Studies Of Preparation And Quality Characteristics Of Whole Wheat Flour

In order to study the impacts of different preparation methods on the quality of the wholewheat flour, this experiment used the red wheat (middle gluten), white wheat (weak gluten)and Canada-wheat (strong gluten) as raw materials to get whole wheat flour. The processingmethod including whole grain crushing which means hammer mill (HM), stone (SM),ultrafine grinding (UM), and bran add-back processing including bran extruded micro puffedback Tim (RME), heat treatment back Tim (RMR), hammermill crushed back Tim (RMH) andultrafine grinding back Tim (RMU). And then roll grinding flour (F) was used as a controlgroup. Gluten quality, Falling number value, Protein content, pasting properties of flour,dough rheological properties and apparent characteristics, powder characteristics and qualityof bread made by whole wheat flour produced in different ways are determined. And therelationships among the indexes are analyzed. The results indicate:Whole wheat flour prepared by whole grain crushing process got a significant moistureloss. There is no significant difference (p>0.05) in crude protein content among whole wheatflour prepared with different processes. There were significant differences in α-amylaseactivity aomong all types of wheat, with that of white wheat flour being the highest. Wheattypes and processing methods have a significant impact on pasting properties of whole wheatflour. In case of different processing methods, the process of whole grain crushing bran hadmore significant effects than that of bran pretreated. There were highly significant positivecorrelation (r=0.837) between water absorption and crude protein content of whole wheatflour, with HM of white wheat being the smallest and SM of Canada wheat being themaximum. The formation time of the whole wheat flour dough and gluten index showed asignificant positive correlation (r=0.477), in the range of4.2~11.7min; the CV of29.0%;and the shortest is HM of white wheat; while the longest is RMH of Canada wheat. Thespecific surface area of the whole wheat flour particles can be positively correlated to with thesettling time, falling number and gluten index between2~16.4min; the CV is54.4%; theshortest is RME of white wheat; the longest is SM of Canada-wheat. Therefore, theappropriate processing methods can improve the Farinograp characteristics of whole wheatflour. For red wheat, white wheat and Canada-wheat, the stabilization time of whole wheatflour obtained from UM, RMH and RMH are higher, the degree of softening are lower, and Farinograp quality index are greater, respectively.The bran speck of whole wheat flour is significantly higher than the flour which leads toan increase in pigment, CGV value, a*value and b*value while a decrease in L value. Thesefactors make the whole wheat flour significantly greater than the flour in chromaticity. Themethod of preparation can change the colour and lustre of whole wheat flour. Thechromaticity of HM is higher than other methods and ultrafine grinding technology (UM,RMU) significantly increased the number of whole wheat bran speck spots (p <0.05).However, it reduced the chromaticity, especially in white wheat RMU. The particle sizedistribution range of whole grain crushing system is smaller than that of bran add-backprocess in whole wheat flour, especially in UM. The flow of the whole wheat flour propertieswas not good. Whole wheat flour from different wheat varieties showed significant differencein their liquidity. The whole wheat flour liquidity of Canada-wheat is strongest. Moreover, theliquidity of the flour is stronger than the whole wheat flour. Different processing methods hadno significant influences on the liquidity whole wheat flour. Flour has quite strong jets, butwhole wheat flour only shows inclined jets characters.The Chinese bread of whole wheat flour obtained from bran pretreatment and reuse hadlarger height/diameter ratio, specific volume than that from whole grain crushing system, withthe RMU sample being the best. Ultrafine grinding process improved the color of whole wheatflour and its bread, with the white wheat RMU being most significant. The texture differencesof steamed bread between whole wheat flour and flour are significant. The steamed bread ofwhole wheat flour has fragrant wheat smell, especially in Canada-wheat steamed bread of HM.However, steamed bread of red wheat RMU owned the best comprehensive quality of sensoryevaluation.