Study On The Quality Characteristics Of Silver Carp Surimi Gel Prepared With Large Yellow Croaker Processing By-product

Restructured fish products have the characteristics of high protein,low fat,fresh and tender taste.Among them,surimi products are diversified in form and color,and are popular among consumers of all ages.Generally,a large number of by-products are produced in the processing of aquatic products.It contains a variety of biologically active substances.If improperly used,they will not only waste resources but also pollute the environment.It can effectively use processing by-products to realize the research and development of high-value surimi products.The aim is to fully apply the nutrients and flavor substances in the by-products of seawater processing to freshwater surimi and lay the foundation for the development of high-quality composite surimi products.In this study,silver carp surimi and by-products of large yellow croaker were used as raw materials.By studying the nutrition and taste characteristics of processing by-products,the byproducts with a high content of major odorants were determined.By optimizing the material-liquid ratio of the water-soluble flavoring extract and analyzed the physical and chemical properties of fish oil prepared from viscera.Based on this,by constructing a surimi system and heat treatment,the rheological properties,hydration characteristics,particle distribution,and flavor characteristics,gel characteristics,moisture distribution and other characteristics in surimi gel were researched.Then,the optimal exogenous additives and the amount were determined.The effects of freeze-thaw cycles on the gelatin flavor characteristics,gel characteristics,chemical forces,and protein conformation changes of surimi were studied.The stability of freeze-thaw quality of surimi gel was discussed.The research contents and findings were mainly as follows:?1?Differences Analysis in Taste Components in Different Processing By-products of Chilled Large Yellow Croaker?Pseudosciaena crocea?Analysis of the basic nutritional composition,overall taste profile,free amino acids and taste nucleotides of processing by-products of fish?fish scale,fish skin,fish viscera,fish roe,fish head meat and fish muscle?.The results showed that:minced muscle,head meat,roes and fish scales all had the characteristics of high protein and low fat;Principal component analysis?PCA?combined with discriminant factor analysis?DFA?could effectively distinguish among the seven by-products.Seventeen free amino acids were detected in all by-products except fish scales;The value of IMP in these by-products showed a taste activity value?TAV?greater than 1,and the TAV values of minced meat and head meat reached 18.27 and 16.51,respectively.The EUC values of minced meat,head meat and fish roes were significantly greater than other by-products,and all were greater than 1.?2?Analysis and Extraction of Fish Oil and Water-soluble Taste Substances from Processing By-productsThe fish oil was extracted from the internal organs by enzymatic hydrolysis and water-soluble flavoring substances were extracted from processed by-products of large yellow croaker?minced meat,fish head meat,fish roe?with the hot extraction method.The content of umami amino acids and taste nucleotides in the water-soluble taste substances were analyzed.The results showed that:The fish oil was extracted under the conditions of ratio of material to liquid 1:3,enzyme addition amount of 4000 U/g,p H value of 10.0,enzymatic hydrolysis temperature 50°C and enzymatic hydrolysis time 2 h.The fish oil acid value:2.870 mg/g,peroxide value:2.558 meq/kg,iodine value:172.205 g/100g,insoluble impurities 0.094%,which belongs to the secondary standard of refined fish oil;Based on the ratio of liquid to liquid 1:2,the fish head meat and fish roe were repeated hot extraction 3 times?“C”state?,the content of umami amino acids between water-soluble taste substance and the original samples?fish head meat and fish roe?content was not significantly different?P>0.05?;minced meat was repeatedly heat-extracted 4 times?“D”state?;In terms of the taste nucleotide content and EUC value,the content of IMP is gradually increased with the increase of the concentration times,and only the minced meat has a taste EUC extract is greater than 1,the minimum kinds of eggs,only 0.49 g MSG/100 g.Therefore,the water-soluble taste substance of minced meat?MM group?,the water-soluble taste substance of fish head meat?HM group?and the fish oil?FO group?in the secondary standard state were determined as external additives.?3?Analysis of physical properties of silver carp surimi prepared with large yellow croaker processing by-product The water-soluble taste substances,FM group,MM group and HM group?2.00%,6.00%,10.00%?obtained above,fish oil,FO group?2.00%,4.00%,5.00%?and yellow croaker muscle?2.00%,6.00%,10.00%?were added to the surimi,respectively.The color,rheology,hydration characteristics,and particle distribution of the surimi system were studied.The results show that:In terms of brightness and whiteness,the FM and the FO increased with the increase of addition,while the water-soluble taste substances groups increased first and then decrease.The FM group,MM group,HM group and FO group all showed at 10.00%,10.00%,10.00%and 2.00%respectively:the particle size distribution?D10,D50,D90,d4,3 and d3,2?had the smallest particle size;The viscosity and shear stress were the largest among the rheological characteristics;in terms of hydration characteristics,the relaxation time is mainly distributed in 0 ms?1 ms,1 ms?10 ms and 120 m?140 ms and the relaxation time were small,indicating in this state the protein molecules,lipid molecules,water molecules and other molecules are tightly bound,and their storage modulus and loss modulus energy are larger when they reach the gelation temperature,indicating that the formed gel has better characteristics.Therefore,the overall characteristics of the surimi system of 10.00%FM group,MM-10.00%,HM-10.00%,and FO-2.00%were initially determined to be good.?4?Analysis of gel properties of silver carp surimi prepared with large yellow croaker processingby-product The above-mentioned surimi prepared was heated in two stages to obtain different surimi gels.Combined with artificial senses,color difference meter,texture analyzer,and amino acid automatic analyzer were used to comprehensively evaluate the quality characteristics of different surimi gels from the aspects of sensory,whiteness,gel characteristics,texture characteristics,water retention,and taste characteristics.The results showed that:The total sensory evaluation scores were highest in the FM-2.00%,MM-10.00%,HM-6.00%,and FO-5.00%respectively;In terms of taste characteristics,the content of umami amino acids increased with the increase of the amount,but the FO reached the maximum at2.00%;In terms of gel properties,all treatment groups increased the brightness value and the whiteness value.The water-holding of the FM and FO also gradually increased and were better than those of the blank group,but there were no significant change in the centrifugal loss and cooking loss in the MM and HM.Except the FO,the strength were increased,the texture characteristics were increased,but the elasticity were not obvious.When the added amount was more than 2.00%,the trend of umami amino acid content and texture characteristics were FM group>MM group>HM group;In terms of water distribution,the relaxation time shifted to the right as a whole,but the FM-10.00%,MM-10.00%and HM-10.00%shifted to the left at 0 ms?1 ms and 1 ms?10 ms,indicating that the binding capacity between protein and ¹H was enhanced,and the relative content of bound water was increased.From the perspective of the degree of change,the relative content of bound water in the MM group was significantly larger than that in the FM and FO groups,and relatively less in the HM group.Therefore,the overall quality of the FM-10.00%,MM-10.00%,HM-10.00%and FO-2.00%were better after comprehensive formula weighted evaluation.?5?Effects of freeze-thaw on the quality of surimi gel and the conformational changes of proteinsThe surimi gel of FM-10.00%group,MM-10.00%group,HM-10.00%group and FO-2.00%group was repeatedly freeze-thawed.The effect of freezing-thawing cycle on freezing-thawing stability of surimi gel were investigated from the aspects of taste characteristics,gel characteristics,chemical forces,microstructure and protein conformational changes.The results showed that:the color,water retention,texture,gel strength,and umami amino acid content of the surimi gel gradually decreased,and the brightness and whiteness of the FO were better than others.In terms of changes in water-holding,texture,gel strength and umami amino acid content,the FM and the MM were relatively better than the other groups;Low-field NMR analysis found that the peaks corresponding to relaxation time T₂₂of all treatment groups were shifted to the left,and the peaks corresponding to relaxation time T₂₃were shifted to the right.In the process of repeated freezing-thawing,the three-dimensional network structure shrinks,restricting the movement of ¹H,which reduces the fluidity of water molecules.Water migrates to the large network void,recrystallizes to form larger crystals,which cannot be reabsorbed after thawing.The mobility of free water increases and the relaxation time T₂₃increases.Solubility,total thiol content,and hydrogen bonds of surimi gel after freeze-thaw cycles were all decreased.Ion bonds was also reduced except for the FO group.The non-specific and hydrophobic bonds were increased.The SDS-PAGE electrophoresis strip showed that the degree of protein denaturation increased and the degree of protein cross-linking and aggregation increased during repeated freeze-thaw cycles.In repeated freeze-thaw cycles,hydrophobic interactions,disulfide bonds,and non-disulfide covalent bonds maintained surimi coagulation.The main chemical force for stable conformational changes of the gum.However,the?-sheet,?-turn,and random curl content in the secondary structure of the protein did not change significantly,while the?-helix content increased significantly.It is speculated that salt loss and gel p H during repeated freeze-thaw processes related changes.During the whole freeze-thaw process,the gels with processed by-products of croaker were relatively less affected by the FO and MM.