THE EFFECT OF VACUUM AND MODIFIED ATMOSPHERE PACKAGING ON GROWTH OF LISTERIA IN RAINBOW TROUT (ONCORHYNCHUS MYKISS) FILLETS

Rainbow trout (Oncorhynchus mykiss) fillets stored at 4 +/- 1C were analyzed with respect to properties of microbiological (Listeria monocytogenes, total aerobic mesophilic count, psychrotrophic bacteria and Enterobacteriaceae) and chemical (pH, total volatile bases nitrogen) under air (control), vacuum and modified atmosphere packaging (MAP) with various gas mixture (50% CO2 : 50% N-2, 80% O-2 : 20% CO2 and 2.5% O-2 : 7.5% N-2 : 90% CO2). The minimum L. monocytogenes counts were determined in the samples packaged with MAP, and no significant differences were found among them. It was determined that the effect of different atmosphere conditions and storage time on total aerobic bacteria count, psychrotrophic bacteria count and Enterobacteriaceae count were significantly different (P < 0.01). The maximum total volatile bases nitrogen value was determined from the control group. The effects of atmosphere condition on pH values were significant (P < 0.05).