Changes In The Conformation And Aggregation Of Wheat Bran Dietary Fibre-gluten System During Thermal Treatment

Wheat bran is an important by-product of wheat processing,which is rich in dietary fiber,and its development and application have been widely concerned.WBDF added to wheat flour is an effective mean to strengthen the nutritional quality of flour products,but WBDF will destroy the gluten network structure and deteriorate the quality of flour products,which limits its application.At present,the research at home and abroad mainly focuses on the influence of WBDF on gluten network structure and rheological properties of dough at room temperature,such as kneading and stirring,but the influence mechanism of WBDF on gluten in cooking stage is not perfect.Based on this,this paper explored the effects of different WBDF additions(0%,3%,6%,9%,12% and 15%)at different heat treatment temperatures(25℃,65℃,95℃,and 130℃)from four perspectives: WBDF-gluten,WBDF-glutenin,WBDF-gliadin and simulated dough(WBDF-gluten-starch),in order to provide a more comprehensive theoretical basis for the quality improvement of high-fiber flour products.The specific research contents and conclusions are as follows.Firstly,taking WBDF-gluten protein system as the research object,through its changes in dynamic rheology,thermal characteristics,molecular weight,protein molecular structure and microstructure,the effects of different dosage of WBDF on the conformation and aggregation behavior of gluten protein during heating were explored.The results showed that during heating(25℃-130℃),the addition of WBDF enhanced WBDF-gluten system’s tanδ,and it was positively correlated with the addition of WBDF,indicating that WBDF increased the viscidity of gluten system.At the same time,with the increase of WBDF content,the weight loss of WBDF-gluten system increased and the thermal degradation temperature decreased.At 130℃,the weight loss of WBDF-gluten at 9% addition increased by 3.2%,and the thermal degradation temperature decreased from 310.32℃ to 306.41℃,forming a looser gluten network structure.The results of molecular exclusion chromatography showed that WBDF weakened the aggregation ability of gluten at 25℃ and 60℃,and at high temperatures(95℃ and 130℃),low addition of WBDF could enhance the aggregation ability of gluten.During heating,WBDF increased the free sulfhydryl content of gluten system,decreased the ratio of α-helix to β-sheet and made the structure of WBDF-gluten looser.During the heating process,WBDF participated in the molecular force rearrangement of glutenin and gliadin.At25℃ and 60℃,WBDF enhanced the hydrophobic interaction between glutenin and gliadin,and weakened the hydrophobic interaction between the two systems at 95℃ and 130℃.In addition,the results show that the effect of WBDF on gluten under heat treatment is that it produces gluten and gliadin together,and the interaction between WBDF and gluten is stronger.Then,taking WBDF-glutenin and WBDF-gliadin systems as the research objects,through their changes in dynamic rheology,molecular weight and protein molecular structure,the effects of different amounts of WBDF on the conformation and aggregation behavior of gluten during heating were explored.The results showed that heating enhanced both WBDFglutenin system and WBDF-gliadin system,but the addition of WBDF increased their fluidity.WBDF-glutenin system’s tanδ basically increased with the increase of WBDF content,and WBDF-gliadin system’s tanδ increased at high content(more than 9%).The results of molecular exclusion chromatography show that during heat treatment,temperature will induce the aggregation and crosslinking of glutenin and gliadin,and excessive WBDF will destroy the aggregation of gluten components.With the increase of WBDF content,the free sulfhydryl content of WBDF-glutenin system and WBDF-gliadin system increased,and the surface hydrophobicity decreased.During the heating process,it was found that WBDF can enhance the hydrophobic interaction between gluten and gliadin at 25℃ and 60℃,and weaken the hydrophobic interaction between gluten and gliadin at 95℃ and 130℃.In addition,the effect of WBDF on gluten under heat treatment is that it produces gluten and gliadin together,and the interaction between WBDF and gluten is stronger.Finally,taking the simulated dough(WBDF-gluten-starch)as the research object,through its changes in dynamic rheology,texture characteristics and protein molecular structure,the effects of different amounts of WBDF on the conformation and aggregation behavior of the simulated dough during heating were explored.The results showed that the addition of starch made the gluten network structure soft and collapsed.During the heating process,the simulated dough tanδ increased at 60℃ and began to decrease after heating to 95℃,while the simulated dough containing WBDF showed an increasing trend at 130℃.At the same time,heating increases the hardness,cohesion and resilience of simulated dough,while the addition of WBDF decreases the hardness,cohesion and resilience of simulated dough.The free sulfhydryl group increased with the increase of temperature until it began to decrease at 130℃,and it was proportional to the amount added.At 60℃,WBDF will enhance the hydrogen bond interaction in the simulated dough system,while at 95℃ and 130℃,it will weaken the hydrogen bond interaction,and hydrophobic interaction also plays an important role in the formation of protein aggregates.PCA principal component analysis also proved that WBDF can weaken the network structure of gluten,and induce the conformation and aggregation characteristics of gluten molecules through covalent and non-covalent interaction.Therefore,at appropriate temperatures(such as 60℃ and 130℃),the quality of high-fiber flour products(WBDF > 9%)can be effectively regulated by using the structural changes of gluten.