| As one of the traditional staple foods in our country,fresh and wet noodles are deeply loved by the public because of their relatively simple production and convenient consumption.Compared with dry noodles,they have better taste.However,due to the high moisture content,it is easy to return to browning under normal temperature conditions,which makes the color of the noodles dark and uneven color distribution,seriously affecting the appearance and reducing the commercial value.Therefore,this paper mainly explores the regularity and influencing factors of the return color of fresh and wet surfaces.Wheat flour was treated with microwave,wet heat and superheated steam to suppress the color return of noodles.The effects of three treatments on inhibiting the color return of noodles were compared.The whiteness of noodles and the quality of wheat flour were used as evaluation indexes to optimize the technical parameters of inhibiting the color return of fresh and wet noodles,providing theoretical support for inhibiting the color return of fresh and wet noodles.The findings are as follows:(1)Study on the regularity and influencing factors of fresh and wet surface color return.During the 24 h storage period,the whiteness value of fresh and wet noodles was divided into two stages:the first stage was 0-4 h,the whiteness value declined sharply in a nonlinear(at~2-bt+c)trend,and the second stage was 4-24 h,the whiteness value declined in a nearly linear(-kt+b)trend.The activity of polyphenol oxidase(PPO)did not change significantly during storage,while free polyphenol was oxidized in the second stage(4-24 h),and its content was reduced by 29.05%.PPO activity mainly catalyzes the oxidation of phenolic substances in the second stage of color return(4-24 h),the increase of protein content promotes the reaction in the first stage of color return(0-4 h),and the addition of water affects the whole stage of fresh and wet noodles color return.(2)Study on the inhibition effect of microwave,moist heat and superheated steam on the return color of fresh and wet surfaces.The three treatment methods can reduce PPO activity,slow down the oxidation of free polyphenol,and inhibit the return of color of the dough,so that the whiteness value of the dough increases and the rate of whiteness decline slows down during storage.The wet heat and superheated steam treatments have better effects,and the whiteness value increased by 29.18%and 28.01%,respectively.Through low-field NMR analysis,microwave and superheated steam treatment of wheat flour can change the state of free water and bound water in the noodle,thus affecting the return color.At the same time,the content of free sulfhydryl and proteinα-helix decreased,the content ofβ-fold increased,the protein structure changed,G’and G"increased,and the viscoelasticity of noodle increased.The formation of disulfide bond was promoted by microwave and superheated steam treatment.However,the fluidity of free water in the chip increased after wet heat treatment,and the content ofα-helix of the protein decreased significantly,and the structure changed to disorder.(3)Study on the effects of microwave,moist heat and superheated steam treatment on wheat flour quality.Microwave treatment has no significant effect on the color,silty characteristics and microstructure of wheat flour.The wet gluten content and gluten index were slightly increased under low intensity treatment.The gelatinization viscosity was increased under high intensity treatment,and the gelatinization characteristics of wheat flour was improved and the settlement value was decreased.After the wet and heat treatment,the color of wheat flour became dark,and when the high intensity wet and heat treatment,the gluten was severely damaged and could not be washed out,the gelatinization temperature decreased,the peak viscosity decreased,the complete starch particles in the microstructure decreased,and the gluten network structure in the dough was seriously damaged.After superheated steam treatment,the color of wheat flour became darker,the formation of gluten network was affected,the content of wet gluten decreased by about 11.06%,the gluten index decreased by about 50.02%.The gelatinization temperature decreased,the viscosity increased,the starch particles were broken,and the cross-linking with protein reduced the integrity of starch particles.(4)Research on optimal combination of different processing methods.Due to the great influence of moisture and heat treatment on the gluten characteristics of wheat flour,the gluten and gelatinization characteristics of wheat flour can be improved by low-intensity microwave treatment,and the effect of superheated steam treatment on inhibiting the return of color is remarkable.Therefore,microwave and superheated steam treatment are selected for further optimization.Three combinations of treatment parameters were optimized based on the whiteness,PPO activity and gluten characteristics of fresh and wet dough by using microwave-superheated steam complex treatment process.Compared with G2 sample treated with superheated steam only,sample Y3(microwave time 80 s,power 462 W,superheated steam time 60 s,temperature 170℃),sample Y3(microwave time 80 s,power 462 W,superheated steam time 60 s,temperature 170℃),The whiteness of wheat flour increased by 4.95%,and the gluten characteristics were less affected at this time,the L*of wheat flour decreased by0.94%,the stability time,the formation time and the flue quality index increased,of which the stability time increased by 4.09 min,the flue quality index increased by 87.88%,the cooking loss of the sheet and the turbidity of the noodle soup decreased after the compound treatment,and the water absorption increased.The cooking loss of Y3 noodles decreased by 15.25%.In the sensory score,compared with the original flour noodles,the sensory of sample F3 noodles is closest to the original flour noodles,and there is no significant difference between the comprehensive score and the original flour noodles.In conclusion,when the microwave time is 80 s,the power is 462 W,the superheated steam time is 60 s,and the temperature is 170℃,the return color of fresh and wet noodles can be effectively inhibited,and the quality of wheat flour is good.There is no significant difference in the comprehensive score of the noodles after cooking with the original flour. |
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