Quality improvement of thermally induced surimi gels by extensive washing for dressed white croaker to remove contamination by body surface mucus proteases

Body surface mucus was scraped off from white croaker Pennahia argentata after washing with two different procedures, suspended in cold water and filtered through a filter paper. The filtrate thus obtained was lyophilized and defined as the fish body surface substances. The relative level of the substances obtained after high-pressure water washing was 28.8% and significantly lower than those obtained after conventional washing (68.8%) and without washing (100%). The breaking strength of thermally induced gels prepared by pre-heating at 65 °C mimicking modori for 60 min after the high-pressure water washing was 3.8 N and was significantly higher than that after the conventional washing (2.6 N) and without washing (2.1 N). These results suggest that rheological properties of thermally induced gels can be improved with an extensive washing of fish material. The degradation of myosin heavy chain was recognized, when the water soluble fraction of the lyophilized powder of the fish body surface mucus was added into the ordinary muscle homogenate at around 60 °C and pH 8.15, suggesting that proteases were present in the fish body surface mucus. Such novel findings are useful for avoiding the modori phenomenon and thus improving the quality of surimi-based products.