Preparation Of Low Sodium Surimi Product And Research On Its Gel Properties From Silver Carp (Hypophthalmichthys Molitrix)

As a kind of four major cultured fish species, silver carp (Hypophthalmichthysmolitrix) has a high output and potential values in Chinese fresh water system.Silver carp has a high nourishment value with its white and high protein fish fresh,but the customer acceptability is limited due to its inherent musty taste andinter-muscular bones. Generally, the salt intake of human body is raised because of2-3%sodium salt addition during the chopping step of surimi production. Thepurpose of this thesis is to get two kinds of modified surimi gels, by comparing thequality of low sodium salt surimi gels with normal group (2.5%NaCl added). Thisthesis is divided into five parts as follows:(1)The basic component contents of fresh silver carp surimi are80.26%moisture,16.89%crude protein,0.52%crude fat and0.31%ash. The ratio of fillet,the ratio of fillet yield, mining meat yield and fresh surimi was55.08%,32.03%and20.37%, respectively;(2)Using calcium chloride and calcium lactate as two types of calcium salt, theeffects of calcium salt adding level on physical properties of surimi including gelstrength, texture profile analysis (TPA) parameters, water-holding capacity, colorand water activity were investigated during the chopping process in order to obtaina modificative gel for surimi. The results showed that as organic calcium, calciumlactate is more suitable for modifying the physical properties of low salt surimi gel.(3)In order to keep the quality of low salt surimi gel, the effects of differentlevels of sodium chloride, potassium chloride and calcium lactate on properties ofsurimi gel were investigated during the chopping process. Using gel strength, TPAparameters, water-holding capacity, color and water activity were investigatedduring the chopping process. Three factor and three level orthogonal experimentswere designed to obtain the optimum conditions on the basis of results ofsingle-factor experiments. The results showed that the optimum conditions for thechopping process were total salt3.5%, the addition of sodium chloride1%,potassium chloride1%and lactic acid calcium1.5%, respectively. The content ofsodium salt was lowered to1%.(4)During the chopping step, sodium chloride, guar gum and locust bean gum as the factor of the single factor experiment and three factors and three levelsorthogonal experiments were designed to obtain the optimum conditions on thebasis of results of single-factor experiments. The results demonstrated that theoptimum conditions for the chopping process were total salt1%, the addition ofsodium chloride1%, guar gum0.4%and locust bean gum1%, respectively. Thecontent of sodium salt was lowered to1%.(5)Using scanning electronic microscope (SEM) technique, the microstructurechanges of surimi gels from three different groups, the mixed salt group, food gumsgroup and the control group (2.5%NaCl added), were compared. The SEM graphsshowed the gel added with mixed salts is more homogeneous and compact than thecontrol; the gel added with food gums become smoother and more stable than thecontrol.