The Quality And Mechanism Of Silver Carp Surimi Improved By Porcine Plasma Protein

Silver carp (Hypophthalmichthys molitrix), is one of the main freshwater aquaculturespecies in China, and the common processed products of this fish is those based on its surimi.Because the quality of freshwater fish surimi products is poorer than that seawater fish, manyeffects have been made to improve the quality of freshwater fish surimi b y adding starch,hydrocolloids, non-muscle protein, transglutaminase (TG enzyme). Nevertheless, themouthfeeling of the fresh water surime was still affected greatly by its instabilities offreeze-thaw and gel. Many studies have showed that the poor quality of surimi fromfreshwater fish is resulted mainly from the high hydrolysis degree of myosin heavy chain bycathepsin in fish muscle. However, it was reported that porcine plasma protein powder hadbetter inhibition on cathepsin in marine fish. Therefore, we measured cathepsin residues ofsilver carp after rinsing and inhibition of porcine plasma protein powder on cathepsin residuesfirstly. Then investigations were carried out onthe effects of porcine plasma protein powderconcentration, the setting time, the setting temperature on silver carp surimi qualities such asgel strength, water loss rate and whiteness. Study was also conducted on the mechanism ofsilver carp surimi quality improved by porcine plasma protein powder and the effect ofporcine plasma protein solution concentrated by rotated on the quality of silver carp surimi.The presented study provides a solid theoretical basis for porcine plasma protein to improvethe quality of surimi-based product, and is also of greater reference value producing highquality surimi products.The inhibiting effects of porcine plasma protein powder on silver carp muscle cathepsinwere investigated. Bycomparing the activities of cathepsin B, L, H in silver carp musclesbefore rinsing, it was known that much of the activity till remained in the muscles afterrinsing. The result showed that the residual rate of cathepsin L, B were26.88%,12.54%respectively after rinsing. When the amount of porcine plasma protein powder was added1.5g/100g, its inhibition of cathepsin L, B had reached to86.1%and86.1%.Gel strength, water loss rate, TPA as minced fish quality evaluation index, the singlefactor experiments was adopted. As a result, the concentration of porcine plasma proteinpowder at1.5g/100g, setting time at1.5h, setting temperature at40℃were proved to obtainthat the the greatest gel strength of silver carp surimi was13215g mm, almost three times ofthat blank sample, water loss rate reduced to3.29%, whiteness was slightly reduced.The mechanism of silver carp surimi improved by porcine plasma protein powder wasstudied by TCA soluble protein, electrophoresis, ultraviolet, endogenous fluorescence,rheological and chemical methods. TCA soluble protein and electrophoresis showed that t heautolysis inhibition of porcine plasma protein powder on silver carp muscle could reach more than80%with the optimum autolysis temperature of silver carp muscle (60℃). UV andendogenous fluorescence results showed that protein hydrophobic interaction decreased,tyrosine and tryptophan residues were embedded into more polar environment. The solubilitystudies and chemical forces analysis indicated that nondisulfide covalent bond, particularlyε-(γ-glutamyl) lysine linkage, hydrophobic bond and hydrogen bonds which were significantincreased in gels when added with porcine plasma protein powder played an important role informing a compact and homogeneous three-dimensional gel network. Comparison, whichmade by the quality of silver carp surimi by adding porcine plasma prote in powder or soyprotein isolated, was proved that the porcine plasma protein powder of silver carp muscleproteases had better inhibitory effect indirectly. Rheology concluded that porcine plasmaprotein powder can greatly improve the final G’of surimi and the ultimate tan delta was lessthan the initial value. It was directly verified that elastic quality of silver carp surimi could bebetter improved by porcine plasma protein powder.We studied the effect that porcine plasma protein liquid obtained by ro tation on qualityof silver carp surimi. Porcine plasma protein solution concentrated by rotating at differenttemperature was added to silver carp surimi at amount of5g/100g, the solution rotated at40℃had a better improvement effect, improved gel strength of about100%and the water loss ratedecreased to4.51%. It had big gap to the silver carp surimi improved by porcine plasmaprotein powder.