Method for preparing soybean milk with low antinutritional factors by utilizing ultrasonic technology

Abstract

The invention discloses a method for preparing soybean milk with low antinutritional factors by using an ultrasonic technology, and belongs to the field of food processing. In order to solve the problems that the content of antinutritional factors in the existing soybean milk is relatively high and the absorption of human bodies is influenced, the invention provides the preparation method of the soybean milk with low antinutritional factors. The method mainly comprises the steps of soaking, grinding, ultrasonic treatment, high-pressure homogenization, heating and the like. Anti-nutritional factors are effectively removed from the soybean milk obtained through ultrasonic treatment, the content of a trypsin inhibitor is remarkably reduced, and the protein content and the in-vitro digestibility are both improved. The soybean milk subjected to ultrasonic treatment is rich in nutrition, easy to absorb by a human body and low in antinutritional factor content, and has a good application prospect in the field.

Description

Technical Field

[0001] The invention relates to a method for preparing low anti-nutritional factor soybean milk by utilizing ultrasonic technology, belonging to the technical field of food processing. Background Art

[0002] Soy milk, one of the most common bean products, is a water extract made by soaking whole soybeans in water and grinding them with water. The product obtained can be further processed into drinkable soy milk or made into other soy products. Soy milk contains almost all the nutrients in soybeans. In addition to being a source of protein, carbohydrates and several trace nutrients (including minerals and B vitamins), they are also rich in dietary fiber and fat. However, compared with dairy protein, plant protein has a lower digestibility. Many research reports point out that soy milk is rich in anti-nutritional factors, such as trypsin inhibitors, tannins, phytic acid, etc., which interfere with digestion and lead to low nutrient absorption.

[0003] Ultrasonic waves have a frequency of 2×10 4 -2×10 9 During the propagation of ultrasound, the origin displacement, acceleration, vibration speed and sound pressure can all allow the mechanical energy of ultrasound to be transmitted. When the sound intensity is large enough and the pressure on the liquid is strong enough, the distance between the medium molecules will increase to exceed the limit distance, thereby destroying the structural integrity of the liquid and causing a cavitation effect. Ultrasonic treatment can effectively reduce the content of anti-nutritional factors in soy milk without changing the quality and original flavor characteristics of soy milk, reducing the negative effects of anti-nutritional factors and increasing the protein content and in vitro digestibility in soy milk. Therefore, preparing low-anti-nutritional factor soy milk through ultrasonic treatment is a feasible technical means. Summary of the invention

[0004] In order to solve the problem that the anti-nutritional factor content in the current soy milk is high and difficult for the human body to absorb, the present invention provides a method for preparing low anti-nutritional factor soy milk using ultrasonic technology, and the preparation method specifically comprises the following steps:

[0005] Step 1, selecting soybean raw materials, selecting soybeans without insect infestation and with full grains, and obtaining impurity-free soybeans;

[0006] Step 2, soaking the impurity-removed soybeans obtained in step 1 in a sodium bicarbonate solution to obtain soaked soybeans;

[0007] Step 3, washing and grinding the soaked soybeans obtained in step 2 to obtain raw soymilk;

[0008] Step 4, subjecting the raw soybean milk obtained in step 3 to ultrasonic treatment, filtering and homogenizing the raw soybean milk after ultrasonic treatment to obtain a homogenized liquid;

[0009] Step 5: subjecting the homogenized liquid obtained in step 4 to high temperature sterilization to obtain soymilk with low anti-nutritional factors.

[0010] It is further defined that the mass fraction of the sodium bicarbonate solution described in step 2 is 0.4-0.6%; the material-liquid ratio of the soaking process is 1:3-1:5, the soaking temperature is 20-30°C, and the soaking time is 8-16h; preferably, the mass fraction of the sodium bicarbonate solution described in step 2 is 0.5%; the material-liquid ratio of the soaking process is 1:4; the soaking temperature is 25°C, and the soaking time is 12h.

[0011] It is further defined that the material-water ratio of soybeans to water in the refining process of step three is 1:7-1:11; preferably, the material-water ratio of soybeans to water in the refining process of step three is 1:9.

[0012] It is further defined that the ultrasonic frequency in step 4 is 20000-30000 Hz, the ultrasonic power is 300-500 W, and the ultrasonic time is 25-35 min; preferably, the ultrasonic frequency in step 4 is 25000 Hz, the ultrasonic power is 400 W, and the ultrasonic time is 30 min.

[0013] It is further defined that the high-pressure homogenization pressure in step 4 is 100-200 MPa; preferably, the high-pressure homogenization pressure in step 4 is 150 MPa.

[0014] It is further defined that the high temperature sterilization treatment in step 5 is to heat the homogenized liquid to 95° C. and then keep it warm for 8 minutes, so as to obtain soy milk with low anti-nutritional factors.

[0015] Beneficial effects of the present invention:

[0016] The method for preparing low anti-nutritional factor soymilk provided by the invention is easy to operate, and the content of trypsin inhibitor in the soymilk after ultrasonic treatment is significantly reduced, thereby avoiding inhibition of intestinal absorption of nutrients; the protein content and in vitro digestibility are both increased, and the nutritional value of the soymilk is improved while the anti-nutritional factors are effectively removed, thus opening up a new way for preparing low anti-nutritional factor soymilk in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The results of protein content detection in the embodiment of the present invention show the influence of different ultrasonic powers on the protein content of soybean milk;

[0018] Figure 2 The test results of the trypsin inhibitor content in the embodiment of the present invention show the influence of different ultrasonic powers on the trypsin inhibitor content in soybean milk;

[0019] Figure 3The results of in vitro digestibility testing of the embodiments of the present invention show the effects of different ultrasonic powers on in vitro digestibility. DETAILED DESCRIPTION

[0020] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0021] Embodiment 1:

[0022] Step 1, prepare raw soy milk: select 200g of soybeans with complete seeds and no insect infestation, add 800g of 0.5% sodium bicarbonate solution to soak for 12h, and after soaking, grind the soybeans, put them into a grinder at a material-liquid ratio of 1:9 to obtain crude soy milk.

[0023] Step 2: Ultrasonic treatment: The crude soymilk obtained in S1 was subjected to ultrasonic treatment with an ultrasonic power of 200 W and an ultrasonic time of 30 min.

[0024] Step 3, high-pressure homogenization treatment: The ultrasonically treated soymilk obtained in S2 is filtered and subjected to high-pressure homogenization treatment. The high-pressure homogenization is carried out at a homogenization pressure of 150 MPa to obtain a homogenized liquid.

[0025] Step 4, preparing sterilized soy milk: keeping the homogenized liquid obtained in S3 at 95° C. for 8 minutes to obtain sterilized soy milk.

[0026] Step 5: Take the soymilk of Example 1 and perform protein content detection, trypsin inhibitor content detection, and in vitro digestibility detection.

[0027] The low anti-nutritional factor soy milk prepared in this example has a protein content of 3.186%, a trypsin inhibitor content of 33.60 mg / g, and an in vitro digestibility of 81.75%.

[0028] Embodiment 2:

[0029] The difference between this embodiment and embodiment 1 is that the ultrasonic power of S2 is 400W, and the remaining operation steps are exactly the same as those of embodiment 1.

[0030] The low anti-nutritional factor soy milk prepared in this example has a protein content of 3.245%, a trypsin inhibitor content of 22.20 mg / g, and an in vitro digestibility of 84.79%.

[0031] Embodiment 3:

[0032] The difference between this embodiment and embodiment 1 is that the ultrasonic power of S2 is 600W, and the remaining operation steps are exactly the same as those of embodiment 1.

[0033] The low anti-nutritional factor soy milk prepared in this example has a protein content of 3.119%, a trypsin inhibitor content of 27.99 mg / g, and an in vitro digestibility of 81.54%.

[0034] Comparative Example:

[0035] The difference between this comparative example and Example 1 is that the ultrasonic operation in S2 is not performed, and the remaining operation steps are exactly the same as those in Example 1.

[0036] The low anti-nutritional factor soy milk prepared in this example has a protein content of 3.026%, a trypsin inhibitor content of 45.89 mg / g, and an in vitro digestibility of 77.85%.

[0037] Attached Figure 1 The protein content graph of Example 1, Example 2, Example 3, and the comparative example, wherein the protein content is the highest in Example 2, i.e., the group with an ultrasonic power of 400 W. The protein content in the comparative example is 3.026%, while the protein content in Example 2 is the highest, reaching 3.245%. The increase in protein content can be considered to be due to the cavitation effect of ultrasound, which causes cavitation bubbles to oscillate, grow, shrink, and collapse repeatedly during the treatment process, causing violent turbulent twitching and high-speed collisions of ions, destroying the structure of the protein and significantly increasing the protein content.

[0038] Attached Figure 2 The figure shows the trypsin inhibitor content of Example 1, Example 2, Example 3, and the comparative example. The one with the lowest trypsin inhibitor content is Example 2, i.e., the group with an ultrasonic power of 400 W. The initial content of trypsin inhibitor (TI) in the comparative example is 45.89 mg / g, while the trypsin inhibitor content of the sample of Example 1 is reduced by 26.7%. With the increase of the processing power, the trypsin inhibitor content in the sample of Example 2 decreases the most, reaching 51.6%. The reduction in the trypsin inhibitor content can be considered to be due to the destruction of the disulfide bond, which causes the secondary structure to change, thereby reducing the activity of the trypsin inhibitor.

[0039] Attached Figure 3 The in vitro digestibility graph of soy milk of Example 1, Example 2, Example 3 and the comparative example shows that the in vitro digestibility of soy milk is the highest in Example 2, i.e., the group with an ultrasonic power of 400 W. The in vitro digestibility of soy milk in the comparative example is 77.85%, while the in vitro digestibility of soy milk in Example 2 is the highest, reaching 84.79%. While the ultrasonic treatment reduces the content of trypsin inhibitors in the soy milk, it changes the secondary structure of the soy milk protein, destroys the disulfide bonds of the soy milk protein, increases the β-folding content of the soy milk protein, and increases the in vitro digestibility of the soy milk.

Claims

1. A method for preparing enzymatically hydrolyzed soybean protein high-soluble soybean milk powder, characterized in that: The preparation method is to hydrolyze soybean protein in soybean milk with double enzymes, and then spray dry the hydrolyzed soybean milk to obtain highly soluble soybean milk powder, which specifically includes the following steps: Step 1: Select soybeans with uniform particles, soak them at 25°C in a ratio of 3:1 (dry soybeans: water, w / w) for 12 hours, drain the water, add ultrapure water in a ratio of soybeans: water = 1:7, grind the soaked soybeans, and grind the soybeans with a high-speed blender for 3 minutes to obtain soy milk; Step 2: firstly, adjusting the temperature of the ground soy milk in step 1 to 50°C and pH=9, adding alkaline protease at an enzyme amount of 3000U / g (per unit / substrate weight), performing enzymolysis for 3.5 hours, and performing enzyme inactivation treatment in a 95°C water bath for 15 minutes after the enzymolysis is completed; then adjusting the temperature to 50°C and pH=6.5, adding flavor protease at an enzyme amount of 3000U / g (per unit / substrate weight), performing enzymolysis for 3.5 hours, and performing enzyme inactivation treatment in a 95°C water bath for 15 minutes after the enzymolysis is completed to obtain an enzymolysate; Step 3: The enzymatic hydrolysate is homogenized by two-stage homogenization, with a first-stage homogenization pressure of 30MPa, a second-stage homogenization pressure of 20MPa, and a homogenization temperature of 60°C. The homogenized liquid is sprayed into the drying chamber at a pressure of 10MPa for spray drying, with a feed temperature of 175°C and a discharge temperature of 65°C. Finally, the finished soybean powder is obtained.

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