| Squid is a high protein,low fat fish product and squid surimi has the advantages of high whiteness,fine tissue and no fishy taste,making it one of the raw materials for surimi products.However,squid is rich in endogenous enzymes and myofibrillar protein is easily degraded,resulting in poor gelation of surimi.Therefore,it is necessary to improve the gel properties of squid surimi products.In this paper,the optimal mixing ratio of the main ingredients for the squid surimi was first investigated,followed by the optimal addition of exogenous additives(modified starch and non-muscle protein)to the squid surimi to determine the overall formulation of the squid surimi.On this basis,the ready-to-eat squid surimi products were developed,and the quality changes during storage were investigated.(1)To explore the effect of mixing ratio of squid and silver carp on gel characteristics of squid surimi products.In this experiment,the optimal mixing ratio of squid and silver carp was obtained through sensory evaluation,gel strength,water holding capacity,whiteness and other characterization indexes of squid surimi products,combined with water distribution,myofibrillar gel electrophoresis and microscopic structure observation of squid surimi products.The results showed that the mixing ratio of main ingredients of squid surimi products had a significant effect on the gel properties.When the mixing ratio of squid and silver carp was 3:4,the total score of sensory evaluation of surimi products was the highest,reaching 76.37 points,indicating that the squid surimi products with this ratio had good flavor and taste.The gel strength and water holding capacity of surimi products increased first and then decreased with the increase of squid addition ratio,indicating that the appropriate amount of squid addition can improve the gel strength and water holding capacity of surimi products.When the mixing ratio was 3:4,the content of whiteness and immovable water of surimi products was higher than that of the other groups,indicating that the gel network of surimi products at this ratio was dense and uniform,and the ability to bind water was better.Myofibrillar protein electrophoresis analysis showed that when the mixing ratio was 3:4,the myosin heavy chains was crosslinked and formed large molecular aggregates.Therefore,when the mixing ratio of squid and silver carp is 3:4,the gel quality of squid surimi products can be improved obviously.(2)To investigate the optimal additive amount of modified starch(ADSP)and nonmuscle protein(egg white protein,EWP and soy protein isolate,SPI)and mechanism of modified starch cooperating with non-muscle protein(ADSP-EWP-SPI,AES)to improve the gel properties of squid surimi products.This experiment used single factor test and orthogonal test to optimize the addition amount of modified starch and non-muscle protein,and explore the influence of modified starch synergizing with non-muscle protein on gel properties and protein conformation.The results showed that the gel properties of squid surimi products were the best when ADSP,EWP and SPI supplemental levels were10%,7% and 6%,respectively.Compared with the control group(without exogenous additives),the relative content of random coil and α-helix of protein in squid surimi products decreased,while the relative content of β-sheet and β-turn increased after adding modified starch and non-muscle protein.The addition of AES was conducive to the retention of β-sheet and β-turn structures during the thermal gel process,promoting hydrophobic interactions between proteins and forming a more compact surimi gel network structure,improving the texture,gel strength,and water holding capacity of squid surimi products.Therefore,adding modified corn starch synergized with nonmuscle protein(egg white protein,soybean protein isolate)at 10%,7% and 6%respectively,significantly improved the gel quality of squid surimi products and provided reference for the development of squid surimi products.(3)In order to study the quality variation of squid surimi products during storage.The squid surimi products were sterilized and stored at 36℃±1℃ for 0-10 d.The quality changes of the surimi products were evaluated comprehensively from the aspects of gel properties,physicochemical indexes and flavor characteristics.The results showed that in terms of gel properties,the gel strength,texture and whiteness of surimi products were significantly reduced by high temperature sterilization(P < 0.05).Compared with D0,the whiteness of surimi products decreased significantly when D10 was stored,but the gel strength did not change significantly(P > 0.05).During storage,there were no significant differences in hardness,chewability and elasticity between D0 and D10(P > 0.05).The water distribution of surimi products had the phenomenon of water migration during storage,but the overall change of water content was not significant(P > 0.05).In terms of physicochemical indexes,with the extension of storage time,the water activity,water content and p H of squid surimi products showed a decreasing trend.TBARS showed an upward trend.In terms of the total number of colonies,the total number of colonies of surimi products changed little during storage,indicating that high temperature sterilization effectively inhibited the propagation of microorganisms.In terms of flavor characteristics,bitterness and astringency changed significantly,bitterness reached its maximum value on the eighth day and astringency reached its maximum value on the tenth day.A total of 66 volatile flavor compounds were identified from surimi products,and 55 were identified,among which alcohols,aldehydes,ketones and esters were the highest.During the storage process,the contents of different kinds of substances change significantly.Among them,the content of alcohol substances increases first and then decreases,the content of aldehydes decreases first and then increases,the content of ketones increases with the storage time,and the content of ester substances decreases with the extension of storage time.Through OPLS-DA and model verification,it is concluded that the volatile flavor components of surimi products vary greatly during storage.Twenty characteristic volatile markers are screened out according to VIP(variable importance analysis)in the model,and the correlation analysis between them and storage time is conducted to further obtain the characteristic markers corresponding to different storage stages.According to the indexes of flavor characteristics,the flavor of squid surimi products deteriorated during the eighth and tenth days of storage.To sum up: In this paper,the ratio of main ingredients and the amount of exogenous additives of squid surimi products were systematically studied.It was found that the gel properties of squid surimi products were the best when the mixing ratio of squid and silver carp was 3:4 and the ADSP,EWP and SPI were 10%,7% and 6%,respectively.Based on the quality changes during storage,it is concluded that the flavor characteristics and quality of squid surimi products deteriorate on the eighth or tenth day of storage at 36℃±1℃,which provides a certain theoretical reference for the development of squid surimi products. |
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