Effect Of Sweet Potato Residue Flour On The Physico-chemical Properties Of Dough And The Quality Of Bread

In this paper,sweet potato residue flour and wheat flour were used as raw materials,studied the basic components、amino acids and minerals of sweet potato residue flour and wheat flour;physic-chemical properties、quality and flavor of sweet potato residue-wheat mixed dough and bread were analysis;the influence of modifier on sweet potato residue bread was studied,then compare the quality difference between sweet potato residue bread and commercially available bread during storage.The determined and analyzed results were as follows:（1）Particle size distribution and thermal analysis of wheat flour and sweet potato residue flour were studied,at the same time,water solubility index,expansion force,water holding capacity,oil holding capacity,color,farinograph characteristics and gelatinization characteristics of sweet potato residue-wheat mixed powder were studied.The conclusion is as follows:when the volume fraction of wheat flour and sweet potato residue flour reaches 10%,the particle size of the two powders is not much different;but when the volume fraction reaches 50%,the particle size of sweet potato residue flour is much larger than that of wheat flour;The diameter of wheat flour is mainly distributed in75～250μm and the particle size of sweet potato residue flour is mainly distributed in250～500μm.The T₀,Tp,Te of wheat flour are lower than sweet potato residue flour.As the proportion of sweet potato residue gradually increases,the water solubility index,expansion force,water holding capacity and oil holding capacity are gradually increasing,L*is gradually decreasing,a*and b*are gradually increasing.When the proportion of sweet potato residue flour was 3%,the water absorption and stabilization time were not significantly different from those of the control group.Then,with the increase of the addition ratio,the water absorption increased significantly and the stabilization time decreased significantly.The formation time decreased significantly as the proportion of sweet potato residue flour increased.When the proportion of sweet potato residue flour is between 0%and 15%,the peak viscosity of the mixed powder increases and the gelatinization temperature decreases.（2）The basic components,amino acids and mineral content of sweet potato residue flour and wheat flour were studied.The results showed that there were significant differences in the contents of water,ash,protein,fat,total starch and dietary fiber between sweet potato residue flour and wheat flour（p<0.05）;the dietary fiber content of sweet potato residue flour was 20.0%,which was more than 6 times that of wheat flour;The sweet potato residue flour is equivalent to the total starch content of wheat flour.The protein content of sweet potato residue flour is only 1/6 of that of wheat flour,and the fat content is about 1/2 of that of wheat flour.The polyphenol content of sweet potato residue flour is 1.39±0.01 mg/g and anthocyanin content is 1.38 mg/g.A total of 16 amino acids were detected in sweet potato residue powder,including 7 essential amino acids（EAA）,1 semi-essential amino acid,8 non-essential amino acids,and 47%of essential amino acids,which is greater than the FAO/WAO standard model（36%）.The first limiting amino acids of wheat flour and sweet potato residue flour are lysine（1.76 mg/g）and methionine+cysteine（0.20 mg/g）.The content of macronutrients and trace elements in wheat flour and sweet potato residue flour is significantly different.The potassium in most elements is the most abundant,and the iron in trace elements is the most abundant.The contents of calcium,magnesium and sodium in sweet potato residue powder are350.39,92.2 and 49.75 mg/100g,respectively.The contents of copper,zinc and selenium were 201.67,320.72 and 3.34μg/100 g,respectively.（3）To study the effect of sweet potato residue flour on wheat flour gluten content,dough extensibility,microstructure,bread quality and flavor.The results showed that with the increase of sweet potato residue flour ratio,wet gluten and dry gluten gradually decreased,and the dough stretched.The maximum force was significantly changed（p<0.05）.When the addition amount was 3%,the maximum tensile force increased,and then the proportion of sweet potato residue flour was increased,and the maximum tensile force was first decreased and then increased.The SEM test results of each sample were as follows:when the ratio of sweet potato residue flour was 0 and 3%,the structure of the gluten network had good continuity.When the proportion of sweet potato residue flour was 6%,the gluten network structure began to break and large holes appear.With the increase of the proportion of sweet potato residue flour,the hardness and chewiness of the bread increased significantly（p<0.05）,and the elasticity did not change significantly（p>0.05）.When the sweet potato residue powder was less than 15%,the cohesiveness was not significant.（p>0.05）change,when the 15%reached,the cohesiveness decreased significantly（p<0.05）.As the proportion of sweet potato residue flour increased gradually,L*decreased significantly（p<0.05）,a*,b*increased significantly（p<0.05）,and the p H of the bread gradually decreased.When the proportion of sweet potato residue flour is 3%,the overall structure and pore structure of the bread is similar to the blank.When the proportion of sweet potato residue flour is 6%,the pores become larger.When the proportion of sweet potato residue flour is more than 9%,the pores become a large number of small pores.The results of electronic nose and electronic tongue showed that the bread containing 9%sweet potato residue flour and the blank group bread had significant differences in flavor,and there was no significant difference in taste;GC-MS results showed that the aldehydes,ketone species increase and the flavor increases of sweet potato residue bread were compared with wheat bread.（4）Analyze the effects of different concentrations of different additives on the quality of sweet potato residue bread.The results are as follows:the bread improver and CMC concentration are positively correlated with the height,and the height increases with the increase of the concentration.The bread height gradually decrease,with the gelatin concentration increases.while bread height increases when XG concentration is0.5%,but when XG concentration is more than 0.5%,bread height decrease.Similarly,the height of bread increases when the SSL concentration is less than 0.7%.Bread improvers and CMC have a positive effect on the texture of the bread.As the concentration increases,the bread hardness decreases and the chewiness decreases.The effect of xanthan gum on the texture of bread is strongly related to the concentration.When the concentration is less than 0.5%,the hardness and chewiness are reduced.When the concentration is more than 0.5%,the hardness and chewiness are improved.Gelatin reduces the hardness of the bread,but the hardness increases with increasing concentration in the range of 0.5%to 2.0%.Adding SSL can reduce the hardness of the bread.As the proportion of XG increased,the area ratio of bread hole increased.The addition of CMC increased the area ratio of the pore area.The addition of SSL and modifier had a positive effect on the area ratio of the bread area,and the area ratio of the pore area increased with the increase of the concentration.The D-optimal mixing design showed the optimum additive usage:0.900%for modifier,0.130%for SSL,0.47%for gelatin.（5）Compare the quality differences between milk toast,miscellaneous grains toast and sweet potato residue bread during storage period（0,1,3,5 days）.The result is as follows:The T₀,T_p,and T_e of sweet potato residue bread are all lower compared with milk toast and miscellaneous grains toast.the moisture content of the three kinds of bread is almost the same at 0 days,but on the 3rd and 5th,the moisture loss of the sweet potato residue bread is large;The peak times of T₂₂ and T₂₃ of the three types of bread move toward a shorter relaxation time as the storage time increases.