Evaluation and characterization of some protective culture metabolites in free and nano-chitosan-loaded forms against common contaminants of Egyptian cheese.

This research attempted to inspect the contribution of lactic acid bacteria (LAB) with nanoparticle application in antimicrobial enhancement. Seven lactic acid cultures-free supernatants (CFSs) in both free and nanoparticles-loaded states were examined against seven foodborne microorganisms. Lactobacillus helveticus followed by Lactobacillus Plantarum possessed considerable antimicrobial activity. Headspace GC-MS characterization of Lactobacillus helveticus CFS identified a mixture of antimicrobial and health-promoting compounds. Minimal inhibitory concentration (MIC) values for tested Gram-positive bacteria represented 50% of that for Gram-negative bacteria, 20% and 7.35% of those for fungus and yeast respectively. Nanoparticles were prepared through chitosan-tripolyphosphate nanoparticle formation giving nanospheres from in the range from 5 to 10 nm, and narrow size distribution. CFS-loaded chitosan nanoparticles (CS-NPs) significantly enhanced the overall inhibition zone diameter, as well as, the decline in MIC values for Salmonella enterica (50%) and Penicillium chrysogenum (12.5%) was observed. Lactobacillus helveticus CFS, however, displayed lower antimicrobial activity vs. nisin and natamycin, it has both antibacterial and antifungal promising activities.

The protective potential of selected lactic acid bacteria against the most common contaminants in various types of cheese in Egypt.

Dairy products, especially cheeses have a great nutritional value and a high consumption level around the world. Considering a widespread consumption of cheeses, there is a growing concern regarding safety and microbiological quality. The current study was designed to conduct a recent evaluation of cheeses microbiological quality. Sixty cheese samples from retailing Egyptian markets were analyzed on different selective microbiological media and 64 bacteria, 35 yeasts and 8 molds were isolated. Out of 60 samples; 26.6% were contaminated with Escherichia coli, 73.3% with Staphylococcus scuiri, 3.33% with Bacillus cereus, 1.66% with Salmonella enterica, and 1.66% with Pseudomonas aeruginosa. The presence of such microorganisms in cheeses referred to the wrong management in cheese manufacturing. These organisms are significant from public health view as they have been associated with the base of human food poisoning. Promising antagonistic behavior was observed using the tested lactic acid bacteria (LAB) either single or in combinations toward the undesired isolates. Lactobacillus helveticus CNRZ 32 (Lb. helveticus) was the most potent culture; recording ≥95% reduction in undesired microbial counts.