Food Protection Trends - July 2008 - (Page 474)

TABLE 1. Some recent recalls of cheeses potentially contaminated with Listeria monocytogenes Date of recall May 2006 August 2005 March 2005 February 2004 January 2004 September 2003 June 2003 March 2003 November 2002 August 2002 March 2002 December 2000 November 2000 September 1999 June 1999 Source: FDA Recalls. www.fda.gov cated on dairy farms, which contributes a unique set of difficulties. In spite of these challenges facing specialty cheese makers, there is little information available that addresses prevention of LM contamination in a small cheese processing operation. The objective of this paper is to outline strategies for preventing LM contamination of milk and cheese, starting with the raw milk source, design and construction of the plant, cleaning and sanitation, and the cheese-making process. Examples are included that describe current prevention strategies at a queso fresco farmstead operation. The plant has been operating for many years, following principles discussed in this paper. No LM has ever been detected in the plant environment or in finished products. Even though this paper focuses on LM prevention, most of the discussion is applicable to prevention of other potential milkborne pathogens as well. • introduction of safety hurdles into the process and cheese composition Heat-shocked or thermized cheese milk is milk that has been heat treated at less than the required time and temperature pasteurization combinations, which for batch pasteurization is 145°F for 30 min and for continuous pasteurization is 161°F for 15 s. The advantage of this treatment is that fewer of the endogenous milk enzymes, such as lipase, are destroyed, while pathogens are partially or completely destroyed (25, 27). Thus this treatment is a compromise that may permit better cheese quality while lowering the initial level of potential pathogens prior to 60 days ripening. Some cheese types, such as Emmental and Comté, are produced with a cook step in which the temperature may reach 131°F for 30 min. The objectives of this cook step to control water and calcium content of the curd particles and to promote the selective survival of certain ripening bacteria. In addition, the cook step acts as a heat shock treatment that helps insure the safety of these cheeses. Because of this added safety hurdle (30), these cheeses are generally not implicated in cheeseborne recalls/outbreaks. In contrast, high moisture soft cheeses do not receive a cook step/heat treatment in the cheese vat. However, because soft cheeses are normally consumed within less than 60 days of production, it is not legal to sell Cheese Types Vintage Irish cheese with Porter Queso Seco Blue cheese Queso Fresco Brie cheese Blue cheese Washed curd cheese Queso Fresco Ricotta cheese Queso Fresco Goat Feta spread, cream cheese String cheese Jack, Queso Fresco, Colby Jack, Cheddar cheeses Queso Fresco Cheddar cheese Treatment of raw milk Raw milk is a source of LM, a pathogen that has been detected in 4.6–6.5% of bulk tank milk on dairy farms (24, 50). Pasteurization destroys LM (11, 15). Non-ripened, or fresh cheeses such as queso fresco, must be made from pasteurized milk because they are consumed without lengthy ripening. However, for some specialty cheeses the pasteurization process is compensated for by requiring a minimum of 60 days ripening of the raw milk cheese at a temperature greater than 35°F (CFR 133.113) (9). The justification for replacing pasteurization with 60 days ripening is that cheese does not support the outgrowth of milkborne pathogens, so that possible pathogen count will decrease during ripening and storage (6). Some fairly recent research has questioned this rationale (7, 8, 36, 41), and it appears that LM growth or survival in cheese depends on cheese type, especially with respect to the parameters of pH, starter culture, and water activity (17, 35, 38). Furthermore, artisan cheeses may experience some day-to-day variability in composition and starter culture activity, which could influence the susceptibility to LM growth. LIsTERIA MONOCYTOgENEs PREVENTION STRATEGIES Strategies to ensure LM free cheeses focus on three general principles: • destruction of LM by treatment of the raw milk • prevention of post-pasteurization contamination 474 FOOD PROTECTION TRENDS | JULY 2008 http://www.fda.gov

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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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