Effects Of Egg White Protein And Heat Induction On Properties Of Gluten Gel And Its Application

Wheat noodles are one of the most common staple foods in China and some other Asian countries,however,wheat noodles have insufficient elasticity,are prone to aging,and lack lysine.Therefore,it is significant to improve the edible quality and nutritional quality of wheat noodles.In this study,wheat gluten as the object to explore the effects and mechanisms of egg white powder combined with heat induction treatment on gel properties and in vitro digestion characteristics of wheat gluten.And then wheat noodles as the research object to investigate the effects of egg white powder addition level on the edible quality and nutritional quality of wheat noodles.It will provide theoretical support for the application of egg white powder in non-fermented flour products through revealing the dose-effect relationship between egg white powder addition level and edible quality and nutritional quality.The main research contents and conclusions are as follows:（1）The effects of the egg white powder amounts on the gel properties and molecular structure of heat-induced wheat gluten was studied,and the molecular mechanism between egg white protein and wheat gluten under heat-induced conditions was revealed.The results showed that the addition of egg white powder significantly improved the gel properties of heat-induced gluten（P<0.05）,and the gel strength of gluten–egg white protein significantly increased from 950 g to 3618 g when the gluten/egg white powder mass ratio increased from 10:1 to 10:4.Besides,T₂₁,T₂₂ and T₂₃ all showed a rapid decrease at first and then leveled off（P<0.05）.The results of correlation analysis showed that gel strength was positively correlated with the content of disulfide（S-S）bond andβ-sheet,while negatively correlated with surface hydrophobicity（H₀）,β-turn and grain size of glutenin macropolymer（GMP）.The results of interaction study showed that the contents ofω-gliadin,α-gliadin,γ-gliadin,low molecular weight glutenin subunit（LMW-GS）and high molecular weight glutenin subunit（HMW-GS）significantly decreased with increasing content of egg white protein added（P<0.05）.It is indicated that both gliadin and glutenin could bind to egg white protein,and the binding force between gliadin and egg white protein was mainly S-S bond,while the binding force between glutenin and egg white protein were mainly hydrophobic interaction and S-S bond.（2）The effects of heat induction time on the digestibility and conformation of gluten–egg white protein gels were investigated to reveal the interaction mechanism between egg white protein and wheat gluten under different heat induction time at the molecular level.The results showed that the digestibility of gluten–egg white protein gels went up at first and then decreased with the rise of heating time（0～30 min）,while increased rapidly at the beginning and then increased gradually with increasing mass ratio of gluten and egg white powder（10:1～10:4）.Besides,the interaction strength between gluten and egg white protein was enhanced when the heating time was longer than 10 min.The H₀,sulfhydryl content of gluten–egg white protein gels significantly decreased（P<0.05）,and S-S bond content significantly increased（P<0.05）.Meanwhile,β-turn significantly raised（P<0.05）,andβ-sheet significantly declined（P<0.05）,indicating that the structure of gluten became denser with the increase of heating time（10～30 min）,which inhibited the hydrolysis of protease.It could be found from the microstructure that the loose gluten structure was conducive to protease action,and then improved the digestion and hydrolysis rate of protein.However,the increase of heating time could promote the aggregation between proteins,and increase the density of network structure,which was not conducive to the digestion.（3）The effects of egg white powder addition on the edible quality（chewiness,elasticity,and hardness）and nutritional quality of noodles were investigated,and the correlation between egg white powder addition level and edible quality as well as nutritional quality were evaluated.The results showed that when the amount of egg white powder added was less than 3%,the tensile force of dough increased,but decreased when the amount was more than 3%,while the adhesive properties of dough decreased with the increase of the amount added.Besides,the addition of egg white powder significantly improved the chewiness（228.19 g·mm to 739.65 g·mm）,elasticity（23.57 g/mm to 32.43 g/mm）,and hardness（79.29 g to 338.60 g）of cooked noodles（P<0.05）.Moreover,the chewiness,elasticity,and hardness of noodles were positively correlated with the S-S bond content of gluten–egg white protein,but negatively correlated with H₀ andβ-turn（P<0.05）.The results of interaction analysis showed that gliadin and glutenin could bind to egg white protein instead of albumin and globulin.In addition,the supplementation of egg white powder could significantly improve the nutritional quality of cooked noodles.The amino acid content significantly increased with the rise of supplementation of egg white powder,especially Lys,which significantly increased from 6.90 mg/g protein to 17.90 mg/g protein（P<0.05）.Actually,the addition of 5%egg white powder can meet the daily needs of adults for Lys.