Assessment of storage stability of smoked and dried fish packaged in polystyrene and vacuum packs

Abstract

Freshly smoked and dried fish were packaged with or without vacuum and in polystyrene. The relative effectiveness of the packaging materials used in preserving the quality of the stored fish was evaluated for physical and biochemical decomposition, microbial load and sensory changes after storage for 8 weeks and over. Vacuum packaging (VP) was found to be the most effective method and provided optimum protection against rancidity, maintaining acceptable microbial and sensory qualities during the storage period. Storage yield of as high as 98% was recorded with corresponding high sensory scores and low microbial load. Proteolytic and lypolytic deterioration was minimal and considered negligible. Storage in polystyrene paks gave the lesser protection, thus resulting in 27% spoilage. However, both packaging methods provided a considerable reduction in microbial population of contaminating microorganisms. Spoilage microorgnisms isolated were predominantly Micrococci, Bacillus, Aspergillus niger and yeasts. Pathogenic bacteriaor mould organisms were absent from the smoked fish before and after storage. Initial moisture content of samples and moisture barrier capacity of the packaging materials were found to be the most critical factors in preserving the quality of the smoked fish. Samples with initial moisture content of between 24-26% stored in both vacuum and polystyrene package became mouldy within 7 days, while those with initial moisture content of less than 10% were preserved for over 24 weeks in vacuum packages. There was a high correlation of flavour and texture quality with moisture absorption which was measured by percent weight gain of the fish in the packages. In a supermarket sales trials, the package appeal to customers/consumers was greater for the vacuum paks than the polystyrene containers