Preparation process of low-bitterness rice active peptide product

Abstract

The invention relates to a preparation process of a low-bitterness rice active peptide product. According to the invention, sugar-making rice residues are used as raw materials, a separated and purified rice protein raw material is obtained after pretreatment and filtration sugar removal, impurities are removed through grinding and sieving treatment of a colloid mill, and diffusivity and dissolvability of the rice protein are improved by a direct steam jet heating method with high thermal efficiency and high heat utilization rate through equipment; the internal structure of the protein is further expanded through two-stage homogenization treatment, more enzyme cutting sites are exposed, the enzymolysis efficiency is improved, and the low-bitterness rice active peptide product with the peptide content being larger than 90% and the molecular weight being 100-1000 Da is produced through two-stage enzymolysis reaction, centrifugal separation, membrane filtration concentration and spray drying. The low-bitterness rice active peptide product which is high in solubility, high in enzymolysis efficiency, low in cost and high in quality is prepared, the flavor is good, the taste is good, and high-value utilization of the rice residues is achieved.

Description

Technical Field

[0001] The invention relates to the field of plant protein deep processing, and in particular to a preparation process of a low-bitter rice active peptide product. Background Art

[0002] In recent years, rice has become one of the most important food products in the world. It is rich in nutrition, containing 80% starch and 7% protein. Rice protein is a high-quality protein with a reasonable amino acid composition. It will not cause allergies and is the only grain protein that is exempt from allergy testing. Its nutritional value is much higher than that of plant proteins such as soybeans, wheat, and corn. It can be used in infant food and nutritional products for special groups of people, with unparalleled superiority.

[0003] Rice residue is a byproduct of rice after sugar production, and its main component is protein. However, it is currently mainly used as animal feed, with very low added value. The protein has a large molecular weight and poor solubility. In addition, the high temperature treatment used in the sugar production process causes the denaturation and agglutination of protein molecules, further reducing the performance of the product, such as solubility, emulsification, and foaming properties. This limits its application in the food industry. At present, rice protein products on the market are mainly made from rice residue, which is further increased to more than 80% through enzymatic hydrolysis with amylase and saccharifying enzyme, sugar removal by plate and frame filtration, and airflow drying. Although the protein content has been greatly improved, its functional properties such as solubility are still low.

[0004] Rice protein is hydrolyzed into polypeptide molecules of different molecular weights by protease. By breaking the original molecular structure of the protein, the molecular chain becomes shorter, the hydrophobicity is reduced, and the solubility is effectively improved. In addition, small molecule peptides are quickly digested and absorbed by the human body and have stronger health care functions. Studies have shown that rice peptides have many functions such as enhancing human immunity, anti-oxidation, anti-fatigue, lowering blood pressure and blood lipids, and preventing cardiovascular system diseases. Therefore, the production of active rice peptides is also an important development discovery in the deep processing of rice.

[0005] At present, the production of rice active peptides still faces certain challenges. First, due to the low water absorption of rice protein raw materials, a large number of enzyme cleavage sites are embedded inside the molecule, resulting in relatively low enzymatic efficiency. In addition, when the degree of enzymatic hydrolysis is high, the produced peptide products have a strong bitter taste, which affects their application. Summary of the invention

[0006] The object of the present invention is to provide a new method for producing active rice peptides in rice residues to solve the current problems of low enzymolysis efficiency and strong taste. Aiming at the technical problems of high degree of rice protein denaturation, low enzymolysis efficiency and strong bitterness of polypeptide products in sugar-making rice residues, the present invention adopts a method combining direct steam jet heating and homogenization to improve the surface hydrophilicity of protein molecules by depolymerizing protein polymers, expose more reaction sites and increase enzyme cleavage sites; adopts two-stage enzymolysis technology to effectively reduce the bitterness of polypeptide products and improve product taste by controlling the addition amount and reaction conditions.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions: A preparation process of a low-bitter rice active peptide product comprises the following steps: (1) Pretreatment of rice residue protein: sugar-making rice residue is used as raw material, 35-45% of water is added and stirred evenly, alkali solution is added to adjust the pH value to 7.0±0.5, 0.2% of neutral amylase and 0.2% of saccharifying enzyme are added, the temperature of the material is adjusted to 50±5°C, enzymolysis is performed under stirring for 2-3 hours, and then the temperature is raised to 80±5°C to inactivate the enzyme for 30 min to obtain the pretreated rice residue liquid; (2) Filtration and sugar removal: The liquid obtained in step (1) is squeezed through a plate-and-frame filter to achieve solid-liquid separation, and then rinsed with hot water at 80±5° C. for 10-20 min to fully remove sugar, thereby obtaining a separated and purified rice protein raw material; (3) Grinding and refining: the wet protein residue after sugar removal is mixed with water in a ratio of 1:2.5-4.0, refined using a colloid mill, and passed through a 100-200 mesh vibrating screen to remove impurities; (4) direct steam heating: the rice protein solution is preheated to 50-70°C and then rapidly heated with 0.5-1.0 MPa steam at a heating temperature of 120-140°C for a heating time of 10-20 s, which is controlled by the length and flow rate of the heating tube; (5) Homogenization: The steam-heated rice protein solution was rapidly cooled to room temperature, alkali solution was added to adjust the pH value to 8.0-10.0, and then a high-pressure homogenizer was used for two-stage homogenization (2500psi / 500psi), and the particle size distribution and suspension stability were measured; (6) First enzymatic hydrolysis reaction: adding a mixture of 0.4-0.6% of Bacillus subtilis neutral protease and a certain proportion of alkaline protease based on the mass of protein to the solution in step (5) for the first enzymatic hydrolysis, the enzymatic hydrolysis time is 1.5-3.5 hours, the enzymatic hydrolysis temperature is 50±5° C., the pH is maintained unchanged during the enzymatic hydrolysis, and the enzyme is inactivated after the enzymatic hydrolysis is completed; (7) a second enzymatic hydrolysis reaction: adjusting the pH value of the enzymatic hydrolyzate obtained in step (6) to 6.0-8.0, raising the temperature to 45-60° C., adding 0.4%-0.6% of at least one of bromelain, papain and flavor protease for a second enzymatic hydrolysis, the enzymatic hydrolysis time being 3-5 hours, the pH does not need to be adjusted during the enzymatic hydrolysis, and performing an enzyme inactivation treatment after the enzymatic hydrolysis is completed; (8) Filtration and concentration: The enzymatic hydrolyzate in step (7) is centrifuged using a horizontal screw centrifuge, and the obtained supernatant is filtered using a 0.1 μm ceramic membrane, and then concentrated to 50-10% of the original volume using a nanofiltration membrane with a molecular cutoff of 100-1000 Da; (9) Spray drying: The concentrated polypeptide liquid is dried by medium-low temperature spray drying, with an inlet air temperature of 145-160°C, an outlet air temperature of 75-85°C, and the moisture content is controlled below 5%.

[0008] Preferably, in the pretreatment of the rice residue protein in step (1), neutral amylase and saccharifying enzyme are added to react enzymolysis at 50±5°C, accompanied by the operation of continuous stirring. The rice protein raw material has low water absorption, and a large number of enzyme cleavage sites are embedded in the molecule, resulting in relatively low enzymolysis efficiency. The dissolution of the rice residue protein is increased by continuous stirring, and the contact area between the enzyme and the rice residue raw material is increased simultaneously, thereby increasing the enzymolysis reaction rate and accelerating the reaction process.

[0009] Preferably, the alkaline solution for adjusting the pH in steps (1) and (5) is one or more of NaOH, Na2CO3 or NaHCO3 with a concentration of 3 mol / L.

[0010] Preferably, the water content of the solution during solid-liquid separation after plate-frame filtration in step (2) is controlled at 45-50%. The plate-frame filter is in a closed filter chamber, and by applying a certain pressure, the liquid in the rice residue suspension passes through the filter cloth, while the solid particles are trapped on the filter cloth, so as to achieve the purpose of liquid-solid separation, and the solution passing through the filter cloth is collected, and the water content is controlled at 45-50%, so that the amount of solution during the flushing process is controllable, which is convenient for machine automation operation.

[0011] Preferably, the average particle size of the rice protein solution in step (5) is less than 2 μm, and the suspension stability is greater than 95%. Under this condition, the effective component of the obtained solution has low viscosity, good hygroscopicity, good moisture retention and strong antioxidant function. Different from the prior art, the Maklad shockwave direct steam jet heating modification technology adopted in the present invention is combined with the homogenization treatment method, which improves the surface hydrophilicity of protein molecules by depolymerizing protein polymers, and effectively improves the solubility of rice protein; more reaction sites are exposed, and the enzyme cleavage sites of rice protein are greatly increased, which is the two-stage enzymolysis method of step (6) and step (7) that effectively improves the enzymolysis efficiency and reduces the enzymolysis time and energy consumption.

[0012] Preferably, the ratio of neutral protease and alkaline protease described in step (6) is 3:1-1:1. Rice protein is hydrolyzed into polypeptide molecules of different molecular weights by protease, and the original molecular structure of protein is broken, and the molecular chain is shortened, and hydrophobicity is reduced, which effectively improves solubility. Rice peptides are polypeptides of different molecular weights obtained by protease hydrolysis of rice protein, which not only have the nutritional characteristics of rice protein but also have small molecule peptide physiological activity and special functions. When the solution environment pH remains at 8.0-10.0, the ratio of neutral protease and alkaline protease is 3:1-1:1, and the protease reaction rate is improved.

[0013] Preferably, the temperature conditions in the enzyme inactivation treatment in step (6) and step (7) are both 90° C., and the enzyme inactivation time is 15 minutes. High temperature enzyme inactivation can completely inactivate the enzyme, produce irreversible inactivation, prevent the residual protease from reacting with other active substances to generate impurity products, and at the same time shorten the enzyme inactivation time, increase the enzyme inactivation rate, and reduce energy loss.

[0014] Preferably, at least one of the bromelain, papain and flavor protease added in step (7) is subjected to a second enzymatic hydrolysis to degrade bitter peptides by cutting off and releasing amino acids at the end of the polypeptide chain, thereby achieving flavor regulation.

[0015] It is known in the prior art that protease can produce polypeptide molecules of different molecular weights by enzymolysis of rice protein, and small molecule peptides are fast in human body digestion and absorption, and health care function is stronger; However, in the process of preparing rice protein peptide by enzymolysis of rice protein, due to the change of rice protein structure, peptide chain is cut off, and some hydrophobic amino acids originally contained in the protein are exposed while generating polypeptides of different molecular weights, and these hydrophobic amino acids will present bitter taste when contacting with bitter taste receptors--taste buds on the tongue. When the degree of enzymolysis is high, the produced peptide products are more bitter, which affects its application. The two-stage enzymolysis process adopted by the present invention not only improves the enzymolysis efficiency, but also combines the flavor improvement mechanism of flavor protease, bromelain, and papain, and can release small molecule peptides and amino acids by cutting peptide bonds inside and outside the peptide chain, effectively reducing the bitter taste of rice peptides, improving food flavor, improving product mouthfeel, improving protein utilization, and reducing production costs.

[0016] Preferably, the rotation speed of the horizontal screw centrifuge used for centrifuging the enzymolysis solution in step (8) is 5000-8000rpm, and the solid-liquid separation is carried out by centrifugal sedimentation principle, so as to efficiently complete the preliminary purification of the enzymolysis solution. The horizontal screw centrifuge can continuously feed, separate, wash and unload at full speed, and the separation of the enzymolysis solution obtained in step (7) is carried out under completely closed conditions, avoiding secondary pollution, and ensuring the cleanliness of the product and the tidiness of the production environment.

[0017] Preferably, step (8) and step (9) use ultrafiltration membrane purification and nanofiltration membrane concentration technology, which effectively improves the purity and quality of the product, reduces the steam consumption during the spray drying process, saves production costs, and produces a low-bitter rice active peptide product with a peptide content of >90% and a molecular weight of 100-1000Da.

[0018] The low-bitter rice active peptide product prepared by a preparation process provided by the present invention has the characteristics of high solubility, high enzymolysis efficiency, low cost and high quality, low bitterness, good flavor and good taste.

[0019] In summary, the present invention has the following beneficial effects: 1. The technology used in the present invention is advanced, and the yield of the prepared rice peptide is >90%. The Makladshockwave direct steam jet heating modification technology and the homogenization treatment method used in the present invention are combined to effectively improve the solubility and enzymolysis efficiency of rice protein, and reduce the enzymolysis time and energy consumption; 2. The ultrafiltration membrane purification and nanofiltration membrane concentration technology adopted in the present invention effectively improves the purity and quality of the product, reduces the steam consumption in the spray drying process, and saves production costs; 3. The present invention utilizes the principle of centrifugal sedimentation to separate solids from liquids, efficiently completes the preliminary purification of the enzymatic hydrolysate, and separates the obtained enzymatic hydrolysate under completely closed conditions, thereby avoiding secondary pollution and ensuring the cleanliness of the product and the production environment; 4. The two-stage enzymolysis process adopted by the present invention not only improves the enzymolysis efficiency, but also combines the flavor improvement mechanism of flavor protease, bromelain and papain to effectively reduce the bitterness of rice peptides. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the preparation process of low-bitter rice active peptide products. DETAILED DESCRIPTION

[0021] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

[0022] Example 1 1. Pretreatment of rice residue protein Take sugar rice residue as raw material, add water and stir evenly, adjust the pH value to 7.0, add 0.2% neutral amylase and 0.2% saccharifying enzyme. Adjust the temperature of the material to 50℃, enzymolysis for 2 hours under stirring conditions, and then heat to 85℃ to inactivate the enzyme for 30 minutes.

[0023] 2. Filter and remove sugar The liquid obtained in step 1 is squeezed through a plate and frame filter to achieve solid-liquid separation, and is rinsed with hot water at about 80° C. for 15 minutes to fully remove sugar, thereby separating and purifying the rice protein raw material.

[0024] 3. Crushing and refining The protein wet residue after sugar removal is mixed with water in a ratio of 1:3, refined using a colloid mill, and passed through a 100-mesh vibrating screen to remove impurities.

[0025] 4. Direct steam heating The rice protein solution was preheated to 60 °C and then rapidly heated with 0.7 MPa steam at 130 °C for 10 s, which was controlled by the length of the heating tube and the flow rate.

[0026] 5. Homogenization The rice protein solution after steam heating was rapidly cooled to room temperature, the pH was adjusted to 8, and then a high-pressure homogenizer was used for two-stage homogenization (2500psi / 500psi).

[0027] 6. First enzymatic hydrolysis reaction 0.4% of Bacillus subtilis neutral protease based on protein mass was added to the solution in step 5 for the first enzymolysis for 3 hours at a temperature of 55° C. and the pH was kept constant during the enzymolysis. After the enzymolysis was completed, the enzyme was inactivated.

[0028] 7. Second enzymatic hydrolysis reaction The pH of the enzymatic hydrolyzate obtained in step 6 was adjusted to 7.0, the temperature was raised to 55° C., and 0.4% bromelain was added for a second enzymatic hydrolysis for 3 hours. The pH did not need to be adjusted during the enzymatic hydrolysis, and the enzyme was inactivated after the enzymatic hydrolysis was completed.

[0029] 8. Filtration and concentration The enzymatic hydrolysate in step 7 was centrifuged using a horizontal screw centrifuge, and the obtained supernatant was filtered using a 0.1 μm ceramic membrane, and then concentrated to 25% of the original volume using a nanofiltration membrane with a molecular cutoff of 100 Da.

[0030] 9. Spray drying The concentrated polypeptide liquid is dried by medium-low temperature spray drying, with an inlet air temperature of 160°C, an outlet air temperature of 85°C, and the moisture content controlled below 5%.

[0031] Example 2 1. Pretreatment of rice residue protein Take sugar rice residue as raw material, add water and stir evenly, adjust the pH value to 7.0, add 0.2% neutral amylase and 0.2% saccharifying enzyme. Adjust the temperature of the material to 50℃, enzymolysis for 2 hours under stirring conditions, and then heat to 85℃ to inactivate the enzyme for 30 minutes.

[0032] 2. Filter and remove sugar The liquid obtained in step 1 is squeezed through a plate and frame filter to achieve solid-liquid separation, and is rinsed with hot water at about 80° C. for 15 minutes to fully remove sugar, thereby separating and purifying the rice protein raw material.

[0033] 3. Crushing and refining The protein wet residue after sugar removal was mixed with water in a ratio of 1:4, refined with a colloid mill, and passed through an 80-mesh vibrating screen to remove impurities.

[0034] 4. Direct steam heating The rice protein solution is preheated to 60°C and then rapidly heated with 0.7MPa steam at a temperature of 120-140°C for 10-20s, which is controlled by the length of the heating tube and the flow rate.

[0035] 5. Homogenization The rice protein solution after steam heating was rapidly cooled to room temperature, the pH was adjusted to 8, and then a high-pressure homogenizer was used for two-stage homogenization (2500psi / 500psi).

[0036] 6. First enzymatic hydrolysis reaction A mixture of 0.5% (1:1) of Bacillus subtilis neutral protease and alkaline protease based on protein mass was added to the solution in step 5 for the first enzymolysis for 3 hours at a temperature of 55° C. The pH value was kept constant during the enzymolysis. After the enzymolysis was completed, the enzyme was inactivated.

[0037] 7. Second enzymatic hydrolysis reaction The pH of the enzymatic hydrolyzate obtained in step 6 was adjusted to 7.0, the temperature was raised to 55°C, and 0.5% bromelain and flavor protease (2:1) were added for a second enzymatic hydrolysis for 4 hours. The pH did not need to be adjusted during the enzymatic hydrolysis, and the enzyme was inactivated after the enzymatic hydrolysis was completed.

[0038] 8. Filtration and concentration The enzymatic hydrolysate in step 7 was centrifuged using a horizontal screw centrifuge, and the obtained supernatant was filtered using a 0.1 μm ceramic membrane, and then concentrated to 40% of the original volume using a nanofiltration membrane with a molecular cutoff of 100 Da.

[0039] 9. Spray drying The concentrated polypeptide liquid is dried by medium-low temperature spray drying, with an inlet air temperature of 160°C, an outlet air temperature of 75°C, and the moisture content controlled below 5%.

[0040] Example 3 1. Pretreatment of rice residue protein Take sugar rice residue as raw material, add water and stir evenly, adjust the pH value to 7.0, add 0.2% neutral amylase and 0.2% saccharifying enzyme. Adjust the temperature of the material to 50℃, enzymolysis for 2 hours under stirring conditions, and then heat to 85℃ to inactivate the enzyme for 30 minutes.

[0041] 2. Filter and remove sugar The liquid obtained in step 1 is squeezed through a plate and frame filter to achieve solid-liquid separation, and is rinsed with hot water at about 80° C. for 15 minutes to fully remove sugar, thereby separating and purifying the rice protein raw material.

[0042] 3. Crushing and refining The protein wet residue after sugar removal was mixed with water in a ratio of 1:4, refined with a colloid mill, and passed through an 80-mesh vibrating screen to remove impurities.

[0043] 4. Direct steam heating The rice protein solution is preheated to 60°C and then rapidly heated with 0.7MPa steam at a temperature of 120-140°C for 10-20s, which is controlled by the length of the heating tube and the flow rate.

[0044] 5. Homogenization The rice protein solution after steam heating was rapidly cooled to room temperature, the pH was adjusted to 8, and then a high-pressure homogenizer was used for two-stage homogenization (2500psi / 500psi).

[0045] 6. First enzymatic hydrolysis reaction A mixture of 0.5% (3:1) of Bacillus subtilis neutral protease and alkaline protease based on protein mass was added to the solution in step 5 for the first enzymolysis for 4 hours at a temperature of 55° C. The pH value was kept constant during the enzymolysis. After the enzymolysis was completed, the enzyme was inactivated.

[0046] 7. Second enzymatic hydrolysis reaction The pH of the enzymatic hydrolyzate obtained in step 6 was adjusted to 7.0, the temperature was raised to 55°C, and 0.5% bromelain, papain and flavor protease (5:3:2) were added for a second enzymatic hydrolysis for 4 hours. The pH did not need to be adjusted during the enzymatic hydrolysis, and the enzyme was inactivated after the enzymatic hydrolysis was completed.

[0047] 8. Filtration and concentration The enzymatic hydrolysate in step 7 was centrifuged using a horizontal screw centrifuge, and the obtained supernatant was filtered using a 0.1 μm ceramic membrane, and then concentrated to 40% of the original volume using a nanofiltration membrane with a molecular cutoff of 100 Da.

[0048] 9. Spray drying The concentrated polypeptide liquid is dried by medium-low temperature spray drying, with an inlet air temperature of 160°C, an outlet air temperature of 75°C, and the moisture content controlled below 5%.

[0049] Comparative Example 1 1. Pretreatment of rice residue protein Take sugar rice residue as raw material, add water and stir evenly, adjust the pH value to 7.0, add 0.2% neutral amylase and 0.2% saccharifying enzyme. Adjust the temperature of the material to 50℃, enzymolysis for 2 hours under stirring conditions, and then heat to 85℃ to inactivate the enzyme for 30 minutes.

[0050] 2. Filter and remove sugar The liquid obtained in step 1 is squeezed through a plate and frame filter to achieve solid-liquid separation, and is rinsed with hot water at about 80° C. for 15 minutes to fully remove sugar, thereby separating and purifying the rice protein raw material.

[0051] 3. Crushing and refining The protein wet residue after sugar removal is mixed with water in a ratio of 1:4, refined using a colloid mill, and passed through a 100-mesh vibrating screen to remove impurities.

[0052] 4. First enzymatic reaction A mixture of 0.5% (1:1) of Bacillus subtilis neutral protease and alkaline protease based on protein mass was added to the solution in step 3 for the first enzymolysis for 3 hours at a temperature of 55° C. The pH value was kept constant during the enzymolysis. After the enzymolysis was completed, the enzyme was inactivated.

[0053] 5. Second enzymatic hydrolysis reaction The pH of the enzymatic hydrolyzate obtained in step 6 was adjusted to 7.0, the temperature was raised to 55°C, and 0.5% bromelain and flavor protease (2:1) were added for a second enzymatic hydrolysis for 4 hours. The pH did not need to be adjusted during the enzymatic hydrolysis, and the enzyme was inactivated after the enzymatic hydrolysis was completed.

[0054] 6. Filtration and concentration The enzymatic hydrolysate in step 7 was centrifuged using a horizontal screw centrifuge, and the obtained supernatant was filtered using a 0.1 μm ceramic membrane, and then concentrated to 40% of the original volume using a nanofiltration membrane with a molecular cutoff of 100 Da.

[0055] 7. Spray drying The concentrated polypeptide liquid is dried by medium-low temperature spray drying, with an inlet air temperature of 160°C, an outlet air temperature of 75°C, and the moisture content controlled below 5%.

[0056] Comparative Example 2 1. Pretreatment of rice residue protein Take sugar rice residue as raw material, add water and stir evenly, adjust the pH value to 7.0, add 0.2% neutral amylase and 0.2% saccharifying enzyme. Adjust the temperature of the material to 50℃, enzymolysis for 2 hours under stirring conditions, and then heat to 85℃ to inactivate the enzyme for 30 minutes.

[0057] 2. Filter and remove sugar The liquid obtained in step 1 is squeezed through a plate and frame filter to achieve solid-liquid separation, and is rinsed with hot water at about 80° C. for 15 minutes to fully remove sugar, thereby separating and purifying the rice protein raw material.

[0058] 3. Crushing and refining The protein wet residue after sugar removal is mixed with water in a ratio of 1:4, refined using a colloid mill, and passed through a 100-mesh vibrating screen to remove impurities.

[0059] 4. Homogenization The rice protein solution was rapidly cooled to room temperature, the pH was adjusted to 8, and then subjected to two-stage homogenization (2500psi / 500psi) treatment using a high-pressure homogenizer.

[0060] 5. First enzymatic hydrolysis reaction A mixture of 0.5% (1:1) of Bacillus subtilis neutral protease and alkaline protease based on protein mass was added to the solution in step 5 for the first enzymolysis for 3 hours at a temperature of 55° C. The pH value was kept constant during the enzymolysis. After the enzymolysis was completed, the enzyme was inactivated.

[0061] 6. Second enzymatic hydrolysis reaction The pH of the enzymatic hydrolyzate obtained in step 6 was adjusted to 7.0, the temperature was raised to 55°C, and 0.5% bromelain and flavor protease (2:1) were added for a second enzymatic hydrolysis for 4 hours. The pH did not need to be adjusted during the enzymatic hydrolysis, and the enzyme was inactivated after the enzymatic hydrolysis was completed.

[0062] 7. Filtration and concentration The enzymatic hydrolysate in step 7 was centrifuged using a horizontal screw centrifuge, and the obtained supernatant was filtered using a 0.1 μm ceramic membrane, and then concentrated to 40% of the original volume using a nanofiltration membrane with a molecular cutoff of 100 Da.

[0063] 8. Spray drying The concentrated polypeptide liquid is dried by medium-low temperature spray drying, with an inlet air temperature of 160°C, an outlet air temperature of 75°C, and the moisture content controlled below 5%.

[0064] Data Analysis: The yield, peptide content and bitterness of the rice active peptide samples prepared in Examples 1-3 and Comparative Examples 1-2 were tested respectively, and the results showed that the yield of Examples 1-3 of the present invention was much greater than that of Comparative Examples 1-2, indicating that the rice active peptide preparation process of the present invention has great advantages, and the production cost of products of the same quality is low; the active peptide content of each product in Examples 1-3 is greater than that in Comparative Examples 1-2, indicating that the product quality of the preparation process of the present invention is good and the effective ingredient is high; the bitterness of each product in Examples 1-3 is less than that in Comparative Examples 1-2, indicating that the product of the preparation process of the present invention has good flavor and good taste, and the high-quality and low-bitterness rice active peptide products prepared have excellent advantages.

[0065] Table 1 Test results of yield, peptide content and bitterness of different rice active peptide samples

[0066] * The more +, the more bitter it tastes.

Claims

1. A preparation process of a low-bitter rice active peptide product, It is characterized in that The following steps are involved: (1) Pretreatment of rice residue protein: sugar-making rice residue is used as raw material, 35-45% of water is added and stirred evenly, alkali solution is added to adjust the pH value to 7.0±0.5, neutral amylase and saccharifying enzyme are added, the temperature of the material is adjusted to 50±5°C, enzymolysis is performed under stirring for 2-3 hours, and then the temperature is raised to 80±5°C to inactivate the enzyme to obtain the pretreated rice residue liquid; (2) Filtration and sugar removal: The liquid obtained in step (1) is squeezed through a plate-and-frame filter to achieve solid-liquid separation, and then rinsed with hot water at 80±5° C. for 10-20 min to fully remove sugar, thereby obtaining a separated and purified rice protein raw material; (3) Grinding and refining: the wet protein residue after sugar removal is mixed with water in a ratio of 1:2.5-4.0, refined using a colloid mill, and passed through a 100-200 mesh vibrating screen to remove impurities; (4) direct steam heating: the rice protein solution is preheated to 50-70°C, and then the steam of 0.5-1.0MPa is adopted to carry out rapid heating treatment, the heating temperature is 120-140°C, and the heat-up time is 10-20s, which is controlled by the heating tube length and flow velocity; (5) homogenization: the rice protein solution after the steam heating treatment is rapidly cooled to room temperature, alkali solution is added to adjust the pH value to 8.0-10.0, and then a high pressure homogenizer is used to carry out a two-stage homogenization process to measure particle size distribution and suspension stability; (6) First enzymatic hydrolysis reaction: adding a mixture of 0.4-0.6% of Bacillus subtilis neutral protease and a certain proportion of alkaline protease based on the mass of protein to the solution in step (5) for the first enzymatic hydrolysis, the enzymatic hydrolysis time is 1.5-3.5 hours, the enzymatic hydrolysis temperature is 50±5° C., the pH is maintained unchanged during the enzymatic hydrolysis, and the enzyme is inactivated after the enzymatic hydrolysis is completed; (7) a second enzymatic hydrolysis reaction: adjusting the pH value of the enzymatic hydrolyzate obtained in step (6) to 6.0-8.0, raising the temperature to 45-60° C., adding 0.4%-0.6% of at least one of bromelain, papain and flavor protease for a second enzymatic hydrolysis, the enzymatic hydrolysis time being 3-5 hours, the pH does not need to be adjusted during the enzymatic hydrolysis, and performing an enzyme inactivation treatment after the enzymatic hydrolysis is completed; (8) Filtration and concentration: The enzymatic hydrolyzate in step (7) is centrifuged using a horizontal screw centrifuge, and the obtained supernatant is filtered using a ceramic membrane, and then concentrated to 50-10% of the original volume using a nanofiltration membrane with a molecular cutoff of 100-1000Da; (9) Spray drying: The concentrated polypeptide liquid is dried by medium-low temperature spray drying, with an inlet air temperature of 145-160°C, an outlet air temperature of 75-85°C, and the moisture content is controlled below 5%.

2. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that In the pretreatment of the rice residue protein in step (1), 0.2 wt % of neutral amylase and 0.2 wt % of saccharifying enzyme are added to perform enzymolysis reaction at 50±5° C., accompanied by continuous stirring, and then the temperature is raised to 80±5° C. to inactivate the enzyme for 30 min to obtain a pretreated rice residue liquid.

3. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that The alkali solution used to adjust the pH in steps (1) and (5) is 3 mol / L NaOH, Na 2 CO 3 or NaHCO 3 One or more of .

4. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that In step (2), the water content of the solution during solid-liquid separation after plate and frame filtration is controlled at 45-50%.

5. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that During the homogenization process in step (5), a high pressure homogenizer is used to perform a two-stage homogenization process (2500psi / 500psi), and the average particle size of the rice protein solution is less than 2μm, and the suspension stability is greater than 95%.

6. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that The ratio of neutral protease to alkaline protease in step (6) is 3:1-1:

1.

7. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that The temperature condition for the enzyme inactivation treatment in step (6) and step (7) is 90°C, and the enzyme inactivation time is 15 min.

8. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that At least one of the bromelain, papain and flavor protease added in step (7) is subjected to a second enzymatic hydrolysis to degrade bitter peptides by cutting off and releasing amino acids at the end of the polypeptide chain, thereby achieving flavor regulation.

9. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that In step (8), the rotation speed of the horizontal screw centrifuge used for centrifuging the enzymatic hydrolyzate is 5000-8000 rpm. The obtained supernatant is filtered with a 0.1 μm ceramic membrane and then concentrated to 50-10% of the original volume using a nanofiltration membrane with a molecular cutoff of 100-1000 Da.

10. The preparation process of a low-bitter rice active peptide product according to claim 1, It is characterized in that The ultrafiltration membrane purification and nanofiltration membrane concentration technology are used in step (8) and step (9), and the peptide content of the low-bitter rice active peptide product produced is greater than 90% and the molecular weight is between 100-1000Da.

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