Effect of different packing methods on the shelf life of marinated rainbow trout

Abstract

The effects of packing in oil and under vacuum on sensory, chemical and microbiological changes in marinated rainbow trout stored at chill temperatures (+4 +/- 1 degrees C) were studied. The quality assessment of marinated trout stored in oil and under vacuum was performed by monitoring sensory quality, total volatile basic nitrogen (TVB-N), peroxide value (PV) and thiobarbituric acid (TBA), psychrotrophic bacteria count and mesophilic bacteria count during storage. The observed organoleptic shelf-life of rainbow trout was found to be 105 days in oil and 90 days in vacuum packed samples. At the beginning of storage, the TVB-N value was 6.78 mg/100 g for marinated trout packed under oil and 7.35 mg/100 g for the vacuum packed samples. The TVB-N values increased to 12.08 mg/100 g and 11.98 mg/100 g by the end of the storage period for marinated rainbow trout packed in vacuum and in oil, respectively. No significant differences (p > 0.05) between the two groups of samples were found in TVB-N concentrations during the storage period. The fat degradation pattern (peroxide value and thiobarbituric acid content) was found to be similar for all storage conditions, showing a continuous increase reaching critical levels after ca. 60 days of storage for both packing types. Psychrotrophic bacteria count and mesophilic bacteria count of marinated trout were < 10 log CFU/g, throughout the storage period. The results of this study indicate that the shelf-life of marinated rainbow trout stored in cold storage (+4 degrees C), as determined by overall acceptability sensory scores, is 105 days for oil and 90 days for vacuum packaged samples.