Study On Digestive Characteristics And Antioxidant Activity Of Green Wheat Kernel Noodles In Vitro

In this paper,green wheat kernel as the research object,after vacuum freeze-drying treatment,grinding and wheat flour mixed at different proportions,analyzed the influence of green wheat kernel flour addition amount on the structure and quality of noodles,optimized the preparation process of green wheat kernel noodles,and investigated its in vitro digestive characteristics and antioxidant activity.1.The differences of microstructure,moisture distribution,starch crystal characteristics,proteinsecondary structure and starch fine structure characteristics of the bottom strip under three different drying methods:vacuum freeze-drying,hot air drying and vacuum drying were studied.The scanning electron microscope results showed that with the increase of the addition amount of green wheat kernel powder,the analysis of the microstructure of the vacuum freeze-drying green wheat kernel noodles showed that the starch particles of the noodles changed from being evenly wrapped by gluten protein to being exposed and the density of starch particles gradually decreased.The gluten network structure of the noodles became tighter and the pores decreased,and the network structure was destroyed.In contrast,vacuum drying is the second,hot air drying is the worst.The distribution of water state in noodles shows that:The relaxation time(T₂₁)of vacuum freeze-dried green wheat kernel noodles decreased,T₂₂and T₂₃increased,and the peak area ratio(A₂₁)decreased from 22.23%to 13.19%,(A₂₂)increased from 76.56%to 85.38%,and(A₂₃)increased from1.21%to 1.43%.After vacuum freeze drying,the water holding capacity of green wheat kernel noodles was better,followed by vacuum drying,and the water holding capacity of hot air drying was worst.The starch crystallization characteristics showed that the relative crystallinity of starch decreased gradually with the increase of the addition amount of green wheat kernel powder,and the relative crystallinity and total crystallinity of A-type crystals were lower than that of the control group.In contrast,the relative crystallinity of starch after vacuum freeze drying is the highest,followed by hot air drying,and vacuum drying is the lowest.Protein secondary structure analysis showed that the wheat flour noodles in the control group mainly consisted ofα-helix andβ-folding,followed byβ-angle,without random curling structure.The proportion ofβ-folding andα-helix decreased and the proportion ofβ-turning increased with the increase of the supplemental level of wheat kernel powder.Vacuum freeze-drying has little damage to the sample,and the transformation ofα-helix andβ-angle can be delayed at low temperature,which is more conducive to the maintenance of sample quality.However,hot air drying and vacuum drying promoted the transformation ofα-helix andβ-angle at a higher temperature of 40℃,resulting in the decrease of regular protein content in the sample itself.The analysis of starch fine structure showed that the ratio of 1047/1022cm^-1of green wheat kernel noodles was lower than the absorbance ratio of the noodles in the control group,and showed a decreasing trend with the increase of the addition level of green wheat kernel flour.The ratio of1022/998cm-1 was higher than the ratio of 1022/998cm^-1in the control group,which showed an increasing trend,indicating that the proportion of internal crystalline zone structure and amorphous zone of starch particles decreased,the degree of crystallization decreased,the number of spiral double chains of starch molecules decreased,and the structure arrangement of starch double helices decreased.2.The thermal mechanical energy,rheological properties,color,thermodynamic properties,texture properties,cooking properties and sensory properties of green wheat kernel noodles were investigated,and the noodle process was optimized.The results of thermal mechanical energy measurement of dough showed that with the increase of the addition of green wheat kernel powder,the water absorption of dough increased,the formation time increased,the stability time decreased,the degree of protein weakening increased,the processing property of dough became worse,the starch gelatinization time became shorter,the gelatinization degree decreased,the starch recovery value decreased,and the cooking stability decreased.The rheological characteristics of dough showed that G’and G"of noodles with green wheat kernel in control group and control group were consistent with the variation trend of frequency,and the energy storage modulus G’was greater than the loss modulus G".With the increase of the addition amount of green wheat kernel powder,the tangent value of green wheat kernel noodles was greater than that of blank noodles in the control group,and the viscosity and elasticity of green wheat kernel noodles were greater than that of blank noodles in the control group.When the amount of green wheat flour is less than20%,the viscoelasticity is moderate,and the elasticity of noodles is better.The color of noodles showed that the L*value of noodles decreased from 84.26 to 76.25,the a*value changed from positive to negative and the negative value gradually increased,and the b*value gradually increased with the increase of the addition amount of green wheat flour.The thermodynamic characteristics of noodles showed that the initial gelatinization temperature did not change much,the peak temperature of gelatinization decreased,the end temperature of gelatinization did not change much,the enthalpy of gelatinization decreased significantly from 1.87J/g to 0.77 J/g,the gelatinization time decreased,and the degree of gelatinization decreased.The texture characteristics showed that the hardness and viscosity of noodles decreased,the elasticity and chewability decreased,and the recovery of noodles decreased with the increase of the addition amount of green wheat kernel powder.The optimum cooking time of green wheat kernel noodles decreased,the breaking rate increased,the water absorption rate of dry matter decreased,the cooking loss rate increased,and the turbidity of noodle soup increased.The analysis of noodle sensory evaluation showed that the sensory score increased first and then decreased.When the additive amount was 20%,the sensory score reached 87.33 points,and the color and apparent state were better.Using single factor experiment and orthogonal experiment,taking the content of gluten,artemisiaannua seed gum and salt as the research object,the optimal technological parameters of green wheat kernel noodles were obtained:the content of wheat kernel flour was 20%,gluten was 3.0%,artemisia annua seed gum was 2.5%,and salt content was 1.5%.3.The digestibility,hydrolysis rate and predicted glycemic index of starch were investigated and analyzed by simulating in vitro digestion.The results showed that the fast digestible starch RDS content was 85.76%,the slow digestible starch SDS content was 11.21%,and the RS content was only 3.03%.The RDS content,SDS and RS of green wheat kernel noodles were 66.59%,21.36%and 12.05%,indicating that the noodles had good slow digestion characteristics.In terms of starch hydrolysis rate,white bread had the highest starch digestion rate in the same time,followed by wheat flour noodles in control group,and green wheat kernel noodles had the lowest starch digestion rate.The predicted glycemic index of wheat flour noodles was 87.58,a high glycemic index food,while that of green wheat kernel noodles was 68.79,a medium glycemic index food.4.The polyphenols and antioxidant activities of green wheat kernel noodles were studied by simulating gastrointestinal digestion.The results showed that the total phenol content of green wheat kernel noodles increased to 1.18mg/g and 1.64mg/g after gastrointestinal digestion,respectively,and the total phenol content increased significantly.In antioxidant activity,the scavenging rate of DPPH free radical increased significantly,which was consistent with the change trend of polyphenol content.In the process of gastric juice digestion,the reducing power was the most prominent,and the scavenging rates of ABTS free radicals and hydroxyl free radicals showed a trend of first decreasing and then increasing after gastric juice digestion.In correlation analysis,DPPH free radical scavenging was significantly positively correlated with total phenol content,while reducing power,ABTS free radical scavenging and hydroxyl free radical scavenging were not significantly correlated with total phenol content.Green wheat kernel noodles showed better in vitro digestive characteristics and antioxidant activity.This study provided theoretical reference for functional pasta foods and the development of new green wheat kernel products.