CN118285413A - Pre-gelatinized rice flour - Google Patents

Abstract

The invention relates to pregelatinized rice flour. The pregelatinized rice flour is prepared by the following method: the pregelatinized rice flour is prepared by the following method: mixing rice flour and water, and gelatinizing; the mesh number of the rice flour is 100-200 mesh, 200-300 mesh or 300-400 mesh; the temperature of the gelatinization treatment is between 50 and 70 ℃; the gelatinization treatment time is 15-25 min; the rice flour and water are mixed to form a mixture, and the water content of the mixture is between 60% and 70%. The pregelatinized rice flour prepared by the method has the advantages of large oil absorption, large water absorption index, large solubility, small hardness and the like, and can improve the texture characteristics and sensory scores of double-protein biscuits and reduce the baking loss rate after being used for preparing the biscuits.

Description

Pregelatinized rice flour

This invention is a divisional application. The original Chinese invention patent application number is: 202211368796.7, the application date is: November 3, 2022, and the name of the invention patent at the time of application is: A method for preparing pregelatinized rice flour and double protein biscuits.

Technical Field

The invention belongs to the technical field of food processing, and in particular relates to pregelatinized rice flour.

Background technique

my country's annual rice production reaches 180-200 million tons, and 15%-20% of broken rice will be produced during the processing. At present, broken rice cannot be fully and effectively utilized, and is mostly processed and used as feed. Through further research, it is found that the nutritional components of broken rice are not much different from those of ordinary rice, including starch, protein, trace elements, etc. Broken rice has the characteristics of high yield and low cost. If broken rice can be processed into food as raw material, it will be of great significance to fully utilize my country's rice resources and maximize the utilization of agricultural product resources.

Pregelatinized starch is a modified starch that is easy to process and widely used. It can be made into a paste with cold water, eliminating the trouble of heating and gelatinization. It is widely used in the fields of medicine, food, cosmetics, etc. The raw materials for preparing pregelatinized starch usually include corn, wheat, potatoes, and rice. The differences in the types of raw materials used to make pregelatinized starch and the differences in the production process lead to differences in the quality of pregelatinized starch. When it is further applied to baked foods, it will also affect the quality of the baked foods. Pregelatinized rice starch is a type of pregelatinized starch. It can be prepared using rice as a raw material through methods such as spraying and extrusion.

Soy protein isolate and whey protein isolate are exogenous proteins, and their introduction can increase the protein content of gluten-free biscuits. However, due to unreasonable formula and process, double protein biscuits with added soy protein isolate and whey protein isolate are prone to defects such as poor texture characteristics, low sensory scores, and high baking loss rate.

There is no report in the prior art on how to add pregelatinized rice starch prepared by what method into double protein biscuits to further improve the quality of rice biscuits.

Summary of the invention

In view of the problems existing in the prior art, the present invention provides a pregelatinized rice flour, a double protein biscuit and a preparation method thereof. A pregelatinized rice flour suitable for making double protein biscuits is provided, and the texture characteristics and sensory scores of the double protein biscuits are improved and the baking loss rate is reduced.

The technical solution of the present invention to solve the above technical problems is as follows:

The invention provides a method for preparing pre-gelatinized rice flour, comprising the following steps: mixing the rice flour and water and performing gelatinization treatment.

The mesh size of the rice flour is between 100-200 mesh, 200-300 mesh or 300-400 mesh, preferably, 200-300 mesh, and optimally, 192-200 mesh; the temperature of the gelatinization treatment is between 50-70° C., preferably, 58-60° C., and optimally, 58-59° C.; the time of the gelatinization treatment is between 15-25 min, and preferably, 20-21 min; the rice flour and water are mixed to form a mixture, and the water content of the mixture is between 60-70%, and preferably, 65-66%.

The beneficial effects of adopting the above technical solution include: the pregelatinized rice flour prepared by the above method has the advantages of high oil absorption capacity, high water absorption index, high solubility, low hardness, etc.

Furthermore, the rice flour is rice flour, preferably, broken rice flour, and pre-gelatinized rice flour can be prepared using broken rice as a raw material.

Furthermore, the broken rice is coarsely crushed and airflow-type ultrafinely crushed to prepare rice flour.

The invention uses broken rice as a raw material, prepares it into pregelatinized rice starch, and further applies it to baked food, for example, double protein biscuits with added soy protein isolate and whey protein isolate, thereby expanding the application scope of broken rice and having important significance for making full use of my country's rice resources and realizing the maximum utilization of agricultural product resources.

Furthermore, the pre-gelatinized rice flour is prepared by the following method: mixing rice flour and water to obtain a mixture, gelatinizing the mixture after the mixture is uniformly mixed, uniformly stirring, cooling, and crushing.

The invention provides pregelatinized rice flour, which is prepared by the method.

The beneficial effects of adopting the above technical solution include: the pregelatinized rice flour prepared by the above method has the advantages of high oil absorption capacity, high water absorption index, high solubility, low hardness, etc.

A method for preparing double protein biscuits comprises the following steps: using rice flour, soy protein isolate, whey protein isolate, butter and pre-gelatinized rice flour as main raw materials to prepare the double protein biscuits.

The beneficial effects of adopting the above technical solution include: the double protein biscuits prepared by the present invention have the advantages of good texture characteristics, high sensory score, low baking loss rate, etc.

Furthermore, the pregelatinized rice flour is prepared by the above method.

The beneficial effects of adopting the above technical scheme include: the pregelatinized rice flour prepared by the above method provided by the present invention is suitable for the preparation method of double protein biscuits, so that the double protein biscuits have the advantages of complete appearance, golden color, uniform texture, crisp taste, good brittleness, small hardness, good rice aroma, low baking loss rate, etc.

Further, the added amount of soy protein isolate is 7.5%-12.5%, preferably 9.5-9.6%, the added amount of whey protein isolate is 7.5%-12.5%, preferably 9.7-9.8%, the added amount of butter is 70%-90%, preferably 81-82%, and the added amount of pregelatinized rice flour is 5%-9%, preferably 7-8%.

The beneficial effects of adopting the above technical solution include: the appropriate amount of addition is conducive to ensuring that the biscuits obtain a higher sensory score, lower hardness and better crispness. If the soy protein isolate is excessive, there will be a beany smell and a bad taste. If the whey protein isolate is excessive, it will inhibit the binding between starch particles and weaken the starch network structure, resulting in a bad taste. If the amount of butter added is insufficient, the sensory score and crispness are low, the surface of the biscuits is dry, and the crispness and aroma are poor; excessive addition of butter will cause the internal structure of the biscuits to be too loose, produce larger holes, make it difficult to shape, have a soft and greasy taste, and have an overly strong aroma.

Furthermore, it also includes low-gluten flour, milk powder, milk, salt, egg liquid, and white sugar; the added amount of milk powder is 21%, the added amount of low-gluten flour is 50%, the added amount of milk is 30%, the added amount of salt is 0.1%, the added amount of egg liquid is 40%, and the added amount of white sugar is 30%.

The beneficial effects of adopting the above technical scheme include: the appropriate proportion is conducive to ensuring the quality of biscuits; the appropriate amount of milk powder added is conducive to the rice biscuits forming an attractive color and a strong milk flavor. If the amount added is too high, the rice biscuits will become hard and have a bad taste. If the amount added is too low, the rice biscuits will have an uneven color and a bad taste. The appropriate amount of low-gluten flour added is conducive to increasing the aroma, looseness and taste of the rice biscuits. If the amount added is too high, the rice biscuits will be soft and not crispy. If the amount added is too low, the rice biscuits will be too hard and have a low sensory score. The appropriate amount of milk powder added is conducive to increasing the aroma, looseness and taste of the rice biscuits. If the amount added is too high, the rice biscuits will be soft and not crispy. If the amount added is too low, the rice biscuits will be too hard and have a low sensory score. The amount of salt added is beneficial to increasing the color, taste and aroma of the rice biscuits. If the amount added is too high, the dough will be too sticky and not crispy. If the amount added is too low, the dough will be difficult to shape and the rice biscuits will be hard and cracked. The appropriate amount of salt added is beneficial to neutralizing the sweetness of the rice biscuits, and can also remove the fishy smell of the egg liquid, inhibit the reproduction of other bacteria, and extend the shelf life of the product. If the amount added is too high, the taste will be too salty and will not be easily accepted by the public. If the amount added is too low, the rice biscuits will be almost tasteless after eating and the internal structure will not be tight.

Further, the following steps are included:

(1) Mix the melted butter, egg liquid and white sugar and beat;

(2) adding rice flour, pregelatinized rice flour, low-gluten flour, soy protein isolate, whey protein isolate milk powder, milk, and salt, and mixing well to form a batter;

(3) After the batter is extruded and formed, it is baked.

The beneficial effects of adopting the above technical scheme include: through reasonable formula and process, the double protein biscuits prepared by the present invention have the advantages of complete appearance, golden color, uniform texture, crisp taste, good brittleness, small hardness, good rice fragrance, low baking loss rate, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the effect of mesh size on oil absorption, water absorption index, solubility and hardness of pregelatinized rice flour;

FIG2 shows the effect of gelatinization temperature on the oil absorption, water absorption index, solubility and hardness of pre-gelatinized rice flour;

FIG3 shows the effect of gelatinization time on oil absorption, water absorption index, solubility and hardness of pre-gelatinized rice flour;

FIG4 shows the effect of water content on oil absorption, water absorption index, solubility and hardness of pregelatinized rice flour;

Figure 5 is a contour plot and a response surface plot;

Fig. 6 is a scanning electron microscope image of rice starch, wherein A1 is the result of 1000× of rice starch, A2 is the result of 1000× of supermicron starch, A3 is the result of 1000× of pregelatinized rice starch, B1 is the result of 5000× of rice starch, B2 is the result of 5000× of supermicron starch, and B3 is the result of 5000× of pregelatinized rice starch;

Fig. 7 is a polarizing microscope image of rice starch, wherein C1 is rice starch under a natural light microscope, C2 is supermicron starch under a natural light microscope, C3 is pregelatinized rice starch under a natural light microscope, D1 is rice starch under a polarized light microscope, D2 is supermicron starch under a polarized light microscope, and D3 is pregelatinized rice starch under a polarized light microscope;

Figure 8 shows the particle size distribution of starch;

FIG9 shows the effect of the amount of soy protein isolate added on the sensory score, hardness and crispness of rice biscuits;

FIG10 is the effect of the amount of whey protein isolate added on the sensory score, hardness and crispness of rice biscuits;

Figure 11 shows the effect of butter addition on the sensory score, hardness and crispness of rice biscuits;

Figure 12 shows the effect of the amount of pregelatinized rice flour added on the sensory score, hardness and crispness of rice biscuits.

The vertical axes in Figures 1 to 4 are, from left to right, the vertical axes of oil absorption, water absorption index, solubility, and hardness. The vertical axes in Figures 9 to 12 are, from left to right, the vertical axes of sensory score, hardness, and brittleness.

Detailed ways

The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

The raw material used in the present invention can be rice, but in order to increase the added value of broken rice and expand the application of broken rice, pre-gelatinized rice flour can also be prepared with broken rice as raw material. The properties of broken rice flour are improved by using ultrafine grinding technology and pre-gelatinization technology, and the influence of water content, gelatinization temperature, time and mesh number on the quality of broken rice flour is studied, and the pre-gelatinized rice flour with better quality is optimized; the ultrafine and pre-gelatinization technology is used to detect the change of starch; two exogenous proteins are added to optimize the rice biscuit production process, and the influence of the addition amount of soy protein isolate, whey protein isolate, pre-gelatinized rice flour and butter on the sensory score and texture characteristics of rice biscuits is studied, and the rice biscuits with better quality are obtained; and the quality characteristics of different biscuits are further compared and analyzed, and the results show that the double protein biscuits prepared by the present invention have the advantages of complete appearance, golden color, uniform texture, crisp taste, good brittleness, small hardness, good rice fragrance, low baking loss rate, etc.

In the present invention, the experimental materials involved are as follows: broken rice, food grade, purchased from Heilongjiang Wuchang Jinhe Rice Industry Co., Ltd.; soy protein isolate, food grade, purchased from Guzhiwei Biotechnology Co., Ltd.; whey protein isolate, food grade, purchased from Guzhiwei Biotechnology Co., Ltd.; flour, food grade, purchased from Shandong Luhua (Yanjin) Flour Food Co., Ltd.; milk powder, food grade, purchased from Inner Mongolia Oushi Mengniu Dairy Co., Ltd.; butter, food grade, purchased from Mogu Industrial (Shanghai) Co., Ltd.

In the present invention, the experimental equipment involved is as follows: a high-speed multifunctional pulverizer, model DC-1500A, purchased from Zhejiang Wuyi Dingzang Daily Metal Manufacturing Factory; an ultrafine pulverizer, model ST-528, purchased from Ruian Saite Electromechanical Co., Ltd.; a texture analyzer, model TA.new p l us, purchased from I SENSO Company of the United States; a portable colorimeter, model NR200, purchased from Shanghai Yuanxi Instrument Co., Ltd.; an electric oven, model MG38CB-AA, purchased from Guangdong Midea Kitchen Appliance Manufacturing Co., Ltd.; an egg beater, model CX-206601, purchased from Zhongshan Canxin Electrical Appliance Products Co., Ltd.; an electronic balance, model LT2001 E, purchased from Changshu Tianliang Instrument Co., Ltd.

The following is an introduction through specific embodiments.

Example 1

1.1 Experimental methods:

The preparation of rice flour comprises the following steps: coarsely grinding broken rice to obtain coarsely ground rice flour, then airflow-type ultrafine grinding the coarsely ground rice flour to obtain ultramicron powder, and sieving out rice flour with mesh size of ≤100, 100< and ≤200, 200< and ≤300, 300< and ≤400, and 400< and ≤500. For the sake of convenience, the following descriptions are abbreviated to 0-100 mesh, 100-200 mesh, 200-300 mesh, 300-400 mesh, and 400-500 mesh, respectively.

The method for preparing pregelatinized rice flour comprises the following steps: mixing the rice flour prepared by the above method and distilled water in a beaker to obtain a mixture, placing the mixture in a water bath for pregelatinization after the mixture is evenly mixed, stirring the mixture evenly with a glass rod, taking out the completely gelatinized rice flour, cooling and crushing the mixture for later use.

The effects of different conditions on the quality of pregelatinized rice flour were investigated through single factor test and Box-Behnken experiment.

1.2 Index analysis and determination methods

(1) The method for determining texture properties includes the following steps: accurately weigh 2.5 g of sample and mix it with 9 mL of water to form a suspension. Heat and stir the mixture on a magnetic thermal stirrer for 1 min, transfer it to a beaker to make it evenly distributed, seal it, and continue gelatinization in a 95°C water bath for 30 min. After taking it out of the water bath, cool it and cool it at 4°C overnight. The TPA mode is used to determine the gel strength. The test probe is P/0.5R, the pre-test speed is 0.5 mm/s, the test speed is 5.0 mm/s, the compression distance is 10.0 mm, the trigger force is 5.0 g, and the compression interval is 2 s.

Texture scoring criteria: Texture score (100 points) = hardness (25 points) + elasticity (25 points) + cohesion (25 points) + adhesiveness (25 points). The scoring calculation method for elasticity, cohesion, and adhesiveness is as follows:

Where: A is the difference between the average value and the minimum value of the indicator; B is the difference between the maximum value and the minimum value of the indicator.

Among them, the hardness index is negatively correlated with other indexes, and its index scoring algorithm is as follows:

Where: C is the difference between the average and minimum hardness values; D is the difference between the maximum and minimum hardness values.

(2) The method for determining the water absorption index and solubility includes the following steps: weigh 2.5 g of sample and mix thoroughly with 30 mL of distilled water in a 50 mL centrifuge tube, keep in a 30°C water bath for 30 min, and then centrifuge at 4000 r/min for 20 min. The supernatant is transferred to a pre-dried and weighed aluminum box and dried at 105°C, and the mass of the precipitate in the centrifuge tube is weighed. The formulas are shown in 2-3 and 2-4.

Wherein: WAI is water absorption index, %; WS is solubility, %; _ms is the final precipitate mass, g; _mu is the dry matter mass in the supernatant, g; m is the mass of the sample, g.

The method for determining the oil absorption capacity comprises the following steps: accurately weigh 1 g of rice flour into a 50 mL centrifuge tube, add 20 mL of edible oil, let stand at room temperature for 1 hour, centrifuge at 3000 r/min for 10 minutes, discard the oil and residue on the upper layer, absorb the free oil with filter paper, and weigh. The formula is shown in 2-5.

(3) A comprehensive evaluation method for WAI, WS, oil absorption and texture of pregelatinized rice flour, comprising the following steps: using a weighted coefficient method, the weight of the water absorption index is set to 0.25, the weight of the solubility is set to 0.25, the weight of the oil absorption is set to 0.25, and the weight of the texture score is set to 0.25, and the sum of the coefficients is 1. Comprehensive score = WAI (0.25) + WS (0.25) + oil absorption (0.25) + texture score (0.25).

1.3 Data processing: Excel 2007 software was used to calculate WAI, WS, texture score and comprehensive score; DesignExpert software was used to process response surface data; and Organization 8.1 software was used for drawing.

1.4 Single factor experimental design and experimental results

The water content in this embodiment refers to the mass percentage of distilled water to the mixture in the step of mixing rice flour and distilled water in a beaker to prepare the mixture.

On the basis of gelatinization temperature of 50℃, time of 20min, mesh size of 200-300 mesh, change the level of each factor accordingly:

(1) Effect of mesh size on oil absorption, water absorption index, solubility and hardness of pregelatinized rice flour. The water content was 60%, the gelatinization temperature was 50°C, the gelatinization time was 20 min, and the mesh sizes were 0-100 mesh, 100-200 mesh, 200-300 mesh, 300-400 mesh, and 400-500 mesh to prepare pregelatinized rice flour. The hardness, water absorption index, solubility and oil absorption of the rice flour were measured as the evaluation indicators to study the effect of pregelatinization on the quality of rice flour.

As shown in Figure 1, as the mesh size increases, the oil absorption capacity and water absorption index show a trend of first increasing and then decreasing, the solubility shows an increasing trend, and the hardness shows a decreasing trend. The inventors speculate that this may be because when the mesh size is low, the starch rehydration rate is too fast, and a layer of paste is easily formed on the starch surface, and the starch inside cannot contact the water; when the mesh size is high, the rehydration rate will be too slow, affecting the quality of the starch. When the mesh size is 200-300 mesh, the oil absorption capacity and water absorption index are the largest. Considering the effect of pregelatinization on rice noodles, the mesh size is selected to be 200-300 mesh.

(2) Effect of gelatinization temperature on oil absorption, water absorption index, solubility and hardness of pregelatinized rice flour

Pre-gelatinized rice noodles were prepared with a moisture content of 60%, a gelatinization time of 20 min, a mesh size of 200-300 mesh, and a gelatinization temperature of 30°C, 40°C, 50°C, 60°C, and 70°C. The hardness, water absorption index, solubility, and oil absorption of the rice noodles were used as evaluation indicators to study the effect of pre-gelatinization on the quality of rice noodles.

As shown in Figure 2, as the gelatinization temperature increases, the oil absorption capacity, water absorption index and solubility all show a trend of first increasing and then decreasing, and the hardness shows a trend of first decreasing and then increasing. The inventors speculate that the reason may be that as the temperature of the starch granules continues to rise, the hydrogen bonds of the starch granule crystal ring layer are destroyed, the association state between starch molecules is destroyed, and the volume expands rapidly; the starch granule temperature further increases, more starch molecules gain energy and become free and dispersed free bodies, the breaking of hydrogen bonds between starch granule molecules and the melting of starch molecules make starch easier to be hydrolyzed by amylase. When the gelatinization temperature is 60°C, the oil absorption capacity, water absorption index and solubility are the largest, and the hardness is the smallest.

(3) Effect of gelatinization time on oil absorption, water absorption index, solubility and hardness of pregelatinized rice flour

Pregelatinized rice flour was prepared with a moisture content of 60%, a gelatinization temperature of 50°C, a mesh size of 200-300 mesh, and a gelatinization time of 10 min, 15 min, 20 min, 25 min, and 30 min. The hardness, water absorption index, solubility, and oil absorption of the rice flour were used as evaluation indicators to study the effect of pregelatinization on the quality of rice flour.

As shown in Figure 3, as the gelatinization time increases, the oil absorption capacity, water absorption index, and solubility all show a trend of first increasing and then decreasing, and the hardness shows a trend of first decreasing and then increasing. The inventors speculate that this may be because as time increases, the number of hydrogen bonds in the molecule breaks increases, and after a certain period of time, all hydrogen bonds break. When the gelatinization time is 20 minutes, the oil absorption capacity, water absorption index, and solubility are the largest, and the hardness is the smallest.

(4) Effect of water content on oil absorption, water absorption index, solubility and hardness of pregelatinized rice flour

The gelatinization temperature was 50℃, the gelatinization time was 20min, the mesh size was 200-300 mesh, and the water content was 50%, 55%, 60%, 65% and 70% respectively to prepare pregelatinized rice flour. The hardness, water absorption index, solubility and oil absorption capacity of the rice flour were measured as evaluation indicators to study the effect of pregelatinization on the quality of rice flour.

As shown in Figure 4, as the gelatinization time increases, the oil absorption capacity, water absorption index, and solubility all show a trend of first increasing and then decreasing, and the hardness shows a trend of first decreasing and then increasing. The inventors speculate that during the starch gelatinization process, the starch granule crystal bundles disintegrate, the hydrogen bonds within the molecules break, and the starch granule structure becomes loose, with a high water content, which is conducive to combining with water. When the water content is 65%, the oil absorption capacity, water absorption index, and solubility are the largest, and the hardness is the smallest.

The optimal parameter range is selected based on the single factor: the mesh size is between 100-200, 200-300 and 300-400 mesh, preferably 200-300; the gelatinization temperature is between 50-70°C, preferably 60°C; the gelatinization time is between 15-25min, preferably 20min; the water content is between 60-70%, preferably 65%.

1.5 Box-Behnken experiment and experimental results

In order to further optimize the conditions of pregelatinized rice flour, the response surface optimization method was used for the final optimization experimental design.

Taking into account the results of the single factor test, according to the Box-Behnken experimental design principle, the mesh size (A), gelatinization temperature (B), gelatinization time (C) and water content (D) were investigated, and the comprehensive score (Y) was taken as the response value. A four-factor three-level response surface analysis experiment was carried out to determine the optimal process parameters. The experimental results are shown in Table 1.

Table 1 Box-Behnken test design and results

Table 2 Regression model and variance analysis

According to the quadratic regression model equation obtained by software analysis: ^{comprehensive} score (Y) ⁼ 88.86-1.53A-2.13B+2.12C+2.88D-1.10AB-0.80AC+0.80AD+1.85BC+1.15BD-1.75CD ^- 8.87A2-6.35B2-7.37C2-6.65D2, the regression model variance analysis and model coefficient significance test were performed on the comprehensive score, as shown in Table ² .

The response regression model reached an extremely significant level (P < 0.01), and the lack of fit term = 0.5673 > 0.05 was not significant, indicating that the regression model fitted well and had a small error. The coefficient of determination R ² = 0.9950, indicating that 99.5% of the variation in the comprehensive score can be explained by the model. Through analysis and related data, it can be seen that the mesh size (A), gelatinization temperature (B), gelatinization time (C) and water content (D) have a significant effect on pre-gelatinized rice flour, and the factor significance is D > B > C >A; the significance of each interaction term on its quality is BC > CD > BD > AB > AC = AD; in addition, the quadratic terms of A, B, C, and D are all extremely significant. The optimal parameters obtained by regression equation analysis are: mesh number (A) = 192.46 mesh, gelatinization temperature (B) = 58.72℃, gelatinization time (C) = 20.55min, water content (D) = 65.94%, and the comprehensive score is 89.4398 points. According to the actual situation, the conditions are modified to: mesh number (A) = 200 mesh, gelatinization temperature (B) = 59℃, gelatinization time (C) = 21min, and water content (D) = 66%. The verification test was repeated for three groups according to the optimal conditions obtained by the response surface software, and the average value was taken to obtain a comprehensive score test value of 89.2842±0.3312 points, which is basically consistent with the predicted theoretical value of 89.4398 points, indicating that the mathematical model is reliable and has high accuracy, and is feasible for optimizing the production process of pregelatinized rice noodles.

On the basis of the results of univariate analysis, in order to further explore the synergistic effect of all factors on the quality of pregelatinized rice noodles, as shown in Figure 5, the response surface opens downward and the contour lines are elliptical. From the entire surface, the comprehensive score of pregelatinized rice noodles presents a parabolic curve as the factors change, indicating that each factor has an effect on the quality of pregelatinized rice noodles.

As shown in Figure 5(a), the comprehensive score first increases and then slightly decreases with the increase of mesh size and gelatinization temperature. As the gelatinization temperature continues to increase, the rice flour undergoes over-gelatinization, resulting in a decrease in the quality of the pre-gelatinized rice flour and a decrease in the comprehensive score. As shown in Figure 5(b), the comprehensive score first increases and then decreases with the increase of gelatinization temperature and gelatinization time. This phenomenon occurs because the high gelatinization temperature destroys the starch crystals, exposing more hydroxyl groups, which are easy to combine with water molecules, thereby increasing the comprehensive score. As shown in Figure 5(c), the comprehensive score first increases and then decreases with the increase of gelatinization temperature and water content. Among them, the appropriate amount of water can maintain the integrity of starch in the water dispersion. The decrease in the comprehensive score may be due to the excessive gelatinization temperature, which leads to the deterioration of the quality of the pre-gelatinized rice flour. As shown in Figure 5(d), the comprehensive score first increases and then decreases with the increase of gelatinization time and water content. The reason for the increase may be that the rice flour contains available hydrophilic groups, which can combine with more water molecules. The reason for the decrease may be that the excessive increase in gelatinization time and water content leads to excessive gelatinization and deterioration of quality.

Example 2

Rice starch, supermicron starch and pregelatinized rice starch were taken as research objects respectively. The gelatinization characteristics, scanning electron microscopy, polarizing microscopy tests, particle size determination, amylose content, solubility and water absorption index were determined, and the effect of pregelatinization treatment on the physicochemical properties and microstructure of rice flour was analyzed.

Rice starch: Rice starch is prepared from rice flour as raw material. The preparation method includes the following steps: soaking rice flour with 0.4% NaOH solution, the mass ratio of alkali solution to rice flour is 5:1, room temperature, stirring every 6 hours during the soaking process, and soaking for a total of 24 hours. Remove the soaking liquid, add fresh alkali solution of the same concentration, and then remove the supernatant after settling for a period of time. Then wash the starch emulsion below with water and centrifuge (3000r/min, 15min) for many times until the supernatant is free of turbidity, neutralize it with HCl to neutrality, and then dry and dehydrate it (40℃ forced drying oven), crush it and pass it through an 80-mesh sieve to obtain rice starch, seal it with a sealed plastic bag, and store it for later use.

Supermicron starch: Supermicron starch was prepared using supermicron powder (prepared in 1.1 in Example 1) as a raw material, and the preparation method was the same as the preparation method of rice starch.

Pregelatinized rice starch: In Example 1, the pregelatinized starch was prepared under the conditions of 200 mesh, 59° C. gelatinization temperature, 21 min. gelatinization time and 66% water content. The pregelatinized rice starch was prepared by the method of extracting rice starch.

2.1 Experimental methods

(1) Determination of starch content: Determination of starch content: acid hydrolysis method, refer to GB 5009.9-2016.

(2) Determination of amylose content: Preparation of standard solution: Take 0.1000 g of pure amylose and amylopectin, respectively, and place them in 100 mL volumetric flasks. Add 1 mL of anhydrous ethanol to moisten the sample, and then add 9 mL of 1 mol/L NaOH solution. Disperse in a boiling water bath for 10 min, cool rapidly, and make up to volume with water.

Standard curve drawing: Take 6 100mL volumetric flasks, add 0, 0.25, 0.50, 1.00, 1.50, 2.00mL of 1 mg/mL amylose standard solution, and then add 5, 4.75, 4.50, 4.00, 3.50, 3.00mL of 1mg/mL amylopectin standard solution in sequence, with a total of 5mL. Take another 100mL volumetric flask, add 5mL of 0.09mol/L NaOH solution as a blank. Then add about 50mL of water, 1mL of 1mol/L acetic acid, and 1mL of iodine reagent to each bottle in sequence, dilute with water and color for 10min, read the absorbance at 620nm, and draw a standard curve with milligrams of amylose as the horizontal axis and absorbance as the vertical axis.

Sample determination: weigh 0.1000g of starch sample into a 100mL volumetric flask, add 1mL of anhydrous ethanol to fully wet the sample, then add 9mL of 1mol/L NaOH solution, disperse in a boiling water bath for 10min, cool rapidly, make up to volume with water, take 5mL of starch dispersion into a 100mL volumetric flask, add 50mL of water, 1mL of 1mol/L acetic acid solution and 1mL of iodine reagent, make up to volume with water, develop color for 10min, and read the absorbance at 620nm.

A-Find the corresponding amylose content (mg) on the standard curve based on the absorbance value;

W-sample weight (mg).

(3) Observation by scanning electron microscope: The microscopic granule morphology of starch is observed by scanning electron microscope (SEM). The size and shape of starch granules can be directly observed.

(4) Polarized light microscope test method: The birefringence spectrum of the sample was observed using a polarized light optical microscope. The sample was suspended in glycerol-water (V/V, 1:1) to prepare a starch solution with a volume fraction of about 1%. A small drop of the mixture was placed on a microscope slide and gently covered with a cover slip. Microscopic photographs were taken using a 60x magnifying glass. The observation mode was switched between bright field and polarized light.

(5) Determination of particle size: Accurately weigh 0.1 g of rice starch into a beaker, add 50 mL of distilled water and place it in an ultrasonic cleaner to fully oscillate for 5 minutes. Large particles settle and small particles are evenly dispersed. The particle sizes of rice starch, ultra-micron starch and pregelatinized rice starch are measured using a Malvern MS2000 laser particle size analyzer. The three samples are placed in a laser particle size analyzer for detection, with a refractive index of 1.000, and water is selected as the optical model for light scattering to measure the sample particle size.

(6) Determination of solubility and water absorption index: Weigh 2.5 g of sample and mix thoroughly with 30 mL of distilled water in a 50 mL centrifuge tube, keep in a 55°C water bath for 30 min, and then centrifuge at 4000 r/min for 20 min. The supernatant is transferred to a pre-dried and weighed aluminum box and dried at 105°C. The mass of the precipitate in the centrifuge tube is weighed, and the same steps are repeated for 55 to 95°C (10°C increments).

(7) Determination of gelatinization properties: The gelatinization properties of the samples were determined using a rapid viscometer (RVA).

2.2 Data analysis: The experimental data were processed using Excel 2007 and the graphics were drawn using Origen 8.1 software.

2.3 Experimental Results

(1) Microstructure analysis: As shown in Figure 6, rice starch has a typical polyhedral and irregular shape with a smooth surface. Similarly, pores can be observed on the surface of rice starch, ultra-micron starch and pregelatinized rice starch, but there are more pores in pregelatinized rice starch. The pore structure is conducive to improving the water holding capacity of starch particles, thereby improving the quality of rice products. Compared with rice starch, ultra-micron starch particles are smaller. Some pregelatinized rice starch particles have depressions or cracks on the surface and aggregation occurs. The pregelatinization destroys the structure of rice starch particles and forms a porous structure.

As shown in Figure 7, before and after pregelatinization, starch granules are mostly round, oval or irregular polygons, rice starch and ultra-micron starch have cross polarization, and the cross polarization of ultra-micron starch decreases because ultra-fine grinding destroys the ordered structure of starch. The cross structure of pregelatinized starch disappears, which may be because pregelatinization breaks its hydrogen bonds and destroys the ordered structure of starch granules.

(2) Analysis of starch and amylose content: As shown in Table 3, the starch content in rice flour, supermicronized flour and pregelatinized rice flour decreases in turn, while the amylose content increases in turn. The starch content in supermicronized flour may be due to the loss of starch granules during the milling process. The starch content in pregelatinized rice flour decreases, probably because starch granules swell and rupture under continuous heating and degrade into small molecules. The reason for the increase in amylose is that amylose affects the gelatinization characteristics of starch and continuously absorbs water. When it reaches a certain limit, it will cause the starch granules to rupture and dissolve, and the amylose in the granules will precipitate.

Table 3 Starch and amylose content in rice flour, supermicronized flour and pregelatinized rice flour

(3) Particle size analysis: As shown in Table 4 and Figure 8, the particle sizes of supermicron starch and pregelatinized rice starch are smaller than those of ordinary rice starch after pulverization. This is mainly because the size of starch granules is related to their degree of damage. The average particle size of pregelatinized starch is larger than that of supermicron starch. This may be because more water molecules gradually squeeze into the starch granules during heating, causing the volume to gradually expand. After freeze-drying, the water evaporates and the starch maintains a basic structural skeleton, resulting in an increase in particle size. It may also be because the increase in water content during gelatinization causes the small starch fragments to collide with each other more after being broken, and they are aggregated into large particles again under the action of hydrogen bonds and van der Waals forces.

Table 4 Particle size of rice starch, supermicron starch and pregelatinized rice starch

(4) Analysis of solubility and water absorption index: As shown in Table 5, the solubility of rice starch, supermicron starch and pregelatinized rice starch increases with the increase of temperature. At the same temperature, the solubility is in the order of pregelatinized rice starch > supermicron starch > rice starch. Supermicron starch is easier to dissolve in water due to its smaller particles. Pregelatinization completely destroys the starch molecules and reduces the insoluble substances, making it easier to dissolve. The water absorption index of rice starch, supermicron starch and pregelatinized rice starch increases with the increase of temperature. The water absorption index is in the order of pregelatinized rice starch > supermicron starch > rice starch. Pregelatinization increases the gelatinization degree of rice starch, strengthens the gel structure formation ability, and makes the structure more loose and porous, exposing more hydrophilic groups, increasing the hydrophilic ability and water absorption index.

Table 5 Solubility and water absorption index of rice starch, supermicronized starch and pregelatinized rice starch

(5) Analysis of gelatinization characteristics: As shown in Table 6, ultrafine grinding and pregelatinization destroy starch particles and crystal structures, resulting in reduced viscosity, gelatinization temperature and regeneration value of modified starch. The crystal structure of starch is destroyed on a large scale after gelatinization, and no more heat is needed to destroy the starch structure during regelatinization. The low peak viscosity may be due to the swelling of part of the starch and the dissolution of amylose caused by pregelatinization. The regeneration value can reflect the short-term regeneration degree of starch, which is mainly caused by the rearrangement and aggregation of starch molecules when the temperature drops. The lower the regeneration value, the lower the degree of aging. Pregelatinization reduces the disintegration value of starch, making the starch more stable during heating.

Table 6 Gelatinization properties of rice starch, supermicronized starch and pregelatinized rice starch

Example 3

The production process of rice biscuits was optimized by adding two exogenous proteins (soy protein isolate and whey protein isolate). The effects of the addition amount of soy protein isolate, whey protein isolate, pregelatinized rice flour and butter on the sensory scores and texture characteristics of rice biscuits were studied, and the effects on the quality characteristics of rice biscuits were compared and analyzed.

3.1 Experimental methods

The invention provides a method for preparing rice biscuits, comprising the following steps: butter→melting→whipping→mixing→batter→forming→baking→cooling→finished product.

Specifically, you can use the following operation methods:

(1) Melt the butter for 5 min at a temperature of 40°C;

(2) Whipping: Whip the softened butter, egg liquid and granulated sugar with a whisk for 6 minutes to expand the volume.

(3) Mixing and preparing batter: Add rice flour, pre-gelatinized rice flour, low-gluten flour, soy protein isolate, whey protein isolate, milk powder, milk, and salt, and mix evenly under pressure to form a batter.

(4) Extrusion molding: Put the batter into a piping bag with a piping nozzle installed, and squeeze out the batter onto a baking tray covered with baking paper with uniform force. Put it in the refrigerator for 5 minutes at a temperature of -18°C.

(5) Baking: Place a baking tray in a preheated oven (upper heat 160° C., lower heat 170° C.) and bake for about 10 minutes to obtain rice biscuits.

(6) Cooling and finished product packaging: After the rice biscuits are taken out of the oven, they are naturally cooled to room temperature (25°C), packed into plastic bags and heat-shrink-sealed. After 24 hours of moisture balance, various indicators are tested.

3.2 Evaluation indicators

(1) Sensory evaluation: Based on the five characteristics of biscuits, namely, taste, hardness, crispness, color and appearance, a weighted sensory scoring table was developed (see Table 7). Ten food major students (male:female ratio was 1:1) were randomly selected as sensory evaluation scorers, and the comprehensive evaluation method was used to evaluate the products.

Table 7 Weighted sensory scoring criteria

(2) Determination of texture characteristics: The hardness, brittleness and elasticity of the biscuits were determined using a texture analyzer. Test conditions: TPA mode, P 0.5 probe, pre-test rate 1.0 mm/s, test rate 5.0 mm/s, post-test rate 5.0 mm/s; compression degree 50%; trigger force 5 g.

(3) Comprehensive score of rice biscuits: The comprehensive score of rice biscuits consists of two parts: texture score and sensory score. The weighted coefficient method was used, with the weight of the texture score set to 0.5, the weight of the sensory score set to 0.5, and the sum of the coefficients being 1. Comprehensive score = gelatinization score × 0.5 + sensory score × 0.5.

Texture score (100 points) = hardness (25 points) + brittleness (25 points) + crispness (25 points) + elasticity (25 points).

The score for each indicator is calculated as follows:

In the formula: D is the score corresponding to the indicator; C is the full score of this indicator (i.e. 100 or 25); A is the difference between the maximum and minimum values of the indicator; B is the difference between the measured value and the minimum value of the indicator.

Among them, since the hardness index of rice biscuits is negatively correlated with the taste, the score calculation formula corresponding to the hardness value is:

(4) Color: The color of the rice biscuits was measured using a colorimeter, and the L*, a*, and b* values were measured. Three parallels were tested for each level. The L* value represents black (0)/white (100), the a* value represents green (-)/red (+), and the b* value represents blue (-)/yellow (+).

(5) Determination of baking loss rate: The baking loss rate is calculated by weighing the cookies before and after baking. The calculation formula is:

3.3 Single-factor experimental design and results

100g rice flour was added (taking this as 100%), 21% milk powder was added (i.e. the mass percentage of milk powder and rice flour was 21%), 40% egg liquid was added (i.e. the mass percentage of egg liquid and rice flour was 40%), 30% white granulated sugar was added (i.e. the mass percentage of white granulated sugar and rice flour was 30%), 50% low-gluten flour was added (i.e. the mass percentage of low-gluten flour and rice flour was 50%), 30% milk was added (i.e. the mass percentage of milk and rice flour was 30%), 0.1% salt was added (i.e. the mass percentage of salt and rice flour was 0.1%), 10% soy protein isolate was added (i.e. the mass percentage of soy protein isolate and rice flour was 10%), 10% whey protein isolate was added The influence of each factor on the quality of rice biscuits was investigated by comparing the addition amount of soy protein isolate of 5%, 7.5%, 10%, 12.5%, 15% and the addition amount of whey protein isolate of 5%, 7.5%, 10%, 12.5%, 15% and the addition amount of butter of 60%, 70%, 80%, 90%, 100% and the addition amount of pregelatinized rice flour of 3%, 5%, 7%, 9% and 11%.

(1) Effect of soy protein isolate addition on sensory scores, hardness and brittleness of rice biscuits

As shown in Figure 9, with the increase of the amount of soy protein isolate added, the sensory score and crispness of the rice biscuits first increased and then decreased, and the hardness first decreased and then increased. When the amount of soy protein isolate added was 10%, the sensory score and crispness were maximum, and the hardness was minimum. The addition of soy protein isolate can act as a gluten-like network structure. When too much soy protein isolate is added, a beany smell can be clearly tasted and the taste is not good, so the amount of soy protein isolate added was selected to be 7.5%-12.5%.

(2) Effect of whey protein isolate addition on sensory scores, hardness and crispness of rice biscuits

As shown in Figure 10, as the amount of whey protein isolate added increases, the sensory score and crispness of the rice biscuits first increase and then decrease, and the hardness first decreases and then increases. When the amount of whey protein isolate added is 10%, the sensory score and crispness are maximum, and the hardness is minimum. The addition of whey protein isolate can act as a gluten-like network structure. Excessive whey protein isolate will inhibit the binding between starch particles and weaken the starch network structure, resulting in a bad taste. Therefore, the amount of whey protein isolate added is selected to be 7.5%-12.5%.

(3) Effect of butter addition on sensory scores, hardness and brittleness of rice biscuits

As shown in Figure 11, as the amount of butter added increases, the sensory score and crispness of the rice biscuits first increase and then decrease, and the hardness first decreases and then increases. When the butter addition is 80%, the sensory score and crispness are the maximum, and the hardness is the minimum. When the butter addition is low, the sensory score and crispness are low, the biscuit surface is dry, and the crispness and aroma are poor; the sensory score increases with the amount of butter added, because the flavor of the butter itself makes the biscuits taste richer. However, when the butter addition is too high, the internal structure is too loose, large holes are produced, the biscuits are difficult to shape, and the taste is soft and greasy, and the aroma is too strong, so the butter addition is selected to be 70%-90%.

(4) Effect of the amount of pregelatinized rice flour added on the sensory score, hardness and brittleness of rice biscuits

As shown in Figure 12, as the amount of pregelatinized rice flour added increases, the sensory score and crispness of the rice biscuits first increase and then decrease, and the hardness first decreases and then increases. When the amount of pregelatinized rice flour added is 7%, the sensory score and crispness are maximum, and the hardness is minimum. Pregelatinized rice flour is added, and the viscosity of gelatinized starch granules is used to form a network structure between protein and protein, protein and starch, and starch and starch, so that the hardness is reduced and the taste is improved. The addition of a large amount of pregelatinized rice flour reduces the gluten protein content, and the starch gel and gluten network cannot form a good network structure, and the taste is not good, so the amount of pregelatinized rice flour added is selected to be 5%-9%.

3.4 Box-Behnken experiment and results

In order to further optimize the conditions of double protein rice biscuits, the response surface optimization method was used for the final optimization experimental design. The experimental design and results of the response surface method are shown in Table 8.

Table 8 Box-Behnken test design and results

Taking the comprehensive score (Y) as the response value, the response surface software was used to perform regression fitting on Table 8, and the quadratic polynomial regression equation Y=89.56-1.52A-2.30B+2.17C+3.13D--1.03AB-0.65AC+0.42AD+2.08BC ⁺ 0.75BD-1.32CD-8.42A2-5.85B2-6.97C2-6.05D2 ^{was obtained .}

The model was tested for significance and the results of variance analysis are shown in Table 9.

Table 9 Regression model and variance analysis

As shown in Table 9, the model p < 0.0001, the difference is extremely significant; the lack of fit term of the regression equation p = 0.0699> 0.05, the difference is not significant; R ² = 0.9946, the degree of fit is > 90%, indicating that the model can well explain the change of the response value, the theoretical value and the actual value can have a good fit, the experimental error is small, the correlation is high, and the data is true, so this equation can be used to analyze the test results. The order of influencing the comprehensive score is the amount of pregelatinized rice flour added > the amount of whey protein isolate added > the amount of butter added > the amount of soy protein isolate added; A, B, C, D, AB, BC, CD have extremely significant effects, BD has significant effects, and AC and AD have no significant effects.

In terms of the production conditions of rice biscuits, in order to further verify the mechanism of the interaction terms of the influencing factors, the contour lines and response surfaces obtained by the quadratic model can evaluate the interaction strength between the experimental factors and determine the optimal level range of each factor. When one factor is fixed, as the other two factors increase or extend, the comprehensive scores show a trend of first rising and then falling; the response surface graphs are all concave upwards, with a maximum value; the contour lines are all elliptical, indicating that the interaction between the two factors is significant.

The optimal conditions of the model can be obtained by Design Expert software: 9.58% soy protein isolate, 9.78% whey protein isolate, 81.25% butter, 7.38% pre-gelatinized rice flour, and the predicted comprehensive score is 90.1935. In order to test the effect of the production conditions on the production of rice biscuits, the accuracy and reliability of the response model, the above optimized conditions were used for three repeated tests. According to the actual production conditions, the preparation process conditions were corrected to 9.6% soy protein isolate, 9.8% whey protein isolate, 81.3% butter, and 7.4% pre-gelatinized rice flour. The comprehensive score of the rice biscuits produced under this condition was 90.19, which was close to the theoretical prediction value.

3.4 Comparison of the quality of pure rice flour biscuits, double protein rice biscuits and wheat biscuits

Pure rice flour biscuits: prepared by method 3.1, without double egg whites, low-gluten flour and pre-gelatinized rice flour; the amount of rice flour added is 150g, the amount of milk powder added is 21g, the amount of egg liquid added is 40g, the amount of white sugar added is 30g, the amount of milk added is 30g, the amount of salt added is 0.1g, and the amount of butter added is 81.3%.

Double protein rice biscuits: prepared by the method in 3.1, with 9.6% soy protein isolate, 9.8% whey protein isolate, 81.3% butter, and 7.4% pregelatinized rice flour added. Other ingredients are the same as in 3.1.

Wheat biscuits: prepared by the method in 3.1, without double egg whites, rice flour and pre-gelatinized rice flour; the amount of low-gluten flour added is 150g, the amount of milk powder added is 21g, the amount of egg liquid added is 40g, the amount of white sugar added is 30g, the amount of milk added is 30g, the amount of salt added is 0.1g, and the amount of butter added is 81.3g.

(1) Color difference and sensory evaluation results of pure rice flour biscuits and double protein rice biscuits

As shown in Table 10, the b* value is a measure of the yellowness of the biscuit surface color, and the trend of the biscuit yellowness is similar to the trend of the redness (a* value). The double protein rice biscuits have higher a* and b* values.

As shown in Table 10, the sensory score of pure rice flour biscuits is low, the taste is too hard, and cracks easily appear on the surface and the cross section is also stratified. The sensory score of double protein rice biscuits is significantly improved, with a complete appearance, golden color, uniform texture, crispy taste, and a unique rice aroma.

Table 10 Color difference and sensory evaluation results of pure rice flour biscuits, double protein rice biscuits and wheat biscuits

(2) Texture results of pure rice flour biscuits, double protein rice biscuits and wheat biscuits

As shown in Table 11, by comparing the texture parameters of pure rice flour biscuits and double protein rice biscuits, it is found that the double protein rice biscuits are more brittle, less hardness, crispness and chewiness, and the double protein rice biscuits have better quality and taste. The reason for the change in hardness may be that the addition of pre-gelatinized rice flour makes the gel not easy to age and regenerate after cooling, showing a smaller hardness. The present invention can make the prepared biscuits have similar texture characteristics to wheat biscuits by reasonably allocating the formula and production process of double protein rice biscuits.

Table 11 Texture results of pure rice flour biscuits, double protein rice biscuits and wheat biscuits

(3) Baking loss rate results of pure rice flour biscuits and double protein rice biscuits

As shown in Table 12, the baking loss rate of double-protein rice biscuits is lower than that of pure rice flour biscuits. This may be because the addition of double-protein and pre-gelatinized rice flour makes the biscuits have better water absorption capacity, less free water available in the batter, and less water lost after baking, showing a lower baking loss rate.

Table 12 Baking loss rate results of pure rice flour biscuits, double protein rice biscuits and wheat biscuits

In summary, the pregelatinized rice flour prepared by a reasonable formula and process of the present invention can be suitable for the preparation of double protein biscuits. By further optimizing the formula and process of the double protein biscuits, the double protein biscuits prepared by the method of the present invention have the advantages of complete appearance, golden color, uniform texture, crisp taste, good brittleness, small hardness, good rice aroma, low baking loss rate, etc.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A pregelatinized rice flour, characterized in that the pregelatinized rice flour is prepared by the following method: rice flour and water are mixed and gelatinized; the mesh size of the rice flour is between 100-200 mesh, 200-300 mesh or 300-400 mesh; the temperature of the gelatinization is between 50-70° C.; the time of the gelatinization is between 15-25 min; the rice flour and water are mixed to form a mixture, and the water content of the mixture is between 60%-70%. 2. according to the described pregelatinized rice flour of claim 1, it is characterized in that the mesh number of rice flour is 200-300 mesh. 3. according to the described pregelatinized rice flour of claim 2, it is characterized in that the mesh number of rice flour is 192-200 mesh. 4. The pregelatinized rice flour according to claim 1, characterized in that the gelatinization temperature is between 58-60°C. 5. The pregelatinized rice flour according to claim 4, characterized in that the gelatinization temperature is between 58-59°C. 6. The pregelatinized rice flour according to claim 1, wherein the gelatinization time is between 20-21 min. 7. The pregelatinized rice flour according to claim 1, wherein the rice flour and water are mixed to form a mixture, and the water content of the mixture is between 65% and 66%. 8. according to any one of claims 1-7 described pregelatinized rice flour, it is characterized in that described rice flour is rice flour. 9. The pregelatinized rice flour according to claim 8, wherein the rice flour is broken rice flour. 10. The pregelatinized rice flour according to any one of claims 1 to 7, characterized in that the pregelatinized rice flour is prepared by the following method: mixing rice flour and water to obtain a mixture, gelatinizing the mixture after the mixture is evenly mixed, uniformly stirring, cooling, and pulverizing.