Preparation,Functional Characteristics And Application In Biscuit Of Soluble Dietary Fibers From Wheat Bran

Baked foods,such as biscuits,are highly favored by all kinds of people,but their high sugar and fat content limit the choice of special people.In order to meet the consumer demand of various groups,domestic and foreign enterprises have made efforts to develop nutritional and health beneficial biscuits by using a variety of functional food raw materials.Soluble dietary fiber(SDF)has exhibited excellent physiological activities,such as lowering blood sugar,anti-oxidation,and anti-tumor,etc.Adding it into food can not only effectively enhance the quality of food,but also improve the functional characteristics of food products.As the main by-product of wheat processing,wheat bran is a good source of dietary fiber,which is rich in SDF.Therefore,in this project,the SDFs were extracted from wheat bran by using subcritical water extraction(SWE),citric acid assisted SWE(SWEC)and ultrasonic pretreatment-assisted SWEC(USWEC),and their physicochemical properties,structural characteristics and biological activities were investigated.Moreover,the process parameters of USWEC for extracting SDF were studied and optimized.On this basis,the effects of the amount of SDF from wheat bran on the functional characteristics and microstructures of the dough were discussed,and the optimum technological formula and baking parameters of the functional biscuits prepared by SDF were determined.The main conclusions are as follows:(1)Based on the physicochemical properties,structural characteristics and biological activities of SDFs from wheat bran,results showed that the SDF-? extracted by USWEC had a higher extraction yield(36.30%),total sugar content(82.90%),uronic acid content(7.41%),reducing sugar content(13.16%)and lower protein content(3.20%),molecular weight(65.2 kDa)and particle size(1.17 ?m),compared with SDF-I and SDF-II extracted by SWE and SWEC,respectively.SDF-I,SDF-II and SDF-? are all acidic heteropolysaccharides and composed of arabinose,xylose,glucose and galactose,showing the similar preliminary chemical structures and different microstructures.The SDF-? showed a higher thermal stability but a lower rheological property than that of SDF-I and SDF-II.Furthermore,the SDF-? possessed remarkable in vitro antioxidant activities and ?-amylase inhibitory activity in a concentration-dependent manner.(2)The effects of ultrasonic pretreatment power,citric acid/wheat bran liquid-to-solid ratio,SWE temperature and time on the extraction yield of SDF-? via USWEC were investigated by using single factor test combined with response surface methodology.Results showed that the maximum extraction yield of SDF-? was 41% ± 0.29% under the following optimal conditions: ultrasonic pretreatment power 195.2 W,citric acid/wheat bran liquid-to-solid ratio 39.1 mL/g,SWE temperature and time were 178.7 ? and 30 min,respectively.(3)The effects of the amount of SDF-? on the functional characteristics and microstructure of dough were studied.Results showed that the addition of SDF-? not only decreased the viscosity and regeneration value of the mixed powder and increased the gelatinization temperature,but also led to the reduction in hardness,recovery,adhesiveness and chewability of the dough and the increase in the adhesion and elasticity.However,there was no significant effect on the cohesion of the dough.With the increase of the amount of SDF-?,the time of elastic behavior of the dough became shorter and shorter,and the viscous behavior was progressively dominant.An appropriate amount(10%)of SDF-? can improve processing characteristics of the dough,but the excessive amount of SDF-? caused the ultra-dilution of gluten,leading to the gluten could not fully wrap the starch particles,deteriorating the characteristics of the dough,which was not conductive to the production and processing.(4)The effects of processing parameters including the amounts of butter,sugar,SDF-?,alkaline leavening agent and baking time on color,hardness and sensory of functional biscuits by single factor and orthogonal design experiments.Results showed that the functional biscuits prepared by SDF-? had good color,hardness and taste under the optimum formula as follows(100 g wheat flour): butter 30 g,SDF-? 10 g,leavening agent 1 g and sugar 20 g.At the same time,the baking temperature and time were set at 180 ? and 15 min,respectively.