KINETICS OF EARLY POST MORTEM TEXTURE DETERIORATION OF HOKI (MACRURONUS NOVAEZELANDIAE)- RAPID CHILLING IMPROVES TEXTURE

摘要

The texture of flesh of some species of fish deteriorates considerably post harvest. Studies on ice-chilled hoki have shown that a rapid softening process precedes gaping as the muscle tissue loses strength and cohesiveness during storage. A concomitant increase in myofibril fragmentation index (MFI) implicated calpain activity as a major factor in flesh softening. Because large volumes of hoki can be caught, at one time, it is important to evaluate the effect of delays in chilling on quality loss. In this study, we determined the kinetics of texture loss and calpain activity over the first 48 hours post-harvest. Texture deterioration was rapid with the greatest loss of tensile strength occurring in the first few hours. At higher temperatures, texture loss (strength and cohesiveness) was faster and overall deterioration was greater. MFI increased to a maximum after 8h at 0°C and only 2 h at 20°C. Increasing temperature affected rate of texture degradation much more than calpain activity. These results show that fast and complete chilling immediately after harvest is essential for producing high quality hoki. For companies that have implemented rapid chilling on-board fishing vessels, the quality of processed hoki (land and at-sea) has improved considerably. Consequently, since the introduction of rapid chilling the value of New Zealand hoki exports has increased considerably as higher value niche markets are targeted with higher quality product.