Analysis and study on the quality of wheat flour with different particle sizes of the same material EDITED BY: www.immy.cn
Analysis and study on the quality of wheat flour with different particle sizes of the same material EDITED BY: www.immy.cn
According to the fixed mechanical parameters, the front core mill system on the production line is pulverized to make three kinds of wheat flour with different particle sizes, so as to ensure that the grain size of the wheat flour sold on the market is within the particle size range of the experimental powder.
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The physicochemical indexes, rheological properties, gelatinization properties and texture properties (dough softness) were studied, the relationship between grain size and the physical and chemical indexes of wheat flour was analyzed, and the differences in the texture characteristics of wheat flour dough with different grain sizes were explored over time, and the influence of grain size on the cooking quality of wheat flour was explored. The experimental results show that some physical and chemical indexes of wheat flour with different grain sizes show obvious changes and significant differences.
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The average particle size of wheat flour was significantly negatively correlated with damaged starch and R/E value, negatively correlated with whiteness, formation time and gelatinization temperature, and positively correlated with gluten index, falling value and peak viscosity. The texture characteristics of wheat flour dough (the degree of return to softness) increased with the decrease of particle size. The cooking quality also decreases with the decrease in particle size.
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Wheat flour particle size is an important parameter to measure the quality index of wheat flour, and the particle size of wheat flour is closely related to grinding strength, powder path, screen configuration, grinding roller speed and moisture conditioning in the process of grinding and sieving
[2]. There are many factors affecting the processing and production quality and sensory quality of steamed bread and noodles, and particle size is one of the most influential factors[3], by studying the influence of particle size on the physical and chemical indexes of wheat flour, as well as on the production and cooking quality of flour products, it can provide a theoretical and practical basis for flour processing enterprises to choose the appropriate grinding strength and milling process.
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1, Materials and methods
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1.3 Experimental Methods
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1.3.1 Preparation of wheat flour with different grain sizes
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10 kg of CM1 experimental flour was taken and crushed into two kinds of wheat flour with different particle sizes according to the fixed mechanical parameters by ultrafine pulverizer, which were named CM2 and CM3 respectively, and the finished product (Xirui Star Royal Kitchen Superfine Wheat Flour) was taken from the market, a total of 4 kinds of flour were used for later use.
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1.3.2 Determination of grain size of wheat flour
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According to GB/T 19077 particle size distribution laser diffraction method, the average particle size distribution of wheat flour with different particle sizes was determined by laser particle size distribution instrument.
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1.3.3 Determination of physical and chemical indicators
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According to national standards and industry standards, the ash, moisture, protein, wet gluten content and gluten index, whiteness and damaged starch of wheat flour with different particle sizes were detected.
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1.3.4 Determination of flour characteristics of wheat flour dough
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According to GB/T 14614 Determination of water absorption and rheological properties of wheat flour dough, the water absorption, dough formation time, stability (stability time) and weakening degree of wheat flour were measured by flour meter.
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1.3.5 Determination of tensile properties of wheat flour dough
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According to the tensile instrument method for determining the physical properties of wheat flour dough, water absorption and rheological properties of wheat flour dough, the energy, maximum tensile resistance, extensibility and R/E ratio of dough were measured by stretching instrument.
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1.3.6 Determination of gelatinizing properties of wheat flour dough
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According to the GB/T 14490 viscometer method for determining the gelatinization characteristics of grains and starch, the gelatinization temperature and peak viscosity of dough were measured.
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1.3.7 Operation and sensory evaluation of wheat flour steamed foods
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(1) Noodles. Refer to the method of LS/T 3202 Appendix A to make noodles. The ingredients are based on the quality of the flour and 36% water is added. The scoring criteria are shown in Table 1.
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Production process: weighing→ dough (5 min), tableting → pressing (12 times of dough pressing→, 6 sheets), cutting strips (1 mm thick, 2 mm wide) → boiling water for 3 min.
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(2) Steamed buns. Refer to the method of LS/T 3204 Appendix A to make steamed bread. The ingredients are based on the quality of flour, with 1% yeast and 48% water.
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Production process: weighing→ dough (5 min), forming →→ proofing (32°C, humidity 75%, about 40 min), steaming →with boiling water (25 min), → natural cooling.
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Production process: weighing→ dough and dough (5 min), → into a dough (repeatedly kneading and relaxing 4 times), → resting dough (covering with plastic wrap for 45 min), → dividing and rubbing strips (75 g/piece), → relaxing (covering with plastic wrap for 15 min), → drawing (repeatedly stretching and beating, folding in half 3 times), → boiling water and boiling noodles for 3 min.
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1.3.8 Data Processing and Analysis
SPSS 26 and Origin 2019 were used to analyze the variance and plot the data, and the significance analysis was performed at the detection level of P<0.05, and all the data were the results of three parallel experiments.
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2, Results & Discussion
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2.1 Particle size distribution of wheat flour with different grain sizes
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It can be seen from Fig. 1 and Table 4 that with the increase of crushing strength, the particle size distribution of wheat flour gradually shifted to the left, and the average particle size and median size became smaller. Among them, the particle size of Xirui Star Royal Kitchen Super Refined Wheat Flour was distributed in the middle of the experimental flour particle size.
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2.2 Analysis of physicochemical indexes of wheat flour with different grain sizes.
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The statistical analysis of other physical and chemical detection indexes of wheat flour samples with different particle sizes is shown in Fig. 2 and Fig. 3. As shown in the figure, some of the physical and chemical characteristics of the samples are different to varying degrees. Whiteness is one of the most intuitive ways for users and consumers to judge the purchase of flour products.
It can be seen from Figure 2 that particle size has a significant effect on damaged starch, generally speaking, wheat flour contains a small amount or an appropriate amount of damaged starch, and the processed flour products have good chewiness and toughness, and high eating quality. The damaged starch granules have higher water absorption than the natural starch granules and are more easily hydrolyzed by amylase, while the excess damaged starch will adversely affect the rheological properties and texture properties of the dough, and reduce the edible quality of the dough products.
As shown in Figure 2, the whiteness and damaged starch content of wheat flour increased with the decrease of particle size, which was due to the fact that with the increase of grinding strength, the particle size decreased, the large endosperm particles were further destroyed, and the reflective effect of wheat flour particles became stronger, so the whiteness value and damaged starch content increased, which was consistent with the results of Sun Lingling et al. [6].
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As can be seen from Figure 3, the gluten index and drop value decreased significantly as the grain size of wheat flour decreased. The gluten index can make the rheological properties of various wheat flours different, affect the balance and stability between dough elasticity and ductility, and then affect the processing technology and production operability of wheat flour. Due to the grinding operation, the damage degree of endosperm particles increased, and the continuous integrity of wet gluten was damaged to a certain extent, and the gluten index was reduced after centrifugal weighing, which affected the gluten network structure of wheat dough. At the same time, the sensitivity of damaged starch in wheat flour to amylase was higher than that of natural starch, and it was easier to be affected by amylase to form reducing sugars and dextrin, so the degradation rate was accelerated, indicating that the falling value decreased with the decrease of particle size.
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2.3 Analysis of flour characteristics of wheat flour with different grain sizes
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The flour characteristics of wheat flour are important indicators reflecting the rheological properties of dough, which are closely related to the quality of flour products, and the flour characteristics of wheat flour with different particle sizes are shown in Fig. 4 and Fig. 5. Among them, the water absorption was related to the protein content and the damaged starch content in wheat flour, which had a significant impact on the quality of flour products, and the particle size and water absorption showed an inverse change, which indicated that the total surface area of wheat flour increased with the decrease of grain size, and the water absorption increased. The degree of weakening is affected by the speed of stirring and is related to the gluten strength of the dough, and it can be seen from Figure 4 that the degree of weakening of wheat flour with different grain sizes increases slightly with the decrease of grain size, but the difference is not significant.
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The formation time and stabilization time represent the elasticity of the dough and the gluten strength, the kneading resistance of the dough and the strength of the gluten [7], respectively, with the decrease of the grain size of wheat flour, the formation time is gradually extended, and the stabilization time does not change significantly, the analysis is that the grain size of wheat flour becomes smaller, the water absorption process of the particles is prolonged, and the flour clumps become slower, which will lead to the reduction of the industrial production efficiency of food.
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2.4 Analysis of tensile characteristics of wheat flour with different grain sizes
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The tensile properties of wheat flour can directly reflect the quality of the dough and provide guidance for the processing of wheat flour and the preparation of flour products. Among them, the energy can reflect the gluten strength of the dough, the extensibility reflects the transverse ductility of the dough, the tensile resistance represents the elasticity of the dough, the R/E tensile ratio represents the balance between the strength and extensibility of the dough, and the smaller the ratio, the stronger the dough has strong viscosity, ductility and higher adhesion [8]. It can be seen from Table 6 that the energy, extensibility and maximum tensile resistance have increased and decreased, and there is no obvious regularity in the trend of change over time.
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The R/E ratio showed a consistent upward trend, as shown in Figure 6, which indicated that with the decrease of wheat flour grain size, the increase of maximum tensile resistance was greater than that of ductility, and the ratio of elasticity to extensibility of dough was increasing.
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2.5 Analysis of gelatinization characteristics of wheat flour with different grain sizes
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The essence of starch gelatinization is to break hydrogen bonds, that is, to break the intermolecular bonds of starch in crystalline and amorphous forms in starch, and complete the gelatinization of starch under the synergistic action of heating and endogenous amylase. Among them, the gelatinization temperature reflects the difficulty of gelatinization of wheat flour, the peak viscosity reflects the amylase activity of wheat flour, and the lowest viscosity reflects the content of amylose in wheat flour [9]. As shown in Figure 7, with the decrease of wheat flour particle size, the peak viscosity and minimum viscosity of wheat flour decreased, which may be due to the fact that wheat flour with small particle size has higher damage starch content, strong binding ability with water molecules, and relatively easy to break intermolecular hydrogen bonds, which adversely affects the peak viscosity of wheat flour, thereby reducing the peak viscosity. The gelatinization temperature is the opposite, which may be due to the fact that as the particle size decreases, the natural starch in wheat flour is converted into small molecule damaged starch and protein fragments through high-intensity commination, which increases the water absorption and promotes gelatinization, resulting in a small increase in temperature [10].
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2.6 Correlation analysis between particle size and physicochemical characteristics, rheology and gelatinization characteristics of wheat flour
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The correlation between the grain size of wheat flour and physicochemical indexes, rheology and gelatinization properties was analyzed by using the volume average grain size of three kinds of wheat flour with different particle sizes as the particle size characteristic values, as shown in Table 7. The results showed that the average particle size of wheat flour was negatively correlated with damaged starch and R/E value (r=-1.000, r=-1.000, P<0.01). There was a significant negative correlation with whiteness, formation time and gelatinization temperature (r=-0.994, r=-0.990, r=-0.990, P<0.05). It was significantly positively correlated with gluten index, falling value and peak viscosity (r=0.998, r=0.997, r=0.999, P<0.05).
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2.7 Analysis of dough texture characteristics of wheat flour with different grain sizes (how fast or slow the dough returns to softness).
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By studying the change of dough texture characteristics with time, the softness of wheat flour dough can be corresponded, and the results are shown in Figure 8, the softness of wheat flour dough with different grain sizes increases with the decrease of grain size. After standing for more than 6 h, the dough hardness tended to decrease slightly. With the extension of time, the hardness of the dough gradually decreases, which may be because the combination of moisture and starch and protein in the dough during the standing process is more fully extended over time, forming a three-dimensional network structure with macromolecular particles such as protein and starch as the main framework, and the water embedded in it. With the increase of crushing strength, the structure of gluten protein and starch is destroyed, the content of damaged starch increases, the water absorption performance is enhanced, it is easier to return to softness, and the viscosity of the dough increases, so the degree of softness of wheat flour dough increases with the decrease of particle size. The characteristics of the dough returning to softening are a key indicator for the end users of dough products, especially in the high temperature season, users hope that fresh noodles, pulled noodles, pulled noodles, ramen noodles and stewed noodles and other raw and wet noodle products can not return to softening too quickly, which is not conducive to the operation of the master and the storage and sales of raw and wet noodle products.
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2.8 Sensory evaluation and analysis of wheat flour flour products
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(1) Fresh noodles. The sensory evaluation results of fresh noodles are shown in Table 8, and it can be seen that different particle sizes of wheat flour have an effect on the color, appearance, palatability, elasticity and taste of fresh noodles. Among them, CM1 had better palatability, smoothness, elasticity and taste, and the total score was also the highest. The color of CM2 is better, and the performance is average in other aspects; CM3 has a fast gray color return, poor palatability, smoothness, elasticity and taste, and the total score is the lowest. With the decrease of particle size, the sensory score of noodles decreased, mainly due to unfavorable factors such as the increase of damaged starch, the increase of weakening degree, and the deterioration of stretching index.
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conclusion
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In this experiment, the changes of physicochemical indexes, rheological properties, gelatinization properties and texture properties of wheat flour under different particle sizes of the same material were explored. Through the correlation between particle size and the physical and chemical indexes of wheat flour, the difference of dough texture characteristics with time, and the influence of particle size on the operation of wheat flour flour products and cooked food quality, the differences in wheat flour quality with different grain sizes were analyzed, in order to provide practical suggestions for the milling process of food enterprises. The conclusion of the experiment is as follows:
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(1) There were significant differences in some physical and chemical indexes of wheat flour with different grain sizes of the same ash content. According to the correlation analysis between the characteristic value of grain size and the physicochemical and quality indexes of wheat flour, the average particle size of wheat flour was significantly negatively correlated with damaged starch and R/E value (r=-1.000, r=-1.000, P<0.01). There was a significant negative correlation with whiteness, formation time and gelatinization temperature (r=-0.994, r=-0.990, r=-0.990, P<0.05). It was significantly positively correlated with gluten index, falling value and peak viscosity (r=0.998, r=0.997, r=0.999, P<0.05).
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(2) According to the comparison results of wheat flour dough texture characteristics, the softness of dough increased with the decrease of particle size. According to this conclusion, under the condition that the wheat formula remains unchanged (without increasing the cost), the milling process can be adjusted, the grinding intensity can be reduced, and the average particle size of wheat flour can be increased, so as to improve the defects of wheat flour products in the use of end users in the market (especially in the high temperature season), such as the dough returns to softness quickly, the gluten strength deteriorates and is not easy to operate.
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(3) According to the cooking scores of the three most common flour products of wheat flour, the larger the particle size of wheat flour with different grain sizes of the same material, the better operation and cooking characteristics of fresh noodles, steamed bread and pulled noodles.
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