| Silver carp (Hypophthalmichthys molitrix) is one of the primary freshwater fishspecies in China with a higher yied. Now this freshwater fish can be processed intosurimi to enhance its added value and improve the ultilization rate. But silver carpsurimi is hard to suwari and easy to modori because the fish fresh is soft, highwater and its protein is sensitive to oxidate. Furthermore, a high sodium saltaddition during the chopping step of surimi production, about2%~3%, can harmour health. Therefore, it is important to reduce the sodium salt addition andoptimize the influence factors of gel forming. In this paper, the silver carp surimiwas investigated and three low sodium salt formulas, one modified process and twomicrowave heating methods were optimized. The main results were as follows:Based on the nutrition analysis of silver carp surimi, the lipid and ash contentsof frozen surimi had a significant decline compared with unwashed surimi, and anincrease in moisture content, but the protein content had little change andaccounted for about18.73%, including12.39%salt soluble protein,2.32%watersoluble protein, and4.02%insoluble protein.To reduce the sodium salt addition of surimi products, potassium chloride,calcium chloride, calcium glutamate, calcium gluconate and wheat gluten werechosen to replace the sodium salt. Three low sodium salt formulas and onemodified process were optimized to improve the surimi gelling properties.Response surface methodology were adopted to obtain the optimum formula, andthe result indicated that the three low sodium salt optimum formulas were:⑴sodium chloride1.0%, potassium chloride1.0%, calcium chloride0.5%;⑵sodium chloride1.0%, potassium chloride1.0%, calcium glutamate0.5%;⑶sodium chloride1.00%, potassium chloride1.00%, calcium gluconate0.05%.Using the above low sodium salt formulas, the problems of surimi modori causedby a decline of sodium chloride addition were well solved. To compare with thesurimi which added2.5%sodium chloride, the surimis which added low sodiumsalt formulas had little difference in gel properties, pH value, water activity, proteinsolubility and myofibril protein content. The patterns of SDS-PAGE showed thesurimis which added low sodium salt formulas had the same degree of myosin crosslink with the surimi which added2.5%sodium chloride, but higher than thesurimi which added1.0%sodium chloride. Through the use of scanning electronmicroscope (SEM) observation, the surimis which added low sodium salt formulaswere more dense, more smooth, and the holes outside or inside the surimis wererelatively smaller than the control.The results of response surface methodology (RSM) analysis indicated that theoptimal technical conditions of wheat gluten on low-sodium silver carp surimi wereas follows: the additive amount of wheat gluten was5.0%, the additive amount ofwater was2.5%, and salt chopping time was14min. The modified process surimihad little difference in gel properties, pH value, and SEM to compare with theconventional process surimi, but had large difference in water activity, proteinsolubility, myofibril protein content and SDS-PAGE. It indicated that themodification mechanism of wheat gluten on gelling properties of low-sodiumsurimi product might be attributed to its own property.To improve the quality of surimi, the effects of microwave heating methods ongel properties of silver carp surimi were investigated. Single-factor experimentsand orthogonal array design were adopted to obtain the optimum formula ofmicrowave heating and waterbath-microwave combined heating respectively. Thechanges of different heating methods on the protein molecular structure of surimiwere further studied through protein solubility, chemical forces, SDS-PAGE andscanning electron micrographs. The study indicate that under the optimal technicalconditions of waterbath-microwave combined heating that the microwave powerwas600W and the microwave time was60s, And under the optimal technicalconditions of microwave heating that the microwave power was450W, themicrowave time was60s and the waterbath temperature was40℃.The researchshowed that microwave heating was better than waterbath heating, whilewaterbath-microwave combined heating was better than only microwave heating. |
PDF Full Text Request