Inhibition of endogenous protease activity and protection of histomorphical integrity during refrigerated storage of grass carp fillets by treatment with natural edible di- and tri-carboxylic acids.

In this study, by dipping grass carp fillets with 10mM di-and tri-carboxylic acid solutions individually before storage at 4 °C for 10days, the application potential of these acids in mitigating softening of fish was investigated through analysing shear force, pH, endogenous cathepsin activities, myofibrillar proteolysis and histomorphological characteristics. The results suggested that maleic acid, fumaric acid and tartaric acid were significantly effective against softening of grass carp muscle, as shown by shear force 26%-31% higher than that of control after storage. Acid treatments led to a decline in the pH of muscle. Besides, the inhibitory effect of these acids on cathepsins was demonstrated by activity reduction by 20%-90%. Further, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and heat shock protein (HSP) analysis supported the protection of these acids against degradation and dissociation of myosin and actin through suppressing HSP loss. Moreover, histomorphological images with higher intensity of acridine orange fluorescence in muscle...