Protein Oxidation And Control In Processing Of Silver Carp(hypophthalmichthys Molitrix)surimi And Surimi-based Food

Surimi is a kind of protein concentrated food processed by the fish meat which was obtained,rinsed and dehydrated.If which added to the amount of carbohydrate and polyphosphate,it could keep well protein activity under low temperature（less than or equal to 18℃）for a long time storage.Adding salt and spice materials to fresh or frozen surimi,chopping or mincing to make stringy meat paste.After then typing and heating to make surimi products with Q elasticity.The fish meat contains more red meat components containing heme,high iron myoglobin,lipid and other cracking factors which are not conducive to the gel.Most of the cracking factors have the effect of inducing protein oxidation.The control of protein oxidation and good processing products need to remove these adverse components.Choicing rinsing treatment could obtain the ideal processing materials as much as possible.In different temperature and time,did rinsing treatment on silver carp to get fresh surimi.The protein oxidation denaturation and physicochemical indexes of the prepared rinsing surimi were detected.It was found that the effect of the number of rinsing times on protein carbonylation was significantly stronger than the temperature.The effect of temperature change on protein sulfhydryl group,crosslinking polymerization and two grade structure was more sensitive.Increasing the temperature,decreasing the content of sulfhydryl group,and the percentage gradient of protein two disorder structure increased.The variation of the order structure was approximately equal to the sum of the variation of the percentage of the alpha helix and the beta fold structure.Other physical and chemical indexes,such as Ca²⁺-ATPase enzyme activity and solubility.All increase with temperature,and rinse time increases slightly.Comprehensive analysis,the changes in protein carbonylation and two stage structure could be used as a significant indicator of the evaluation of protein oxidation during the rinsing process.The selection of 2 times（1 times:10 min）at low temperature（4℃）could not only guarantee less water soluble protein loss and obtained fresh fish surimi with less oxidation degree.Chopping is one of the most important processes in the processing of surimi products.The effect of high speed shearing force brought about muscle fiber cell membrane of minced meat breakage,further damaged to muscle cells,created good condition for the the dissolution（stripping）of salt soluble protein and sufficient.In the expriment of chapter 3,the Malvin laser particle size analyzer determination was used to detecte surimi particles distribution characteristics dealed with different shear speed（600r/min or 1450r/min）and different shearing time（1⁶ min）.the degree of protein oxidative were determined.Meanwhile Making Correlation analysis between protein oxidative and particle characteristic index based on Pearson.The results showed that there was oxidative denaturation in the process of chopping,the particle per size and specific surface area had a positive correlation with the degree of carbonylation.Higher the chopping rate was,the smaller the particle size and the larger the specific surface area was.Bigger the particle size is,more the distribution curve will changed from"Double-peak type"to"Single-peak type".Meanwhile,the physical and chemical properties of the protein would be deteriorated,which decided subsequent processing.The selection of low speed chopping 600r/min for 5 min could do better for improving the oxidation degree of protein,and also ensured the good physical and chemical properties.In the stage of heat treatment（water-bath heat treatment）,nutritional quality of surimi products was evaluated by adding Omega-3 soybean oil and protein oxidation by lipid oxidation could be promoted.The experimental results show that the addition of oil with different mass fraction could promote the reaction of protein oxidation and had a significant influence on the nutritional quality of the products.With the increase of oil consumption,the protein oxidation degree increased and the chroma became white.When the soybean oil was added to 3%,the product had the maximum gel strength of3133.81 g?cm,the amino acid nutritional evaluation results was excellent.To synthesize many indexes,adding 3%of soybean oil could improve the gelation quality of the surimi and the products with good nutritional quality.Combined with the experimental results of three important stages in surimi and its products processing,result would be obtained:washing treatment 2 times under 4℃of silver carp meat could inhibit protein oxidative denaturation and kept enzyme activity and other functional properties,avoided excessive loss of water-soluble protein.In the process of chopping,the low rotational speed of 600 r/min in 5 min was selected promoted the oxidation degree of the protein,and the surface hydrophobicity and other good physicochemical properties were maintained.Combined with the above process methods,3%soybean oil rich in Omega-3 was added to promote protein oxidation during the heat treatment stage.Finally surimi products with good gel quality and nutritional value were obtained.