| Highland barley(Hordeum vulgare L.var.nudum Hook.f.)is a cereal crop in the barley genus of the Gramineae family,with the nutritional characteristics of "three highs and two lows".Adding highland barley flour to bread is of great significance for maintaining human health and preventing chronic diseases due to its high dietary fiber content.However,compared to wheat,highland barley has larger grains,lower gluten protein content,and a poor gluten network structure in the dough,which limits its addition in baking products.Therefore,in order to improve the quality characteristics of highland barley bread,this article studied the physicochemical and processing characteristics of highland barley flour with different particle sizes,and compounded highland barley flour with wheat flour to study the effect of highland barley flour addition on the dough characteristics and bread quality of highland barley wheat mixed flour;At the same time,different quality improvers were used to improve the quality of highland barley-wheat bread,and the effects of the amount of highland barley flour added and different improvers on the in vitro digestion characteristics of highland barley bread starch were discussed.The main research results obtained are as follows:(1)The study on the physicochemical and processing characteristics of highland barley flour with different particle sizes(80 mesh,100 mesh,120 mesh,140 mesh)by sieving found that as the grain size of highland barley flour decreased,the contents of fat,protein,starch,and amylose significantly increased(p < 0.05),while the moisture content did not change significantly.The brightness value and total color difference of the color difference Δ E significantly increased(p < 0.05),which increased by 9.07%,11.15%,and 34.99% compared to the L * value of 80 mesh,respectively.In addition,the water-holding capacity,oil-holding capacity,and swelling power of highland barley flour significantly decreased with the decrease of average particle size(p < 0.05),and the freeze-thaw stability of the paste showed a trend of first decreasing and then increasing.The transparency of the 120 mesh paste was the highest,while the transparency and stability of the 100 mesh paste were the best.The sedimentation ability of highland barley flour with different particle sizes decreased with the extension of storage time,and the sedimentation ability of the 80 mesh paste was the best.The enthalpy value of highland barley flour decreased without any structural changes.(2)The study on the effect of adding highland barley flour on the characteristics of highland barley-wheat mixed flour dough and bread quality showed that with the increase in the amount of added highland barley flour,the hardness and chewiness of highland barleywheat dough increased by 90.68% and 89.47%,respectively,compared to the control group;The wet gluten content significantly decreased(p < 0.05)by 39.48%;The specific volume of highland barley-wheat bread decreased by 22.54%;The organization,shape,and odor of bread decrease,and the overall sensory score of bread decreases.Adding highland barley flour can significantly increase the hardness and chewiness of bread(p < 0.05).Through the study of the starch digestion characteristics of barley wheat bread,it was found that the addition of barley flour reduced the starch digestibility of barley wheat bread,decreased the content of Rapidly digestible starch(RDS),and increased the content of Resistant starch(RS)and estimated Glycemic index(e GI).(3)The effects of three quality improvers,namely,Hydroxypropyl methyl cellulose(HPMC),Sodium stearoyl lactate(SSL),and Transglutaminase(TG),on the characteristics of highland barley-wheat dough and bread quality were studied.It was found that with the increase of HPMC,SSL,and TG,the free sulfhydryl content of highland barley-wheat dough decreased first and then increased;Dough β-sheet significantly increased(p < 0.05),the relative content of random coil significantly decreased(p < 0.05),and the secondary structure of the protein was more stable;The hardness and chewiness of highland barleywheat bread showed a trend of first decreasing and then increasing,while the specific volume,elasticity,and sensory scores showed a trend of first increasing and then decreasing;Scanning electron microscope images showed that the gluten network structure of highland barley-wheat dough was enhanced,and the optimal amount of HPMC was 1.25%.At this time,the specific volume increased by 23.56%,and the hardness and chewability decreased by 61.83% and 42.92% respectively;The optimal amount of SSL is 0.20%,at which time the specific volume increases by 35.99%,and the hardness and chewability decrease by60.33% and 40.68% respectively;The optimum content of TG is 0.015%,at which time the specific volume increases by 16.44%,and the hardness and chewability decrease by 41.42%and 12.46% respectively.Adding HPMC and TG can reduce the in vitro digestibility of bread,decrease the content of RDS,and increase the content of slow digestible starch(SDS)and e GI value.Adding SSL increases the RDS content and e GI value of bread,but adding SSL does not reduce the in vitro digestibility of bread.(4)The response surface method was used to optimize the composition of highland barley-wheat bread improver.The optimal combination was HPMC1.15%,SSL0.20%,TG0.015%.Compared with highland barley bread,the hardness and chewability of the bread were reduced by 61.99%,46.15%,and the specific volume was increased by 23.20%.The quality of the bread under this optimized condition was the best.The addition of quality improver increased the content and type of volatile flavor substances in highland barleywheat bread,especially the content of alcohols and alkanes.Compared with the control group,the compound highland barley-wheat bread also produced ethyl octanoate,laurene α-Terpinene and other new substances not detected in highland barley-wheat bread indicate that the compound highland barley-wheat bread can also improve the flavor of bread. |
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