Extraction method of soybean isoflavone and new application of soybean straw

Abstract

The invention belongs to the field of agriculture, and discloses an extraction method of soybean isoflavone, which comprises the following steps: taking soybean straws as raw materials, and carrying out ultrasonic-assisted alcohol extraction to obtain soybean isoflavone; the extraction rate of the soy isoflavone is not lower than 6mg / g. By means of the method, a considerable amount of soybean isoflavone can be extracted from the soybean straw, and the cognition on the extraction rate of the soybean straw and the soybean isoflavone in the prior art is far better than the cognition on the extraction rate of the soybean straw and the soybean isoflavone. Meanwhile, the invention further provides new application of the soybean straw.

Description

Technical Field

[0001] The present invention relates to the field of agriculture, and specifically to a method for extracting soybean isoflavones and a new use of soybean straw. Background Art

[0002] The extraction sources of soybean isoflavones are mainly soybeans, soybean germ, soybean meal or other soy products;

[0003] Among them, the extraction rate from soybeans or soybean germ is relatively high, usually at 12 - 20 mg / g.

[0004] The extraction rates from soybean meal or other soy products are not high, generally 4 - 5 mg / g.

[0005] Specifically, the following literature and patent materials can be seen:

[0006] Literature 1: Research and Optimization on the Conditions for Ultrasonic-Assisted Extraction of Soybean Isoflavones - Li Baoli

[0007] Literature 2: Optimization of the Extraction Process of Isoflavones from Soybean Hilum - Zhou Wenhong

[0008] Literature 3: Optimization of the Extraction Process of Soybean Isoflavones from Soybean Meal by Box-Behnken Response Surface Methodology - Hua Jiaojiao

[0009] Patent 1: Publication No. CN116903572A, with the theme of a process for producing soybean isoflavone products with multiple purities; it uses soybean germ as the raw material;

[0010] Patent 2: Publication No. CN117777083A, with the theme of a method for extracting isoflavones from soybeans; it uses soybean meal as the raw material;

[0011] Patent 3: Publication No. CN113827632A, with the theme of a soybean extract, its preparation method and application, which uses soybeans as the raw material.

[0012] The generally recognized technical basis of the prior art is that soybean isoflavones often come from soybeans or their derivatives.

[0013] It is well-known to those skilled in the art that soybean straw contains isoflavones. Specifically, the following literature can be seen:

[0014] Literature 4: "The Effects of Isoflavones in Soybean Straw on the Growth Metabolism and Meat Quality of Hu Sheep", which records that "the contents of daidzein and genistein in the wild and conventional soybean straws in our county are not much different, being 837.7 - 955.3 μg·g-1"; after conversion, the content is approximately 0.8 - 0.9 mg / g.

[0015] The above information can prove that the economic feasibility of extracting soy isoflavones from soybean straw is not great.

[0016] The technical problem solved by this case is: how to realize the economic utilization of soybean straw. Summary of the Invention

[0017] The first object of the present invention is to provide a method for extracting soy isoflavones. Through this method, a considerable amount of soy isoflavones can be extracted from soybean straw, far exceeding the existing technical understanding of the extractable rate of soybean straw and soy isoflavones.

[0018] The second object of the present invention is to provide a new use of soybean straw.

[0019] To achieve the above first object, the present invention provides the following technical solutions:

[0020] A method for extracting soy isoflavones, using soybean straw as the raw material, and obtaining soy isoflavones through ultrasonic-assisted ethanol extraction; the extraction rate of soy isoflavones is not less than 6 mg / g.

[0021] In the above extraction method, the soybean straw is dried soybean straw, and the moisture content of the dried soybean straw does not exceed 8.2 wt%.

[0022] In the above extraction method, the solvent used in the ultrasonic-assisted ethanol extraction is an ethanol solution with a concentration of 40-80 vol%.

[0023] In the above extraction method, the material-liquid ratio in the ultrasonic-assisted ethanol extraction is 1:10-50.

[0024] In the above extraction method, the extraction time in the ultrasonic-assisted ethanol extraction is 15-35 min.

[0025] In the above extraction method, the power of the ultrasonic wave is 120 w, the ultrasonic wave stops for 3 s after 7 s, and the cycle repeats.

[0026] At the same time, the present invention also discloses a new use of soybean straw, which is used as a raw material for extracting soy isoflavones, and soy isoflavones are extracted by any of the above methods.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The present invention obtains soy isoflavones with a yield of not less than 6 mg / g through ultrasonic-assisted ethanol extraction, which far exceeds the scope of people's understanding of the economy of soybean straw. Its yield is higher than that of soybean meal and other soy products, and its cost is lower than that of soybean germ and soybeans themselves, providing a new way for the economic utilization of soybean straw. Description of the Drawings

[0029] Figure 1 is the standard curve graph of genistein standard product concentration and absorbance;

[0030] Figure 2 is the yield graph of changing ethanol concentration in the single-factor experiment;

[0031] Figure 3 is the yield graph of changing ultrasonic extraction time in the single-factor experiment;

[0032] Figure 4 is the yield graph of changing solid-liquid ratio in the single-factor experiment;

[0033] Figure 5 is the response surface graph (left) and contour graph (right) of ethanol concentration (A) and ultrasonic time (B) on the yield (R1) of soybean isoflavones;

[0034] Figure 6 is the response surface graph (left) and contour graph (right) of ethanol concentration (A) and solid-liquid ratio (C) on the yield (R1) of soybean isoflavones;

[0035] Figure 7 is the response surface graph (left) and contour graph (right) of ultrasonic time (B) and solid-liquid ratio (C) on the yield (R1) of soybean isoflavones. Detailed implementation mode

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] The experimental materials and reagents used, unless otherwise specified, are all conventional consumables and reagents that can be obtained from commercial channels.

[0038] Embodiment

[0039] 1. Sample preparation: Soybean straw is dried in an oven at 65°C for 24 hours to reach the air-dried basis with a moisture content of 8.2 wt%, and then crushed using a pulverizer and sieved through a 60-mesh sieve.

[0040] 2. Ultrasonic-assisted extraction: Take 5 g of soybean straw sample in a beaker and add the required ethanol solution according to the solid-liquid ratio required for the experiment. Place it in the Ningbo Xinzhi ultrasonic cell disruptor SCIENTZ-IID and ultrasonicate for 7 s at a power of 120 w, stop for 3 s to avoid overheating, and ultrasonicate for the required time of the experiment.

[0041] 3. Suction filtration: Take a Buchner funnel and a suction flask. Place a filter paper in the Buchner funnel and moisten it with distilled water. Connect a vacuum suction pump. Pour the treated solution obtained after ultrasonic treatment into the Buchner funnel for suction filtration. Take the filtrate in the suction flask.

[0042] 4. Rotary evaporation: Place the filtrate after suction filtration into a rotary evaporator for low-pressure distillation and concentration to recover ethanol. Take the concentrated solution.

[0043] 5. Freeze drying: Freeze the concentrated solution obtained after rotary evaporation, and then place it in a freeze dryer for drying. Take the solid after freeze drying and grind it to obtain the soybean isoflavone extract.

[0044] The relevant parameters involved in this example were carried out by single-factor experiments and Box-Behnken response surface experiments. The relevant parameters can be seen in Table 1 and Table 2 below;

[0045] Table 1 is for single-factor experimental design; Table 2 is for Box-Behnken response surface experimental design;

[0046] Table 1 Single-factor experimental design parameters

[0047]

[0048] Combined Figures 2 to 4 It can be seen that in the single-factor experiment, Figure 2 By changing the ethanol concentration, the result is that the optimal ethanol concentration is 70 vol%; Figure 3 By changing the ultrasonic extraction time, the result is that the yield increases with time. However, considering the cost, the optimal test time is designed to be 30 min; Figure 4 By changing the solid-liquid ratio, the optimal solid-liquid ratio is 1:40.

[0049] Based on this, a Box-Behnken response surface experimental design is carried out.

[0050] Table 2 Response surface experimental design parameters

[0051]

[0052]

[0053] The detection method for soybean isoflavone content is as follows:

[0054] 1. Establishment of standard curve

[0055] Take 5 mg of genistein standard, dissolve it in 5 ml of absolute ethanol, transfer it to a 50-ml volumetric flask, and then make up the volume with distilled water to obtain a genistein standard solution with a concentration of 0.1 mg / ml. Respectively measure 0.1, 0.3, 0.5, 0.7, and 0.9 ml of the standard solution, add them to a 10-ml volumetric flask, then add 1 ml of absolute ethanol, and make up the volume with distilled water. Use an ultraviolet spectrophotometer to measure its absorbance at 260 nm. With the genistein concentration (X) as the abscissa and the absorbance (Y) as the ordinate, the linear relationship between the two and the standard curve equation can be obtained; the standard curve method can be seen Figure 1 .

[0056] 2. Sample treatment

[0057] Take 25 mg of the extract, dissolve it in 2.5 ml of absolute ethanol, transfer it to a 25-ml volumetric flask, and then make up the volume with distilled water to obtain an extract solution with a concentration of 1 mg / ml. Measure 1 ml of the well-made extract solution, add it to a 10-ml volumetric flask, then add 1 ml of absolute ethanol, and make up the volume with distilled water to obtain an extract solution with a concentration of 0.1 mg / ml. Use an ultraviolet spectrophotometer to measure its absorbance at 260 nm. Substitute it into the standard curve to obtain the concentration of soy isoflavones in the 0.1 mg / ml extract solution.

[0058] 3. Calculation

[0059] The content of soy isoflavones in the extract (mg / mg) = the concentration of soy isoflavones calculated from the standard curve / the concentration of the extract solution (0.1 mg / ml)

[0060] The results of the response surface experiment can be referred to Table 3 and Figures 5 to 7 ;

[0061] Table 3 Statistical table of extraction rate

[0062]

[0063]

[0064] The variance results can be seen in Table 4;

[0065] Table 4 Table of variance analysis results

[0066]

[0067] In Table 4 above, the P of this model = 0.0155 < 0.05, with a significant difference, indicating that this model is reliable. The lack-of-fit term P = 0.9458 > 0.05, with no significant difference, indicating that the fitting degree of this model is good.

[0068] Figure 5Response surface plot (left) and contour plot (right) of the effects of ethanol concentration (A) and ultrasonic time (B) on the yield of soybean isoflavones (R1);

[0069] Figure 6 Response surface plot (left) and contour plot (right) of the effects of ethanol concentration (A) and liquid-to-solid ratio (C) on the yield of soybean isoflavones (R1);

[0070] Figure 7 Response surface plot (left) and contour plot (right) of the effects of ultrasonic time (B) and liquid-to-solid ratio (C) on the yield of soybean isoflavones (R1).

[0071] According to the model prediction, the optimal extraction process for extracting soybean isoflavones from soybean straw is an ethanol concentration of 67.34 vol%, an ultrasonic time of 31.51 min, and a liquid-to-solid ratio of 1:38.92. The predicted optimal extraction amount is 6.19 mg / g. Considering practical operation convenience, the process was modified to an ethanol concentration of 70 vol%, an ultrasonic time of 30 min, and a liquid-to-solid ratio of 1:40. Parallel experiments were carried out under these conditions, and the average yield of soybean isoflavones from soybean straw was 6.14 mg / g, which is close to the predicted value, indicating that the established model is reliable. The ultrasonic-assisted extraction based on the response surface method can be used to optimize the extraction process of soybean isoflavones from soybean straw.

[0072] 4. Result analysis:

[0073] 1. Through single-factor experiments, it can be learned that the optimal ethanol concentration of the present invention is 60 - 80 vol%, the best is 70 vol%, the ultrasonic time is not less than 15 min, the best is 30 min, the liquid-to-solid ratio is not less than 1:10, the best is 1:40, and the extraction efficiency can reach 5 mg / g in all cases.

[0074] 2. Through response surface experiments and optimization of experimental parameters, it can be known that the optimal extraction process is an ethanol concentration of 70 vol%, an ultrasonic time of 30 min, and a liquid-to-solid ratio of 1:40, and the average yield of soybean isoflavones from soybean straw is 6.14 mg / g.

[0075] Through the above experiments, it is fully demonstrated that the extraction method of the present invention can effectively change the inherent perception of the traditional view that the net content of soybean flavonoids in soybean straw is not high. The method of the present invention is an effective means to realize the utilization of agricultural waste.

[0076] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for extracting soybean isoflavones, characterized in that, Using soybean straw as raw material, soybean isoflavones are obtained by ultrasonic-assisted alcohol extraction method; the extraction rate of soybean isoflavones is not less than 6 mg / g.

2. The extraction method according to claim 1, characterized in that, The soybean straw is dried soybean straw, and the moisture content of the dried soybean straw does not exceed 8.2 wt%.

3. The extraction method according to claim 1, characterized in that, The solvent used in the ultrasonic-assisted alcohol extraction method is an ethanol solution with a concentration of 40 - 80 vol%.

4. The extraction method according to claim 1, wherein The solid-liquid ratio in the ultrasonic-assisted alcohol extraction method is 1:10 - 50.

5. The extraction method according to claim 1, characterized in that, The extraction time in the ultrasonic-assisted alcohol extraction method is 15 - 35 min.

6. The extraction method according to claim 1, wherein The power of ultrasonic is 120 w, stop for 3 s after ultrasonic for 7 s, and reciprocate in cycles.

7. New use of soybean straw, characterized in that, As the extraction raw material of soybean isoflavones, soybean isoflavones are obtained by the method described in any one of claims 1 to 6.

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