Optimal storage conditions for fresh farmed tilapia (Oreochromis niloticus) fillets

Abstract

The main aim was to establish optimal storage conditions for fresh tilapia fillets, by determining its shelf life from the sensory and microbiological evaluation, as well as monitoring its physical-chemical properties. With this intent, Nile tilapia (Oreochromis niloticus) farmed in recirculation aquaculture system was filleted and packaged in 100% air and 50% CO2: 50% N2 MA prior to storage at different temperature; 1˚C and -1˚C. Initial samples from filleting (control d0) were also evaluated for comparison. This report further describes the development of a Quality Index Method (QIM) scheme and a sensory vocabulary for fresh and cooked tilapia fillets accordingly and application in a shelf life study. The application of the QIM scheme for tilapia fillets showed a linear relationship between QIM scores and storage time with significant correlations (r > 0.93) for all sample groups experimented in the main study. The results from sensory analysis of cooked samples as well as microbial growth indicated fillets packaged in 100% air had a shelf life of 13-15 days during storage at 1˚C and 20 days during storage at -1˚C. At the end of shelf life in 100% air packaged groups, TVC and pseudomonads counts reached log 7 CFU/g in flesh. In MA packaged fillets, the lag phase and generation time of bacteria was extended and recorded counts below the limit for consumption (< log 4 CFU/g) up to 27 days of storage at both 1˚C and -1˚C. However, MA packaging affected negatively on fillets colour characteristics soon after packaging (as from d6) yet colour is an important indicator of quality and a major factor in influencing retail purchase decisions. Chemical analyses (TVB-N and TMA) were not good indicators of spoilage of tilapia fillets in the present study Physical parameters (drip and water holding capacity) were observed to be a function of storage temperature and atmosphere, with storage at 1˚C as well MA recoding low quality (undesired) scores. 100% air packaged fillets stored at -1˚C recorded superior quality characteristics during storage as well as extended shelf life. For that reason, it is plausible that 100% air packaging at -1˚C storage temperature is the optimal storage conditions for fresh tilapia fillets.