Study On The Key Processing Technology Of Freshwater-fish Surimi Products

Fish surimi product is a kind of leisure fish product processed by pretreatment of raw material fish,seasoning and baking.At present,the fish surimi product can be divided into fish slice and surimi product.The production process is slightly different.It is favored by consumers because of its long shelf life and easy-to-eat.However,on the one hand,it is costly to make fish fillets from whole fish fillets;on the other hand,fish fibres are shorter than pork fibres,and they are prone to breakage.Fish surimi products made from surimi are not easy to mould and have poor chewability and toughness.While the lipids of fish are mainly unsaturated fatty acids,which are more prone to fat oxidation than pork to form bad odors,then it would affect the quality of products.Therefore,the penetration rate of fish surimi products is far lower than that of pork.This paper is to carry out experimental research on the above issues,using grass carp and carp carp as raw materials,by studying the changes in the microstructure and fiber tensile strength of grass carp under different water contents to instruct the setting of process parameters,and the effects of fat oxidation,flavor composition and sensory quality with different combination drying methods on fish carp to develop a freshwater fish fillet with good texture and taste.The results will lay a theoretical foundation for industrialization,large-scale production and standardization of product quality control.First,the changes in the microstructure and fiber tensile strength of grass carp under different water contents was studied.The drying characteristics of grass carp dried by hot air were studied and a hot-air drying model was established.Then the microstructure,breaking force,extensibility,elongation and other indicators of grass carp under different moisture content(77~11.7 g/100 g)were studied.The results showed that when the water content was 77~60.7 g/100 g,the myofibrillar tissues of grass carp became dense.However,moisture content less than 22.6 g/100 g,myofibril contraction,diameter decreases,and the cracks become larger.With the water content of grass carp reduced from 77 g/100 g to 11.7 g/100 g,the longitudinal breaking force increased from 0.256 MPa to 2.744 MPa,the longitudinal extensibility decreased from 7.877 mm to 1.756 mm,and the longitudinal elongation decreased from 37.886% to 8.774%.The moisture content is about 22.6 g/100 g,the fiber structure is close,the longitudinal breaking force is 0.956 MPa,the extensibility and elongation are respectively 4.235 mm and 26.177%.The fibers have high fiber breaking force and a dense microstructure,which maintains the fiberiness of grass carp fish.Therefore,grass carp should be dried to a moisture content of about 20 g/100 g to keep the fiber sense of grass carp fish to the greatest extent.Then,the freshwater fish surimi processing technology was optimized and its quality was evaluated.Surimi and fish fillet were as the raw materials.The varieties of fish,the ratio of surimi and fish,the amount of exogenous additives on the product quality were studied by analyzing the texture,color,micro structure,thiobarbital acid value.,the sensory evaluation and product quality of fish surimi product to determine the optimum conditions for developing a processing technology of freshwater-fish surimi products.The results showed that the grass carp is the best raw material;the optimum ratio of raw materials is 3:7;Based on the 100 g fish carp mixture,the best formulas for other additives were as follows: white sugar 10 g,rice wine 10 g,soy sauce 5 g,soy protein isolate 6 g,complex phosphate 0.5 g,t-butylhydroquinone 0.010 g,ginger powder 0.15 g and white pepper powder 0.05 g.Finally,the effects of combination drying methods on fat oxidation and flavor components of fish surimi products were studied.The change on moisture content,water activity,thiobarbituric acid value,acid value,peroxide value,free amino acid,free fatty acid and volatile flavor components and sensory of the fish surimi products under three different combination drying modes were analyzed to determine the optimum drying method.The results showed that three combination drying methods—C1(microwave drying for 7 min at 350 W,hot-air drying for 35 min at 70?.),C2(microwave drying for 5 min at 560 W,hot-air drying for 45 min at 70?.)and C3(microwave drying for 5 min at 560 W,vacuum drying for 80 min at 60?.)can reduce the water activity of the product to approximately 0.7 and the moisture content to approximately 20%.The thiobarbital acid value and the peroxide value of C2 were 3.683 ?g/g and 0.41 g/100 g,respectively,so its oxidation was the highest.The thiobarbituric acid value of C1 was 3.062 ?g/g,and peroxide value of C1 was 0.09 g/100 g.After drying,the composition ratio of fatty acids changed a lot.The proportion of saturated fatty acids in C1 and C2 decreased,the ratio of monounsaturated fatty acids and polyunsaturated fatty acids increased,and the composition of fatty acids in C3 had a relatively small change.The amino acid contents of C1 and C3 are basically similar,and the increase of most amino acids in C2 is higher than that of C1 and C3.A total of 40 volatile flavors were identified in the four fish surimi product samples by GC-MS;29 were detected in the undried group,37 were detected in C1,32 were detected in C2,and 35 were detected in C3.C1 had the most flavors species.,followed by C3.The optimum of drying condition is microwave drying for 7 min at 350 W,hot-air drying for 35 min at 70?.