Method for preparing bean flour through cooperation of freeze thawing, radio frequency heating, extrusion puffing and pressure heating

Abstract

The invention discloses a method for preparing bean flour through cooperation of freeze thawing and radio frequency heating and extrusion puffing and pressure heating. The method specifically comprises the following steps: (1) performing freeze thawing and radio frequency heating treatment on soybeans; (2) drying and peeling; (3) extrusion expansion-autoclaving treatment; and (4) adding a sodium bicarbonate aqueous solution, and sequentially performing enzyme deactivation, centrifugal deslagging, sterilization and fishy smell removal, cooling, enzymolysis, concentration sterilization, spray drying, fluidized bed powder screening and packaging to obtain the bean flour. According to the method, freeze thawing-radio frequency heating treatment and extrusion puffing-autoclaving treatment are creatively combined to prepare the bean flour, and the content of isoflavone and phytic acid in the bean flour can be remarkably reduced, so that the nutritional value and physical properties of the bean flour are improved.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and more particularly to a method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving. Background Art

[0002] Children's complementary food nutrition pack is a food matrix-based complementary food nutrient supplement, which contains soy powder, milk powder, and high-density multivitamins and minerals. It can effectively improve and prevent children's iron deficiency anemia and other micronutrient deficiency symptoms.

[0003] Among them, soy flour, also known as soy milk powder, is a powdered product made from soybeans as the main raw material, through selection, soaking or not soaking, grinding, removing residue, heating to kill enzymes, concentration, adding or not adding soybean oil or other vegetable fats, sugars, salt and other auxiliary materials, adding or not adding food additives, food nutrient enhancers, and then drying. As an important part of children's complementary food nutrition package, the primary contribution of soy flour is to provide children with the basic nutritional framework needed for growth. It contains rich protein, high-quality fats, and carbohydrates, which are not only sources of energy, but also the cornerstones for building body tissues and organs and promoting cell metabolism. In addition, soy flour is also rich in various vitamins and minerals. These trace nutrients play an indispensable role in improving children's immunity, bone development, vision protection and overall health maintenance.

[0004] It is particularly worth mentioning that the rich content of B vitamins in soy flour plays an important role in nutrient absorption and utilization. Specifically, vitamin B12 shows unique advantages in promoting red blood cell production and maintaining the health of the nervous system; folic acid helps prevent anemia and nervous system diseases. The presence of these nutrients in soy flour not only enhances the effectiveness of soy flour as a nutritional supplement, but also significantly improves the comprehensive nutritional value of children's complementary food nutrition packages containing soy flour, laying a solid nutritional foundation for the healthy growth of children.

[0005] However, anti-nutritional factors such as isoflavones and phytic acid contained in soy flour have certain adverse effects on children's health. Among them, isoflavones are phytoestrogens. Excessive intake may interfere with children's endocrine system, affect the normal secretion of hormones, and may even lead to precocious puberty. Excessive levels of phytic acid can chelate with divalent or trivalent metal ions to form insoluble phytate complexes, thereby interfering with children's absorption of minerals such as iron and zinc. Long-term excessive intake may lead to nutritional deficiencies, especially for children in the growth and development period.

[0006] Therefore, how to effectively reduce the content of isoflavones and phytic acid in soy flour is a problem that those skilled in the art need to solve urgently. Summary of the invention

[0007] In view of this, the object of the present invention is to provide a method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving to solve the deficiencies in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving, specifically comprising the following steps:

[0010] (1) subjecting soybeans to freeze-thaw-radio frequency heating treatment to obtain product A;

[0011] (2) drying and peeling product A to obtain product B;

[0012] (3) subjecting product B to extrusion expansion-autoclave treatment to obtain product C;

[0013] (4) adding sodium bicarbonate aqueous solution to product C, and sequentially carrying out enzyme inactivation, centrifugal slag removal, sterilization and deodorization, cooling, enzymolysis, concentration and sterilization, spray drying, fluidized bed powder screening, and packaging to obtain soybean powder.

[0014] Furthermore, in the above step (1), the freeze-thaw-RF heating treatment includes freeze-thaw treatment and RF heating treatment; the freeze-thaw treatment includes freezing treatment and thawing treatment, the number of times is 3 times; the temperature of the freezing treatment is (-30)-(-50)°C, and the time is 11-15h; the temperature of the thawing treatment is 10-50°C; the temperature of the RF heating treatment is 120-150°C, and the time is 3-7min.

[0015] A further beneficial effect of the above-mentioned method is that the soybean freeze-thaw-RF heating treatment mainly includes three stages of soybean freezing treatment, thawing treatment and RF heating treatment, which can significantly reduce the content of isoflavones in soybean powder, thereby reducing its impact on children's own endocrine system.

[0016] Among them, freezing treatment can effectively inhibit the growth of microorganisms and enzyme activity in soybeans, thereby extending their shelf life. During the freezing process, the moisture in the soybeans will form ice crystals, and the size and distribution of these ice crystals will affect the effect of subsequent thawing and radio frequency heating treatments.

[0017] Thawing is a necessary step after freezing, its purpose is to restore the original state of soybeans for subsequent processing.

[0018] Radio frequency heating is the process of heating soybeans with radio frequency energy after thawing. As an emerging electromagnetic heating technology, radio frequency heating has the advantages of fast heating, uniform heating, deep penetration and low energy consumption. In soybean processing, radio frequency heating can improve the texture of soybeans, improve the solubility and functionality of soybean protein, etc.

[0019] Furthermore, in the above step (2), the inlet air temperature for drying and peeling is 90-110°C, and the exhaust air temperature is 60-70°C.

[0020] The further beneficial effect of the above method is that drying improves the processing performance and quality of soybeans by reducing moisture content, improving processing performance, inactivating anti-nutrients and reducing beany smell, etc. Peeling further improves the quality and value of soybean flour by increasing protein content, improving soybean flour quality and increasing yield, etc.

[0021] Furthermore, in the above step (3), the extrusion puffing-autoclave treatment includes extrusion puffing treatment and autoclave treatment; the temperatures of zones 2 to 7 of the extrusion puffing treatment are 70°C, 80°C, 100°C, 110°C, 113°C and 150°C respectively, the main engine frequency is 32-35HZ, the feeding frequency is 15HZ, and the rotary cutting frequency is 25HZ; the autoclave temperature is 100-120°C, and the time is 5-10min.

[0022] The further beneficial effect of adopting the above-mentioned method is that the extrusion puffing-pressure heat treatment can significantly reduce the content of phytic acid in soybean powder, and effectively passivate or destroy the anti-nutritional factors in soybeans, such as trypsin inhibitors, lipoxygenase, urease, etc., which can significantly reduce their activity, thereby improving the digestibility and nutritional value of soybean protein. At the same time, during the extrusion puffing process, soybeans are extruded and puffed under high temperature and high pressure, and the volume increases and the density increases. This change makes the soybean powder easier to mix and disperse in food processing, and improves the uniformity and stability of the product. Moreover, the soybean powder after extrusion puffing has a more delicate texture and a better taste. In addition, extrusion puffing-pressure heat treatment is a continuous and automated production method that can significantly improve the production efficiency of soybean processing. This production method reduces the manual operation link, reduces the labor intensity, and improves the stability and reliability of the production line.

[0023] Furthermore, in the above step (4), the sodium bicarbonate aqueous solution is added to the slurry until the pH value is 7.0-7.4.

[0024] The further beneficial effect of adopting the above is that sodium bicarbonate is an alkaline substance that can neutralize the acidic components in soybeans, thereby changing the acid-base environment of soybeans. At the same time, the alkaline environment also helps to reduce the unpleasant odors in soybeans, such as beany smell. Moreover, in an alkaline environment, the growth of some microorganisms will be inhibited, which can reduce microbial contamination to a certain extent and improve the sanitary quality of soybean powder. More importantly, after extrusion puffing-autoclaving, the addition of sodium bicarbonate can promote the gelatinization of starch in soybeans, and the gelatinized starch has better viscosity and stability, which helps to improve the texture, taste and nutritional value of soybean powder.

[0025] Furthermore, in the above step (4), the temperature of the hot water for inactivating the enzyme is 70-90° C., and the steam pressure is 0.1-0.5 MPa.

[0026] The above further beneficial effect is that the lipoxygenase in soybeans can promote the oxidation of unsaturated fatty acids, produce undesirable flavor substances, and make soybean milk produce beany smell. The present invention can inactivate the lipoxygenase through hot water treatment, thereby reducing the generation of beany smell. In addition, soybeans contain trypsin inhibitors and chymotrypsin inhibitors, which can reduce the digestibility and bioavailability of protein. The present invention can inactivate these inhibitors through enzyme inactivation treatment, thereby improving the digestibility and bioavailability of protein. At the same time, the sodium bicarbonate aqueous solution can react with the enzymes in the soybeans, thereby assisting the enzyme inactivation treatment. Although sodium bicarbonate itself does not directly have an enzyme inactivation effect, its alkaline environment can affect the activity state of the enzyme and promote the inactivation of the enzyme.

[0027] Furthermore, in the above step (4), the sterilization and deodorization temperature is 125-145°C, the sterilization time is 10-18s, until the material urease test is negative; and the material is cooled to a temperature of ≤65°C.

[0028] A further beneficial effect of the above method is that the present invention uses high temperature to kill or inhibit the growth of microorganisms, thereby slowing down or preventing the reproduction of microorganisms in bean powder and extending the shelf life of bean powder. At the same time, it can also effectively remove or reduce the beany smell, making the flavor of bean powder more pure and delicious.

[0029] Furthermore, in the above step (4), the enzyme for enzymatic hydrolysis is flavor protease, the added mass is 0.5%, the enzymatic hydrolysis temperature is 45-50° C., and the enzymatic hydrolysis time is 15 min.

[0030] A further beneficial effect of the above is that the present invention can not only improve the flavor of soybean powder but also help to improve the digestibility and bioavailability of protein by adding an appropriate amount of flavor protease to decompose the protein and other components in soybeans.

[0031] Furthermore, in the above step (4), the temperature for concentrated sterilization is 90-94°C.

[0032] A further beneficial effect of the above method is that the present invention can remove most of the water through concentration and sterilization, thereby significantly increasing the solid content of the soy milk. At the same time, it can also reduce impurities and undesirable flavor substances in the soy powder, thereby improving the overall quality of the soy powder.

[0033] Furthermore, in the above step (4), the inlet air temperature of the spray drying is 170-185°C, and the exhaust air temperature is 70-80°C.

[0034] The further beneficial effect of the above method is that the present invention can finely atomize liquid soybean milk to form tiny droplets through spray drying, and these droplets quickly contact with hot air in the drying chamber, so that the water evaporates in a large amount in a short time, thereby efficiently removing the water in the material and forming a stable powder product. Moreover, in the spray drying process of the present invention, due to the short drying time and proper temperature control, the nutrients in the soybean powder can be retained to the maximum extent, thereby maintaining the high nutritional value of the soybean powder.

[0035] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] The present invention creatively combines freeze-thaw-radio frequency heating treatment and extrusion puffing-autoclave treatment to prepare soybean powder, which can significantly reduce the content of isoflavones and phytic acid in the soybean powder, thereby improving the nutritional value and physical properties of the soybean powder. DETAILED DESCRIPTION

[0037] 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 the embodiments. 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.

[0038] Example 1

[0039] The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving specifically comprises the following steps:

[0040] (1) The soybeans were first frozen at -30°C for 15 h, then thawed at 10°C, and freeze-thawed for 3 times, and finally radio-frequency heated at 120°C for 7 min to obtain product A;

[0041] (2) Add product A to an oven, set the inlet air temperature to 90°C and the exhaust air temperature to 70°C, dry and peel, and obtain product B;

[0042] (3) First, add product B into the extruder, set the temperature of zone 2 to zone 7 to 70°C, 80°C, 100°C, 110°C, 113°C and 150°C respectively, set the main machine frequency conversion to 32HZ, the feeding frequency conversion to 15HZ, and the rotary cutting frequency conversion to 25HZ, extrude and expand, and then press heat at 100°C for 10 minutes to obtain product C;

[0043] (4) First, add sodium bicarbonate aqueous solution to product C until the pH value of the slurry is 7.0, then inactivate the enzyme in 70°C hot water and 0.5MPa steam, centrifuge to remove slag, sterilize and remove fishy smell at 125°C for 18s until the material urease test is negative, cool to 45°C, add 0.5% by weight of flavor protease to perform enzymolysis at 45°C for 15min, concentrate and sterilize at 90°C, set the inlet air temperature to 170°C and the exhaust air temperature to 80°C for spray drying, sieve the powder in a fluidized bed, and finally package to obtain soybean powder.

[0044] Example 2

[0045] The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving specifically comprises the following steps:

[0046] (1) The soybeans were first frozen at -40°C for 13 h, then thawed at 30°C, and freeze-thawed for 3 times, and finally radio-frequency heated at 120°C for 5 min to obtain product A;

[0047] (2) Add product A to an oven, set the inlet air temperature to 100°C and the exhaust air temperature to 65°C, dry and peel, and obtain product B;

[0048] (3) First, add product B into the extruder, set the temperature of zone 2 to zone 7 to 70°C, 80°C, 100°C, 110°C, 113°C and 150°C respectively, set the main machine frequency conversion to 34HZ, the feeding frequency conversion to 15HZ, and the rotary cutting frequency conversion to 25HZ, extrude and expand, and then heat at 110°C for 8 minutes to obtain product C;

[0049] (4) First, add sodium bicarbonate aqueous solution to product C until the pH value of the slurry is 7.2, then inactivate the enzyme in 80°C hot water and 0.3MPa steam, centrifuge to remove the residue, sterilize and remove the fishy smell at 135°C for 15s until the material urease test is negative, cool to 48°C, add 0.5% by weight of flavor protease to perform enzymolysis at 48°C for 15min, concentrate and sterilize at 92°C, set the inlet air temperature to 180°C and the exhaust air temperature to 75°C for spray drying, sieve the powder in a fluidized bed, and finally package to obtain soybean powder.

[0050] Example 3

[0051] The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving specifically comprises the following steps:

[0052] (1) The soybeans were first frozen at -50°C for 15 h, then thawed at 50°C, and freeze-thawed for 3 times, and finally radio frequency heated at 150°C for 3 min to obtain product A;

[0053] (2) Add product A to an oven, set the inlet air temperature to 110°C and the exhaust air temperature to 60°C, dry and peel, and obtain product B;

[0054] (3) First, add product B into the extruder, set the temperature of zone 2 to zone 7 to 70°C, 80°C, 100°C, 110°C, 113°C and 150°C respectively, set the main machine frequency conversion to 35HZ, the feeding frequency conversion to 15HZ, and the rotary cutting frequency conversion to 25HZ, extrude and expand, and then press heat at 120°C for 5 minutes to obtain product C;

[0055] (4) First, add sodium bicarbonate aqueous solution to product C until the pH value of the slurry is 7.4, then inactivate the enzyme in 90°C hot water and 0.1MPa steam, centrifuge to remove the residue, sterilize and remove the fishy smell at 145°C for 10s until the material urease test is negative, cool to 50°C, add 0.5% by weight of flavor protease and perform enzymolysis at 50°C for 15min, concentrate and sterilize at 94°C, set the inlet air temperature to 185°C and the exhaust air temperature to 70°C for spray drying, screen the powder in a fluidized bed, and finally package to obtain soybean powder.

[0056] Comparative Example 1

[0057] The method for preparing soybean powder by freeze-thaw-radio frequency heating specifically comprises the following steps:

[0058] (1) The soybeans were first frozen at -40°C for 13 h, then thawed at 30°C, and freeze-thawed for 3 times, and finally radio-frequency heated at 120°C for 5 min to obtain product A;

[0059] (2) Add product A to an oven, set the inlet air temperature to 100°C and the exhaust air temperature to 65°C, dry and peel, and obtain product B;

[0060] (3) First, add sodium bicarbonate aqueous solution to product B until the pH value of the slurry is 7.2, then inactivate the enzyme in 80°C hot water and 0.3MPa steam, centrifuge to remove slag, sterilize and remove fishy smell at 135°C for 15s until the material urease test is negative, cool to 48°C, add 0.5% by weight of flavor protease to perform enzymolysis at 48°C for 15min, concentrate and sterilize at 92°C, set the inlet air temperature to 180°C and the exhaust air temperature to 75°C for spray drying, sieve the powder in a fluidized bed, and finally package to obtain soybean powder.

[0061] Comparative Example 2

[0062] The method for preparing soybean powder by extrusion puffing-autoclaving specifically comprises the following steps:

[0063] (1) Add soybeans into an oven, set the inlet air temperature to 100° C., the exhaust air temperature to 65° C., dry and peel the soybeans to obtain product A;

[0064] (3) First, add product A into the extruder, set the temperature of zone 2 to zone 7 to 70°C, 80°C, 100°C, 110°C, 113°C and 150°C respectively, set the main machine frequency conversion to 34 Hz, the feeding frequency conversion to 15 Hz, the rotary cutting frequency conversion to 25 Hz, extrude and expand, and then press heat at 110°C for 8 minutes to obtain product B;

[0065] (4) First, add sodium bicarbonate aqueous solution to product B until the pH value of the slurry is 7.2, then inactivate the enzyme in 80°C hot water and 0.3MPa steam, centrifuge to remove the residue, sterilize and remove the fishy smell at 135°C for 15s until the material urease test is negative, cool to 48°C, add 0.5% by weight of flavor protease to perform enzymolysis at 48°C for 15min, concentrate and sterilize at 92°C, set the inlet air temperature to 180°C and the exhaust air temperature to 75°C for spray drying, sieve the powder in a fluidized bed, and finally package to obtain soybean powder.

[0066] Comparative Example 3

[0067] The preparation method of soybean powder specifically comprises the following steps:

[0068] (1) adding soybeans into an oven, setting the inlet air temperature to 100° C. and the exhaust air temperature to 65° C., drying and peeling the soybeans to obtain peeled soybeans;

[0069] (2) First, add sodium bicarbonate aqueous solution to the dehulled soybeans and grind them to a pH value of 7.2. Then, inactivate the enzyme in 80°C hot water and 0.3MPa steam, centrifuge to remove the residue, sterilize and remove the odor for 15s at 135°C until the material urease test is negative, cool to 48°C, add 0.5% by weight of flavor protease and perform enzymolysis at 48°C for 15min, concentrate and sterilize at 92°C, set the inlet air temperature to 180°C and the exhaust air temperature to 75°C for spray drying, sieve the powder in a fluidized bed, and finally package to obtain soybean powder.

[0070] Performance Testing

[0071] The soy flours prepared in Examples 1-3 and Comparative Examples 1-3 were respectively taken to detect the contents of isoflavones and phytic acid. The results are shown in Table 1.

[0072] Table 1 Contents of isoflavones and phytic acid in soybean powder of Examples 1-3 and Comparative Examples 1-3

[0073]

[0074] It can be seen from Table 1 that, compared with Comparative Examples 1-3, the contents of isoflavones and phytic acid in the soybean powder of Examples 1-3 of the present invention are significantly reduced.

[0075] The above experiments show that the present invention creatively combines freeze-thaw-radio frequency heating treatment and extrusion puffing-autoclave treatment to prepare soy flour, which can significantly reduce the content of isoflavones and phytic acid in the soy flour, thereby improving the nutritional value and physical properties of the soy flour.

[0076] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing soybean powder by freeze-thaw-radio frequency heating synergistic extrusion puffing-autoclaving, characterized in that: The specific steps include: (1) subjecting soybeans to freeze-thaw-radio frequency heating treatment to obtain product A; (2) drying and peeling product A to obtain product B; (3) subjecting product B to extrusion expansion-autoclave treatment to obtain product C; (4) adding sodium bicarbonate aqueous solution to product C, and sequentially performing enzyme inactivation, centrifugal slag removal, sterilization and deodorization, cooling, enzymolysis, concentration and sterilization, spray drying, fluidized bed powder screening, and packaging to obtain the soy flour.

2. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (1), the freeze-thaw-radio frequency heating treatment includes freeze-thaw treatment and radio frequency heating treatment; the freeze-thaw treatment includes freezing treatment and thawing treatment, the number of times is 3 times; the temperature of the freezing treatment is (-30)-(-50)°C, and the time is 11-15h; the temperature of the thawing treatment is 10-50°C; the temperature of the radio frequency heating treatment is 120-150°C, and the time is 3-7min.

3. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (2), the inlet air temperature of the drying and peeling is 90-110°C, and the exhaust air temperature is 60-70°C.

4. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (3), the extrusion puffing-autoclave treatment includes extrusion puffing treatment and autoclave treatment; the temperatures of zones 2 to 7 of the extrusion puffing treatment are 70°C, 80°C, 100°C, 110°C, 113°C and 150°C respectively, the main engine frequency is 32-35HZ, the feeding frequency is 15HZ, and the rotary cutting frequency is 25HZ; the temperature of the autoclave treatment is 100-120°C, and the time is 5-10min.

5. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (4), the sodium bicarbonate aqueous solution is added to the slurry until the pH value is 7.0-7.

4.

6. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (4), the temperature of the hot water for inactivating the enzyme is 70-90° C., and the steam pressure is 0.1-0.5 MPa.

7. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (4), the sterilization and deodorization temperature is 125-145°C, the sterilization time is 10-18s, until the material urease test is negative; and the cooling is to a material temperature ≤65°C.

8. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (4), the enzyme used for enzymolysis is flavor protease, the added mass is 0.5%, the enzymolysis temperature is 45-50° C., and the enzymolysis time is 15 min.

9. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (4), the temperature of the concentrated sterilization is 90-94°C.

10. The method for preparing soybean powder by freeze-thaw-radio frequency heating coordinated extrusion puffing-autoclaving according to claim 1, characterized in that: In step (4), the inlet air temperature of the spray drying is 170-185°C, and the exhaust air temperature is 70-80°C.

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