The impact of collagen on softening of grass carp (Ctenopharyngodon idella) fillets stored under superchilled and icestorage

The objective of this work was to study the impact of collagen on softening of grass carp (Ctenopharyngodon idella) fillets during chilled storage. The fillets were stored under superchilling (-1.5 +/- 0.2 degrees C) and with ice (0.2 +/- 0.1 degrees C) for 21days, and texture properties, collagen and the related enzyme activities were measured. Results showed that firmness and collagen content were strongly influenced by storage temperature and time. Fillet firmness decreased by 32.3% (superchilling) and 49.6% (ice stored) of the initial values after 3days of storage, respectively. Total collagen content decreased with time, but different collagen fractions showed variations. Collagen degraded to different extents depending on storage conditions as indicated by SDS-PAGE and amino acid analysis. In addition, collagenase activity declined significantly during the first 3days, followed by a slow increase. This study demonstrated that collagen degradation was involved in grass carp fillet softening and provided useful information for fillet quality improvement.