Retention of shelf life and microbial quality of seer fish stored in modified atmosphere packaging and sodium acetate pretreatment,

Abstract

Preliminary shelf life tests were performed to select the best gas composition and the best sodium acetate concentrations in the modified atmosphere. Bacterial quality assessment was carried out by the monitoring of total aerobic bacteria, H2S producing bacteria, lactic acid bacteria, pseudomonads, Enterobacteriaceae, Staphylococcus aureus, streptococci, sulphite reducing clostridia and botulinum toxin by mouse bioassay. Bacteria grew most quickly in seer fish stored in air, followed by those in MAP and the lowest counts were with MAP pre-treated with sodium acetate. The application of sodium acetate treatment to seer fish steaks resulted in a bacteriostatic effect, contributing to the improvement of the microbiological quality of seer fish steaks. There was less trimethylamine in the modified atmosphere packed samples pretreated with sodium acetate than in air packed samples by the factor of seven, at the end of the shelf life. Modified atmosphere packaging alone increased the shelf life from 8 (air pack) to 22 days; however, addition of sodium acetate further extended the shelf life to 28 days. The results showed that the combined effect of MAP (70 vol.% CO2:30 vol.% O2) and sodium acetate (1%, w/v) is a valuable tool to allow an effective extension of the shelf life of raw fish products.