Antimicrobial effect of spices’ extracts against Salmonella typhimurium in chicken patties during frozen storage and its detection by PCR method
INDERJIT SINGH, A.S. YADAV, N.K.PANDEY AND R.P. SINGH
Central Avian Research Institute, Izatnagar-243 122 (UP)
E-mail: [email protected]
Since chemical preservatives are not preferred now a days due to their residual effect and declining consumer preference and therefore, more and more emphasis is being given for use of natural preservatives in reduction of pathogens in foods including poultry meat. Thus the present study has been undertaken to evaluate the inhibitory effect of spices’ extract such as aqueous extract of garlic (4.0% v/w level), alcoholic (ethyl) extracts of cinnamon (0.15% w/w) and clove (0.15% w/w) alone or in combinations in chicken patties against Salmonella Typhimurium during frozen storage (-18 oC) up to 90 days. Salmonella Typhimurium E 402 was inoculated artificially in chicken patties (10 3 cfu/g) and detection of Salmonella in chicken patties was carried using genus specific hisJ gene.
The results of this study showed that the extracts of spices alone or in combinations were found to inhibit growth of Salmonella Typhimurium significantly (P<0.01) as compared to control untreated group. However, clove extract alone was found to exert higher antimicrobial effect both against Salmonella Typhimurium and other spoilage bacteria as compared to other spices’ extracts. The group having clove extract or its combination with cinnamon extract caused maximum decrease in Salmonella Typhimurium counts as compared to control and this decrease was one log cfu/ g at 90 th day of storage. Counts of Salmonella Typhimurium in all the groups on 15 th day of frozen storage decreased by one log scale from initial count of 5 log cfu/g and subsequently no significant increase or decrease in counts was observed. Mesophilic bacteria were also inhibited by spices’ extracts as compared to untreated control group and this decrease was 1 log cfu/g at the end of storage period. The pH values in all the groups increased as the storage period advanced, however, pH values in extract treated groups were lower than control group.
Representative samples of Salmonella inoculated chicken patties were enriched in tetrathionate broth and then PCR assay for detection of genus specific hisj gene was employed using a set of primers (cohen-1 and cohen-2). The electrophoresis analysis of PCR product revealed that all the inoculated samples were positive for Salmonella Typhimurium with amplification of 496 bp fragment. Based on the results of this study, it was concluded that extracts of these spices can be added in chicken patties as natural antimicrobial agents against Salmonella Typhimurium during storage at frozen temperature. Furthermore, PCR based method was found to be a rapid and sensitive method for detection of Salmonella Typhimurium from chicken patties after enrichment in selective media.