EFFECT OF MICROBIAL CONTAMINATION WITH FUNGI, AFLATOXIN M1 AND ENTERIC GRAM NEGATIVE BACTERIA ON MILK AND SOME DAIRY PRODUCTS

Abstract

milk and milk products are excellent high quality foods, providing nutritional values through important elements in the healthy human diet. In this study, 75 samples of dried milk, raw milk, butter, cream and cooked (processed) cheese (15 of each) were collected randomly from various dairy shops and supermarkets in Giza Governorate, and tested microbiologically for fungal and enteric gram negative bacterial contamination; detection of AFM1 residues using ELISA technique as well as detection of lipolytic and proteolytic activities of the most isolated fungi and bacteria. Six genera of moulds were recovered from the examined samples and three genera of yeasts. The most isolated moulds were species of genera Penicillium followed by Aspergillus, Cladosporium, Geotrichum, Mucor and Scopulariopsis, while the most isolated yeasts were species of genera Candida followed by Rhodotorula and Saccharomyces. AFM1 levels were detected in all analyzed samples of raw milk and milk products. AFM1 levels exceed EU legal limits (50 ppt) (0.05 μg/L/kg) while the detected limits were below the international legal limits of USA (FDA) (500 ppt) (0.50 μg/L/kg) in raw milk and dairy products for human consumption. The highest lipolytic and proteolytic activities were detected in A. niger and Mucor spp. (100%) while Cladosporium spp. possessed the lowest activities (50%), Candida albicans had activities (80%) and Rhodotorula had activities (62.5% and 75%). Pseudomonas spp. isolates were examined for proteolytic and lipolytic activities; three isolates had lipolytic activity (27.27%), also three isolates had proteolytic activity (27.27%). On the other hand,the most isolated enteric gram negative bacteria from the examined samples were identified as E. coli followed by species of Psudomonas, Klebsiella, Shigella and Salmonella. Moreover, no any bacteria were isolated from butter and dry milk samples. The economic importance and public health significance to the present results as well as apply the proposed sanitary measures to reduce microbial contamination and food safety for human health were discussed.