Use of Laminated High and Low Density Polyethylene Flexible Packaging to Store Trout ( Salmo Gairdneri ) in a...

The effect on extension of refrigerated shelf life of boned trout, treated or not treated with a 2.3% potassium sorbate dip and packaged in laminated high/low density "semi-permeable" polyethylene bags in the presence of a CO₂-enriched modified atmosphere (MA), was studied. The combination of packaging, refrigeration, and MA was effective in doubling the fresh shelf life of the trout product. Potassium sorbate limited bacterial growth but did not extend shelf life beyond what was obtained with MA alone. Changes in pH and ammonia concentration in the fish samples were not good quality indicators in this study. Although not detected by sensory evaluations, TBA analyses indicated the possible development of oxidative rancidity in the MA-held fish. Carbon dioxide content in the flesh of the trout appeared to be a function of CO₂ in the headspace of the bags which was reduced by about 50% during the first 20 d of storage. Based on changes in organoleptic characteristics, the quality of the raw trout, including the potassium sorbate-treated trout, was only marginally acceptable after 25 d of storage in the MA. However, the cooked product was rated favorably by a consumer type taste panel. The maximum post-MA refrigerated shelf life of the trout held under the experimental conditions of this study, including those treated with potassium sorbate, was about 1 week.