, there is often little or no control over LM content. LM counts do not generally correlate with total plate count; therefore it is difficult to assess the potential level of LM contamination of the raw milk. However, when assessing the contamination of raw milk with pathogens, it seems more appropriate to view the situation from a “qualitative” perspective than a “quantitative” one. In other words, the important point is if the pathogen is present or not — the specific level of contamination is less important. This is especially true for LM , because the Food and Drug Administration (FDA) follows a “zero-tolerance” policy for this pathogen and considers all ready-to-eat foods with any detectable LM as adulterated. Prevention of post-processing contamination Pasteurization controls LM only in the raw milk supply. Cheeses made from pasteurized milk can become contaminated with LM from numerous other sources (26, 32) following pasteurization. In fact, retail level testing has shown that LM contamination levels in pasteurized milk cheeses can be similar to levels encountered in raw milk cheeses (40). JULY 2008 | FOOD PROTECTION TRENDS 475

Table of Contents Feed for the Digital Edition of Food Protection Trends - July 2008

Food Protection Trends - July 2008 Contents Sustaining Members Lone Star Perspective from Your President Commentary from the Executive Director An Integrated Assay for Rapid Detection of Escherichia coli O157:H7 on Beef Samples Listeria Prevention Practices for Small Cheese Operations New Members News Industry Products Award Winners Committee Meetings Ivan Parkin Lecture John H. Silliker Lecture Preliminary Program Networking Opportunities General Information Registration Form Workshops Exhibitors Special Contributors and Sponsors Coming Events Advertising Index Journal of Food Protection Table of Contents Audiovisual Library Order Form Booklet Order Form Membership Application

Food Protection Trends - July 2008

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