Survival of pathogens in "Graviera Kritis" cheese made with raw and pasteurized milk

Abstract

A field trial was carried out to investigate the hygienic status of Graviera 'Kritis' cheese made with raw and pasteurized milk. Graviera was manufactured in a small plant in Crete under traditional manufacturing conditions. Forty-two samples were examined during the manufacturing process for Colifoms, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Salmonella spp., Escherichia coli O157:H7 and VRE (Vancomycin Resistant Enterococci). All samples were negative for Salmonella spp., E. coli O157:H7 and VRE. Populations of Colifoms and E. coli before cooking of the curd were 3-3.5 log10MPN/g higher in cheese made with raw milk in comparison to that made with pasteurized milk and populations of both bacteria decreased sharply during the aging period in both types of cheese. L. monocytogenes type 4b was isolated from the cheeses of two trials until after the salting period and remained under the detection limit of 100 cfu/g. At the end of the ripening period, all the examined bacteria were declined or eliminated to safe level.