The Effect of Different Grinding Methods on the Quality of Wheat Flour

As a food base, there are many types of wheat that can be processed, but due to the inherent characteristics of wheat, the milling process is complicated and difficult. The application of mechanical crushing and air flow classification to wheat milling is undoubtedly a new and highly efficient process. The effect of mechanical crushing on the quality of wheat flour and its processing characteristics is worthy of careful research and demonstration. At the same time, analyzing the functional properties of the main components of wheat will help to open up the ideas of wheat food processing. In this study, wheat flour was used as a reference to analyze and study the similarities and differences between the quality characteristics of wheat flour prepared by mechanical comminution and its processing characteristics and common wheat flour, and the feasibility and application of laboratory comminution milling method applied to wheat milling were verified. Effect of Wheat Whole Powder Quality Characteristics.
The instruments needed during the experiment: Kjeldahl (Zhejiang Top Instrument Co., Ltd.); Ultraviolet spectrophotometer; Farinograph; Stretcher; laboratory grinding mill; Sulfuric acid, potassium sulfate, copper sulfate, boric acid , Sodium hydroxide, etc. are all analytically pure. Wheat starch extraction process: Wheat flour was sieved through 100 mesh, soaked in alkali water with a ratio of material to water of 1:12 plus pH = 11 for 15 minutes. Centrifugal separation was performed. The residue was filtered and dried to obtain wheat starch.
Experimental procedure: Determination of blue value: Accurately weigh 1mg of starch and prepare a solution, in which iodine 2mg, potassium iodate 20mg, constant volume to 100mL. The absorbance of this solution at a wavelength of 680 nm was measured. Determination of transparency: Weigh 1g of starch, adjust it into 1% of starch milk, measure 50mL of it into a 100mL beaker, place in a boiling water bath and stir with heat for 15min, cool to 25°C, and measure the transmittance at 620nm wavelength. That is transparency. Freeze-thaw stability measurement: Weigh the quantitative starch into a mass fraction of 6% of the starch paste, heat and stir in a boiling water bath for 15 minutes, and cool to room temperature. Weigh a certain amount of starch paste into a centrifuge tube, place it in a refrigerator at -20 to -18°C overnight, and take it out and thawed at room temperature. Centrifuge at 3000 r/min for 15 min and discard the supernatant. Weigh the quality of the sediment and calculate the rate of precipitation. If water does not precipitate, continue freezing until water is deposited.

Table 1 Basic chemical composition of two powder samples

Test and analysis of processing performance of wheat flour: determination of water absorption of flour and kneading properties of dough (flour analyzer method): GB/T14614-93 ISO5530-1-1988. Determination of dough tensile properties: GB/T14615-93. The determination and analysis of the basic composition of the two types of wheat flour: It was determined that the contents of various chemical constituents of the two types of wheat flour are quite different. The data are shown in Table 1. The main reason is that: the laboratory grinding and grinding method directly crushed the whole grain wheat. Therefore, after the wheat peel is crushed, it is all mixed in and causes changes in the content of several components in the flour: including the increase of protein, fat, cellulose and ash content . Obviously, the test results are consistent with the actual situation, namely: the wheat cortical structure (mainly aleurone layer) is rich in protein, fat, cellulose, trace elements and ash. After the common wheat flour prepared by the traditional grinding process is mechanically sieved, almost all cortical tissues are removed as bran, which is a loss and waste of resources.
Physicochemical properties of wheat flour extracted starch: The amount of free starch is an important indicator to measure the quality of starch. Amylose has a higher degree of coloration, while amylopectin absorbs less than 1/10 of the amylose at the same concentration. Therefore, in the samples containing the same free starch, the blue value of the higher amylose content was correspondingly higher. The experimental data shows that the starch content in starch in common wheat flour is higher than that in mechanical milling wheat flour, but the difference is not significant. After starch gelatinization, the degree of molecular rearrangement and mutual association is an important factor affecting the transparency of the starch paste. The amylose starch first escapes from the starch granules during the gelatinization process, and molecular rearrangements and mutual associations easily occur. From the test results, it can be known that starch contained in ordinary wheat flour has low transparency, which may be due to the high content of amylose in the starch. After gelatinization, it is prone to ageing, resulting in gelation or retrogradation, making the transparency lower. Poor transparency will cause aging and affect processing characteristics. Freeze-thaw stability was calculated by freezing and thawing, and the water shrinkage rate of the starch paste was calculated to examine the phenomenon of the occurrence of syneresis. The mechanical starch crushing wheat flour has a high rate of starch precipitation, poor freeze-thaw stability, and is less suitable for making frozen food than the starch contained in ordinary wheat.

Table 2 Physical and Chemical Indexes of Starch in Two Kinds of Powder Samples

From the data of Table 1 and Table 2, it can be inferred that the starch content of common wheat flour is higher than that of mechanically pulverized wheat flour, and the freeze-thaw stability of starch is better than the latter, but the transparency is worse than the latter. The analysis of the rheological properties of dough using flour curves and tensile curves is mostly applied to dough made from wheat flour or powder made by adding a small amount of other food crops; however, the test and analysis of all kinds of coarse grains are almost Blank. In this experiment, dough rheological properties of wheat flour obtained by the two methods were analyzed by farinograph and tensile apparatus, and the differences in the processing characteristics of the two powders were initially compared to provide a reference for further study of the processing performance of various grain flours. The formation of gluten in wheat flour is the main reason for this difference. The rheological properties of dough made from common wheat flour are not stable, which may be related to the milling process and particle uniformity of the powder: the fineness and uniformity of the powder are poor, making the process of forming wheat flour dough unstable; and the laboratory The crushing mill crushes wheat flour with high fineness and good uniformity, so that the dough formation process tends to be stable. The silt curve diagram has a similarity with the wheat flour dough curve, and may have some similarities with wheat flour. Processing properties. The mechanism of the above phenomenon and the analysis of the rheological properties of various types of dough using the silty curve require further experimental research and analysis. The stretching curve of the dough formed by the two types of flour is completely different from the trend of the stretching curve of the wheat flour dough. The stretching curves of the two flours also show a great difference. The lack of elastic gluten in wheat flour is still the main reason. Both of them have smaller stretched area and poorer quality. The stretching of ordinary wheat flour dough is higher than that of mechanically crushed wheat flour dough, indicating that the latter has low resistance and large ductility, ie, small elasticity and large fluidity.
Milling in the laboratory enabled the utilization of wheat to reach almost 100%, which changed the proportion of the main components in wheat flour and improved the yield. The starch content in common wheat flour is higher than that contained in mechanically ground wheat flour. The freeze-thaw stability of starch is better than that of the latter, but the transparency is worse than the latter. Due to the lack of gliadin and glutenin in wheat flour, gluten quality cannot be formed and the dough rheological properties are greatly different from wheat dough. However, the better homogeneity of the mechanical comminution of the wheat flour makes the formation process of the dough more stable; the drawing of the tensile curve shows that the dough has small elasticity and high fluidity.

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