Effect of Organic Acids on Pathogenic and Lactic Acid Bacteria in Directly Raw Milk Cheddar Cheese

This study investigates the antimicrobial properties of lactic and acetic acids against both pathogenic and lactic acid bacteria (LAB), with a focus on their application in the direct acidification of raw milk for Cheddar cheese production. The acids effectively inhibited key pathogenic strains, including Salmonella Enteritidis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa, while largely preserving the viability of beneficial LAB (Lactobacillus acidophilus, Streptococcus thermophilus, Lactobacillus bulgaricus, and Lacticaseibacillus paracasei), except under highly acidic conditions. When used in cheese manufacturing, direct acidification with lactic (LRC) and acetic acids (ARC) enhanced microbial safety by eliminating pathogens and spoilage organisms and promoted biochemical changes associated with accelerated ripening. Treated cheeses showed increased levels of moisture, acidity, ripening indices, total viable counts, and LAB populations, though with slightly reduced protein and fat content. Sensory evaluation indicated comparable flavor among cheeses, with pasteurized cheese (PC) receiving the highest overall acceptability. These findings demonstrate that direct acidification using organic acids is a promising strategy for producing microbiologically safe raw milk Cheddar cheese with improved ripening potential. However, adjusting pH to 5.4 and optimizing ripening conditions are recommended to enhance sensory quality and consumer acceptance.