Characteristics Of Wheat Brewer’s Spent Grain Treated By Sieving,Extrusion And Enzymatic Degradation And Its Effect On Cookie Quality

The by-products generated during the brewing process of cereals contain a variety of bioactive substances such as phenolic compounds,novel carbohydrates,carotenoids,amino acids,vitamins and minerals,which can be used as food processing aids and nutritional fortifiers.In this study,wheat brewer’s spent grain（WBSG）were used to investigate the physicochemical properties of different particle sizes of WBSG and their effects on the quality of cookies.The untreated WBSG was used as a control to study the effects of extrusion,enzymatic digestion and combined extrusion and enzymatic digestion on the improvement of the physicochemical properties of WBSG and the effects of modified WBSG on the dough characteristics and quality of cookies.The experimental results were as follows:（1）Five different particle sizes of WBSG were obtained by sieving treatment.with the decrease in particle size,the content of protein,fat and phenolics in WBSG increased and the antioxidant capacity increased significantly,but the content of ash,carbohydrate and insoluble dietary fibre decreased significantly.WBSG5（particle size less than 147μm）compared to WBSG1（particle size greater than 420μm）the content of protein,fat and phenolics The content of protein,fat and phenolics increased by 34.89%,136.13%and 14.28%respectively,while the content of ash and dietary fibre decreased by 33.74%and 30.01%respectively.As particle size decreased,WBSG brightness increased significantly,water holding properties increased significantly and oil holding properties decreased,with no significant difference in bulk density（P>0.05）.At a fixed WBSG addition of 10%,the phenolic content and antioxidant capacity of the crisp biscuits increased as the particle size of WBSG decreased,and the hardness showed a trend of first decreasing and then increasing.（2）The soluble dietary fiber（SDF）content,water solubility index and adsorption capacity of WBSG treated by extrusion,enzymatic digestion and combined extrusion and enzymatic digestion methods increased significantly,with the highest SDF content of 10.05g/100 g in the extrusion and enzymatic digestion group,the highest water retention capacity and swelling capacity of WBSG in the extrusion treatment group,and the highest adsorption capacity of nitrite and cholesterol in the extrusion and enzymatic digestion group.The highest adsorption capacity of nitrite and cholesterol was observed in the squeeze treated group.The phenolic content of WBSG decreased after the extrusion treatment,while the other treatments increased the phenolic content of WBSG,and its antioxidant capacity also showed a significant positive correlation with the phenolic content.The three treatments were able to disrupt the molecular polymerisation network structure of SDF,destroying its crystalline structure and transforming it into irregular and amorphous structures.The extrusion enzyme digestion group of SDF showed better thermodynamic properties,water and oil retention capacity,cholesterol and nitrite adsorption capacity and pancreatic lipase inhibition.（3）Using wheat flour as a control,extruded,enzymatically digested and extruded enzymatically digested combination treated WBSG were mixed with wheat flour at 10%addition each,resulting in dough with lower pasting properties（peak viscosity,grain viscosity,final viscosity）than the control group,The addition of WBSG reduced the dough extensibility and increased the wet gluten content of the dough;the addition of WBSG resulted in an increase in the adsorbed water content(A₂₂)in the dough and a shift of the transverse relaxation time(T₂₂)towards negative time;the addition of WBSG to the extrusion enzymatic digestion group increased the content of disulphide bonds and the proportion ofβ-folding in the dough,which had a negative effect on The best improvement in physicochemical,flavour quality and antioxidant properties of cookies was achieved.