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Modified atmosphere packaging of pink prawn (Pandalus platyceros) Dheeragool, Panadda


Pandalus platyceros (pink prawn or spot shrimp) was stored under (1) aerobic control (bags left open to air), (2) carbon dioxide (CMAP), and (3) nitrogen atmospheres (NMAP) at 1°C. Facultative anaerobes were the majority of psychrotrophic bacteria which contaminated the prawns in this study. Tissue pH of the CMAP prawns was the lowest of all prawns and brought about the greatest exudat ion of the muscle tissue. The microorganisms were markedly inhibited under the CMAP and were slightly inhibited under the NMAP. Consequently, formation of salt-soluble proteins, water-soluble proteins, TMA, and TVB progressed most slowly in the CMAP prawns. TMA production was favored under the NMAP. No ATP was detected in the prawns at the time of packaging. ADP degradation was accelerated under the CMAP but delayed under the NMAP. AMP degraded most rapidly in the control prawns followed by the NMAP and the CMAP prawns respectively. No effect of storage atmospheres was found on IMP, inosine, and hypoxanthine decompositions. Development of K-value in prawns was most strongly influenced by IMP decomposition rate and was slower under the CMAP than under the NMAP. Redness of prawn colour (Hunter a value) was maintained under the NMAP and the CMAP. But carbon dioxide in the CMAP and the NMAP likely caused destruction of the pigments during storage resulting in lighter colour of the stored prawns (Hunter L value). Shelf-life of the pink prawns was at least doubled under the CMAP system but no shelf-life extension was afforded by the NMAP system. The first principal component of the prawn quality parameter accounted for 59.07% of the data variance. This means the most important quality descriptors of the prawns were all microbiological variables, raw prawn meat odour and colour scores, TMA, cooked prawn meat odour and colour scores, water-soluble protein and overall sensory score. Stepwise discriminant analysis of pH and total aerobic sulphide-producing psychrotrophic bacterial count data of the prawns with TMAN concentration as the grouping variable, resulted in 97.2% correct classification of the prawn samples. Two equations for the canonical variables were obtained. A plot of these two canonical variables will visually indicate the region of prawn quality (good, acceptable, or unacceptable).

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