A process for recovering amino acids from soy protein water

Abstract

The application discloses a new process and system for efficiently recovering amino acids from soy protein water, wherein, under the condition of 15-65 DEG C, dihydrogen sodium pyrophosphate and calcium chloride are added into the soy protein water and mixed, and then centrifugal separation is performed to obtain upper clear liquid 1 and lower precipitate 1; dihydrogen sodium pyrophosphate and calcium chloride are added into the upper clear liquid 1, and then natural sedimentation is performed to obtain upper clear liquid 2 and lower flocculent suspension; the lower flocculent suspension is subjected to centrifugal separation to obtain upper clear liquid 3 and lower precipitate 3; and the lower precipitate 1 and the lower precipitate 3 are recovered as amino acid recovery products. The process and system can recover about 85% of the amino acids in the soy protein water, have high recovery rate, simple steps and high efficiency, are implemented in a normal temperature environment, are energy-saving and environment-friendly, and have good industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of soybean protein processing technology, and in particular to a process and system for efficiently recovering amino acids from soybean protein water. Background Technology

[0002] my country produces hundreds of thousands of tons of soy protein isolate annually, generating millions of tons of soy protein water. Currently, there are two main technologies for extracting various soy proteins from this water: acid precipitation and alkali extraction, and ultrafiltration membrane technology. Ultrafiltration membranes require significant investment, have high operating costs, and are prone to clogging, leading to membrane failure. Acid precipitation and alkali extraction is the primary method currently used. It utilizes the isoelectric point of soy protein to first precipitate the protein, then uses alkali to adjust the pH to harvest the protein. The main process flow diagram is shown below. Figure 1 .

[0003] The existing acid precipitation and alkali extraction process for soybean protein production ranges from soybean protein extract or soybean water to the solid phase soybean protein stage. Figure 1 The section within the dashed box (partially shown) has the following main problems: 1. High energy consumption. It requires heating the soybean water to 70-80℃. 2. Excessive reagent addition, damaging proteins and amino acids. Precipitation with calcium ions (calcium chloride + calcium hydroxide) followed by pH adjustment to acidity is required. For example, in Example 1 of CN 107624950 B, even with minimal reagent addition (0.5% calcium chloride and calcium hydroxide in the soybean water), the pH reaches above 12. Then, a large amount of acidic reagent is used to adjust the pH to 5.2. This is not only cumbersome but also causes damage to proteins and amino acids due to the strong alkalinity. 3. The disc centrifugation separation conditions are too narrow, with a separation factor of 6000.

[0004] Existing methods do not offer a better solution to the aforementioned technical problems, and there is an urgent need for those skilled in the art to develop new technical methods. Summary of the Invention

[0005] The purpose of this invention is to provide a process and system for efficiently recovering amino acids from soybean protein water, in order to solve the problems of high energy consumption, harsh operating conditions and improved yield in soybean protein production mentioned in the background art.

[0006] Specifically, the new process for efficiently recovering amino acids from soybean protein water according to the present invention includes the following steps:

[0007] a. At 15–65°C, add disodium dihydrogen pyrophosphate and calcium chloride to soybean protein water, mix well, and centrifuge to separate the supernatant ① and the precipitate ①.

[0008] For the technical solution described above, a further preferred embodiment of the process includes the following steps:

[0009] b. After adding sodium dihydrogen pyrophosphate and calcium chloride to the upper clear liquid ①, it is allowed to settle naturally into the upper clear liquid ② and the lower flocculent suspension;

[0010] c. The lower layer of flocculent suspension is separated by centrifugation into an upper clear liquid ③ and a lower precipitate ③;

[0011] In addition, the process may include the following step d: the lower precipitate ① and lower precipitate ③ are amino acid recovery products; the upper clear liquid ② and upper clear liquid ③ are waste liquids;

[0012] For the technical solution described above, a further preferred embodiment is that the amount of amino acids in the soybean protein water is 0.4–10.0 g / 100 mL; a further preferred embodiment is 1.0–7.5 g / 100 mL; an even more preferred embodiment is 1.5–6.0 g / 100 mL; and the most preferred embodiment is 1.5–5.0 g / 100 mL.

[0013] For the technical solution described above, a further preferred embodiment is that the proportion of disodium dihydrogen pyrophosphate added to the soybean protein water in step a is 0.05-0.50 g / 100 mL soybean protein water; a further preferred embodiment is 0.07-0.40 g / 100 mL soybean protein water; and a further preferred embodiment is 0.10-0.35 g / 100 mL soybean protein water.

[0014] For the technical solution described above, a further preferred embodiment is that the ratio of calcium chloride added to the soybean protein water in step a is 0.18–1.80 g / 100 mL soybean protein water; a further preferred embodiment is 0.20–1.50 g / 100 mL soybean protein water; and a further preferred embodiment is 0.20–1.30 g / 100 mL soybean protein water.

[0015] For the technical solution described above, a further preferred embodiment is that the proportion of disodium dihydrogen pyrophosphate added to the supernatant ① in step b is 0.05-0.35 g / 100 mL of supernatant ①; a further preferred embodiment is 0.07-0.27 g / 100 mL; a further preferred embodiment is 0.10-0.25 g / 100 mL; a further preferred embodiment is 0.10-0.17 g / 100 mL.

[0016] For the technical solution described above, a further preferred embodiment is that the proportion of calcium chloride added to the supernatant ① in step b is 0.18–0.85 g / 100 mL supernatant ①; a further preferred embodiment is 0.20–0.70 g / 100 mL; a further preferred embodiment is 0.40–0.65 g / 100 mL.

[0017] For the technical solution described above, a further preferred embodiment is that the natural settling is allowed to occur for 30 to 150 minutes; more preferably, for 45 to 90 minutes.

[0018] For the technical solution described above, a further preferred embodiment is that the centrifugation conditions in steps a and c are a centrifugal force of 100–8000 g and a centrifugation time of 1.0–15.0 min; a further preferred embodiment is a centrifugal force of 225–6500 g and a centrifugation time of 1.0–10.0 min; and the most preferred embodiment is a centrifugal force of 1250–6000 g and a centrifugation time of 1.0–6.0 min.

[0019] For the technical solution described above, a further preferred embodiment is that the temperature is 20-60℃, and a more preferred embodiment is that the temperature is room temperature.

[0020] Another aspect of this application discloses a system for efficiently recovering amino acids from soybean protein water for the process described above. The system includes a mixing tank, an automatic feeder I, and a centrifuge I. The mixing tank is connected to the automatic feeder I and is connected to the centrifuge I via a pipeline. The centrifuge I is provided with an upper clear liquid ① output port and a lower sediment ① collection port.

[0021] For the technical solution described above, in a further preferred embodiment, the system also includes an automatic feeder II, a liquid storage tank, and a centrifuge II; their connection methods are as follows:

[0022] The mixing tank is connected to an automatic feeder I, and the mixing tank is connected to a centrifuge I via a pipeline. The centrifuge I is provided with an upper clear liquid ① output port and a lower sediment ① collection port, and the upper clear liquid ① output port is connected to a downstream storage tank via a pipeline. The upstream of the storage tank is also connected to an automatic feeder II via a pipeline. The bottom of the storage tank is provided with a lower flocculent suspension collection port and an upper clear liquid ② collection port. The flocculent suspension collection port is connected to the downstream centrifuge II via a pipeline.

[0023] In a further preferred embodiment of the above-described technical solution, the mixing tank and the storage tank are respectively equipped with a stirring device to achieve thorough mixing of the raw materials and reagents.

[0024] In a further preferred embodiment of the technical solution described above, both the automatic feeder I and the automatic feeder II are equipped with a drug metering pump.

[0025] For the technical solution described above, a further preferred embodiment is that the settling time of the liquid storage tank is preferably 30 to 150 minutes; more preferably, 45 to 90 minutes.

[0026] In a further preferred embodiment of the above-described technical solution, the side wall of the liquid storage tank is also provided with a transparent observation window.

[0027] In a further preferred embodiment of the technical solution described above, the downstream outlets of the upper clear liquid ② and upper clear liquid ③ converge to form a waste liquid disposal pipeline.

[0028] In a further preferred embodiment of the technical solution described above, an amino acid recovery pipeline is provided downstream of the output ports of the lower precipitate ① and the lower precipitate ③.

[0029] For the technical solution described above, it is further preferred that the type of centrifuge is not limited, as long as it can meet the corresponding production needs and achieve the separation effect; further, in the embodiment, a horizontal centrifuge is used when separating soybean protein water, and a butterfly centrifuge is used when separating the lower flocculent matter.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) Amino acids are the building blocks of protein and are true nutrients. Current soybean protein production methods primarily use the Kjeldahl method to determine the protein content, which may result in high protein content but not necessarily high amino acid content. However, the method of this invention directly recovers and detects amino acids, providing direct nutritional data.

[0032] (2) Under optimal conditions, about 87% of the amino acids in soybean protein water can be recovered. Even by using only the first step of the new process, namely adding reagents (disodium dihydrogen pyrophosphate + calcium chloride) to soybean protein water, about 85% of the amino acids in soybean protein water can be recovered, which is highly efficient.

[0033] (3) Existing processes require heating soybean protein to above 70°C. However, this invention is carried out at room temperature and does not require heating, which saves energy and is convenient to operate.

[0034] (4) In this invention, only disodium dihydrogen pyrophosphate and calcium chloride are added to the soybean protein water, which reduces the cumbersome process in the existing production (first add calcium chloride + calcium hydroxide, and then use acid reagent to adjust the pH to 5.2), reduces the types and amounts of reagents added, and reduces the damage to the quality of protein and amino acids, so as to harvest more amino acids. Attached Figure Description

[0035] Figure 1 This is a traditional method for extracting soybean protein using acid precipitation and alkali treatment.

[0036] Figure 2 A flowchart of a new process for the efficient recovery of amino acids from soybean protein water;

[0037] Figure 3 A new system for the efficient recovery of amino acids from soybean protein water. Detailed Implementation

[0038] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0039] In this invention, unless otherwise explicitly stated, percentages and contents are all by mass. Unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available.

[0040] All reagents used in the embodiments of this invention are food-grade, and the water used is sterile deionized water.

[0041] The soybean protein water used in the specific embodiments of this invention was sourced from multiple batches of soybean protein processing plants in Liaoning Province. Testing revealed that its amino acid content ranged from 1.0 to 3.0 per 100.0 mL. Each batch of soybean protein water was tested separately without mixing, resulting in similar experimental results. Three parallel samples were used in each group, expressed as mean ± standard deviation, and analyzed using a one-way ANOVA method.

[0042] In the embodiments of this invention, all instances of "disodium dihydrogen pyrophosphate" are abbreviations, referring to a 0.8M aqueous solution of disodium dihydrogen pyrophosphate; all instances of "calcium chloride" are also abbreviations, referring to a 6.0M aqueous solution of calcium chloride.

[0043] This invention employs a system for the efficient recovery of amino acids from soybean protein water, such as... Figure 2 and 3 It includes a mixing tank 1, automatic feeders I2 and II4, a storage tank 5, and centrifuges I3 and II6;

[0044] The mixing tank 1 is connected to an automatic feeder I2, and the mixing tank 1 is connected to a centrifuge I3 via a pipeline; the centrifuge I3 is provided with an upper clear liquid ① output port and a lower sediment ① collection port, and the upper clear liquid ① output port is connected to a downstream storage tank 5 via a pipeline; the upstream of the storage tank 5 is also connected to an automatic feeder II 4 via a pipeline, and the bottom of the storage tank 5 is provided with a lower flocculent suspension collection port and an upper clear liquid ② collection port; the flocculent suspension collection port is connected to a downstream centrifuge I6I via a pipeline;

[0045] The mixing tank 1 and the storage tank 5 are each equipped with a stirring device to ensure thorough mixing of raw materials and reagents. The automatic feeders I2 and II 4 are each equipped with a drug metering pump to control the amount of drug added to the protein water or the upper clear liquid ① according to the drug metering. The settling time of the storage tank 5 is preferably 30-150 minutes. A transparent observation window is also provided on the side wall of the storage tank 5 to observe the liquid state inside, such as the state of the flocculent suspension or the state of the flocculent suspension being discharged from the bottom collection port. The downstream outlets of the upper clear liquid ② and upper clear liquid ③ converge to form a waste disposal pipeline. The downstream outlets of the lower sediment ① and lower sediment ③ are provided with an amino acid recovery pipeline. Amino acids can be recovered using conventional techniques skilled in the art, which is not the inventive point of this application and will not be elaborated upon. In the embodiments, a horizontal centrifuge is used to separate soybean protein water; a disc centrifuge is used to separate the lower flocculent material. Example 1: Amino acids are harvested by centrifugation after adding reagents to soybean protein water.

[0046] (1) Experimental procedure,

[0047] a. The effect of different dosages of reagents added to soybean protein water on the harvesting of amino acids.

[0048] Add 40.0 mL of soybean protein water to each of 18 plastic centrifuge tubes, with 3 tubes per group. Then add reagent (0.8 M disodium dihydrogen pyrophosphate + 6.0 M calcium chloride) in the following concentrations: (0.0 mL + 0.0 mL), (0.125 mL + 0.125 mL), (0.250 mL + 0.250 mL), (0.375 mL + 0.375 mL), (0.500 mL + 0.500 mL), and (0.750 mL + 0.750 mL), respectively, as reagent dosage groups D-0, D-1, D-2, D-3, D-4, and D-5. After centrifugation at 3000 rpm (1980 g) for 3 minutes, the mixture is separated into upper and lower layers.

[0049] b. The effect of soybean protein water temperature on the harvested amino acid effect

[0050] Add 40.0 mL of soybean protein water to each of the nine plastic centrifuge tubes, with three centrifuge tubes per group. Add reagent (0.8 M disodium dihydrogen pyrophosphate + 6.0 M calcium chloride) to each centrifuge tube in a ratio of (0.375 mL + 0.375 mL). Then heat to 20, 50, and 80 °C respectively, designated as temperature groups T-1, T-2, and T-3. After centrifugation at 3000 rpm (1980 g) for 3 min, separate into upper and lower layers.

[0051] c. The effect of centrifugation conditions (centrifugal force and centrifugation time) on the harvesting of amino acids from soybean protein water.

[0052] Add 40.0 mL of soybean protein water to each of the nine plastic centrifuge tubes, with three centrifuge tubes per group. At room temperature (18–25°C), add reagent (0.8 M disodium dihydrogen pyrophosphate + 6.0 M calcium chloride) to each centrifuge tube in a ratio of (0.375 mL + 0.375 mL). Centrifuge at 1000 rpm (225 g) for 15 min, 3000 rpm (1980 g) for 3 min, and 4200 rpm (3520 g) for 2 min, respectively, as centrifugation conditions C-1, C-2, and C-3. Add 8.0 mL of soybean protein water to each of the five 10.0 mL plastic centrifuge tubes, add reagent in the same proportion as above, and then centrifuge at 9000 rpm (7770 g) for 1 min, as group C-4. After centrifugation, the mixture separates into upper and lower layers.

[0053] d. Detection of soybean protein water and the supernatant ① and lower precipitate ① formed by centrifugation.

[0054] In experiments a, b, and c above, except for group D-0 which did not add reagents, each centrifuge tube separated into upper and lower layers after centrifugation. The upper liquid (referred to as "superior clear liquid ①") was collected and its volume was measured. At the same time, the lower precipitate (referred to as "lower precipitate ①") was collected and its mass (wet weight) was weighed. Then, it was dried at 60°C to constant weight and its mass (dry weight) was weighed.

[0055] Take 40.0 mL of soybean protein water and the supernatant ① into pre-weighed glass petri dishes, weigh them (after subtracting the mass of the petri dish, this is called "wet weight"), dry them at 60℃ to constant weight, and weigh them again (after subtracting the mass of the petri dish, this is called "dry weight"). Each sample is tested in triplicate.

[0056] The amino acid content of the aforementioned soybean protein water, supernatant ①, and lower precipitate ① was determined using an automated amino acid analyzer. If the sample volume was insufficient for testing, the experiment was repeated.

[0057] (2) Experimental Results

[0058] The experimental results show that the combination of reagents (sodium dihydrogen pyrophosphate + calcium chloride) can recover amino acids from soybean protein water with relatively high efficiency (Tables 1, 2, and 3). With increasing reagent dosage, the yield of amino acids recovered from soybean protein water increased from 77.61% to 85.07% (Table 1); the temperature of the soybean protein water had no effect on the recovery of amino acids, with a yield of approximately 82% (Table 2); centrifugation conditions had a slight impact on the recovery effect, but the yield remained approximately 82% (Table 3).

[0059] Table 1. Effects of reagent dosage in soybean protein water on harvested amino acids

[0060]

[0061]

[0062] Note: Add the following reagents to 40.0 mL of soybean protein solution: 0.8 M disodium dihydrogen pyrophosphate + 6.0 M calcium chloride.

[0063] Based on the results of Example 1, the optimal conditions for direct recovery of amino acids from soybean protein water are: (0.375 mL of 0.8 M disodium dihydrogen pyrophosphate + 0.375 mL of 6.0 M calcium chloride) / 40.0 mL soybean protein water [that is, (0.067 g of disodium dihydrogen pyrophosphate + 0.250 g of calcium chloride) / 40.0 mL soybean protein water], at room temperature, centrifuged at 3000 rpm (1980 g) for 3 min, at which point the amino acid yield is approximately 82%.

[0064] Table 2. Effect of soybean protein water temperature on harvested amino acids

[0065]

[0066]

[0067] Note: Add the following reagents to 40.0 mL of soybean protein solution: 0.8 M disodium dihydrogen pyrophosphate.

[0068] 0.375 mL + 0.375 mL of 6.0 M calcium chloride.

[0069] Table 3. Effects of centrifugation conditions on harvested amino acids after adding reagents to soybean protein water.

[0070]

[0071] Note: 1. For all groups, add reagents according to the ratio of (0.375 mL of 0.8 M disodium dihydrogen pyrophosphate + 0.375 mL of 6.0 M calcium chloride) / 40.0 mL of soybean protein water;

[0072] 3. For group C-4, add 8.0 mL of soy protein water to each of five 10.0 mL plastic centrifuge tubes; for the other groups, add 40.0 mL of soy protein water to each centrifuge tube.

[0073] Example 2: After adding reagents to the supernatant ①, amino acids were recovered by allowing it to settle.

[0074] The recovery of amino acids from soybean protein water produces a supernatant ① and a lower precipitate. The supernatant ① contains amino acids, and this embodiment aims to recover amino acids from it.

[0075] Add 400.0 mL of soybean protein water to each of the four centrifuge bottles, and harvest the supernatant ① under the optimal conditions according to Example 1, which will be used for the following experiments.

[0076] (1) Experimental procedure,

[0077] a. The effect of adding different dosages of reagents to the supernatant ① on the recovery of amino acids.

[0078] Add 40.0 mL of supernatant ① to each of 12 plastic centrifuge tubes, with 3 tubes per group. Then add reagent (0.8 M disodium dihydrogen pyrophosphate + 6.0 M calcium chloride) in the following amounts: (0.0 mL + 0.0 mL), (0.125 mL + 0.125 mL), (0.250 mL + 0.250 mL), and (0.375 mL + 0.375 mL), respectively, as reagent dosage groups D-0, D-1, D-2, and D-3. Let stand at room temperature for 60 min to separate the supernatant into upper and lower layers.

[0079] b. The effect of the temperature of the supernatant ① on the recovery efficiency of amino acids

[0080] Add 40.0 mL of supernatant ① to each of the nine plastic centrifuge tubes. Similarly, in groups of three centrifuge tubes, add reagent (0.250 mL of 0.8 M disodium dihydrogen pyrophosphate + 0.250 mL of 6.0 M calcium chloride) to each centrifuge tube. Then heat to 20, 50 and 70 °C respectively, which are designated as temperature groups T-1, T-2 and T-3. After removing the centrifuge tubes and letting them stand at room temperature for 60 min, separate them into upper and lower layers.

[0081] c. Detection of the supernatant ①, the supernatant ② formed by sedimentation separation, and the lower flocculent material.

[0082] In experiments a and b above, the liquid separated into upper and lower layers after settling. The upper liquid (referred to as "upper clear liquid ②") was collected and its volume was measured; at the same time, the lower flocculent material was collected, and the volume of the lower flocculent material was calculated based on the volumes of the upper clear liquid ① and ②.

[0083] Take 40.0 mL of the supernatant ① and ② respectively into pre-weighed glass petri dishes, weigh them (after subtracting the mass of the petri dish, this is called "wet weight"), dry them at 60℃ to constant weight, and weigh them again (after subtracting the mass of the petri dish, this is called "dry weight"). Each sample is tested in triplicate.

[0084] The amino acid content of the supernatant ① and ② and the lower flocculent matter was determined using an automated amino acid analyzer. If the sample volume was insufficient for testing, the experiment was repeated.

[0085] (2) Experimental Results

[0086] The experimental results show that in group D-0 without added reagents, the supernatant ① did not separate into layers. In groups D-1, D-2, and D-3 with added reagents (sodium dihydrogen pyrophosphate + calcium chloride), the supernatant ② and the lower flocculent layer separated into a supernatant ② and a lower flocculent layer. Different dosages of added reagents had little effect on the recovery of amino acids; approximately 22%–27% of amino acids could be recovered from the lower flocculent layer (Table 4). The same temperature had almost no effect on the recovery of amino acids from the supernatant ① (Table 5); approximately 26% of amino acids could be recovered from the lower flocculent layer.

[0087] Table 4. Effect of reagent dosage on amino acid recovery in the supernatant ①

[0088]

[0089] Note: 1. Add the following reagents to 40.0 mL of the supernatant ①: 0.8 M disodium dihydrogen pyrophosphate + 6.0 M calcium chloride;

[0090] 2. The amount of amino acids in the lower layer of flocculent matter = the amount of amino acids in the upper clear liquid ① - the amount of amino acids in the upper clear liquid ②.

[0091] Based on the results of Example 2, the optimal conditions for recovering amino acids from the supernatant ① are: (0.25 mL of 0.8 M disodium dihydrogen pyrophosphate + 0.25 mL of 6.0 M calcium chloride) / 40.0 mL of supernatant ① [that is, (0.045 g of disodium dihydrogen pyrophosphate + 0.167 g of calcium chloride) / 40.0 mL of supernatant ①], room temperature, and standing for 60 min.

[0092] Table 5. Effect of temperature of the supernatant ① on the harvesting of amino acids.

[0093]

[0094] Note: 1. Add the following reagents to 40.0 mL of the supernatant ①: two aqueous solutions are: 0.25 mL of 0.8 M disodium dihydrogen pyrophosphate + 6.0 M...

[0095] 0.25 mL of calcium chloride;

[0096] 2. The amount of amino acids in the lower layer of flocculent matter = the amount of amino acids in the upper clear liquid ① - the amount of amino acids in the upper clear liquid ②.

[0097] Example 3: Centrifugation of the lower flocculent material to recover amino acids

[0098] The recovery of amino acids from soybean protein water produces an upper clear liquid ① and a lower precipitate. The upper clear liquid ① is added with a reagent and allowed to settle, producing an upper clear liquid and a lower flocculent material. In this example 3, the aim is to recover amino acids from the lower flocculent material.

[0099] Add 400.0 mL of soybean protein water to several centrifuge bottles respectively, and harvest the supernatant ① under the optimal conditions according to Example 1. Then harvest the lower flocculent material under the optimal conditions according to Example 2 for the following experiments.

[0100] (1) Experimental procedure,

[0101] a. Effect of centrifugation conditions on the recovery of amino acids from the lower flocculent layer

[0102] Add 40.0 mL of the lower layer flocculent material to each of the nine plastic centrifuge tubes, forming groups of three. Centrifuge at 1500 rpm (505 g) for 15 min, 3000 rpm (1980 g) for 5 min, and 4200 rpm (3520 g) for 2 min, respectively, as centrifugation conditions C-1, C-2, and C-3. Add 8.0 mL of the lower layer flocculent material to each of the five 10.0 mL plastic centrifuge tubes, and then centrifuge at 9000 rpm (7770 g) for 1 min, as group C-4. After centrifugation, the mixture separates into upper and lower layers.

[0103] b. Detection of the lower layer flocculent matter and the supernatant ③ and lower precipitate ③ formed by its sedimentation and separation.

[0104] In the experiment described above, the centrifuge tube separated into upper and lower layers after centrifugation. The upper liquid (referred to as "superior clear liquid ③") was collected and its volume was measured; at the same time, the lower precipitate (referred to as "lower precipitate ③") was collected and its mass (wet weight) was weighed. Then, it was dried at 60°C to constant weight and its mass (dry weight) was measured.

[0105] Take 40.0 mL of the supernatant ③ into a pre-weighed glass petri dish, weigh it (subtract the mass of the petri dish, which is called "wet weight"), dry it at 60℃ to constant weight, and weigh it again (subtract the mass of the petri dish, which is called "dry weight"). Each sample is tested in triplicate.

[0106] The amino acid content of the supernatant ① and ② and the lower flocculent precipitate was determined using an automated amino acid analyzer. If the sample volume was insufficient for testing, the experiment was repeated. The amino acid content of the lower precipitate ③ was calculated based on the amino acid content of the flocculent precipitate and the supernatant ③.

[0107] (2) Experimental Results

[0108] The experimental results show that centrifugation conditions have almost no effect on the recovery of amino acids from the lower flocculent material, and about 55% to 58% of amino acids can be recovered from the lower flocculent material (Table 6).

[0109] Table 6. Effect of centrifugation conditions on the recovery of amino acids from the lower flocculent layer.

[0110]

[0111]

[0112] Note: 1. For group C-4, add 8.0 mL of the lower layer flocculent material to each of five 10.0 mL plastic centrifuge tubes; for other groups, add 40.0 mL of the lower layer flocculent material to one centrifuge tube.

[0113] 2. The amount of amino acids in the lower precipitate ③ is obtained by subtracting the amount of amino acids in the upper clear liquid from the amount of amino acids in the lower flocculent matter.

[0114] Based on the results of Example 3, the optimal conditions for recovering amino acids from the lower flocculent material are: centrifugation at 3000 rpm (1980 g) for 5 min.

[0115] Example 4: A novel process for recovering amino acids from soybean protein water.

[0116] Flowchart of a new process for efficient amino acid recovery from soybean protein water ( Figure 2 )

[0117] (1) Experimental procedure,

[0118] a. After adding reagents to the soybean protein water, centrifugation separated it into a supernatant ① and a lower precipitate ①.

[0119] Add 400.0 mL of soybean protein solution to each of four plastic centrifuge bottles, along with reagents (using a ratio of 3.75 mL (4.45 g) of 0.8 M disodium dihydrogen pyrophosphate + 3.75 mL (2.50 g) of 6.0 M calcium chloride to 400.0 mL of soybean protein solution). Centrifuge at 3000 rpm (1980 g) for 3 min to separate the liquid into upper and lower layers. Collect the upper layer liquid (referred to as "supernatant ①") and measure its volume. Simultaneously, collect the lower layer precipitate (referred to as "lower precipitate ①") and weigh its mass (wet weight). Then, dry the precipitate at 60°C to constant weight and weigh it again (dry weight).

[0120] b. After adding reagents, the supernatant ① naturally settles and separates into the supernatant ② and the lower flocculent layer.

[0121] After mixing the supernatant ①, add reagent (at a ratio of "2.50 mL (0.445 g) of 0.8 M disodium dihydrogen pyrophosphate + 2.50 mL (1.665 g) of 6.0 M calcium chloride" per 100.0 mL of supernatant ①), stir well, and then let it stand for 30-60 minutes to separate into upper and lower layers (the time can be extended, and the separation effect is better with longer time). Collect the upper liquid (called "supernatant ②") and the lower flocculent matter, and measure their volumes. At the same time, weigh the mass of the lower flocculent matter (liquid).

[0122] c. The lower layer of flocculent matter (liquid) is separated by centrifugation into a clear upper layer ③ and a lower layer of precipitate ③.

[0123] The lower layer of flocculent matter (liquid) from step b above was mixed and centrifuged at 3000 rpm (1980 g) for 5 min, separating into upper and lower layers. The upper layer liquid (referred to as "superior clear liquid ③") was collected and its volume was measured. Simultaneously, the lower layer precipitate (referred to as "lower precipitate ③") was collected and its mass (wet weight) was weighed. The precipitate was then dried at 60℃ to constant weight and its mass (dry weight) was measured. d. Detection of indicators for the above-mentioned soybean protein water, lower precipitate ①, and upper clear liquids ①, ②, and ③.

[0124] Take 40.0 mL of soybean protein solution, and the supernatant ①, ②, and ③ respectively, and place them in pre-weighed glass petri dishes. Weigh the samples (subtracting the mass of the petri dishes, this is called "wet weight"), dry them at 60℃ to constant weight, and then weigh them (subtracting the mass of the petri dishes, this is called "dry weight"). Each sample is tested in triplicate.

[0125] The amino acid content of the above-mentioned soybean protein water, the upper clear liquid ①, ② and ③, the lower flocculent matter, and the lower sediment ① was detected using an automatic amino acid analyzer.

[0126] (2) Experimental Results

[0127] The above experimental process used four 400.0 mL protein-water centrifugations. All experimental results were converted into the amount of subsequent materials, dry matter, crude protein, and amino acids produced by one 400.0 mL protein-water centrifugation (Table 7).

[0128] Table 7. Flowchart of a new process for efficient recovery of amino acids from soybean protein water

[0129]

[0130] Note: A. According to the material balance, the amount of amino acids in the lower layer of flocculent matter is obtained by subtracting the amount of amino acids in the upper clear liquid ② from the amount of amino acids in the upper clear liquid ①, that is, 0.636-0.439=0.197g;

[0131] B. According to the material balance, the amino acid content of the lower sediment ③ is obtained by subtracting the amino acid content of the upper clear liquid ③ from the amino acid content of the lower flocculents, that is, 0.197-0.085=0.113g.

[0132] 400.0 mL of protein water contains 6.379 g of amino acids. After adding reagents and centrifuging, 400.0 mL of soybean protein water separates into two layers. The upper layer is a clear, transparent supernatant ① of 328.0 mL, containing 0.636 g of amino acids, approximately 9.98% of the total amino acids in 400.0 mL of soybean protein water. The lower layer is a white precipitate ①, containing 5.435 g of amino acids, approximately 85.20% of the total amino acids in 400.0 mL of soybean protein water.

[0133] The supernatant ① was treated with reagents added according to the ratio ("0.045g disodium dihydrogen pyrophosphate + 0.167g calcium chloride" / 40.0mL supernatant ①), and allowed to stand at room temperature for 30-60 minutes, resulting in two layers. The upper layer was a clear, transparent 271.0mL supernatant ②, and the lower layer was a white flocculent liquid with a volume of 57.0mL, containing 0.197g of amino acids, accounting for 3.09% of the total amino acids in 400.0mL of soybean protein water.

[0134] The flocculent liquid separated into two layers after centrifugation (1980g, 5min) at room temperature. The upper layer was a clear, transparent supernatant ③ with a volume of 52.0mL; the lower layer was a grayish-white precipitate ③ containing 0.113g of amino acids, which accounted for approximately 1.76% of the total amino acids in 400.0mL of soybean protein water.

[0135] The lower precipitates ① and ③ were combined, and they contained 5.548g of amino acids, which accounted for approximately 87% of the total amino acids in 400.0mL of soybean protein water. This demonstrates that the method of the present invention can efficiently recover amino acids from soybean protein water.

[0136] (2) Energy consumption calculation for recovering amino acids from soybean protein water using the new process

[0137] The new process is implemented at room temperature and only requires energy to separate soybean protein water and lower flocculent matter by centrifugation.

[0138] Based on 1000.0 kg of protein water, the above experiment shows that 400.0 mL of protein water produced 57.0 mL of flocculent matter in the new process. Following this ratio, 1000.0 kg (approximately 1000.0 mL) of soybean protein water can produce 142.5 kg of flocculent matter. Therefore, the energy consumption required for 1000 kg of protein water in the new process is as follows:

[0139] A. Energy consumption for centrifuging 1000 kg of protein in water:

[0140] 18.5KW × 0.1h = 1.85 kWh = 1.85 kWh × 3.6 × 10 3 kJ / kWh = 6.7 × 10 3 kJ

[0141] Energy consumption for centrifugation of 142.5 kg of lower layer flocculent material:

[0142] 18.5KW × 0.1h = 1.85 kWh = 1.85 kWh × 3.6 × 10 3 kJ / kWh = 6.7 × 10 3 kJ

[0143] Therefore, the total energy consumption for the new process to recover amino acids from 1000.0 kg of soybean protein water is:

[0144] 6.7×10 3 kJ + 6.7 × 10 3 kJ = 13.4 × 10 3 kJ.

[0145] (3) Energy consumption calculation for harvesting protein from soybean protein water using existing processes

[0146] The existing process requires heating the soybean protein water to above 70°C and centrifuging the lower layer of the material, which consumes energy.

[0147] Using the same calculation of 1000.0 kg of protein water, and substituting the specific heat capacity of water [4.2 kJ / (kg·℃)] for the specific heat capacity of soybean protein water,

[0148] A. Energy consumption for heating 1000kg of protein water from 30℃ to 70℃:

[0149] 4.2kJ / (kg·℃)×(70℃-30℃)×1000.0kg=168.0×10 3 kJ

[0150] B. Energy consumption for centrifugal separation of approximately 142.5 kg of lower layer flocculent material:

[0151] 18.5KW × 0.1h = 1.85 kWh = 1.85 kWh × 3.6 × 10³ kJ / kWh = 6.7 × 10³ kJ

[0152] Therefore, the total energy consumption for harvesting protein from 1000.0 kg of soybean protein water using the existing process is:

[0153] 168.0×10 3 kJ + 6.7 × 10 3 kJ = 174.7 × 10 3 kJ.

[0154] Comparing the energy consumption of (2) and (3) above, it can be seen that the energy consumption of the existing process is 174.7 × 10⁻⁶. 3 kJ, energy consumption of the new process is 13.4×10 kJ. 3 kJ, which is only 7.67% of the energy consumption of existing processes.

[0155] The above description, in conjunction with specific preferred embodiments of the present invention, further illustrates the invention and should not be construed as limiting the scope of the invention to these descriptions. Any modifications or alterations made by those skilled in the art without departing from the technical scope of the invention will be considered to be covered within the scope of the claims of the present invention.

Claims

1. A process for recovering amino acids from soybean protein water, characterized in that, Includes the following steps: a. At 15~65℃, only sodium dihydrogen pyrophosphate and calcium chloride were added to the soybean protein water and mixed well. The pH was not adjusted, and the mixture was centrifuged to separate the supernatant ① and the lower precipitate ①. b. After adding only sodium dihydrogen pyrophosphate and calcium chloride to the upper clear liquid ① without adjusting the pH, it settles naturally into an upper clear liquid ② and a lower flocculent suspension. c. The lower flocculent suspension is centrifuged to separate the upper clear liquid ③ and the lower precipitate ③; the lower precipitate ① and the lower precipitate ③ are recovered as amino acid recovery product; The amount of amino acids in the soybean protein water is 1.0–3.0 g / 100 mL; In step a, the proportion of disodium dihydrogen pyrophosphate added to the soybean protein water is 0.055–0.333 g / 100 mL, and the proportion of calcium chloride added is 0.208–1.249 g / 100 mL. In the supernatant ① of step b, the proportion of disodium dihydrogen pyrophosphate added is 0.055-0.167 g / 100 mL, and the proportion of calcium chloride added is 0.208-0.624 g / 100 mL.

2. The process according to claim 1, characterized in that, The centrifugation conditions in steps a and c are: centrifugal force 100–8000 g and centrifugation time 1.0–15.0 min.

3. The process according to claim 1, characterized in that, The temperature is 20~60℃.

4. The process according to claim 1, characterized in that, A system for recovering amino acids from soybean protein water for the process is provided, the system comprising a mixing tank (1), an automatic feeder I (2), and a centrifuge I (3); the mixing tank (1) is connected to the automatic feeder I (2), and the mixing tank (1) is connected to the centrifuge I (3) via a pipeline; the centrifuge I (3) is provided with an upper clear liquid ① output port and a lower sediment ① collection port.

5. The process according to claim 4, characterized in that, The system also includes an automatic feeder II (4), a liquid storage tank (5), and a centrifuge II (6); their connection methods are as follows: The mixing tank (1) is connected to an automatic feeder I (2), and the mixing tank (1) is connected to a centrifuge I (3) through a pipeline; the centrifuge I (3) is provided with an upper clear liquid ① output port and a lower sediment ① collection port, and the upper clear liquid ① output port is connected to the downstream storage tank (5) through a pipeline; the upstream of the storage tank (5) is also connected to an automatic feeder II (4) through a pipeline, and the bottom of the storage tank (5) is provided with a lower flocculent suspension collection port and an upper clear liquid ② collection port; the flocculent suspension collection port is connected to the downstream centrifuge II (6) through a pipeline.

6. The process according to claim 5, characterized in that, The mixing tank (1) and the storage tank (5) are respectively equipped with stirring devices.

7. The process according to claim 5, characterized in that, The automatic feeder I (2) and automatic feeder II (4) are respectively equipped with drug metering pumps.

8. The process according to claim 5, characterized in that, Its features are, The side wall of the liquid storage tank (5) is also provided with a transparent observation window.

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