High-fiber rice cake prefabricated flour rich in buckwheat hulls, preparation method and application thereof

Abstract

The present invention belongs to the field of food processing technology, and in particular relates to a high-fiber rice cake preformed powder rich in buckwheat hulls, and a preparation method and application thereof. The average particle size of the ultrafine buckwheat hull powder is ≤25 μm, of which the proportion of particles with a particle size exceeding 100 μm is ≤10%, the proportion of particles with a particle size of 25 μm to 100 μm is ≤50%, and the rest are particles with a particle size of less than 25 μm, all of which can pass through a 100-mesh sieve. Adding 30% of the ultrafine buckwheat hull powder of the present invention can increase the water holding capacity of rice flour by 45.00%, the viscosity of rice paste by 122.73%, and the gas production of rice paste by 26.38%, which can avoid the problems of rice cake collapse and rough taste caused by insoluble dietary fiber, so that the high-fiber rice cake has the same specific volume and texture quality as the control rice cake (no dietary fiber added), and the wet basis proportion of dietary fiber in the rice cake is 11.25%.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, in particular to ultrafine buckwheat hull powder, high-fiber rice cake preformed flour rich in the ultrafine buckwheat hull powder, and rice cake prepared from the same. Background Art

[0002] Buckwheat, as a food and medicine crop, contains nutrients such as starch, dietary fiber and flavonoids. It is an important food for people in the Yi area in southwest my country, the Tibetan area in the border areas and the high-altitude cold mountainous areas. In recent years, with the increasing awareness of healthy eating among people, foods made from buckwheat have attracted much attention. Common buckwheat noodles, buckwheat steamed buns and buckwheat bread are all made from dehulled buckwheat flour. Buckwheat produces more than 14% buckwheat hull by-products during the dehulling and grinding process (Buckwheat (Fagopyrum esculentum) Hulls Are a Rich Source of Fermentable Dietary Fiber and Bioactive Phytochemicals, International Journal of Molecular Sciences, 2023, 24(22), 16310). Studies have shown that buckwheat hulls are rich in bioactive components such as dietary fiber, bioactive polysaccharides, and polyphenolic compounds, with insoluble dietary fiber accounting for over 90% (Basic chemical composition and bioactive compounds content in selected cultivars of buckwheat whole seeds, dehulled seeds and hulls, Journal of Cereal Science, 2016, 69:1–8). Wheat bran is currently used as a dietary fiber fortification ingredient in staple food processing. However, the dietary fiber content of wheat bran is only 35%, primarily concentrated in the exocarp. It also contains other essential components, such as starch and protein, that interfere with the fortification effect (Wheat bran layers: composition, structure, fractionation, and potential uses in foods, Critical Reviews in Food Science and Nutrition, 2023:1-24). Compared to wheat bran, buckwheat hulls have a single component and are a high-quality source of insoluble dietary fiber fortification. However, buckwheat hulls are primarily used in feed, fertilizer, and pillows, resulting in a significant waste of edible resources.

[0003] High-fiber foods have become a healthy choice for people (according to GB28050-2011 "National Food Safety Standard General Rules for Nutrition Labeling of Pre-packaged Foods", a product can only be called a high-fiber food if its dietary fiber content is ≥6g / 100g). However, the problem that high amounts of insoluble dietary fiber will cause the staple food products to have negative effects such as poor molding, poor chewiness and rough taste still needs to be solved. For example, after adding 22% microfluidized corn bran (average particle size of 500μm), the specific volume of the bread decreased by 43.82%, the hardness increased by 5 times, and the cohesion and elasticity were significantly lower than those of white bread without bran (Development of high-fiber wheat bread using microfluidized corn bran, Food Chemistry, 2020, 310:125921). After adding 10% coarse oat fiber (average particle size 250 μm) to gluten-free rice bread based on rice and corn starch, the specific volume of the bread decreased by 13.33% and the hardness increased by 42.29%, which seriously affected the sensory quality of the bread (Effect of different microstructural features of soluble and insoluble fibers on gluten-free dough rheology and bread-making, Journal of Food Engineering, 2014, 142: 49-56). Under the premise of adding carboxymethyl cellulose as a bread improver, adding only 6% buckwheat hull powder (average particle size 62.70 μm) still reduced the specific volume of gluten-free bread by 13% and increased the hardness by 1 time (Valorisation of Buckwheat By-Product as a Health-Promoting Ingredient Richin Fiber for the Formulation of Gluten-Free Bread, Foods, 12(14): 2781). Under the premise of adding xanthan gum modifier to improve the specific volume of high-fiber cakes, the amount of orange peel dietary fiber added to gluten-free cakes can only reach 16%, and the wet basis ratio is only 3.88% (Large Amplitude Oscillatory Shear (LAOS) analysis of gluten-free cake batters: The effect of dietary fiber enrichment, Journal of Food Engineering, 2020, 275: 109867).In the relevant patent CN201610942207.X, although the ultrafine grinding technology is used to reduce the particle size of by-products such as bran to 160 mesh (about 96μm) to increase the dietary fiber content in the premix powder to 30%, the subsequent use of steam explosion technology to process the dietary fiber is aimed at increasing the soluble dietary fiber content, and it still fails to solve the fundamental problem of insoluble dietary fiber destroying the texture of rice cakes. In addition, the addition of a large amount of cheese, butter and milk in the patented formula makes the wet basis content of dietary fiber in the rice cake less than 4%.

[0004] At present, the common methods to improve the insoluble dietary fiber content of staple food products are to add modifiers such as hydrophilic colloids, enzyme preparations, gluten and emulsifiers to alleviate the deterioration of texture quality, chemically and enzymatically modify the insoluble dietary fiber, or add soluble dietary fiber to increase the total dietary fiber content in staple food products. However, these methods are complicated to operate and have a negative impact on the nutrition, flavor and sensory quality of staple food products. Reducing the particle size is an effective physical method to improve the rough taste of insoluble dietary fiber, and according to the average particle size of the raw materials, it can be divided into tissue scale (500-100μm) and cell scale (50-10μm). It is difficult to achieve uniformity in the degree of grinding and raw material components with traditional grinding methods, and the subsequent screening process will further cause differentiation of raw material components (the raw material particle size decreases, the proportion of dietary fiber decreases, and the proportion of starch and protein increases). Our previous research has shown that ultrafine grinding can reduce the average particle size of raw materials while maintaining the integrity of the raw materials. It also increases the specific surface area and porosity by disrupting the rigid structure of the bran, improving the water-holding capacity of the bran byproduct and facilitating its application in rice cakes. However, even when the wheat bran is added at a level of 30%, the dietary fiber content is only 9%. Therefore, developing buckwheat hulls as a raw material with a single nutritional composition and higher dietary fiber purity can significantly increase the dietary fiber content of rice products.

[0005] Currently, research on the ability of cellular-scale insoluble dietary fiber to alleviate the deterioration of the texture and quality of staple food products is limited to wheat flour products, which are subject to interference from gluten proteins and lack specific applications in gluten-free systems. Patents related to high-fiber gluten-free cakes also have limitations, such as the addition of only soluble dietary fiber (CN201910502745.0), the use of compounding improvers to improve texture (CN201510361765.2), and the high amount of dietary fiber added to premixed flour but insufficient dietary fiber wet basis content in rice cakes (CN201610942207.X).

[0006] Rice cakes, a traditional Chinese delicacy, suffer from a limited nutritional profile, primarily consisting of fast-digesting starch, which doesn't meet the dietary requirements of those seeking to maintain stable blood sugar levels. This invention focuses on the insoluble dietary fiber found in buckwheat hulls. By using ultrafine grinding to physically modify the hulls to a cellular scale, this method improves the water-holding capacity of rice flour while maintaining a high dietary fiber content in the rice product, thereby addressing issues such as the rough texture and easy collapse of the rice cakes. Summary of the Invention

[0007] In view of this, the present invention uses ultrafine grinding technology to grind buckwheat hulls to cellular scale, and then mixes them with rice flour in a certain proportion to produce a high-fiber rice cake preformed powder rich in buckwheat hull powder, which solves the problem of rough taste and poor texture quality of high-fiber rice cakes.

[0008] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0009] The first aspect of the present invention is to provide an ultrafine buckwheat hull powder, characterized in that: the average particle size of the buckwheat hull powder is ≤25μm, of which the particles with a particle size exceeding 100μm account for ≤10%, the particles with a particle size of 25μm to 100μm account for ≤50%, and the rest are particles with a particle size less than 25μm, all of which can pass through a 1000-mesh sieve.

[0010] Furthermore, the average particle size of the ultrafine buckwheat hull powder is 13.43 μm, particles with a particle size exceeding 100 μm account for 8.44%, particles with a particle size of 25 to 100 μm account for 31.90%, and the rest are particles with a particle size less than 25 μm, and all of them can pass through a 1000-mesh sieve;

[0011] Furthermore, the ultrafine buckwheat hull powder is prepared by the following method: buckwheat hulls are crushed using turbulent ultrafine grinding technology, with technical parameters of 300-500 Hz, feed speed of 100-1000 r / min, and fan frequency of 10-50 Hz; preferably, the technical parameters of the method are 450 Hz, feed speed of 500 r / min, and fan frequency of 25 Hz.

[0012] The second aspect of the present invention is to provide a method for preparing ultrafine buckwheat hull powder, the method comprising: crushing buckwheat hulls using turbulent ultrafine grinding technology, with technical parameters of 300-500 Hz, feed speed of 100-1000 r / min, and fan frequency of 10-50 Hz;

[0013] Furthermore, the technical parameters of the method are 450 Hz, feed speed 500 r / min, and fan frequency 25 Hz.

[0014] The third aspect of the present invention is to provide the use of the ultrafine buckwheat hull powder described in the first aspect in preparing high-fiber rice cake pre-made flour.

[0015] A fourth aspect of the present invention provides a high-fiber rice cake pre-made flour, the pre-made flour comprising 20-30% of the ultrafine buckwheat hull powder of the first aspect of the present invention, 50-80% of rice flour, 2-5% of dry yeast powder and 5-15% of sugar;

[0016] Furthermore, the insoluble dietary fiber content in the high-fiber rice cake pre-made flour is ≥17%.

[0017] The fifth aspect of the present invention provides use of the high-fiber rice cake preformed flour described in the fourth aspect in preparing rice cakes.

[0018] A sixth aspect of the present invention provides a high-fiber rice cake, characterized in that the high-fiber rice cake comprises the ultrafine buckwheat hull powder of the first aspect or the rice cake pre-made flour of the fourth aspect;

[0019] Furthermore, the high-fiber rice cake is prepared by fermenting and ripening the high-fiber rice cake preformed flour described in the fourth aspect;

[0020] Furthermore, the fermentation step comprises: adding 130% to 150% water by weight to the high-fiber rice cake pre-made powder to prepare rice paste; performing a primary fermentation at 30°C and 85% humidity for 30 to 50 minutes; pouring the rice paste into a mold and performing a secondary fermentation at room temperature for 5 to 10 minutes;

[0021] Furthermore, the aging is: steaming at 100° C. for 30 to 50 minutes; or baking at 165-180° C. for 15 to 30 minutes.

[0022] A seventh aspect of the present invention provides a method for preparing a high-fiber rice cake, the method comprising:

[0023] 1) Add 130% to 150% water by weight to the high-fiber rice cake preformed powder of the fourth aspect to prepare rice paste; perform a primary fermentation at 30°C and 85% humidity for 30 to 50 minutes. Pour the rice paste into a mold and perform a secondary fermentation at room temperature for 5 to 10 minutes;

[0024] 2) Rice cake ripening: steam at 100℃ for 30-50 minutes; or bake at 165-180℃ for 15-30 minutes.

[0025] The beneficial effects of the present invention are:

[0026] 1) Ultrafine buckwheat hull powder was prepared by ultrafine grinding technology with an average particle size of ≤25 μm (passing a 1000-mesh sieve). The average particle size of common coarse buckwheat hull powder (passing a 100-mesh sieve) on the market is 13.73 times that of the ultrafine buckwheat hull powder of the present invention;

[0027] 2) After reducing the buckwheat hull particle size to the cellular scale, adding 30% ultrafine buckwheat flour can increase the water holding capacity of mixed rice flour by 45.00% and the viscosity of rice paste by 122.73%;

[0028] 3) The gas production of fermented rice paste increased by 26.38%;

[0029] In summary, when buckwheat hull particles are reduced to a cellular scale, their surface hydroxyl groups are exposed, promoting hydrogen bonding between dietary fiber and starch granules, increasing yeast gas production, and reducing the fiber particles' hindrance to the physical support of gas in rice paste. Consequently, the high-fiber rice cakes of this invention possess excellent texture and sensory qualities, with stickiness, chewiness, and specific volume comparable to those of the control rice cakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A is the average particle size of buckwheat hull powder; B is the particle size distribution of buckwheat hull powder (Note: a, b, c represent statistical differences of P < 0.05).

[0031] Figure 2 Effect of adding 30% buckwheat hull flour on the water holding capacity of rice flour and moisture distribution of rice cakes: A is the comparison of the water holding capacity of mixed rice flour; B is the comparison of different moisture ratios of rice cakes; C is the moisture distribution of the cross-section of the rice cake (Note: a, b, c indicate statistical differences of P < 0.05).

[0032] Figure 3 Effects of adding 30% buckwheat hull flour of different particle sizes on the viscosity of rice paste, gas retention after fermentation, and specific volume of rice cakes: A is a comparison of the viscosity of rice paste and gas production after fermentation; B is a comparison of the volume of rice paste after fermentation; C is the specific volume of rice cakes; D is a photo of the cross-section of the rice cake (Note: a, b, c indicate statistical differences of P < 0.05). DETAILED DESCRIPTION

[0033] The following is a further description of the concept of the present invention and the technical effects produced in conjunction with specific embodiments, so as to fully understand the purpose, features and effects of the present invention. The methods described are all conventional methods unless otherwise specified. The materials described can be obtained from public commercial channels unless otherwise specified. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute undue limitations of the present invention. It should be noted that, unless there is a conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0034] Example 1: Effect of different addition amounts of buckwheat hull powder on the texture quality of rice cake

[0035] (1) Preparation of buckwheat hull powder: Buckwheat hulls were crushed using turbulent ultrafine grinding technology with technical parameters of 450Hz, feed speed of 500r / min, and fan frequency of 25Hz to obtain the ultrafine buckwheat hull powder of the present invention. The average particle size of the ultrafine buckwheat hull powder is 13.43μm (D50), particles with a particle size of more than 100μm account for 8.44%, particles with a particle size of 25-100μm account for 31.90%, and the rest are particles with a particle size of less than 25μm, and all can pass through a 1000 mesh sieve. The average particle size of the coarse buckwheat hull powder for comparison is 184.33μm (D50). The average particle size and particle size distribution of buckwheat hull powder detected by laser particle size analyzer are shown in Figure 2. Figure 1 .

[0036] (2) The formula of rice cake pre-made flour: by weight percentage, buckwheat hull powder 0% to 30%, rice flour 50 to 80%, dry yeast powder 5% and sugar 15%. The specific formula is shown in Table 1.

[0037] (3) Rice Paste Fermentation: Add 120% to 150% water by weight to the high-fiber rice cake pre-mix (the specific water amount is shown in Table 1). Place the rice paste in a proofing box and ferment at 30°C and 85% humidity for 40 minutes. Pour the rice paste into a mold and ferment it at room temperature for 10 minutes.

[0038] (4) Rice cake ripening: The fermented rice paste was placed in an oven and baked at 180°C for 30 minutes. The texture analysis of the baked rice cake is shown in Table 2.

[0039] Table 1 Recipe of high-fiber rice cake pre-made powder (by weight percentage)

[0040]

[0041] like Figure 1 As shown in Figure A, the average particle size (D50) of the ultrafine buckwheat hull powder is 13.43 μm, which is consistent with the cell scale range. The average particle size of the coarse buckwheat hull powder is 13.73 times that of the ultrafine buckwheat hull powder in the present invention, and the D10 and D90 of the coarse buckwheat hull powder are 44.37 times and 3.59 times that of the ultrafine buckwheat hull powder, respectively. The particle size distribution range of the ultrafine buckwheat hull powder exceeds 100 μm ≤ 10%, which is within the tissue scale range ( Figure 1 B).

[0042] like Figure 1As shown in Figure C, rice cakes can be formed when 10%-30% buckwheat hull powder is added. When the buckwheat hull powder addition amount is 35%-40%, the rice cake structure is loose and its texture quality cannot be further measured. After adding 35% coarse buckwheat hull powder, the rice cake texture is significantly loose and barely maintains its shape. When the coarse buckwheat hull powder addition amount reaches 40%, the rice cake cannot maintain its basic shape when demolded. Compared with coarse buckwheat hull powder, after adding 35% and 40% buckwheat hull powder of the present invention, although the rice cake structure is loose and the texture is not as good as the rice cake with 30% addition, it can still maintain its basic shape.

[0043] As shown in Table 2, compared with the control rice cake (with 0 buckwheat hull addition), buckwheat hull significantly increased the hardness of the rice cake (P < 0.05), except for the rice cake with 10% coarse buckwheat hull, and the hardness of the rice cake increased with the increase of buckwheat hull addition. Among them, at the high addition level (30%) of coarse buckwheat hull powder, the hardness of the rice cake was 3.24 times that of the control rice cake, but at the same addition level, the hardness of the rice cake with the ultrafine buckwheat hull powder of the present invention was only 1.6 times that of the control rice cake, and the hardness level of the rice cake with 30% ultrafine buckwheat hull powder and 20% coarse buckwheat hull powder was the same. This shows that compared with coarse buckwheat hull powder, the ultrafine buckwheat hull powder of the present invention significantly alleviates the negative effect of increased hardness of rice cake caused by insoluble dietary fiber. In addition, the elasticity of the rice cake was significantly reduced after adding buckwheat hull (P < 0.05), and it was significantly reduced with the increase of buckwheat hull powder addition (P < 0.05), especially the coarse buckwheat hull powder. Although the elasticity of rice cakes decreases with increasing addition of the ultrafine buckwheat hull powder of the present invention, the reduction is much lower than that of coarse buckwheat hull powder, and the structural destructive effect on rice cakes is smaller. 10% coarse buckwheat hull powder significantly reduces the stickiness and chewiness of rice cakes (P < 0.05). When the addition amount exceeds 10%, the stickiness and chewiness of rice cakes increase, indicating that the negative impact of coarse buckwheat hull powder on the texture quality of rice cakes changes very drastically, leading to problems such as high-fiber rice cake foods (addition amount ≥ 20%) being difficult to process and having poor edible quality. However, the stickiness and chewiness of rice cakes after adding ultrafine buckwheat hull powder were not significantly different from those of control rice cakes (P > 0.05). This shows that ultrafine buckwheat hull powder can reduce the negative impact of insoluble dietary fiber on the edible quality of rice cakes, and when the addition amount is within 30%, the quality of rice cakes is not affected by the insoluble dietary fiber content.

[0044] Table 2 Effects of buckwheat hull powder with different particle sizes and addition amounts on the texture quality of rice cakes

[0045]

[0046] Note: a, b, c, d indicate statistical differences with P < 0.05 in the same column.

[0047] Example 2: Effect of 30% Buckwheat Hull Flour Addition on Water Holding Capacity of Rice Flour and Rice Cake

[0048] (1) Preparation of buckwheat hull powder: Buckwheat hulls were crushed using turbulent ultrafine grinding technology with technical parameters of 450 Hz, feed speed of 500 r / min, and fan frequency of 25 Hz to obtain the ultrafine buckwheat hull powder of the present invention. The average particle size of the ultrafine buckwheat hull powder is 13.43 μm (D50), of which particles with a particle size of more than 100 μm account for 8.44%, particles with a particle size of 25 to 100 μm account for 31.90%, and the rest are particles with a particle size of less than 25 μm, and all of them can pass through a 1000 mesh sieve. The average particle size of the coarse buckwheat hull powder for comparison is 184.33 μm (D50).

[0049] (2) Formula of high-fiber rice cake pre-made flour: by weight percentage, buckwheat hull powder 30%, rice flour 55%, dry yeast powder 5%, sugar 10%. The water holding capacity of the mixed rice flour was measured, and the results are shown in Figure 2 A.

[0050] (3) Rice paste fermentation: Add 150% water by weight to the high-fiber rice cake pre-made powder to make rice paste. Ferment for 50 minutes at 30°C and 85% humidity. Pour the rice paste into a mold and ferment for 5 minutes at room temperature.

[0051] (4) Rice cake ripening: The fermented rice paste was placed in a steamer and steamed at 100°C for 30 min. The moisture ratio and moisture distribution of the steamed rice cake were measured using low-field nuclear magnetic resonance. Figure 2 A and Figure 2 B.

[0052] like Figure 2 As shown in Figure A, buckwheat hull powder significantly increased the water-holding capacity of rice flour (P < 0.05). The ultrafine buckwheat hull powder of the present invention increased the water-holding capacity of the mixed rice flour by 45.00%, which was 12.52% higher than that of coarse buckwheat hull powder. The hydroxyl groups in dietary fiber can enhance the water-holding capacity of the mixed rice flour. When the particle size of buckwheat hulls is reduced from the tissue scale to the cellular scale, the increased specific surface area creates larger pores that promote water retention. Furthermore, the exposed hydroxyl groups form more hydrogen bonds between the dietary fiber and starch.

[0053] At the same time, the improvement of water holding capacity of rice flour by ultrafine buckwheat hull powder also has a positive effect on high-fiber rice cakes. Figure 2As shown in B, P21 is strongly bound water, P22 is weakly bound water, and P23 is free water. In the control rice cake, the proportion of strongly bound water is 10%, the proportion of weakly bound water is 89%, and the proportion of free water is 1%. After adding the ultrafine buckwheat hull powder of the present invention, the proportion of strongly bound water in the rice cake decreases, and the proportion of weakly bound water increases, indicating that the moisture in the starch gel network of the rice cake increases, which is beneficial to the uniform distribution of moisture in the internal pores. Ultrafine buckwheat hull powder has better water affinity, which can make the insoluble dietary fiber-starch form a stronger hydrogen bond network, which is more conducive to binding water molecules. On the contrary, the proportion of strongly bound water in the coarse buckwheat hull powder rice cake increases, and the proportion of weakly bound water decreases, indicating that the coarse buckwheat hull powder is more inclined to the combination of fiber itself and moisture, rather than promoting moisture retention in the fiber-starch network. Therefore, the internal moisture of the rice cake is easy to evaporate during the steaming process, and the rice cake is easy to collapse. As Figure 2 As shown in Figure C, the bright color in the figure indicates the area where moisture is concentrated. The ultrafine buckwheat hull powder of the present invention maintains uniform moisture distribution in the rice cake, which is conducive to the close combination of moisture and starch in the rice cake, thereby promoting full gelatinization of starch to form a uniform rice cake structure.

[0054] Example 3: Effect of 30% Buckwheat Hull Powder on Gas Production and Viscosity of Rice Paste

[0055] (1) Preparation of buckwheat hull powder: Buckwheat hulls were crushed by turbulent grinding to obtain the ultrafine buckwheat hull powder of the present invention and the coarse buckwheat hull powder for comparison. The average particle size of the ultrafine buckwheat hull powder was 13.43 μm (D50), of which 8.44% were particles with a particle size of more than 100 μm, 31.90% were particles with a particle size of 25 to 100 μm, and the rest were particles with a particle size of less than 25 μm, all of which could pass through a 1000 mesh sieve. The average particle size of the coarse buckwheat hull powder for comparison was 184.33 μm (D50).

[0056] (2) The formula of high-fiber rice cake pre-made powder: by weight percentage, buckwheat hull powder 30%, rice flour 58%, dry yeast powder 2% and sugar 10%. The viscosity of rice paste was measured, see Figure 3 A.

[0057] (3) Rice paste fermentation: Add 140% water to the high-fiber rice cake pre-made powder by weight to make rice paste. Ferment for 40 minutes at 30°C and 85% humidity. Pour the rice paste into the mold and ferment for 10 minutes at room temperature. Detect the gas production of the rice paste after fermentation. Figure 3 A and Figure 3 B.

[0058] (4) Rice cake ripening: The fermented rice paste was placed in a steamer and steamed at 100°C for 30-50 min. The specific volume and conformation of the rice cake after steaming were measured. Figure 3 C and Figure 3 D.

[0059] like Figure 3 As shown in Figure A, the gas production of the control rice paste after fermentation was 81.5 mL. After adding 30% coarse buckwheat hull powder, the gas production of the rice paste decreased to 68 mL, but after adding 30% ultrafine buckwheat hull powder, the gas production of the rice paste increased by 26.38%. The addition of coarse buckwheat hull powder significantly reduced the viscosity of the rice paste (P < 0.05), but the ultrafine buckwheat hull powder increased the viscosity of the rice paste by 122.74%. Since the carbon dioxide produced by yeast in the cake batter after fermentation requires the physical support of the batter, the addition of dietary fiber will weaken this physical support in the cake. At the same addition amount, the particle size of ultrafine buckwheat hull powder is much smaller than that of coarse buckwheat hull powder. Therefore, the rice paste with the addition of ultrafine buckwheat hull powder is sufficient to support the bubbles produced by the yeast ( Figure 3 B) The insoluble dietary fiber in the ultrafine buckwheat hull powder can promote the binding of starch and water, increasing the viscosity of the rice paste and thus enhancing the physical support of carbon dioxide. During the fermentation process, the change in the gas production of the fermented rice paste can predict the volume of the rice cake. Figure 3 As shown in Figure C, the specific volume of rice cakes containing ultrafine buckwheat hull flour was not significantly different from that of the control (P>0.05), while coarse buckwheat hull flour reduced the specific volume of rice cakes by 39.88%. Reducing the particle size of buckwheat hull flour from the tissue scale to the cellular scale can reverse the damage to the fermented starch gel structure caused by high insoluble dietary fiber addition.

[0060] The embodiments described above are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

Claims

1. An application of ultrafine buckwheat hull powder in preparing high-fiber rice cake pre-made flour, characterized in that: The ultrafine buckwheat hull powder has an average particle size of 13.43 μm, with particles with a particle size exceeding 100 μm accounting for 8.44%, particles with a particle size of 25 to 100 μm accounting for 31.90%, and the remainder being particles with a particle size less than 25 μm, all of which can pass through a 1000-mesh sieve; wherein the high-fiber rice cake pre-made flour comprises 20 to 30% ultrafine buckwheat hull powder, 50 to 80% rice flour, 2 to 5% dry yeast powder, and 5 to 15% sugar; The ultrafine buckwheat hull powder is prepared by the following method: buckwheat hulls are crushed using turbulent ultrafine grinding technology, with technical parameters of 450 Hz, feed speed of 500 r / min, and fan frequency of 25 Hz.

2. Application of the high-fiber rice cake preformed flour according to claim 1 in preparing rice cake.

3. A method for preparing high-fiber rice cake, the method comprising: 1) Adding 130% to 150% water by weight to the high-fiber rice cake preformed powder of claim 1 to prepare rice paste; performing a primary fermentation at 30°C and 85% relative humidity for 30 to 50 minutes, pouring the rice paste into a mold, and performing a secondary fermentation at room temperature for 5 to 10 minutes; 2) Cooking the rice cakes: Steam at 100°C for 30-50 minutes; or bake at 165-180°C for 15-30 minutes.

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