出版社：International Medical Journal Management and Indexing System
摘要：Milk preservation is closely related with its microbiological quality. The spoilage may occur at any stage from production, during processing and till consumption. Many potent antimicrobials were discovered recently but, it is important to test their efficacy against undesirable bacteria inside the food materials that help to improve food safety and validity. Our research was focused on comparative antibacterial activities between chitosan, lysozyme and their different mixtures against different undesirable bacterial strains by agar well diffusion assay. Then apply the selected antibacterial substances in raw cow milk contaminated with food borne pathogens and spoilage bacteria then monitoring the bacterial growth or inhibition. Our preliminary investigation showed that, chitosan 0.5% exhibited the largest inhibition zones diameter followed by lysozyme hydrolysates with chitosan complex against Salmonella enteritidis and Bacillus subtilus in-vitro by agar well diffusion method. During application in raw cow milk, lysozyme hydrolysates and chitosan complex exhibited powerful bactericidal effect followed by chitosan especially against Clostridium perfringens, Staphylococcus aureus and Listeria monocytogenes after 24h from cooling storage of raw cow milk. The bactericidal activity of lysozyme and lysozyme hydrolysates were greatly enhanced upon their combination with chitosan. But, the bactericidal activity of lysozyme hydrolysates with chitosan complex exhibited great killing power than the conjugation between lysozyme with chitosan complex at same concentrations. This may be attributed to chitosan oligomers and lysozyme peptides acting in a synergistic manner in penetrating and killing the undesirable bacteria. Although chitosan was effective in inhibiting the growth of spoilage microorganisms but, it is induce changes in raw milk pH. Accordingly, we suggest lysozyme hydrolysates with chitosan complex will be a promising antibacterial additive to produce a highly safe raw milk with recommendation further future studies to explore its antibacterial mechanism.
