Effect of organic acid and salt mixture on shelf-life extension and growth inhibition of Staphylococcus aureus and Escherichia coli O157:H7 in moo yor.

This research investigated the effects of organic acids and salts solution on shelf-life extension and growth inhibition of Staphylococcus aureus and Escherichia coli O157:H7 in moo yor (pork bologna). A mixture of lactic acid, acetic acid, citric acid and their sodium salts was added to moo yor at various concentrations of 0 (control), 0.5, 0.75 and 1% (w/v) then stored at 4C for 31 days. Total microbial counts and sample qualities were determined during storage. Total microbial counts significantly decreased with increasing mixture concentration and storage time (p<0.05). The 0.75 % solution was selected for further study due to its inhibitory effects against bacteria and some economic aspects. Throughout storage, treated samples had less % yield loss with slightly pale colour and less firmness than the untreated samples, whereas pH values were not different. For all attributes, no significant difference in sample acceptances between treatments was found and overall difference was not observed (p>0.05). When compared to untreated and commercial-preservative-added controls, the 0.75 % solution showed promising inhibitory effects toward S. aureus and significantly suppressed both S. aureus and E. coli O157:H7 growths throughout the experiment (p<0.05). In summary, the mixture of organic acids and their salts shows great potential in extending shelf-life and inhibiting growth of S. aureus and E. coli O157:H7 in refrigerated moo yor while maintaining acceptable product qualities.