Extraction process and application of donkey-hide gelatin

Abstract

The invention provides an extraction process and application of donkey-hide gelatin, and the extraction process of donkey-hide gelatin comprises the following steps: S1, impurity removal and soaking; s2, unhairing and shearing; s3, melting skin and extracting gelatin; s4, concentrating the gel; and S5, dicing according to specification requirements, airing glue, wiping the glue, sterilizing and packaging. According to the extraction process of the donkey-hide gelatin, the gelatin yield can be remarkably improved, the content of amino acid and polypeptide in the donkey-hide gelatin can be effectively increased, and powerful support is provided for modern production and application of the donkey-hide gelatin.

Description

Technical Field

[0001] The invention belongs to the technical field of health food, and specifically relates to an extraction process of donkey-hide gelatin and application thereof. Background Art

[0002] As one of the traditional precious Chinese medicinal materials, donkey-hide gelatin has a long history of medicinal use and a wide range of pharmacological effects. It is widely used in the fields of blood tonic, yin nourishing and moistening, and beauty and skin care. Its unique pharmacological effects mainly come from its rich active ingredients such as amino acids and peptides. However, the extraction process of donkey-hide gelatin has a significant impact on the quality and active ingredient content of the final product, especially the gelatin yield, amino acid and peptide extraction efficiency, which are directly related to the efficacy and market value of donkey-hide gelatin.

[0003] The traditional extraction process of donkey-hide gelatin often relies on experience and judgment, and there are problems such as low production efficiency, incomplete extraction, and large loss of active ingredients. In particular, in key steps such as peeling, extraction, and concentration, improper control of process parameters often leads to low gelatin yield and insufficient content of active ingredients such as amino acids and peptides, which seriously affects the quality and efficacy of donkey-hide gelatin.

[0004] At present, there is still a lack of a gelatin extraction process that can simultaneously improve the gelatin yield, amino acid and polypeptide content in the market. Therefore, developing an efficient, stable and controllable gelatin extraction process is of great significance for improving the quality and market competitiveness of gelatin products.

[0005] The present invention aims to provide a novel extraction process of donkey-hide gelatin and its application, which can achieve efficient extraction of donkey-hide gelatin and sufficient retention of active ingredients by optimizing key process parameters and adopting advanced extraction technology. The process can not only significantly improve the yield of donkey-hide gelatin, but also effectively increase the content of amino acids and polypeptides in donkey-hide gelatin, providing strong support for the modern production and application of donkey-hide gelatin. Summary of the invention

[0006] The purpose of the present invention is to provide an extraction process of donkey-hide gelatin and its application. The extraction process of donkey-hide gelatin described in the present invention can not only significantly improve the gelatin yield, but also effectively increase the content of amino acids and polypeptides in donkey-hide gelatin, providing strong support for the modern production and application of donkey-hide gelatin.

[0007] A process for extracting donkey-hide gelatin comprises the following steps:

[0008] S1, impurity removal and soaking: after picking out impurities from the donkey skin and cleaning it, add water until the water covers the surface of the donkey skin by more than 10 cm and soak for 5 to 7 days, wherein the water is changed every 1 to 2 days to obtain a wet donkey skin;

[0009] S2, depilation and shearing: the wet donkey skin is depilated and washed to obtain the depilated donkey skin, the depilated donkey skin is cut into pieces, put into a steaming ball, after adding sodium carbonate and water, steam is introduced, the steam pressure is controlled to be 0.12-0.15MPa, the skin is blanched for 30-60min, washed, and cut into donkey skin pieces;

[0010] S3, extracting glue from skin: extract the donkey skin obtained in step S2 by adding water and heating twice, combine the filtrates obtained by the two extractions by adding water and heating, cool to room temperature, add complex enzyme, stir evenly and adjust the system to neutral, heat to 45-55°C, react for 5-7h, and obtain glue;

[0011] S4, concentrated gel: after the gel is initially concentrated to a relative density of 1.08-1.09, the foam is further concentrated, soybean oil, crystal sugar and rice wine are added in sequence, and the floating gel foam is skimmed off, and the gel is produced when the water content is 26%-29%. The gel is placed in a special stainless steel gel box coated with vegetable oil and gelled to obtain a gel lump;

[0012] S5. Take the glue lump, cut it into pieces according to the specifications, dry it, wipe it, sterilize it, and package it.

[0013] Preferably, the added amount of sodium carbonate is 0.4% to 0.6% of the mass of the donkey hide.

[0014] Preferably, the amount of water added is 48% to 52% of the mass of the dehaired donkey hide.

[0015] Preferably, the two water-adding and heating extractions include a first water-adding and heating extraction and a second water-adding and heating extraction.

[0016] Preferably, the specific steps of the first water-adding heating extraction are: putting the donkey skin obtained in step S2 into a steaming ball, adding water, passing steam, starting the steaming ball, controlling the steam pressure to be 0.12-0.15 MPa, dynamically extracting for 0.5-1.5 hours, stopping the ball to vent once every 0.5 hours, then statically extracting for 5-7 hours, rotating the steaming ball to stir for 2-5 minutes every 0.5 hours, and filtering to obtain a filtrate and a residue after the extraction is completed.

[0017] Preferably, the specific steps of the second water-adding and heating extraction are: putting the filter residue obtained by the first water-adding and heating extraction into a steam ball, adding water, passing steam, starting the steam ball, controlling the steam pressure to 0.12-0.15 MPa, and dynamically extracting for 0.5-1.5 hours, and then filtering to obtain the filtrate.

[0018] Preferably, during the first water-adding and heating extraction, the amount of water added is 58% to 62% of the mass of the donkey hide obtained in step S2.

[0019] Preferably, during the second water-adding and heating extraction, the amount of water added is 48% to 52% of the mass of the donkey hide obtained in step S2.

[0020] The inventor found that the combination of steam pressurization and dynamic and static extraction can improve the content of amino acids and polypeptides in donkey-hide gelatin while improving the glue yield. This may be because on the one hand, steam pressurization and heating not only soften the donkey skin tissue under high temperature and high pressure, but also rupture the cell wall, which is conducive to the dissolution and diffusion of the effective ingredients in the cell, thereby improving the glue yield, and can also promote the degradation of protein in the donkey skin, and hydrolyze the macromolecular protein into small molecular polypeptides and amino acids. On the other hand, the dynamic and static combined extraction, the rotation and stirring of the steaming ball promote the full contact of donkey skin with water, and help the protein to be fully dissolved and extracted, while the static extraction is conducive to the stable dissolution of polypeptides and amino acids, avoiding the loss caused by stirring, thereby improving the content of amino acids and polypeptides in donkey-hide gelatin blocks. The second water-adding heating treatment can extract the remaining filter residue after the first extraction again, which can further improve the glue yield, and recover the effective ingredients such as amino acids and polypeptides in the donkey skin.

[0021] Preferably, the added amount of the complex enzyme is 5% to 10% of the mass of the combined filtrate.

[0022] Preferably, the complex enzyme is papain and trypsin.

[0023] Preferably, the mass ratio of papain to trypsin is (4-6):1; more preferably, it is 5:1.

[0024] Preferably, the enzymatic activity of the papain is ≥90,000 U / g.

[0025] Preferably, the trypsin has an enzymatic activity of ≥180,000 U / g.

[0026] In some preferred embodiments, the papain and trypsin are purchased from Ningxia Xiasheng Industrial Group Co., Ltd.

[0027] The inventors found that after adding water and heating for extraction, two specific enzymes were selected to enzymolyze the filtrate, which could further increase the content of amino acids and polypeptides in donkey-hide gelatin, thereby improving the quality and efficacy of donkey-hide gelatin products. This may be because under the specific conditions of the present invention, the two enzymes have different enzymolysis specificities and action sites. They can not only complement each other and act together on the protein in the filtrate to make it more thoroughly hydrolyzed, generate smaller peptides and amino acids, but also accelerate the hydrolysis process of protein, improve the hydrolysis efficiency, thereby reducing the time and energy consumption in the extraction process, and reduce costs. In addition, the synergistic effect of the two enzymes can also make the hydrolyzate more uniform and delicate, with better taste and higher nutritional value, and improve the quality of the glue. However, the high enzymolysis temperature not only leads to enzyme inactivation, but also easily destroys collagen fibers, causing collagen decomposition and loss, affecting the content of amino acids and polypeptides.

[0028] Preferably, the specific steps of the continuous concentration and foaming are: skimming off the floating foam, adding water and pressurizing for 0.5 to 2 hours, and concentrating at low temperature and low pressure for 1.5 to 2.5 hours to make the foam slowly float up. Repeat this step five times.

[0029] Preferably, the amount of water added is consistent with the mass of the concentrated gel.

[0030] Preferably, the pressurized pressure is 0.12-0.15 MPa.

[0031] Preferably, the low temperature is 50-60°C.

[0032] Preferably, the low pressure is 0.05-0.1 MPa.

[0033] The inventors found that by a specific continuation and foaming step, the loss of effective substances in the gelatin can be reduced while the gelatin yield is increased, thereby improving the efficacy of donkey-hide gelatin. This may be because the specific low-temperature and low-pressure concentration conditions not only gradually evaporate the water in the gelatin, but also increase the relative concentration of components such as polypeptides and amino acids, directly increasing the content of polypeptides and amino acids in donkey-hide gelatin products, but also reducing the degradation and loss of amino acids, avoiding the Maillard reaction of amino acids under high temperature and high pressure, thereby affecting the amino acid content in donkey-hide gelatin blocks. In the process of continuous concentration and foaming, as collagen is gradually hydrolyzed and concentrated, its molecular chain is gradually cut into smaller polypeptides and amino acids, which gradually accumulate in the extract, thereby further increasing the content of polypeptides and amino acids in donkey-hide gelatin. At the same time, by removing impurities and repeatedly concentrating, the concentration of polypeptides in the extract can be further increased. At the same time, skimming the floating gelatin can remove most of the impurities and undissolved substances. Although it is inevitable that some polypeptides and amino acids combined with impurities will be removed, by controlling the temperature, pressure and concentration time, the loss can be minimized, thereby retaining more polypeptides and amino acids in the donkey-hide gelatin blocks, improving the quality and efficacy of donkey-hide gelatin. In addition, adding water and pressurizing for a period of time helps to further dissolve and diffuse collagen and other soluble components, allowing them to be more fully released into the extract, thereby increasing the yield of gelatin. Repeating this step five times can further remove impurities and enrich amino acids and peptides, ensuring the stability of the amino acid and peptide content in the final product.

[0034] Preferably, the specific steps of sequentially adding soybean oil, rock sugar, and rice wine are: skimming off the floating foam, adding soybean oil, continuing to add water and pressurize, concentrating at low temperature and low pressure, so that the foam slowly floats up; skimming off the floating foam, adding melted rock sugar, continuing to add water and pressurize, concentrating at low temperature and low pressure, so that the foam slowly floats up; skimming off the floating foam, adding rice wine, continuing to add water and pressurize, concentrating at low temperature and low pressure, so that the foam slowly floats up. Among them, the conditions of adding water and pressurizing and concentrating at low temperature and low pressure are the same as those in the step of continuous concentration and foaming.

[0035] Preferably, the added amount of the soybean oil is 3% to 3.5% of the mass of the donkey hide.

[0036] Preferably, the added amount of the rock sugar is 3% to 3.5% of the mass of the donkey hide.

[0037] Preferably, the added amount of the rice wine is 0.5% to 1% of the mass of the donkey hide.

[0038] The inventors found that adding soybean oil, crystal sugar, and yellow wine in order and carrying out the continuous concentration and foaming treatment at the same time can improve the retention rate of the effective ingredients in the glue juice, thereby increasing the content of the effective ingredients in the donkey-hide gelatin block, and then improving its efficacy. This may be because the addition of soybean oil can not only reduce the viscosity of the glue liquid, making it easier for the effective ingredients such as amino acids and polypeptides to be retained during the concentration process, but also the oil layer formed by soybean oil on the surface of the glue liquid can prevent the oxidation and degradation of the ingredients such as amino acids and polypeptides, thereby increasing the content of the effective ingredients in the donkey-hide gelatin block. The synergistic effect of crystal sugar and yellow wine not only adjusts the taste of the donkey-hide gelatin block, but also promotes the enhancement of the solubility of the glue liquid, and further promotes the dissolution and enrichment of ingredients such as amino acids and polypeptides. At the same time, the addition of yellow wine also helps to improve the fluidity and stability of the glue liquid, which is conducive to the subsequent concentration and foaming operations. In actual operation, the order of addition needs to be strictly controlled. If rice wine or rock sugar is added first, it may affect the dispersion effect of soybean oil and the stability of the gelatin, thereby reducing the retention rate of effective ingredients such as amino acids and polypeptides; if rice wine is added immediately after soybean oil concentration, it may affect the dissolution effect of rice wine on donkey-hide gelatin, resulting in the effective ingredients in donkey-hide gelatin cannot be fully dissolved, and the rock sugar added at last will not be able to be fully mixed with the donkey-hide gelatin, affecting the gelation effect and final quality of the donkey-hide gelatin.

[0039] Preferably, the specific conditions of the gel are: after condensing at a temperature of 2 to 7° C. for 10 to 12 hours, the temperature is further lowered to 0 to 2° C. for condensing for 10 to 12 hours.

[0040] The donkey-hide gelatin can be applied to the field of food and health care.

[0041] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0042] 1. The present invention provides an extraction process of donkey-hide gelatin, which achieves efficient extraction of donkey-hide gelatin and sufficient retention of active ingredients by optimizing key process parameters and adopting advanced extraction technology. The process can not only significantly improve the yield of gelatin, but also effectively increase the content of amino acids and polypeptides in donkey-hide gelatin, providing strong support for the modern production and application of donkey-hide gelatin.

[0043] 2. The present invention adopts a combination of steam pressurization and dynamic and static extraction, which can increase the content of amino acids and polypeptides in donkey-hide gelatin while increasing the gelatin yield.

[0044] 3. The present invention can further increase the content of amino acids and polypeptides in donkey-hide gelatin by selecting two specific enzymes to enzymolyze the filtrate, thereby improving the quality and efficacy of donkey-hide gelatin products.

[0045] 4. The present invention can improve the gelatin yield while reducing the loss of effective substances in the gelatin juice through specific steps of continuous concentration and frothing, thereby improving the efficacy of donkey-hide gelatin.

[0046] 5. The present invention adds soybean oil, crystal sugar and rice wine in sequence and performs a continuous concentration and foaming process at the same time, which can improve the retention rate of effective ingredients in the gelatin juice, thereby increasing the content of effective ingredients in the donkey-hide gelatin block and further improving its efficacy. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The raw materials used in the present invention are all commercially available, specifically:

[0049] Donkey skin, Aorun (Shandong) Pharmaceutical Co., Ltd.

[0050] Rock sugar, single crystal rock sugar, was purchased from Guangdong Nanzi Technology Co., Ltd.

[0051] Soybean oil, peroxide value ≤10 mg / kg, acid value ≤0.2 mg / g, saponification value 188-200 mgKOH / g, was purchased from Shanxi Jinyang Pharmaceutical Excipients Co., Ltd.

[0052] Yellow rice wine, with a degree of 12% VOL, was purchased from Shandong Lizhikang Biotechnology Co., Ltd.

[0053] Papain, with an enzyme activity of about 100,000 U / g, and trypsin, with an enzyme activity of about 200,000 U / g, were purchased from Ningxia Xiasheng Industrial Group Co., Ltd.

[0054] Example 1

[0055] This embodiment provides a process for extracting donkey-hide gelatin, the steps are:

[0056] S1, impurity removal and soaking: after picking out impurities from the donkey skin and cleaning it, add water until the water covers the donkey skin surface by 10 cm and soak for 6 days, wherein the water is changed every 2 days to obtain a wet donkey skin;

[0057] S2, depilation and shearing: wet donkey skin is cleaned after depilation to obtain depilated donkey skin, the depilated donkey skin is cut into pieces of leather with a length and width of 30mm × 30mm, put into a steaming ball, add sodium carbonate and water, pass into steam, control the steam pressure to 0.13MPa, blanch the skin for 45min, wash, and cut into pieces of donkey skin with a length and width of 5mm × 5mm;

[0058] S3, extracting glue from skin: extract the donkey skin obtained in step S2 by adding water and heating twice, combine the filtrates obtained by the two extractions by adding water and heating, cool to room temperature, add complex enzyme, stir evenly and adjust the system to neutral, heat to 50°C, react for 6h, and obtain glue;

[0059] S4, concentrated gel: after the gel is initially concentrated to a relative density of 1.09, the foam is further concentrated, soybean oil, crystal sugar and rice wine are added in sequence, and the floating gel foam is skimmed off, and the gel is produced when the water content is 28%. The gel is placed in a special stainless steel gel box coated with vegetable oil and waits for gelation to obtain a gel lump;

[0060] S5. Take the glue lump, cut it into pieces according to the specifications, dry it, wipe it, sterilize it, and package it.

[0061] The added amount of the sodium carbonate is 0.5% of the mass of the donkey hide.

[0062] The amount of water added is 50% of the mass of the dehaired donkey hide.

[0063] The two water-adding and heating extractions include a first water-adding and heating extraction and a second water-adding and heating extraction.

[0064] The specific steps of the first water-adding heating extraction are: putting the donkey skin obtained in step S2 into a steaming ball, adding water, passing steam, starting the steaming ball, controlling the steam pressure to be 0.13 MPa, dynamically extracting for 1 hour, stopping the ball to vent once every 0.5 hour, then statically extracting for 5 hours, rotating the steaming ball to stir for 3 minutes every 0.5 hour, and filtering to obtain filtrate and filter residue after extraction.

[0065] The specific steps of the second water-adding and heating extraction are: putting the filter residue obtained by the first water-adding and heating extraction into a steam ball, adding water, passing steam, starting the steam ball, controlling the steam pressure to 0.13 MPa, and filtering to obtain a filtrate after dynamic extraction for 1 hour.

[0066] During the first water-adding and heating extraction, the amount of water added is 60% of the mass of the donkey hide obtained in step S2.

[0067] During the second water-adding and heating extraction, the amount of water added is 50% of the mass of the donkey hide obtained in step S2.

[0068] The added amount of the composite enzyme is 8% of the mass of the combined filtrate.

[0069] The complex enzyme is papain and trypsin.

[0070] The mass ratio of papain to trypsin is 5:1.

[0071] The specific steps of the continuous concentration and foaming are: skimming off the floating foam, adding water and pressurizing for 1.5 hours, and concentrating at low temperature and low pressure for 2 hours to make the foam slowly float up. Repeat this step five times.

[0072] The amount of water added is consistent with the quality of the concentrated gum.

[0073] The pressurized pressure is 0.13 MPa.

[0074] The low temperature is 55°C.

[0075] The low pressure is 0.07 MPa.

[0076] The specific steps of sequentially adding soybean oil, rock sugar and rice wine are: skimming off the floating foam, adding soybean oil, continuing to add water and pressurize, concentrating at low temperature and low pressure, so that the foam slowly floats up; skimming off the floating foam, adding melted rock sugar, continuing to add water and pressurize, concentrating at low temperature and low pressure, so that the foam slowly floats up; skimming off the floating foam, adding rice wine, continuing to add water and pressurize, concentrating at low temperature and low pressure, so that the foam slowly floats up. Among them, the conditions of adding water and pressurizing and concentrating at low temperature and low pressure are the same as those in the step of continuous concentration and foam extraction.

[0077] The added amount of the soybean oil is 3.2% of the mass of the donkey skin.

[0078] The added amount of the crystal sugar is 3.2% of the weight of the donkey skin.

[0079] The added amount of the rice wine is 0.8% of the weight of the donkey skin.

[0080] The specific conditions of the gel are: after condensing at a temperature of 5° C. for 10 hours, continue to cool to 0° C. and condense for 12 hours to obtain the gel.

[0081] Example 2

[0082] The difference between this embodiment and embodiment 1 is that the specific steps of the first water-adding heating extraction are: putting the donkey skin obtained in step S2 into a steaming ball, adding water, passing steam, starting the steaming ball, controlling the steam pressure to be 0.15 MPa, dynamically extracting for 1.5 hours, stopping the ball to vent once every 0.5 hours, then statically extracting for 5 hours, rotating the steaming ball to stir for 2 minutes every 0.5 hours, and filtering to obtain a filtrate and a filter residue after the extraction is completed.

[0083] Example 3

[0084] The difference between this embodiment and embodiment 1 is that the added amount of the composite enzyme is 10% of the mass of the combined filtrate.

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 1 is that the specific steps of the first water-adding heating extraction are: putting the donkey skin obtained in step S2 into a steaming ball, adding water, passing steam, starting the steaming ball, controlling the steam pressure to 0.13 MPa, dynamically extracting for 6 hours, stopping the ball to vent every 0.5 hours, and filtering to obtain a filtrate and a filter residue after the extraction is completed.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is as follows: S3, extracting glue from skin: subjecting the donkey skin obtained in step S2 to a water-adding heating extraction, combining the filtrates obtained from the water-adding heating extraction, adding complex enzyme after cooling to room temperature, stirring evenly and adjusting the system to be neutral, heating to 50°C, reacting for 6 hours, and obtaining glue; the specific steps of the water-adding heating extraction are: putting the donkey skin obtained in step S2 into a steaming ball, adding water, passing steam, starting the steaming ball, controlling the steam pressure to 0.13 MPa, dynamically extracting for 1 hour, stopping the ball to vent once every 0.5 hour, then statically extracting for 5 hours, rotating the steaming ball to stir for 3 minutes every 0.5 hour, and filtering to obtain filtrate and filter residue after extraction.

[0089] Comparative Example 3

[0090] The difference between this comparative example and Example 1 is that the specific steps of the first water-adding and heating extraction are as follows: water is added to the donkey skin obtained in step S2, the temperature is raised to 120° C., and maintained for 7 hours. After the extraction is completed, filtrate is filtered to obtain a filtrate and a filter residue.

[0091] The specific steps of the second water-adding and heating extraction are: adding water to the filter residue obtained by the first water-adding and heating extraction, heating to 120° C., maintaining for 1 hour, and then filtering to obtain a filtrate.

[0092] Comparative Example 4

[0093] The difference between this comparative example and Example 1 is that the mass ratio of papain to trypsin is 1:1.

[0094] Comparative Example 5

[0095] The difference between this comparative example and Example 1 is as follows: S3, extracting glue from skin: extract the donkey skin obtained in step S2 by adding water and heating twice, combine the filtrates obtained by the two extractions by adding water and heating, cool to room temperature, add complex enzyme, stir evenly and adjust the system to neutral, heat to 70°C, react for 6 hours, and obtain glue.

[0096] Comparative Example 6

[0097] The difference between this comparative example and Example 1 is that the specific steps of the continuous concentration and foaming are: skimming off the floating foam, adding water and pressurizing for 1 hour, and concentrating at low temperature and low pressure for 2 hours to make the foam slowly float up.

[0098] Comparative Example 7

[0099] The difference between this comparative example and Example 1 is that the low temperature is 80°C.

[0100] Comparative Example 8

[0101] The difference between this comparative example and Example 1 is as follows: S4, after the gel juice is initially concentrated to a relative density of 1.08, the gel juice is further concentrated and foamed, and yellow wine, soybean oil, and rock sugar are added in sequence, and the floating gel foam is skimmed off, and the gel is discharged when the water content is 28%, and the gel is placed in a special stainless steel gel box coated with vegetable oil and waits for it to gel to obtain gel lumps; the specific steps of adding yellow wine, soybean oil, and rock sugar in sequence are: skimming off the floating gel foam, adding yellow wine, and continuing to add water and pressurize, and then concentrating at low temperature and low pressure to make the gel foam slowly float up; skimming off the floating gel foam, adding soybean oil, and continuing to add water and pressurize, and then concentrating at low temperature and low pressure to make the gel foam slowly float up; skimming off the floating gel foam, adding the melted rock sugar, and continuing to add water and pressurize, and then concentrating at low temperature and low pressure to make the gel foam slowly float up. Among them, the conditions of adding water and pressurizing and concentrating at low temperature and low pressure are consistent with those in the step of continuing to concentrate and foam.

[0102] Comparative Example 9

[0103] The difference between this comparative example and Example 1 is as follows: S4, after the gel juice is initially concentrated to a relative density of 1.08, the gel juice is further concentrated and foamed, and soybean oil, yellow rice wine, and rock sugar are added in sequence, and the floating gel foam is skimmed off, and the gel is discharged when the water content is 28%, and the gel is placed in a special stainless steel gel box coated with vegetable oil and waits for it to gel to obtain gel lumps; the specific steps of adding soybean oil, yellow rice wine, and rock sugar in sequence are: skimming off the floating gel foam, adding soybean oil, and continuing to add water and pressurize, and concentrating at low temperature and low pressure to make the gel foam slowly float up; skimming off the floating gel foam, adding yellow rice wine, and continuing to add water and pressurize, and concentrating at low temperature and low pressure to make the gel foam slowly float up; skimming off the floating gel foam, adding dissolved rock sugar, and continuing to add water and pressurize, and concentrating at low temperature and low pressure to make the gel foam slowly float up. Among them, the conditions of adding water and pressurizing and concentrating at low temperature and low pressure are consistent with those in the step of continuing to concentrate and foam.

[0104] Performance Testing

[0105] The contents of four representative amino acids, L-hydroxyproline, glycine, endothecin, and L-proline, as well as donkey-derived polypeptides in donkey-hide gelatin blocks were tested with reference to the methods and quality standards specified in the 2015 edition of the Chinese Pharmacopoeia. The residue after extracting the filtrate in step S3 was collected and tested, and its mass was M1, the mass of donkey skin was M0, the moisture content of donkey skin was W0, and the gelatin yield = {1-M1 / [M0×(1-W0)]}×100%. The results are shown in Table 1.

[0106] Table 1 Measurement results

[0107]

[0108]

[0109] According to statistics, the extraction process of donkey-hide gelatin prepared by Examples 1 to 3 of the present invention has high content of L-hydroxyproline, glycine, endoline, L-proline and polypeptide, low loss in the preparation process, and high gelatin yield. Comparative Example 1 did not perform static extraction, Comparative Example 2 did not perform secondary water addition and heating extraction, Comparative Example 3 did not use steam pressure heating to peel, Comparative Example 4 added too little papain, Comparative Example 5 had too high enzymolysis temperature, Comparative Example 6 did not repeat the concentrating and frothing, Comparative Example 7 had too high concentrating and frothing temperature, Comparative Examples 8 and Comparative Examples 9 did not add soybean oil, crystal sugar and rice wine in the order of each other, and the content of L-hydroxyproline, glycine, endoline, L-proline and polypeptide in the prepared donkey-hide gelatin was low, and the gelatin yield was also reduced. Therefore, the extraction process of donkey-hide gelatin described in the present invention can not only significantly improve the gelatin yield, but also effectively increase the content of amino acids and polypeptides in donkey-hide gelatin, providing strong support for the modern production and application of donkey-hide gelatin.

[0110] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for extracting donkey-hide gelatin, characterized in that: The following steps are involved: S1, impurity removal and soaking: after picking out impurities from the donkey skin and cleaning it, add water until the water covers the surface of the donkey skin by more than 10 cm and soak for 5 to 7 days, wherein the water is changed every 1 to 2 days to obtain a wet donkey skin; S2, depilation and shearing: the wet donkey skin is depilated and washed to obtain the depilated donkey skin, the depilated donkey skin is cut into pieces, put into a steaming ball, after adding sodium carbonate and water, steam is introduced, the steam pressure is controlled to be 0.12-0.15MPa, the skin is blanched for 30-60min, washed, and cut into donkey skin pieces; S3, extracting glue from skin: extract the donkey skin obtained in step S2 by adding water and heating twice, combine the filtrates obtained by the two extractions by adding water and heating, cool to room temperature, add complex enzyme, stir evenly and adjust the system to neutral, heat to 45-55°C, react for 5-7h, and obtain glue; S4, concentrated gel: after the gel is initially concentrated to a relative density of 1.08-1.09, the foam is further concentrated, soybean oil, crystal sugar and rice wine are added in sequence, and the floating gel foam is skimmed off, and the gel is produced when the water content is 26%-29%. The gel is placed in a stainless steel gel box coated with vegetable oil and waits for gelation to obtain a gel lump; S5. Take the glue lump, cut it into pieces according to the specifications, dry it, wipe it, sterilize it, and package it.

2. The extraction process of donkey-hide gelatin according to claim 1, characterized in that: The added amount of the sodium carbonate is 0.4% to 0.6% of the mass of the donkey hide.

3. The extraction process of donkey-hide gelatin according to claim 2, characterized in that: The two water-adding and heating extractions include a first water-adding and heating extraction and a second water-adding and heating extraction.

4. The extraction process of donkey-hide gelatin according to claim 3, characterized in that: The specific steps of the first water-adding heating extraction are: putting the donkey skin obtained in step S2 into a steaming ball, adding water, passing steam, starting the steaming ball, controlling the steam pressure to be 0.12-0.15 MPa, dynamically extracting for 0.5-1.5 hours, stopping the ball to vent once every 0.5 hours, then statically extracting for 5-7 hours, rotating the steaming ball to stir for 2-5 minutes every 0.5 hours, and filtering to obtain filtrate and residue after extraction.

5. The extraction process of donkey-hide gelatin according to claim 3, characterized in that: The specific steps of the second water-adding and heating extraction are: putting the filter residue obtained by the first water-adding and heating extraction into a steam ball, adding water, passing steam, starting the steam ball, controlling the steam pressure to 0.12-0.15 MPa, and dynamically extracting for 0.5-1.5 hours, and then filtering to obtain a filtrate.

6. The extraction process of donkey-hide gelatin according to claim 3, characterized in that: The added amount of the complex enzyme is 5% to 10% of the mass of the combined filtrate.

7. The extraction process of donkey-hide gelatin according to claim 6, characterized in that: The complex enzyme is papain and trypsin.

8. The extraction process of donkey-hide gelatin according to claim 7, characterized in that: The mass ratio of papain to trypsin is (4-6):

1.

9. Donkey-hide gelatin prepared according to the extraction process of donkey-hide gelatin according to any one of claims 1 to 8.

10. Use of the donkey-hide gelatin according to claim 9 in preparing health food.

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