Refining method for rice processing

Abstract

The invention discloses a refining method for rice processing, and relates to the technical field of grain processing, and the refining method comprises the following steps: pre-treating aged rice and adjusting moisture; carrying out solid-state fermentation by adopting a compound probiotic leavening agent containing lactobacillus plantarum, bacillus subtilis and saccharomyces cerevisiae; drying the fermented rice at low temperature; performing multi-stage light grinding to obtain refined rice and rice bran; carrying out superfine grinding and enzymolysis treatment on rice bran to obtain an extract; the extract is added into the refined rice as a nutrition enhancer, and the rice husks can be carbonized and then returned to the rice field for use. According to the method, the flavor of the aged rice is improved through fermentation of the compound probiotics, nutrition enhancement is achieved through the rice bran extract, cooperation of microbiome engineering, aged rice improvement and by-product utilization is achieved by combining resource utilization of the rice husks, the quality and the additional value of the aged rice are improved, processing energy consumption and cost are reduced, and a green and cyclic processing mode is formed.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of grain processing, in particular to a refining method for rice processing. BACKGROUND

[0002] As the main grain crop of Chinese residents, the processing quality of rice is closely related to the market value. The aged rice is prone to problems such as increase of fatty acid value, deterioration of flavor, rough taste and the like due to too long storage time, which leads to a substantial decrease of commodity value. The traditional processing method cannot effectively improve these defects, resulting in a large amount of waste of grain resources. Meanwhile, the by-products such as rice bran and rice hull generated in the rice processing process are low in utilization rate and high in environmental treatment cost due to lack of efficient utilization technology, which restricts the sustainable development of the rice processing industry.

[0003] In the prior art, the methods for improving aged rice are mostly concentrated in physical conditioning (such as high-temperature cooking and high-pressure treatment) or chemical treatment (such as enzyme addition), but there are problems such as high cost, great loss of nutrients or residual risk; and the utilization of by-products is limited to single component extraction (such as rice bran oil extraction), which cannot form a synergistic linkage with the main processing flow.

[0004] Therefore, the application is provided. SUMMARY

[0005] The application aims to provide a refining method for rice processing to solve the problems in the background.

[0006] To solve the above technical problems, the application provides a refining method for rice processing, which comprises the following steps:

[0007] S1: pretreating aged paddy to remove impurities and adjust the moisture content to 14-16%;

[0008] S2: performing solid-state fermentation on the pretreated paddy by using a composite probiotic starter, wherein the composite probiotic starter comprises Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae;

[0009] S3: performing low-temperature drying on the fermented paddy to a moisture content of 13-14%;

[0010] S4: performing rice milling by using a multi-stage light milling process to obtain refined rice and by-product rice bran;

[0011] S5: performing ultrafine grinding on the rice bran obtained in S4, adding an enzyme to perform enzyme treatment to obtain a rice bran extract;

[0012] S6: adding the rice bran extract of S5 as a nutritional fortifier to the refined rice of S4; improving the flavor of aged rice through composite probiotic fermentation, while using the byproduct rice bran to make a nutritional fortifier to add back to the refined rice, realizing the synergy of microbial community engineering, aged rice quality improvement, and byproduct comprehensive utilization, improving the quality and added value of aged rice, and reducing processing costs.

[0013] Further, in S2, the fermentation temperature is 30-35℃, and the time is 12-24 hours; the appropriate fermentation temperature and time are limited, which is conducive to the growth and metabolism of composite probiotics, fully plays the role of improving the flavor of aged rice, and ensures the stability of the fermentation effect.

[0014] Further, in S2, the ratio of viable counts of Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae is 3:2:1, and the total viable count is ≥1×10 8 CFU / g; the strain ratio and viable count of the composite probiotic starter are optimized, so that the strains can synergistically act to improve the fermentation efficiency, better reduce the content of free fatty acids in aged rice, and improve the taste and flavor of aged rice.

[0015] Further, in S2, 0.1-0.5% of rice bran enzymatic hydrolysate by weight is added during the fermentation process, and the rice bran enzymatic hydrolysate is obtained by enzymatic hydrolysis in step S5; the enzymatic hydrolysate of the byproduct rice bran is used as a fermentation promoter, realizing the recycling of resources and reducing the cost of the fermentation agent, while promoting the fermentation of probiotics and further improving the improvement effect of aged rice.

[0016] Further, in S3, the low-temperature drying temperature is ≤45℃, and the microwave-assisted hot air drying technology is used, with a microwave power density of 0.5-1.5 W / g and a hot air speed of 1.5-3 m / s; low-temperature drying combined with microwave-assisted hot air drying technology can not only avoid the damage of high temperature to the nutrients and flavor substances produced by fermentation, but also improve the drying efficiency, shorten the drying time, and reduce the processing energy consumption.

[0017] Further, in S4, the multi-stage light milling process adopts 3-5 milling processes, the milling rate of each process is controlled at 5-10%, and the milling pressure is ≤0.3 MPa; through the multi-stage light milling process, the broken rice rate in the milling process is reduced, the integrity and quality of the refined rice are improved, and the energy consumption in the milling process is reduced.

[0018] Further, in the S5, the enzymatic treatment uses a complex enzyme preparation containing cellulase, xylanase and protease, the enzymatic temperature is 45-55 DEG C, the pH value is 4.5-6.0, and the time is 3-6 hours; the specific complex enzyme preparation and enzymatic parameters can effectively destroy the cell wall structure of rice bran, improve the extraction rate of soluble dietary fiber and protein and other nutritional ingredients in rice bran, and make the rice bran extract more suitable as a nutritional fortifier.

[0019] Further, in the S6, the addition amount of rice bran extract is 0.5-2% of the weight of refined rice; the reasonable addition amount of rice bran extract can increase the nutrition of refined rice and improve the nutritional value without adversely affecting the taste and flavor of rice.

[0020] Further, it also includes S7: the rice hull produced in step S4 is subjected to carbonization treatment to obtain biochar, and the biochar is used as a soil conditioner and returned to the paddy field; the rice hull is resourcefully utilized to make biochar and returned to the paddy field, realizing the recycling of agricultural waste and reducing the cost of waste treatment, while being beneficial to improving the soil structure and promoting the growth of rice, forming a virtuous ecological cycle.

[0021] Compared with the prior art, the beneficial effects of the present application are:

[0022] 1. The complex probiotic fermentation technology effectively improves the flavor and taste of aged rice, solving the problems of obvious aged taste and rough texture caused by long storage time. The synergistic effect of complex probiotics can neutralize the undesirable components in aged rice and generate metabolites with pleasant flavor, making the quality of treated aged rice close to that of new rice, significantly improving the commodity value of aged rice and reducing the waste of grain resources.

[0023] 2. The resource utilization of rice bran, rice hull and other by-products constructs a recycling system from main product processing to by-product value-added. The rice bran is converted into a nutritional fortifier and added to refined rice, improving the nutritional added value of the product; the rice hull is carbonized and used as a soil conditioner for recycling, realizing efficient conversion of agricultural waste, reducing waste treatment cost, and improving the economy and environmental protection of the entire processing process. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A flowchart of a refining method for rice processing. DETAILED DESCRIPTION

[0025] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0026] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. Figure 1 The present application provides a technical solution: a refining method for rice processing, comprising:

[0027] I. Example 1

[0028] Raw material preparation: select aged indica rice with a storage period of 12 months, initial moisture content of 12.5%, fatty acid value of 35 mg KOH / 100 g, and broken rice rate of 18%.

[0029] S1. Pretreatment

[0030] The vibration screen (screen hole diameter 2.5 mm) is used to remove stones, weeds and other impurities in the aged rice, and the impurity removal rate reaches 99.5%; the stone removal efficiency is 99% by using the specific gravity stone removal machine; the spray water machine is used to adjust the moisture content of the rice to 15%, and the rice is placed for 2 hours after spraying water, so that the water is uniformly distributed.

[0031] S2. Solid-state fermentation

[0032] The composite probiotic fermenting agent includes Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae, and the ratio of viable bacteria is 3:2:1, and the total viable bacteria number is 2×10 8 CFU / g; the fermenting agent is inoculated at 0.3% by weight of the rice, and 0.3% by weight of the rice bran enzymolysis liquid (obtained by subsequent S5 step of enzymolysis treatment) is added; the solid-state fermentation is carried out at 32℃, the fermentation time is 18 hours, and the material is turned over every 6 hours during the fermentation process to maintain the ventilation property.

[0033] S3. Low-temperature drying

[0034] The microwave-assisted hot air drying technology is used to dry the fermented rice, the microwave power density is 1.0 W / g, the hot air speed is 2.0 m / s, and the drying temperature is controlled at 42℃; the rice is dried to a moisture content of 13.5%, and the drying time is 40 minutes.

[0035] S4. Multi-stage light milling

[0036] The multi-stage light milling is carried out by using four rice milling processes, the first rice milling process has a milling rate of 5% and a rice milling pressure of 0.2 MPa; the second rice milling process has a milling rate of 7% and a rice milling pressure of 0.25 MPa; the third rice milling process has a milling rate of 8% and a rice milling pressure of 0.28 MPa; and the fourth rice milling process has a milling rate of 6% and a rice milling pressure of 0.22 MPa; after the rice milling, refined rice and by-product rice bran are obtained, and the yield of the rice bran is 8% of the weight of the paddy.

[0037] S5. Enzymatic treatment of rice bran

[0038] The rice bran is subjected to ultrafine grinding, and the particle size after grinding is ≤50 μm; a composite enzyme preparation (the mass ratio of cellulase, xylanase and protease is 2:1:1) is added, and the enzyme addition amount is 0.5% of the weight of the rice bran; the enzymolysis is carried out at 50°C and pH 5.0 for 4 hours; after the enzymolysis is completed, a plate and frame filter is used to obtain a rice bran extract, wherein the soluble dietary fiber content is 38%, the protein content is 20%, and the retention rate of γ-oryzanol is 85%.

[0039] S6. Addition of a nutrition fortifier

[0040] The rice bran extract is added to the refined rice at 1.2% of the weight of the refined rice, and mixed by a double-screw mixer for 15 minutes, and the uniformity of the mixture reaches 98%.

[0041] S7. Carbonization treatment of rice hulls

[0042] The rice hulls generated in the step S4 are collected, and subjected to carbonization treatment at 500°C for 2 hours to obtain biochar; the particle size of the biochar is controlled to be 1-3 mm, and the biochar is used as a soil conditioner and returned to the paddy field.

[0043] Product indexes of the example one: the fatty acid value of the refined rice is 22 mgKOH / 100g, the chalkiness is 0.8%, and the broken rice rate is 4%; the unit energy consumption is reduced by 28% compared with the traditional process, and the comprehensive utilization rate of the by-products is 96%.

[0044] Effects of the example one: the example one significantly improves the flavor and quality of the aged rice by optimizing the cooperation of each step, and realizes efficient utilization of by-products, reduces the processing energy consumption and cost.

[0045] II. Comparative example

[0046] Comparative example 1: without fermentation treatment

[0047] Except that the step S2 of the solid-state fermentation is not performed, the remaining steps are the same as those of the example one.

[0048] Product indexes: the fatty acid value is 32 mgKOH / 100g, the chalkiness is 1.5%, and the broken rice rate is 15%; the aged rice has a distinct aged flavor and a rough taste.

[0049] Comparative analysis: without fermentation treatment, it cannot effectively reduce the fatty acid value of aged rice and improve its flavor, and the product quality is poor.

[0050] Comparative example 2: single probiotic fermentation

[0051] In step S2, only Lactobacillus plantarum was used for fermentation, and the viable bacterial count was 2×10 8 CFU / g, and the remaining steps were the same as example one.

[0052] Product indicators: fatty acid value 28 mgKOH / 100g, chalkiness 1.2%, broken rice rate 6%; flavor improvement effect is poorer than example one, and rice elasticity is insufficient.

[0053] Comparative analysis: the effect of single probiotic is limited, and it cannot play a synergistic role in improving flavor and quality like compound probiotic, and the effect is not as good as example one.

[0054] Comparative example 3: fermentation temperature deviates from the optimal value

[0055] In step S2, the fermentation temperature was controlled at 25℃, and the remaining steps were the same as example one.

[0056] Product indicators: fatty acid value 30 mgKOH / 100g, chalkiness 1.3%, broken rice rate 7%; low fermentation efficiency, and less flavor substances are generated.

[0057] Comparative analysis: too low fermentation temperature is not conducive to the growth and reproduction of probiotics and metabolic activity, resulting in poor fermentation effect and affecting the improvement effect of aged rice.

[0058] Comparative example 4: fermentation time is too short

[0059] In step S2, the fermentation time was 6 hours, and the remaining steps were the same as example one.

[0060] Product indicators: fatty acid value 33 mgKOH / 100g, chalkiness 1.4%, broken rice rate 8%; the aged flavor of aged rice is not completely removed, and the taste is still hard.

[0061] Comparative analysis: insufficient fermentation time, probiotics cannot fully play a role, cannot effectively reduce the fatty acid value and improve the flavor, and the product quality is not ideal.

[0062] Comparative example 5: without microwave-assisted hot air drying

[0063] In step S3, only hot air drying was used, the temperature was 42℃, the hot air speed was 2.0 m / s, and the remaining steps were the same as example one.

[0064] Product indicators: fatty acid value 23 mgKOH / 100g, chalkiness 1.0%, broken rice rate 5%; the drying time is extended to 90 minutes, and the unit energy consumption is 40% higher than example one.

[0065] Comparative analysis: Without microwave assistance, the drying efficiency is greatly reduced, and the energy consumption increases. Although the product quality is close to that of Example 1, the processing cost increases.

[0066] Comparative Example 6: Reduction of rice milling process

[0067] In the S4 step, two rice milling processes were used, with a first rice milling rate of 15% and a second rice milling rate of 10%. The remaining steps were the same as in Example 1.

[0068] Product indicators: fatty acid value 22 mgKOH / 100g, chalkiness 0.9%, broken rice rate 12%; the surface finish of the polished rice is poor, with more bran powder residue.

[0069] Comparative analysis: The reduction of the rice milling process leads to uneven milling and an increase in the broken rice rate. At the same time, the surface bran cannot be completely removed, affecting the appearance and quality of the product.

[0070] Comparative Example 7: Different enzyme treatment parameters

[0071] In the S5 step, the enzyme treatment temperature was 35°C, and the time was 2 hours. The remaining steps were the same as in Example 1.

[0072] Product indicators: soluble dietary fiber content in rice bran extract 25%, protein content 12%; after adding to polished rice, the nutritional improvement effect is not obvious.

[0073] Comparative analysis: The enzyme treatment temperature is too low and the time is too short, which cannot fully destroy the cell wall of rice bran, leading to low extraction rate of nutritional components and poor utilization effect of by-products.

[0074] Comparative Example 8: Excessive addition of rice bran extract

[0075] In the S6 step, the addition amount of rice bran extract was 3% of the weight of polished rice. The remaining steps were the same as in Example 1.

[0076] Product indicators: the polished rice has a rough texture and a distinct bran taste; consumer acceptance is low.

[0077] Comparative analysis: Excessive addition of rice bran extract has an adverse effect on the taste and flavor of rice, although the nutritional components increase, the palatability of the product decreases.

[0078] Comparative Example 9: No carbonization treatment of rice hulls

[0079] Except for not performing the S7 step of rice hull carbonization treatment, the remaining steps were the same as in Example 1.

[0080] Product indicators: basically the same as in Example 1; but the rice hulls are treated as waste, increasing the processing cost and not realizing the recycling of resources.

[0081] Comparative analysis: the lack of resource utilization of rice hulls not only increases the cost of waste disposal, but also cannot form a benign ecological cycle, which does not meet the concept of green production.

[0082] Comparative Example 10: traditional processing technology

[0083] Using traditional rice processing technology: direct milling after cleaning (3 milling processes), without fermentation and by-product recycling, and the rest of the parameters are set according to the conventional setting.

[0084] Product indicators: fatty acid value 34 mgKOH / 100g, chalkiness 2.0%, broken rice rate 16%; unit energy consumption is 35% higher than Example 1, and by-product comprehensive utilization rate is only 30%.

[0085] Comparative analysis: traditional technology cannot effectively improve the quality of old rice, has high energy consumption and low by-product utilization rate, and has obvious disadvantages in quality, energy consumption and resource utilization compared with Example 1.

[0086] III. Comparison and summary of each example and comparative example

[0087] Through the comparison of Example 1 and each comparative example, it can be seen that Example 1 has significant advantages in improving the quality of old rice, reducing processing energy consumption, and increasing by-product utilization rate through the synergistic effect of reasonable pretreatment, compound probiotic fermentation, low-temperature drying, multi-stage light milling, rice bran enzymolysis, and rice hull carbonization, etc. The comparison data is shown in Table 1 as follows:

[0088]

[0089] Table 1: Comparison of data of examples and comparative examples.

[0090] Comparative Examples 1-10 deviate from the best parameters or process steps of Example 1 at different links, resulting in different degrees of decline in product quality, energy consumption, cost or resource utilization. For example, not using fermentation treatment or single probiotic fermentation will not effectively improve the flavor and quality of old rice; unreasonable fermentation temperature and time will affect the fermentation effect; changing the drying method will increase energy consumption; reducing the milling process will increase the broken rice rate; improper enzyme parameters will reduce the utilization value of by-products; inappropriate amount of rice bran extract will affect the taste of the product; and not treating rice hulls will not achieve resource recycling.

[0091] In summary, the process steps and parameter settings of Example 1 are the best optimized scheme, which can realize low-energy, high-resource utilization rate rice processing under the premise of ensuring product quality, and has good economic and environmental benefits.

Claims

1. A refining method for rice processing, characterized by: The method comprises the following steps: S1: pretreating aged rice to remove impurities and adjust the moisture content to 14-16%; S2: using a composite probiotic starter to ferment the pretreated rice, the composite probiotic starter comprising Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae; S3: low-temperature drying the fermented rice to a moisture content of 13-14%; S4: using a multi-stage light milling process to mill rice to obtain refined rice and by-product rice bran; S5: ultra-finely grinding the rice bran obtained in S4, adding an enzyme preparation for enzyme hydrolysis treatment to obtain a rice bran extract; S6: adding the rice bran extract of S5 as a nutritional fortifier to the refined rice of S4.

2. The refining method for rice processing according to claim 1, characterized by: In S2, the fermentation temperature is 30-35℃, and the time is 12-24 hours.

3. The refining method for rice processing according to claim 1, characterized by: The ratio of viable cell number of Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae in S2 is 3:2:1, and the total viable cell number is ≥1×10 8 CFU / g.

4. The refining method for rice processing according to claim 1, wherein: In S2, 0.1-0.5% of rice bran enzyme hydrolysate by weight is added during the fermentation process, and the rice bran enzyme hydrolysate is obtained by enzyme hydrolysis treatment in step S5.

5. The method for refining rice according to claim 1, wherein: In S3, the low-temperature drying temperature is ≤45℃, and a microwave-assisted hot air drying technology is used, with a microwave power density of 0.5-1.5 W / g and a hot air speed of 1.5-3 m / s.

6. The refining method for rice processing according to claim 1, wherein: In S4, the multi-stage light milling process uses 3-5 rice milling processes, with a milling rate of 5-10% for each process and a rice milling pressure ≤0.3 MPa.

7. The method for refining of rice as claimed in claim 1 wherein: In S5, the enzyme hydrolysis treatment uses a composite enzyme preparation comprising cellulase, xylanase and protease, with an enzyme hydrolysis temperature of 45-55℃, a pH value of 4.5-6.0, and a time of 3-6 hours.

8. The method for refining of rice as claimed in claim 1 wherein: In S6, the addition amount of rice bran extract is 0.5-2% of the weight of refined rice.

9. The method for refining of rice as claimed in claim 1 wherein: S7: carbonizing the rice hull produced in step S4 to obtain biochar, and returning the biochar as a soil conditioner to the paddy field.

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