Application of combined effect of sodium acetate and nisin on reduction of contamination by Listeria monocytogenes in vacuum packaged grass carp ud(Ctenopharyngodon idella) fillets kept at 4°C

摘要

In this study microbiological , chemical quality and fatty acid composition ofudgrass carp (Ctenopharyngodon idella) fillets treated by dipping in sodiumudacetate (%1 and %3), nisin (% 0.1 and % 0.2) and combination of sodiumudacetate and nisin was evaluated during 16 days of refrigerated of 4°CudAntilisterial effect of nisin was enhanced with the increased concentration ofudsodium acetate. At day 12 post storage, Listeria monocytogenese count wasudhigher in the control group than the recommended value, however in sodiumudacetate and nisin treated samples, the count was lower (5.17-5.91 log cfu/g).udWith increasing the concentrations of sodium acetate, mesophilic counts wereudlower. Regarding nisin, better results was obtained by applying %0.1 nisin.udGreater inhibition of mesophile bacteria was observed when combinationudtreatment was used. The number of lactobacillus was lower when higherudconcentrations of sodium acetate and nisin were used.udTotal Volatile Nitrogen values at the end of the experiment were lower in theudsamples treated with both nisin and sodium acetate and the better results wereudobtained in combination treatments. Peroxide (PV) at the end of the experimentudwas 1.9 meq/kg in control, and the lowest values were observed for theudtreatments 3(%0 sodium acetate +% 0.2 nisin) and 9(%3 sodium acetate +% 0.2udnisin) between 1.08 and 1.62 meq/kg without significant difference.udThiobarbituric acid (TBA) levels at the end of experiment have been shown toudbe 0.46 mg malonaldehyde per kg in the control. On the other hand treatments 9udhad the TBA values of 0.19 mg malonaldehyde per kg which was significantlyudlower than that of control.udPolyunsaturated fatty acids increased by increasing the sodium acetate dosesudand instead saturated fatty acids and n-6/n-3 ratio decreased. The ratio ofudUFA/SFA and also C22:6/C16:0 increased when a higher concentration ofudsodium acetate has been used. The best result obtained by using 3% of sodiumudacetate but no such relation with nisin was observed.