Preparation method of rice oligosaccharide

Abstract

The application discloses a preparation method of rice oligosaccharide, and belongs to the technical field of oligosaccharide production. The method is characterized in that early indica rice or broken rice is used as raw material, and the rice oligosaccharide is prepared through the steps of multi-stage vibration screening + spin-rolling type cleaning and impurity removal, sand wheel grinding coupling rubber grinding, high-pressure jet + multi-stage series continuous liquefaction, three-layer vacuum suction filter for deslagging, fungal saccharifying enzyme hydrolysis for 105 min, three times of decolorization, ion exchange + nanofiltration membrane refining, concentration and drying and the like. The product stability under different raw materials and process parameters is verified through multiple embodiments, and the high-purity product with a total oligosaccharide content of 85.15%, a 3-7 sugar proportion of more than 50% and a glucose content of only 1.92% can be stably produced. The method can realize efficient and controllable production of rice oligosaccharide and other products, and form a key technology and industrialization for producing high-value-added series products from early indica rice or broken rice.

Description

Technical Field

[0001] This invention relates to the field of oligosaccharide preparation technology, and in particular to a method for preparing rice oligosaccharides. Background Technology

[0002] Functional oligosaccharides are a class of carbohydrates that cannot be broken down by human digestive enzymes and can selectively promote the proliferation of beneficial bacteria in the gut. They have various physiological functions, such as regulating gut microbiota, enhancing immunity, and promoting mineral absorption. Currently, most oligosaccharides on the market are made from corn and cassava, while products made from rice, especially early indica rice and broken rice, are less common.

[0003] Existing rice oligosaccharide preparation processes have the following drawbacks: 1) The DE value is difficult to control precisely, leading to unstable oligosaccharide composition; 2) Poor protein separation, resulting in unclear filtrate and high impurity content; 3) Low oligosaccharide purity, high glucose content, and poor probiotic effects; 4) Lack of systematic product efficacy verification, limiting industrial application. To address these problems, this invention provides an industrial method for preparing high-purity rice oligosaccharides using early indica rice or broken rice as raw materials. Summary of the Invention

[0004] The purpose of this invention is to provide an industrial method for preparing high-purity rice oligosaccharides using early indica rice or broken rice as raw materials.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for preparing rice oligosaccharides includes the following steps: (1) Raw material pretreatment: Early indica rice or broken rice is used as raw material. The rice is screened through multiple stages to remove sand, metal fragments, husks and rice bran impurities. The screened rice grains are sent into a special swirling washing tank. Water is added to the bottom and air at a pressure of 0.2-0.3 MPa is introduced to form a swirling washing water flow to wash away soil and dust. A three-stage recovery sedimentation device is used to remove impurities from the soaking water. The soaking time is 2-3 hours in summer and 4-5 hours in winter. (2) Grinding and slurry preparation: The soaked rice grains are wet-ground using a grinding wheel mill coupled with a rubber mill to obtain rice slurry with uniform particle size; 0.05-0.1% (w / w) of calcium chloride and 10-15 U / g starch of heat-resistant α-amylase are added to the rice slurry and stirred evenly; (3) Multi-stage series continuous liquefaction: The rice slurry after slurry preparation is sent to a high-pressure jet liquefaction unit and jet liquefaction is carried out at 95-100℃; the liquefied slurry enters 6-10 laminar flow tanks in series for continuous liquefaction reaction, and the liquefaction DE value is controlled to be 10-15 according to the target product requirements at different series stages. (4) Slag removal and separation: The liquefied slurry is sent to a three-layer vacuum filter press for slag removal and separation. The three-layer vacuum filter press consists of a stainless steel porous partition layer, a filter paper layer, and an activated carbon layer from top to bottom, and the clarified filtrate and rice protein filter residue are obtained. (5) Saccharification and enzymatic hydrolysis: The clarified filtrate is sent to the saccharification tank, the pH value is adjusted to 4.5-5.0, 50-80 U / g starch of fungal saccharifying enzyme is added, and enzymatic hydrolysis is carried out at 55-60℃ for 105 min; (6) Refining and purification: The saccharified liquid is subjected to three activated carbon decolorizations and three ion exchange desaltings in sequence, and then separated and purified by nanofiltration membrane to retain components with a molecular weight of 300-2000 Da; (7) Concentration and drying: The purified oligosaccharide solution is concentrated by vacuum flash evaporation to a solid content of 50-60%, and then spray dried to obtain the rice oligosaccharide product.

[0006] In summary, the present invention has the following beneficial effects: 1. This invention uses early indica rice or broken rice as raw material, and prepares rice oligosaccharides through a series of steps including multi-stage vibrating sieving + tumbling washing and impurity removal, grinding with a grinding wheel mill coupled with a rubber mill, high-pressure jetting + multi-stage series continuous liquefaction, slag removal with a three-layer vacuum filter, enzymatic hydrolysis with fungal saccharifying enzyme for 105 minutes, three-stage decolorization and ion exchange + nanofiltration membrane refining, concentration and drying, which are suitable for large-scale industrial application.

[0007] 2. The present invention optimizes the saccharification and enzymatic hydrolysis time to 105 min, so that the total oligosaccharide (2-10 sugar) content is stable at 85.15%, of which the 3-7 sugar accounts for > 50% and the glucose content is only 1.92%. This invention can form a key technology and industrialize the production of high value-added series products from early indica rice or broken rice. Attached Figure Description

[0008] Figure 1 These are HPLC-ELSD chromatograms of standard samples and rice oligosaccharide samples at different enzymatic hydrolysis times; Figure 2 These are infrared spectra of oligosaccharide samples at different enzymatic hydrolysis times; Figure 1 In the formula, a represents glucose, b represents maltose, c represents maltotriose, d represents maltotetraose, e represents maltopentose, f represents maltohexaose, g represents maltoheptaose, h represents maltooctaose, i represents maltononose, and j represents maltodexaose. Detailed Implementation

[0009] The present invention will be further described in detail below with reference to the accompanying drawings. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0010] This embodiment provides a method for preparing rice oligosaccharides, the specific steps of which are as follows: (1) Raw material pretreatment: Take 100kg of early indica broken rice and remove sand, metal fragments, rice husks and bran by three-stage vibrating sieve (sieve hole sizes are 5mm, 2mm and 0.5mm respectively); send the sieved rice grains into a 0.5m³ vortex washing tank, add 300L of tap water, and introduce compressed air at 0.25MPa pressure from the bottom to form a vortex water flow for rinsing for 15min; send the washed rice grains into a rice soaking tank, add 300L of tap water, and soak at 25℃ for 2.5h; the soaking water is recycled for the next batch of washing after sedimentation in a three-stage sedimentation tank.

[0011] (2) Grinding and preparing the rice slurry: After soaking, the rice grains are fed into a grinding wheel mill for coarse grinding, and then into a rubber mill for fine grinding to obtain rice slurry; 0.08% (w / w) of calcium chloride and 12 U / g starch of heat-resistant α-amylase (Novozymes Termoyl SC) are added to the rice slurry and stirred evenly.

[0012] (3) Multi-stage series continuous liquefaction: The rice slurry after slurry preparation is sent to a high-pressure jet liquefaction unit and liquefied by jetting at 98°C; the liquefied slurry enters 8 series laminar flow tanks in sequence and reacts at 95°C. The total liquefaction time is 90 min and the final liquefaction DE value is controlled to be 12.

[0013] (4) Slag removal and separation: The liquefied slurry is sent into a three-layer vacuum filter press. The upper layer is a stainless steel porous partition layer with a pore size of 0.5 mm, the middle layer is polypropylene filter paper, and the lower layer is a 10 cm thick granular activated carbon layer. The filtrate is filtered under a vacuum of -0.08 MPa to obtain a clear filtrate and rice protein filter residue. The filter residue is dried to obtain rice protein powder.

[0014] (5) Saccharification and enzymatic hydrolysis: The clarified filtrate was sent into a 1m³ saccharification tank, the pH was adjusted to 4.8 with citric acid, and 60U / g starch-containing fungal saccharifying enzyme (Novozymes AMG 300L) was added. The enzyme was hydrolyzed at 58℃ for 105min. After the enzymatic hydrolysis was completed, the temperature was raised to 90℃ to inactivate the enzyme for 10min.

[0015] (6) Purification: The saccharified liquid is sent to the decolorization tank, 0.5% (w / w) of powdered activated carbon is added, and the mixture is stirred and decolorized at 80℃ for 30 min and then filtered. The above decolorization operation is repeated twice. The decolorized filtrate is desalted by passing it through a cation exchange column, an anion exchange column and a mixed ion exchange column in sequence, and the conductivity is controlled to be <10μS / cm. The desalted filtrate is separated and purified by passing it through a nanofiltration membrane (molecular weight cutoff of 1000Da), and the retentate is collected.

[0016] (7) Concentration and drying: The retentate is sent to a vacuum flash concentrator and concentrated to a solid content of 55% at 60℃ and -0.09MPa. The concentrate is then spray-dried (inlet air temperature 180℃, outlet air temperature 80℃) to obtain 28.5kg of rice oligosaccharide product.

[0017] Product testing: Determination of oligosaccharide composition in enzymatic hydrolysis products at different hydrolysis times The oligosaccharide composition in rice oligosaccharide samples was determined by HPLC-ELSD. Chromatographic column: Amide-80 (OCS) amino column (250 mm × 4.6 mm, 5 μm); column temperature: 40 ℃; mobile phase gradient: 0-4 min, phase A (ultrapure water) increased from 40% to 45%, held for 1 min, 5-18 min, increased from 45% to 50%; phase B was acetonitrile; injection volume: 10 μL; flow rate: 1.0 mL / min; drift tube temperature: 90 ℃; evaporation light temperature: 90 ℃; N2 flow rate: 1.6 mL / min. Quantitative analysis of samples was performed using the external standard method based on peak area. A standard curve was established with sample concentration as the independent variable (X, mg / mL) and peak area as the dependent variable (Y, mV·s). The concentration range of the standards glucose, maltose, isomaltose, maltotriose, panose, isomalttriose, maltotetraose, isomaltetose, maltopentose, maltohexaose, maltoheptaose, maltooctaose, maltononose, and maltodecanose was 0.1–0.8 mg / mL.

[0018] Test results: by Figure 1As shown in Table 1, rice oligosaccharides at different enzymatic hydrolysis times are mainly composed of a glucose, b maltose, c maltotriose, d maltotetraose, e maltopentose, f maltohexaose, g maltoheptaose, h maltooctaose, i maltononose, and j maltodecanose. With the extension of enzymatic hydrolysis time, rice oligosaccharides first increase rapidly, then the rate of increase gradually slows down, and finally tends to stabilize at 90 min. The total oligosaccharide (2-10 sugars) increased to 85.15 ± 0.39% after 105 min, meeting the product's technical specifications. Among them, maltopentose (23.65 ± 0.32%) had the highest content, followed by maltotriose (15.90 ± 0.46%), maltohexaose (14.58 ± 0.75%), maltose (11.79 ± 1.08%), maltotetraose (9.26 ± 0.65%), maltoheptaose (3.61 ± 0.60%), maltooctaose (2.11 ± 0.03%), maltononose (1.97 ± 0.14%), and maltodecanose (2.28 ± 0.06%). Glucose had the lowest content (1.92 ± 0.19%).

[0019] Table 1. Composition of rice oligosaccharides at different enzymatic hydrolysis times

[0020] (2) Infrared spectroscopy analysis Weigh 1 mg of oligosaccharide samples with different enzymatic hydrolysis times, add 150 mg of potassium bromine, grind thoroughly and evenly, compress into tablets, and place in an infrared spectrometer. Scan in the wavelength range of 4000-400 cm-1, resolution: 4 cm-1, scan 16 times, and draw infrared spectra.

[0021] Test results: such as Figure 2As shown, typical absorption peaks of polysaccharides appear in the spectral ranges of 3600-3200 cm⁻¹, 3200-2800 cm⁻¹, 1400-1200 cm⁻¹, and 1200-1000 cm⁻¹. A broad peak appears at 3449.34 cm⁻¹, which is the stretching vibration peak of OH. Due to the formation of hydrogen bonds by the hydroxyl group, the absorption peak broadens, indicating that the oligosaccharide contains both intramolecular and intermolecular hydrogen bonds. The absorption peak at 2931.11 cm⁻¹ is the stretching vibration absorption peak of CH in sugars. The absorption peaks at 1249.94 cm⁻¹ and 1347.94 cm⁻¹ are the angular vibration absorption peaks of CH in sugars. The absorption peaks at 1025.69 cm⁻¹ and 1074.18 cm⁻¹ are caused by two CO stretching vibrations of the pyranose ring, one belonging to COH and the other to COC of the sugar ring. The α-type CH exhibits an absorption peak at 844 ± 8 cm⁻¹, while the β-type CH shows an absorption peak at 891 ± 7 cm⁻¹. The presence of a stretching vibration absorption peak at 1670.60 cm⁻¹, indicating the possible presence of uronic acid in this component, suggests the presence of uronic acid. The oligosaccharide shows no peak at 891 ± 7 cm⁻¹, indicating that it may not contain β-glycosidic bonds. With prolonged reaction time, the characteristic peaks show no significant change, but their intensity gradually decreases, possibly indicating a gradual reduction in polysaccharide content and conversion to oligosaccharides. Example 2

[0022] This embodiment verifies the feasibility of preparing rice oligosaccharides using whole early indica rice as raw material. The specific steps are as follows: (1) Raw material pretreatment: Take 100kg of ordinary early indica rice and remove sand, metal fragments, husks and bran by three-stage vibrating sieve; send the sieved rice grains into a 0.5m³ vortex washing tank, add 300L of tap water, and introduce compressed air at 0.2MPa pressure from the bottom to form a vortex water flow for rinsing for 20min; send the washed rice grains into a rice soaking tank, add 300L of tap water, and soak at 10℃ for 4.5h; the soaking water is recycled for the next batch of washing after sedimentation in a three-stage sedimentation tank.

[0023] (2) Grinding and preparing the rice slurry: After soaking, the rice grains are fed into a grinding wheel mill for coarse grinding, and then into a rubber mill for fine grinding to obtain rice slurry; 0.05% (w / w) of calcium chloride and 10 U / g starch of heat-resistant α-amylase are added to the rice slurry and stirred evenly.

[0024] (3) Multi-stage series continuous liquefaction: The rice slurry after slurry preparation is sent into a high-pressure jet liquefaction device and liquefied by jetting at 95°C; the liquefied slurry enters 10 laminar flow tanks in series (each with a volume of 0.2 m³) and reacts at 95°C. The total liquefaction time is 100 min, and the final liquefaction DE value is controlled to be 15.

[0025] (4) Slag removal and separation: The liquefied slurry is sent into a three-layer vacuum filter press. The upper layer is a stainless steel porous partition layer with a pore size of 0.5 mm, the middle layer is polypropylene filter paper, and the lower layer is a 10 cm thick granular activated carbon layer. The filtrate is filtered at a vacuum of -0.07 MPa to obtain a clear filtrate and rice protein filter residue. The filter residue is dried to obtain rice protein powder.

[0026] (5) Saccharification and enzymatic hydrolysis: The clarified filtrate was sent into a 1m³ saccharification tank, the pH was adjusted to 4.5 with citric acid, and 50U / g starch of fungal saccharifying enzyme was added. The enzyme was hydrolyzed at 55℃ for 105min. After the enzymatic hydrolysis was completed, the temperature was raised to 90℃ for 10min to inactivate the enzyme.

[0027] (6) Purification: The saccharified liquid was sent to the decolorization tank, 0.3% (w / w) of powdered activated carbon was added, and the mixture was stirred and decolorized at 70°C for 40 min and then filtered. The above decolorization operation was repeated twice. The decolorized filtrate was desalted by passing it through a cation exchange column, an anion exchange column and a mixed ion exchange column in sequence, and the conductivity was controlled to be < 10 μS / cm. The desalted filtrate was separated and purified by passing it through a nanofiltration membrane (molecular weight cutoff of 1000 Da), and the retentate was collected.

[0028] (7) Concentration and drying: The retentate is sent to a vacuum flash concentrator and concentrated to a solid content of 50% at 55℃ and -0.08MPa. The concentrate is spray-dried (inlet air temperature 170℃, outlet air temperature 75℃) to obtain 27.8kg of rice oligosaccharide product.

[0029] Product test results: The total oligosaccharide (2-10 sugar) content was 84.72±0.45%, the glucose content was 1.87±0.21%, and the 3-7 sugar content was 51.23±0.68%. All indicators met the product requirements. Example 3

[0030] This embodiment verifies product quality under different liquefaction stages and DE values. The specific steps are as follows: (1) Raw material pretreatment: Take 100kg of early indica broken rice, remove impurities by three-stage vibrating sieve, and send it into a rotary washing tank. Introduce compressed air at 0.3MPa pressure for 10min to rinse; soak the rice grains at 30℃ for 2h; and recover the soaking water through a three-stage recovery sedimentation device.

[0031] (2) Grinding and preparing the slurry: Grind the rice slurry using a grinding wheel mill coupled with a rubber mill to obtain a uniform particle size; add 0.1% (w / w) calcium chloride and 15 U / g starch-resistant α-amylase, and stir evenly.

[0032] (3) Multi-stage series continuous liquefaction: The rice slurry after slurry preparation is sent to a high-pressure jet liquefaction unit and liquefied by jetting at 100°C; the liquefied slurry enters six laminar flow tanks in series in sequence and reacts at 95°C. The total liquefaction time is 80 min and the final liquefaction DE value is controlled to be 10.

[0033] (4) Slag removal and separation: A three-layer vacuum filter is used to filter the liquid at a vacuum of -0.09MPa to obtain a clear filtrate.

[0034] (5) Saccharification and enzymatic hydrolysis: Adjust the pH value to 5.0, add fungal saccharifying enzyme of 80 U / g starch, enzymatic hydrolysis at 60℃ for 105 min, and then heat to 90℃ to inactivate the enzyme for 10 min.

[0035] (6) Purification: Add 0.8% (w / w) of powdered activated carbon, stir and decolorize at 85°C for 20 min, repeat 3 times; desalt through three ion exchanges until conductivity < 10 μS / cm; separate and purify by nanofiltration membrane with molecular weight cutoff of 2000 Da.

[0036] (7) Concentration and drying: Vacuum flash evaporation was carried out at 65℃ and -0.095MPa until the solid content was 60%; spray drying (inlet air temperature 190℃, outlet air temperature 85℃) yielded 28.2kg of rice oligosaccharide product.

[0037] The remaining undefined parameters are the same as in Example 1.

[0038] Product test results: The total oligosaccharide (2-10 sugar) content is 84.96±0.37%, the glucose content is 1.95±0.17%, the 3-7 sugar content is 50.87±0.59%, and the product quality is stable.

[0039] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing rice oligosaccharides, characterized in that, Includes the following steps: (1) Raw material pretreatment: Early indica rice or broken rice is used as raw material. After being screened by multi-stage vibration to remove impurities, it is sent to a rotary washing tank for washing and then soaked. (2) Grinding and preparing the slurry: The soaked rice grains are ground into a slurry using a grinding wheel mill coupled with a rubber mill to obtain rice slurry. Calcium chloride and high-temperature resistant α-amylase are added and stirred evenly. (3) Multi-stage series continuous liquefaction: After the rice slurry is liquefied by a high-pressure jet liquefaction device, it enters 6-10 laminar flow tanks in series for continuous liquefaction reaction, and the liquefaction DE value is controlled to be 10-15. (4) Slag removal and separation: The liquefied slurry is sent to a three-layer vacuum filter press for separation to obtain a clear filtrate; (5) Saccharification and enzymatic hydrolysis: After adjusting the pH value of the clarified filtrate, fungal saccharifying enzyme is added, and enzymatic hydrolysis is carried out at 55-60℃ for 105 min; (6) Refining and purification: The saccharified solution is subjected to three decolorizations, three ion exchange desaltings, and nanofiltration membrane separation in sequence; (7) Concentration and drying: The purified oligosaccharide solution is concentrated and then spray-dried to obtain the rice oligosaccharide product.

2. The method for preparing rice oligosaccharides according to claim 1, characterized in that: In step (1), the multi-stage vibrating screen removes sand, metal fragments, rice husks and rice bran impurities in sequence; water is added to the bottom of the swirling washing tank and air at a pressure of 0.2-0.3 MPa is introduced to form a swirling rinsing water flow; a three-stage recovery sedimentation device is used to remove impurities from the rice soaking water and recover it; the soaking time is 2-5 hours.

3. The method for preparing rice oligosaccharides according to claim 1, characterized in that: The amount of calcium chloride added in step (2) is 0.05-0.1% (w / w), and the amount of heat-resistant α-amylase added is 10-15 U / g starch.

4. The method for preparing rice oligosaccharides according to claim 1, characterized in that: The high-pressure jet liquefaction temperature in step (3) is 95-100℃; the heat preservation temperature of the laminar flow tank is 95℃, and the total liquefaction time is 80-100min.

5. The method for preparing rice oligosaccharides according to claim 1, characterized in that: The three-layer vacuum filter described in step (4) consists of a stainless steel porous partition layer, a filter paper layer, and an activated carbon layer from top to bottom; the filtration vacuum degree is -0.07 to -0.09 MPa.

6. The method for preparing rice oligosaccharides according to claim 1, characterized in that: In step (5), the pH value is adjusted to 4.5-5.0; the amount of fungal saccharifying enzyme added is 50-80 U / g starch; after the enzymatic hydrolysis is completed, the temperature is raised to 90℃ to inactivate the enzyme for 10 min.

7. The method for preparing rice oligosaccharides according to claim 1, characterized in that: In step (6), the decolorization is carried out using powdered activated carbon at an addition rate of 0.3-0.8% (w / w), the decolorization temperature is 70-85℃, and the decolorization time is 20-40 min; the conductivity of the ion exchange desalination is controlled to be <10μS / cm; and the molecular weight cutoff of the nanofiltration membrane is 300-2000 Da.

8. The method for preparing rice oligosaccharides according to claim 1, characterized in that: The vacuum flash concentration in step (7) is at a temperature of 55-65℃, a vacuum degree of -0.08 to -0.095MPa, and is concentrated to a solid content of 50-60%; the inlet air temperature of the spray drying is 170-190℃, and the outlet air temperature is 75-85℃.

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