The antimicrobial activity of chitosan and its application on kariesh cheese shelf life

الملخص EN

Chitosan is a natural and non-toxic polysaccharide with many biological applications, largely known for its activity against a wide range of microorganisms, particularly as an antimicrobial agent.

in the present study, antimicrobial properties of two kind of commercial chitosan ( High (CSH) and low (CSL) molecular weight Chitosan) were evaluated, against Staphylococcus aureus, Escherichia coli, Lactobacillus delbruekii spp.

bulgaricus , and Lactococcus lactis spp.

Cremoris (LAB)as model bacteria besides isolated yeast culture from kariesh cheese surface in vitro was carried out using standard method (broth dilution method).

The antimicrobial activities of chitosan were explored by calculation of the Minimum Inhibitory Concentration (MIC) for the tested culture in media supplemented with various concentrations lying between 0.0004% (4 μg/ml) and 0.02% (200 μg/ml).

The results revealed that E.coli and S.

aureus were more sensitive in CSL (0.001, 0.0008% respectively) than in CSH 0.006%.

While the MIC of LAB strains (Lb.

bulgaricus and Lc.

cremoris) were higher than the previous strains (0.01% and 0.02%).

Adding CSL to the milk used in Kariesh cheese manufacturing by 0.03 and 0.05% level of CSL which previously inoculated with E.

coli, S.

aureus and yeast showed a significant decreased in the log CFU/g of E.

coli, S.

aureus and yeast in cheese which slightly decreased during storage period at 4oC for 10 days compared with other treatment without chitosan.

On other hand addition of chitosan led to keep survival of LAB during cheese making and storage at 4oC.

It could be concluded that the chitosan concentration dependence antibacterial activity with variation against several pathogenic bacterial strains which indicates their possibility to be used as antimicrobial agents in dairy products.