MICROBIAL STABILITY AND SAFETY OF TRADITIONAL GREEK CHEESES: RESEARCH NEEDS AND CONTROL MEASURES IN ACCORDANCE WITH THE EU REGULATION 1441/2007

摘要

This is an overview presentation dealing with the microbial stability and safety of traditional Greek cheeses in accordance with the new microbiological criteria that have been incorporated in the EU Regulation 1441/2007 (modification of the EU 2073/2005) for ready-to-eat (RTE) foods. Specifically, the survival or growth ability of frequent milk contaminating pathogenic bacteria, such as Listeria monocytogenes, Stophylococcus aureus and Escherichia coli O157:H7, in different cheeses produced from raw, thermized or pasteurized milk are discussed. Emphasis is given on L. monocytogenes since the microbiological criteria in EU Regulation 1441/2007 specify a maximum allowable concentration of 100 cfu/g horizontally in all RTE foods, provided the pathogen is unable for growth under the conditions of pH or a_w, or pH/a_w combined, or within the pre-estimated shelf life of the food product. On this basis, theoretically, many traditional cheeses do not belong to the "safe food" categories, and thus, there is a need to conduct challenge studies to demonstrate and validate microbial stability and safety of cheese, especially of the Sreek PDO cheese products. This overview is based on research conducted in the Dairy Research Institute under the framework of the "Traditional United Europe Food"- TRUEFOOD project plus bilateral "Greece-France" collaborating projects. Three popular cheeses representative of the respective traditional product categories, namely whey cheeses (Anthotyros), rennin-based ripened cheeses (Graviera) and fresh acid-curd cheeses (Galotyri), were studied; these cheeses are considered of high, medium and low risk, respectively, as regards the probability of L. monocytogenes to survive or grow. Also the fate of S. aureus and E. coli O157:H7 was studied, depending on the cheese type. All pathogens were artificially contaminated in several batches, which were manufactured either commercially or under pilot-scale conditions in the laboratory. Sometimes, protective strains of lactic acid bacteria or bacteriocins were combined with the starter cultures added to the cheeses. Pathogen inocula were applied either to RTE (fresh or ripened) cheeses ready for retail distribution and storage, or upon cheese manufacture to evaluate the behavior of the pathogens during ripening. This overview summarizes the behavior of each of the above pathogens. Moreover, the technological and, mainly, micro-ecological factors affecting inhibition, or potentially favoring growth, of pathogens are discussed for every cheese under validation.