Effects Of Washing On Proteins And Gel Properties Of Grass Carp And Silver Carp Surimi

Nowadays freshwater fish has been taken high propotion of surimi and surimi products industry in China. Grass carp and silver carp as the major freshwater aquaculture species in China played an important role in fishery economy. In surimi products processing freshwater fish has poor gel-forming properties compared with marine fish. Also during the washing process of minced fish the large amounts of water expended. However the research about the effect of ionic strength and p H of washing liquid on properties of surimi has been rarely reported.This research studied the effect of washing with different ionic strength and p H on surimi proteins and gel-forming ability. Grass carp and silver carp were chosed as the material in this work. The washing solution was designed by different concentration of Na Cl(0%, 0.25%, 0.5%, 1.0%, 2.0%) and p H(3, 5, 7, 9). Firstly the fundamental properties of surimi were analyzed by protein yield, water-soluble protein and salt-soluble protein content. Meanwhile the effect of washing on surimi was explored by SDS-PAGE, ultraviolet absorption, tryptophan fluorescence spectrum and circular dichroism of actomyosin. The effects of washing on surimi gels characteristics were investigated, including color properties, texture properties, water holding capacity and intermolecular chemical interactions. The study could provide a new washing method of surimi processing and theoretical reference in the influence of washing on surmi. The results were as follows:The protein yield of grass carp and silver carp surimi declined with Na Cl concentration increased to 1.0% and 2.0%. There was no significant difference among the different p H treatment. The water-soluble protein content of p H 3 treatment was significantly higher than other p H treatment. The salt-soluble protein content declined with increased with Na Cl concentration increased to 2.0%.The results of SDS-PAGE showed that myosin heavy chain and actin were mainly bands in grass carp and silver carp surimi protein of two kinds of protein. The low molecular weight protein bands were found in p H 3 treatment. Through the ultraviolet absorption spectra and tryptophan fluorescence spectrum of the minced fish actomyosin, the results shows that washing with acid(p H 3) or alkali(p H 9) made absorption and intensity higher than p H 7 treatment. The a-helix content of actomyosin of p H 3 treatment was significantly lower than other p H treatment.The gel-forming ability of surimi washed by different Na Cl concentration(0.25%, 0.25%) and p H(3, 5, 7, 9) was studied. The water holding capacity of surimi gels prepared by acid or alkali washing process declined compared with p H 7 treatment. Cohesion and resilience of p H 3 treatment was significantly lower than other p H treatment group. The chemical intereaction results shows that groups hydrogen bond or electrovalent bond content of p H 3 treatment was significantly lower than other p H treatment group.