A torreya grandis polypeptide for lowering blood pressure and its preparation method

Abstract

The present invention belongs to the technical field of food processing and relates to a blood-pressure-lowering torreya grandis polypeptide and a preparation method thereof. The preparation method comprises the following steps: S1. Adding water to torreya grandis cake residue for extraction, after solid-liquid separation, repeating the extraction of the residue for 1 to 3 times, combining the extraction liquids, and then concentrating to obtain a crude protein extract; S2. Adjusting the pH of the above crude protein extract to 8 to 10, adding alkaline protease for enzymatic hydrolysis, then adjusting the pH to 6 to 7, adding papain for enzymatic hydrolysis, heating to 85 to 95 °C for 5 to 15 min to inactivate the enzyme after the enzymatic hydrolysis reaction ends, and cooling to below 30 °C; S3. Taking the crude polypeptide solution prepared in step S2, intercepting polypeptides with a molecular weight of 1000 to 5000 Da, and drying to obtain the blood-pressure-lowering torreya grandis polypeptide. The present invention adopts sequential compound enzymatic hydrolysis with alkaline protease and papain, which can greatly improve the yield of polypeptides with a molecular weight of 1000 to 5000 Da.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and relates to a blood-pressure-lowering torreya grandis polypeptide and a preparation method thereof. Background Art

[0002] Cardiovascular and cerebrovascular diseases have become the number one factor threatening human health, and hypertension has been recognized by the World Health Organization as the main factor leading to the increase in the world's population mortality rate. People approaching the defined value of hypertension tend to have much higher incidences and mortality rates of cardiovascular and cerebrovascular diseases than those with normal blood pressure values, and it affects the health of nearly one-fifth of the adults in the world. Hypertension can cause a series of diseases, such as lesions in the brain, kidneys, heart, etc. Studies have shown that nearly half of the patients with coronary heart disease and stroke are caused by hypertension. Angiotensin-converting enzyme (ACE) is closely related to the regulation of human blood pressure. It converts angiotensin I into angiotensin II, causing a rapid increase in blood pressure. Inhibiting the activity of ACE is an important way to control blood pressure and keep it normal.

[0003] ACE inhibitory peptides are a class of polypeptide substances with ACE inhibitory activity, which play a role in lowering blood pressure by inhibiting the activity of ACE. Many synthetic ACE inhibitors have been widely used in clinical experiments and the treatment of hypertension. However, long-term use of this type of ACE inhibitor will cause side effects such as dizziness, angioedema, fatigue, etc., and even have a toxic effect on the internal organs of the human body. Therefore, preparing food-derived ACE inhibitory peptides from food has the advantages of low cost and small toxic and side effects. The cake and residue after oil extraction are rich in proteins and are important sources for preparing ACE inhibitory peptides. Currently, bioactive polypeptides with blood-pressure-lowering effects have been prepared from buckwheat protein, zein, black bean protein, etc. by enzymatic hydrolysis and are used as additives in functional foods.

[0004] Torreya grandis is an evergreen coniferous tree of the genus Torreya in the family Taxaceae and is one of the top ten woody oil tree species in China, with a rapid industrial development. Torreya grandis seeds are rich in nutrients and are popular leisure foods. Torreya grandis seeds contain 50-60% oil, which can be used as an edible oil source. The torreya grandis cake and residue after oil extraction are rich in nutrients such as proteins and polysaccharides. Among them, the protein content exceeds 20%, and albumin accounts for 90% of the proteins, making it an excellent raw material for functional foods and the preparation of active ingredients such as those for lowering blood pressure. However, the current utilization of torreya grandis cake and residue has not been effectively carried out, especially the proteins and polypeptides have not been effectively utilized. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a blood-pressure-lowering torreya grandis polypeptide and the blood-pressure-lowering torreya grandis polypeptide prepared therefrom in view of the deficiencies in the prior art.

[0006] The above object of the present invention is achieved by the following technical solutions:

[0007] A method for preparing blood pressure-lowering torreya grandis polypeptide, comprising the following steps:

[0008] S1. Add water to torreya grandis cake residue for extraction. After solid-liquid separation, the residue is repeatedly extracted 1 to 3 times, and the extraction liquids are combined, then concentrated to obtain a crude protein extract;

[0009] S2. Adjust the pH of the above crude protein extract to 8 - 10, add alkaline protease for enzymatic hydrolysis, then adjust the pH to 6 - 7, add papain for enzymatic hydrolysis. After the enzymatic hydrolysis reaction ends, heat to 85 - 95 °C to inactivate the enzyme for 5 - 15 min, and cool to below 30 °C;

[0010] S3. Take the crude polypeptide solution prepared in step S2, intercept polypeptides with a molecular weight of 1000 - 5000 Da, and dry them to obtain blood pressure-lowering torreya grandis polypeptide.

[0011] The polypeptide with a molecular weight of 1000 - 5000 Da, which is extracted from torreya grandis and subjected to enzymatic hydrolysis treatment, has excellent blood pressure-lowering efficacy. The present invention uses alkaline protease and papain for sequential complex enzymatic hydrolysis, which can greatly improve the yield of polypeptides with a molecular weight of 1000 - 5000 Da.

[0012] Preferably, the torreya grandis cake residue is prepared by a method comprising the following steps: drying torreya grandis seeds with hot air not higher than 65 °C until the water content is 6 - 12%, removing the outer shell, subjecting the torreya grandis seeds to low-temperature pressing and then re-pressing the cake residue, and then pulverizing and sieving. Preferably, sieve through a 30 - 60 mesh sieve.

[0013] Preferably, in step S1, the mass ratio of torreya grandis cake residue to water is 1:10 - 1:55.

[0014] Preferably, the extraction in step S1 is carried out at a pH of 7.5 - 11.5 and a temperature of 40 - 60 °C for 60 - 240 min.

[0015] Extracting the torreya grandis cake residue by a suitable process can effectively improve the extraction rate of protein, thus facilitating the obtaining of polypeptides with a molecular weight of 1000 - 5000 Da.

[0016] Preferably, in step S1, it is concentrated to a crude protein extract with a solid content of 20 - 100 g / L.

[0017] Preferably, the enzymatic hydrolysis temperature of alkaline protease is 45 - 60 °C.

[0018] Preferably, the enzymatic hydrolysis time of alkaline protease is 70 - 130 min.

[0019] Preferably, the enzyme-substrate concentration of alkaline protease is 1000 - 4000 U / g solids.

[0020] Preferably, the enzymolysis temperature of papain is 35 - 45 °C.

[0021] Preferably, the enzymolysis time of papain is 40 - 60 min.

[0022] Preferably, the enzyme-substrate concentration of papain is 1000 - 4000 U / g solids.

[0023] Preferably, the enzymolysis temperature of alkaline protease is 48 - 53 °C, the enzyme-substrate concentration of alkaline protease is 2500 - 3500 U / g solids, and the enzymolysis time of alkaline protease is 90 - 110 min.

[0024] Preferably, the enzymolysis temperature of papain is 38 - 43 °C, the enzyme-substrate concentration of papain is 2500 - 3500 U / g solids, and the enzymolysis time of papain is 40 - 60 min.

[0025] The present invention is conducive to enzymatically degrading torreya grandis protein into polypeptides with a molecular weight of 1000 - 5000 Da and improving the yield of polypeptides with this molecular weight by controlling the enzymolysis processes of alkaline protease and papain.

[0026] Preferably, in step S3, the step of intercepting polypeptides with a molecular weight of 1000 - 5000 Da includes: passing the crude polypeptide solution through a 10000 Da ultrafiltration membrane, collecting the permeate, passing it through a 5000 Da ultrafiltration membrane, collecting the permeate, and passing it through a 1000 Da ultrafiltration membrane to obtain the retentate.

[0027] Another object of the present invention is achieved by the following technical solution:

[0028] A torreya grandis polypeptide with blood pressure-lowering effect, which is prepared by the above preparation method.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention can effectively improve the protein extraction rate by extracting torreya grandis cake meal with a suitable process, thus facilitating the obtaining of polypeptides with a molecular weight of 1000 - 5000 Da; 2. The present invention uses alkaline protease and papain to sequentially carry out complex enzymolysis of torreya grandis protein, which can greatly improve the yield of polypeptides with a molecular weight of 1000 - 5000 Da;

[0031] 3. The present invention is conducive to enzymatically degrading torreya grandis protein into polypeptides with a molecular weight of 1000 - 5000 Da and improving the yield of polypeptides with this molecular weight by controlling the enzymolysis processes of alkaline protease and papain;

[0032] 4. The polypeptide with a molecular weight of 1000 - 5000 Da extracted from Torreya grandis Fort. var. Merrillii and subjected to enzymatic hydrolysis has excellent anti - hypertension efficacy; the product obtained after enzymatic hydrolysis of the Torreya grandis Fort. var. Merrillii protein of the present invention has an excellent ACE inhibition rate. Detailed implementation mode

[0033] The technical solutions of the present invention will be further described and illustrated through specific embodiments below. It should be understood that the specific embodiments described here are only used to help understand the present invention and are not used for specific limitations of the present invention. It is only to better illustrate the disclosed content of the present invention and does not limit the protection scope. If there is no special description, the raw materials used in the embodiments of the present invention are all common raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0034] Alkaline protease: food - grade, purchased from Solarbio Company, enzyme activity is 2×10 5 U / g;

[0035] Papain: food - grade, purchased from Solarbio Company, enzyme activity is 8×10 5 U / g;

[0036] Flavor protease: food - grade, purchased from Solarbio Company, enzyme activity is 3×10 4 U / g;

[0037] Neutral protease: food - grade, purchased from Solarbio Company, enzyme activity is 5×10 4 U / g;

[0038] Example 1

[0039] Take 10 kg of torreya grandis seeds and dry them in a dryer at 60 °C until the moisture content is about 8%. After shelling, crush them, wrap them into cakes, and place them in a vertical hydraulic oil press for pressing for about 40 minutes. Collect the pressed oil and take out the cake. Crush the cake and re-press the cake residue. Take the crushed cake residue and pass it through a 40-mesh sieve; Take the crushed and sieved torreya grandis cake residue powder and add it to a reaction kettle, and add deionized water with a pH of 10.5 according to a solid-liquid ratio of 1:30. Extract at 50 °C for 120 minutes at a rotation speed of 45 rpm / min, pump it into a horizontal centrifuge for liquid-solid-liquid separation, repeat the extraction of the residue once, combine the extraction liquids, and remove the water to obtain a crude protein extract with a solid content of 50 g / L; Take the above crude protein extract, adjust the pH to 9, add alkaline protease for enzymatic hydrolysis (the addition amount is about 3000 U / g of solid), carry out enzymatic hydrolysis at 50 °C for 100 minutes at a rotation speed of 45 rpm / min, then adjust the pH to 6.8, lower the temperature to 40 °C, add papain for enzymatic hydrolysis (the addition amount is about 3000 U / g of solid), carry out enzymatic hydrolysis at 40 °C for 50 minutes at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat it to 90 °C to inactivate the enzyme for 10 minutes, and cool it to below 30 °C to obtain a crude polypeptide solution; Take the crude polypeptide solution and pass it through a 10000 Da ultrafiltration membrane, collect the permeate and pass it through a 5000 Da ultrafiltration membrane, collect the permeate, and pass it through a 1000 Da ultrafiltration membrane to obtain the retentate and dry it into powder. A total of about 0.561 kg of torreya grandis polypeptide powder is prepared, among which 0.436 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da accounts for 77.7%.

[0040] Example 2

[0041] Take 10 kg of torreya grandis seeds and dry them in a dryer at 55 °C until the moisture content is about 10%. After shelling, crush them, wrap them into cakes, and place them in a vertical hydraulic oil press for pressing for about 40 minutes. Collect the pressed oil and take out the cake. Crush the cake and re-press the cake residue. Take the crushed cake residue and sieve it through a 40-mesh sieve; Take the crushed and sieved torreya grandis cake residue powder and add it to a reaction kettle, and add deionized water with a pH of 11.0 according to a solid-liquid ratio of 1:20. Extract at 45 °C at a rotation speed of 50 rpm / min for 150 minutes, pump it into a horizontal centrifuge for liquid-solid-liquid separation, repeat the extraction of the residue once, combine the extraction liquids, and remove the moisture to obtain a crude protein extract with a solid content of 40 g / L; Take the above crude protein extract and adjust the pH to 9.5, add alkaline protease for enzymatic hydrolysis (the addition amount is about 3200 U / g of solid), carry out enzymatic hydrolysis at 52 °C at a rotation speed of 50 rpm / min for 95 minutes, then adjust the pH to 6.5, lower the temperature to 42 °C, add papain for enzymatic hydrolysis (the addition amount is about 3200 U / g of solid), carry out enzymatic hydrolysis at 42 °C at a rotation speed of 50 rpm / min for 52 minutes. After the enzymatic hydrolysis reaction is completed, heat it to 90 °C to inactivate the enzyme for 12 minutes, and cool it to below 30 °C to obtain a crude polypeptide solution; Take the crude polypeptide solution and pass it through a 10000 Da ultrafiltration membrane, collect the permeate and pass it through a 5000 Da ultrafiltration membrane, collect the permeate, and pass it through a 1000 Da ultrafiltration membrane to obtain the retentate and dry it into powder. A total of about 0.545 kg of torreya grandis polypeptide powder is prepared, among which 0.415 kg of 5000-1000 Da polypeptide powder, accounting for 76.1%.

[0042] Example 3

[0043] Take 10 kg of torreya grandis seeds and dry them in a dryer at 55 °C until the moisture content is about 7%. After shelling, crush them and wrap them into cakes, then place them in a vertical hydraulic oil press and press for about 45 minutes. Collect the pressed oil and take out the cake. After crushing, the cake residue is re-pressed. Take the crushed cake residue and pass it through a 40-mesh sieve; take the crushed and sieved torreya grandis cake residue powder and add it to a reaction kettle, and add deionized water with a pH of 9.5 according to a solid-liquid ratio of 1:40. Extract at 55 rpm and 55 °C for 90 minutes, pump it into a horizontal centrifuge for liquid-solid-liquid separation, repeat the extraction of the residue once, combine the extraction liquids, and remove the moisture to obtain a crude protein extract with a solid content of 30 g / L; take the above crude protein extract and adjust the pH to 9.7, add alkaline protease for enzymatic hydrolysis (the addition amount is about 2800 U / g of solids), hydrolyze at 55 rpm and 48 °C for 110 minutes, then adjust the pH to 6.2, lower the temperature to 39 °C, add papain for enzymatic hydrolysis (the addition amount is about 3300 U / g of solids), hydrolyze at 55 rpm and 39 °C for 60 minutes. After the enzymatic hydrolysis reaction is completed, heat it to 85 °C to inactivate the enzyme for 15 minutes, and cool it to below 30 °C to obtain a crude polypeptide solution; take the crude polypeptide solution and pass it through a 10000 Da ultrafiltration membrane, collect the permeate and pass it through a 5000 Da ultrafiltration membrane, collect the permeate, and pass it through a 1000 Da ultrafiltration membrane to obtain the retentate and dry it into powder. A total of about 0.57 kg of torreya grandis polypeptide powder is prepared, among which 0.435 kg of 5000-1000 Da polypeptide powder, accounting for 76.3%.

[0044] Example 4

[0045] The difference between Example 4 and Example 1 is that the enzymatic hydrolysis step is as follows: take the above crude protein extract and adjust the pH to 9, add alkaline protease for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), hydrolyze at 45 rpm and 50 °C for 50 minutes, then adjust the pH to 6.8, lower the temperature to 40 °C, add papain for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), hydrolyze at 45 rpm and 40 °C for 100 minutes. After the enzymatic hydrolysis reaction is completed, heat it to 90 °C to inactivate the enzyme for 10 minutes, and cool it to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.555 kg of torreya grandis polypeptide powder is prepared, among which 0.412 kg of 5000-1000 Da polypeptide powder, accounting for 74.2%.

[0046] Example 5

[0047] Example 5 is different from Example 1 in that the enzymatic hydrolysis step is as follows: Adjust the pH of the above-mentioned crude protein extract to 9, add alkaline protease for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 100 min at a rotation speed of 45 rpm / min, then adjust the pH to 6.8, lower the temperature to 40 °C, add papain for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 40 °C for 100 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.562 kg of torreya grandis polypeptide powder was prepared, among which 0.424 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da, accounting for 75.4%.

[0048] Comparative Example 1

[0049] Comparative Example 1 is different from Example 1 in that the enzymatic hydrolysis step is as follows: Adjust the pH of the above-mentioned crude protein extract to 9, add alkaline protease for enzymatic hydrolysis (the addition amount is about 6000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 150 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.565 kg of torreya grandis polypeptide powder was prepared, among which 0.361 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da, accounting for 63.9%.

[0050] Comparative Example 2

[0051] Comparative Example 2 is different from Example 1 in that the enzymatic hydrolysis step is as follows: Adjust the pH of the above-mentioned crude protein extract to 6.8, add papain for enzymatic hydrolysis (the addition amount is about 6000 U / g of solids), carry out enzymatic hydrolysis at 40 °C for 150 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.552 kg of torreya grandis polypeptide powder was prepared, among which 0.301 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da, accounting for 54.5%.

[0052] Comparative Example 3

[0053] Comparative Example 3 is different from Example 1 in that the enzymatic hydrolysis step is as follows: Adjust the pH of the above-mentioned crude protein extract to 6.5, add flavor protease for enzymatic hydrolysis (the addition amount is about 6000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 150 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.559 kg of torreya grandis polypeptide powder was prepared, among which 0.338 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da, accounting for 60.5%.

[0054] Comparative Example 4

[0055] The difference between Comparative Example 4 and Example 1 is that the enzymatic hydrolysis step is as follows: Take the above crude protein extract, adjust the pH to 7.0, add neutral protease for enzymatic hydrolysis (the addition amount is about 6000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 150 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.563 kg of torreya grandis polypeptide powder is obtained, among which 0.336 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da, accounting for 59.7%.

[0056] Comparative Example 5

[0057] The difference between Comparative Example 5 and Example 1 is that the enzymatic hydrolysis step is as follows: Take the above crude protein extract, adjust the pH to 9, add alkaline protease for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 100 min at a rotation speed of 45 rpm / min, then adjust the pH to 6.5, lower the temperature to 50 °C, add flavor protease for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 50 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.568 kg of torreya grandis polypeptide powder is obtained, among which 0.351 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da, accounting for 61.8%.

[0058] Comparative Example 6

[0059] The difference between Comparative Example 6 and Example 1 is that the enzymatic hydrolysis step is as follows: Take the above crude protein extract, adjust the pH to 6.5, add flavor protease for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 100 min at a rotation speed of 45 rpm / min, then adjust the pH to 6.8, lower the temperature to 40 °C, add papain for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 40 °C for 50 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. A total of about 0.56 kg of torreya grandis polypeptide powder is obtained, among which 0.320 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da, accounting for 57.1%.

[0060] Comparative Example 7

[0061] The difference between Comparative Example 7 and Example 1 lies in that the enzymatic hydrolysis steps are as follows: adjust the pH to 6.8, add papain for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 40 °C for 50 min at a rotation speed of 45 rpm / min, then adjust the pH to 9, add alkaline protease for enzymatic hydrolysis (the addition amount is about 3000 U / g of solids), carry out enzymatic hydrolysis at 50 °C for 100 min at a rotation speed of 45 rpm / min. After the enzymatic hydrolysis reaction is completed, heat to 90 °C to inactivate the enzyme for 10 min, and cool to below 30 °C to obtain a crude polypeptide solution. Others are the same as in Example 1. About 0.552 kg of torreya grandis polypeptide powder was obtained in total, among which 0.366 kg of polypeptide powder with a molecular weight of 5000 - 1000 Da accounted for 66.3%.

[0062] The ACE inhibitory rates of the crude polypeptide solutions of Examples 1 - 5 and Comparative Examples 1 - 7 were determined by HPLC method. HHL was used as the substrate for the action of ACE. Through the HA generated in the reaction system, the peak area value of HA was then determined by HPLC method to indicate its production amount, and the inhibitory rate of the ACE inhibitory peptide was calculated. The results are shown in Table 1.

[0063] Table 1 Amount of torreya grandis polypeptide, amount and proportion of polypeptide with a molecular weight of 5000 - 1000 Da, and ACE inhibitory rate of Examples 1 - 5 and Comparative Examples 1 - 7

[0064]

[0065] It can be seen from Table 1 that when torreya grandis protein is enzymatically hydrolyzed with a single protease, a high proportion of polypeptide with a molecular weight of 5000 - 1000 Da cannot be obtained, and the ACE inhibitory rate is also relatively low; when other enzymes are used for combined enzymatic hydrolysis, the synergistic effect between the two is not exerted either; while in the stepwise combined enzymatic hydrolysis with alkaline protease and papain adopted in the present invention, as shown in Examples 1 - 5, the proportion of polypeptide with a molecular weight of 5000 - 1000 Da reaches 75%, and the ACE inhibitory rate reaches more than 94%.

[0066] All aspects, embodiments, and features of the present invention should be considered illustrative in all respects and do not limit the present invention. The scope of the present invention is only defined by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will understand other embodiments, modifications, and uses.

[0067] In the preparation method of the present invention, the order of each step is not limited to the listed order. For those of ordinary skill in the art, without creative efforts, the changes in the sequence of each step are also within the protection scope of the present invention. In addition, two or more steps or actions can be carried out simultaneously.

[0068] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present invention and do not limit the implementation of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. It is not necessary and impossible to list all embodiments here. And these obvious changes or variations derived from the essence of the present invention still fall within the protection scope of the present invention. Interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. A preparation method of torreya grandis polypeptide for reducing blood pressure, characterized in that, It includes the following steps: S1. Add water to torreya grandis cake meal for extraction. Extract at a pH of 7.5 - 11.5 and a temperature of 40 - 60 °C for 60 - 240 min. After solid-liquid separation, repeat the extraction of the residue 1 - 3 times, combine the extraction solutions, and then concentrate to obtain a crude protein extract. S2. Adjust the pH of the above crude protein extract to 8 - 10, add alkaline protease for enzymatic hydrolysis. The enzymatic hydrolysis temperature of the alkaline protease is 45 - 60 °C, the enzymatic hydrolysis time is 70 - 130 min, and the enzyme-substrate concentration is 1000 - 4000 U / g of solids. Then adjust the pH to 6 - 7, add papain for enzymatic hydrolysis. The enzymatic hydrolysis temperature of papain is 35 - 45 °C, the enzymatic hydrolysis time is 40 - 60 min, and the enzyme-substrate concentration is 1000 - 4000 U / g of solids. After the enzymatic hydrolysis reaction, heat to 85 - 95 °C to inactivate the enzyme for 5 - 15 min, and cool to below 30 °C. S3. Take the crude polypeptide solution prepared in step S2, intercept polypeptides with a molecular weight of 1000 - 5000 Da, and dry them to obtain torreya grandis polypeptides with blood pressure-lowering effect.

2. The preparation method according to claim 1, characterized in that, Torreya grandis cake meal is prepared by a method including the following steps: Dry torreya grandis seeds with hot air not higher than 65 °C until the water content is 6 - 12%, remove the outer shell, perform low-temperature pressing on torreya grandis seeds and then re-press the cake meal, and then pulverize and sieve.

3. The preparation method according to claim 1, wherein In step S1, the mass ratio of torreya grandis cake meal to water is 1:10 - 1:

55.

4. The preparation method according to claim 1, characterized in that, In step S1, concentrate to obtain a crude protein extract with a solid content of 20 - 100 g / L.

5. The preparation method according to claim 1, wherein The enzymatic hydrolysis temperature of the alkaline protease is 48 - 53 °C, the enzyme-substrate concentration of the alkaline protease is 2500 - 3500 U / g of solids, and the enzymatic hydrolysis time of the alkaline protease is 90 - 110 min.

6. The preparation method according to claim 1, characterized in that, The enzymatic hydrolysis temperature of papain is 38 - 43 °C, the enzyme-substrate concentration of papain is 2500 - 3500 U / g of solids, and the enzymatic hydrolysis time of papain is 40 - 60 min.

7. The preparation method according to claim 1, characterized in that, In step S3, the step of intercepting polypeptides with a molecular weight of 1000 - 5000 Da includes: Pass the crude polypeptide solution through a 10000 Da ultrafiltration membrane, collect the permeate and pass it through a 5000 Da ultrafiltration membrane, collect the permeate, and pass it through a 1000 Da ultrafiltration membrane to obtain the retentate.

8. A torreya grandis polypeptide for lowering blood pressure, characterized in that, It is prepared by the preparation method described in claim 1.

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