CN111802588A

CN111802588A - Preparation method of functional fermented bean product, fermented bean product and application

Info

Publication number: CN111802588A
Application number: CN202010706247.0A
Authority: CN
Inventors: 刘晓兰; 郑喜群; 丛珊滋; 薛晨; 苏靖元; 李冠龙
Original assignee: Qiqihar University
Current assignee: Qiqihar University
Priority date: 2020-07-21
Filing date: 2020-07-21
Publication date: 2020-10-23

Abstract

The invention belongs to the technical field of bean product fermentation, and provides a preparation method of a functional fermented bean product, the fermented bean product and application. The method comprises soaking soybean, and performing microwave treatment; soaking the microwave-treated soybean again, absorbing enough water, pressurizing, steaming, and fermenting to obtain fermented soybean product. Compared with the fermented bean product which is not subjected to microwave treatment, the fermented bean product obtained by microwave treatment of the raw materials has the advantages that the activities of protease, saccharifying enzyme and amylase are improved, the content of amino acid nitrogen is also improved, the content distribution of small molecular peptides in the product is increased, flavor substances and functional substances are increased, the flavor is excellent, the nutrition is richer, the fermented bean product is more beneficial to being digested and absorbed by a human body, and the fermented bean product has the effects of relieving and protecting damage caused by hyperlipidemia.

Description

Preparation method of functional fermented bean product, fermented bean product and application

Technical Field

The invention belongs to the field of fermented bean products, and particularly relates to a preparation method of a fermented bean product, the prepared fermented bean product and application of the fermented bean product in preventing hyperlipidemia.

Background

The soybean is rich in nutrition, China is a main soybean production country and a processing country, and the edible soybean products have the history of thousands of years. The bean products are rich in vegetable protein, have the advantages of low fat and low calorie, have nutritional values conforming to the health principle of modern consumers, and are mainly divided into two categories, namely fermented bean products and non-fermented bean products. The fermented bean product is prepared with soybean as main material and through one or several microbial fermentation processes, and has one complicated biochemical process and unique form, flavor and nutrients.

The fermentation mode of the conventional bean product is that soybeans are soaked for absorbing water and are fermented after being cooked, and in the fermentation process, the microorganisms decompose macromolecular substances such as protein, starch and the like in the soybeans into micromolecular substances which are easy to absorb, and meanwhile, the macromolecular substances are metabolized to generate various flavor substances beneficial to body health, so that the fermented bean product is endowed with good flavor and certain functionality. In order to improve the flavor and taste and the health-care performance of fermented bean products, most people pay attention to factors influencing fermentation in the fermentation process, such as zymophyte, fermentation conditions and the like. Patent CN 102448319 a discloses a method for modifying the flavour of a soy protein containing substrate by fermenting a soy protein and carbohydrate containing substrate with thermophilic lactic acid bacteria as well as mesophilic lactic acid bacteria, which, depending on the reaction conditions (e.g. fermentation time), can produce a product with more milky or less salty characteristics and also reduce the content of off-flavour components. The quality of the fermented bean product is improved from the fermentation raw materials, the existing resources can be better utilized, and the achievements are easier to apply.

Disclosure of Invention

The invention aims to provide a method for preparing a fermented bean product, which is characterized in that a microwave treatment process is independently added on the basis of the prior process, so that the degradation degree of macromolecules such as raw material protein, starch and the like is improved, the fermented bean product is easy to digest, and the flavor of the fermented bean product is more in line with the taste of mass consumers.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a preparation method of a fermented bean product, which comprises the following steps:

(1) soaking soybeans;

(2) performing microwave treatment on the soaked soybeans;

(3) soaking the microwave-treated soybean again to absorb enough water;

(4) the soybeans processed in the step (3) are steamed under pressure;

(5) and (4) treating the obtained soybean raw material in the fermentation step to obtain a fermented soybean product.

As an implementable technical solution, the microwave treatment method is as follows: the microwave is firstly carried out for 30-50 min under the power of 100-150W, and then the microwave is carried out for 15-35 min under the power of 400-500W.

As an implementable technical scheme, the soaking time in the step (1) is 4-24 h.

As an implementable technical scheme, the mass ratio of the soybeans to the water in the soaking in the step (3) is 1: 2-4.

As an implementable technical scheme, the soaking temperature in the step (3) is 20-28 ℃, and the soaking time is 0.5-2 h.

As a practical technical solution, the pressure cooking conditions are as follows: pressurizing to 0.1MPa, and decocting at 121 deg.C for 15-20 min.

As an implementable technical scheme, the soybeans are selected from the soybeans which have full grains, uniform granularity, no broken skin, no fold, no mildew and no worm damage.

Another object of the present invention is to provide a fermented soybean product obtained by the above method.

As an implementable technical scheme, the fermented bean product is natto, fermented soybeans, soy sauce or fermented bean curd.

Another object of the present invention also includes the use of the above fermented soybean product for preparing a composition for preventing hyperlipidemia.

The invention has the beneficial effects that:

the invention takes soybean as raw material to prepare fermented bean product, soaking the soybean raw material, then straightening the grain and carrying out microwave treatment, so that macromolecular substances such as soybean protein, starch and the like are properly denatured under the shearing action of high temperature or sudden pressure drop, the high-grade structure of the protein is changed, in the subsequent solid state fermentation process, the soybean raw material can generate more flavor substances and functional substances, the flavor is excellent, the content distribution of small molecular peptides in the product is increased, the nutrition is more abundant, and the product is more beneficial to being digested and absorbed by human body.

Compared with the traditional soybean fermented product, after the soybeans are subjected to microwave treatment, the anti-nutritional factors of the soybeans are removed, the anti-nutritional factors such as anti-trypsin inhibitory factors, anti-thyroid and urease are thoroughly damaged, the nutritional ingredients of the soybeans are reserved, the fermented soybean product obtained after fermentation has good flavor, and the taste and health general requirements of people in China are better met.

The seasoning brewing enterprises in China are large in number and wide in distribution, and all have traditional basic equipment and facilities for raw material cooking and solid state fermentation. The pretreatment measure of the key microwave technology for whole soybean material particles can be realized by only adding one microwave treatment unit on the basis of basic facilities of the existing seasoning brewing enterprises, and the method has the advantages of easy achievement application and good industrialization prospect.

Drawings

FIG. 1 is a standard protein molecular weight curve map;

FIG. 2 is an electropherogram of microwave treated soybeans versus untreated soybeans; wherein, M is marker, 1, 2 and 3 are sample liquid of the non-microwave-treated soybean, and 4, 5 and 6 are sample liquid of the microwave-treated soybean.

Detailed Description

The invention provides a method for preparing fermented bean products, which comprises the following steps:

(1) soaking soybeans;

(2) performing microwave treatment on the soaked soybeans;

(3) soaking the microwave-treated soybean again to absorb enough water;

(4) the soybeans processed in the step (3) are steamed under pressure;

The invention takes soybean as raw material to prepare fermented bean product. The soybean varieties are not limited to the scheme of the invention, and the soybean varieties known at present can be used in the invention. The soybeans are preferably small-grain soybeans which are full in grains, uniform in granularity, free of broken skins, folds, mildew and worm damage. Before the soybean treatment, the soybeans are preferably subjected to dust removal and cleaning, so that the post-sterilization pressure is reduced, and the food safety is improved.

The soybean is soaked for absorbing water, preferably for 4-24 hours, further for 8-16 hours, and further for 10-12 hours. The soaking and water absorption of the soybeans are beneficial to the removal of anti-nutritional factors of the soybeans and the denaturation of protein and starch during microwave treatment.

The microwave treatment of the present invention is a whole grain microwave treatment of the soybean material soaked in the step (1). As an optional embodiment, the microwave treatment mode is as follows: the microwave is firstly carried out for 30-50 min under the low fire power of 100-150W, then the microwave is carried out for 15-35 min under the medium fire power of 400-500W, and more preferably, the microwave is firstly carried out for 40-45 min under the low fire power of 120-130W, and then the microwave is carried out for 25-30 min under the medium fire power of 450-470W. Specifically, soaked soybeans can be flatly placed into microwave equipment and uniformly heated, so that the soybeans are not completely expanded and have moderate denaturation with certain volume expansion degree, the moisture of the soybeans is reduced, and the taste is crisp. Cooling to room temperature after microwave treatment, and sealing for later use. When the microwave treatment is carried out, local overheating is avoided, so that the microwave treatment is not uniform. After microwave treatment, the soybean protein and starch are properly modified, which is beneficial to fermentation, and the soybean raw material can generate more flavor substances and functional substances, has excellent flavor and richer nutrition, and is more beneficial to digestion and absorption by human bodies.

The invention soaks the soybeans after the microwave treatment again, so that the soybeans can fully absorb water as much as possible. In this case, the ratio of the soybean to water is 1:2 to 4 by mass, and it is more preferable to soak the soybean in water in an amount of 3 times the mass of the soybean material after the microwave treatment. The temperature during soaking is preferably 20-28 ℃, and more preferably 23-26 ℃; the soaking time is reasonably adjusted according to the soaking temperature and the water absorption condition of the soybeans, and the optional soaking time is 0.5-2 h, and more preferably 1 h.

The invention carries out pressure cooking and sterilization treatment on the soybeans after microwave treatment. Optionally, the cooking is performed using a high pressure steam sterilization pot. The preferred pressure cooking conditions of the invention are: pressurizing to 0.1MPa, and decocting at 121 deg.C for 15-20 min. The cooked beans should be yellow brown to be cooked without rotting. Cooling to prepare for fermentation.

The invention selects proper fermentation mode according to different types of fermented bean products. The soybean may be fermented by those skilled in the art with reference to conventional soybean fermentation processes.

The fermented bean product prepared by the method has the advantages that the protease, the glucoamylase and the amylase are all improved, the content of amino acid nitrogen is also improved, flavor substances and functional substances are increased, the flavor is excellent, the nutrition is rich, and the digestion and absorption by a human body are facilitated. Has application prospect in preparing composition for preventing hyperlipidemia.

The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.

The Bacillus natto, Aspergillus oryzae and Mucor used in the following examples of the present invention are commercially available and the sources thereof are not limited by the present invention.

Example 1

A method for producing natto comprises the following steps:

(1) pretreatment of raw materials: selecting small-sized soybeans which are full in grains, uniform in granularity, free of broken skins, folds, mildew and worm damage. Removing dust from semen glycines, cleaning, and soaking overnight.

(2) And (3) finishing the grains with microwaves: and (3) performing size grading treatment on the raw materials treated in the step (1) by adopting a microwave method, and filling the raw materials in a special preservation box for a microwave oven. The method comprises the following steps of firstly carrying out microwave for 40min under the power of 120W and then carrying out microwave for 25min under the power of 450W, so that the soybeans are not completely expanded and have moderate denaturation with certain volume expansion degree, the moisture content of the soybeans is reduced, the soybeans are crisp to eat, cooling to room temperature, and sealing for later use. When the puffing is carried out, local overheating is avoided, so that the puffing is not uniform.

(3) Soaking: soaking the raw materials treated in the step (2) by 3 times of water, standing and soaking for 1h at the constant temperature of 20 ℃, so that the puffed soybeans can fully absorb water as much as possible.

(4) And (3) cooking: and (4) performing pressure cooking sterilization treatment on the puffed soybeans by adopting a pressure cooking mode on the raw materials treated in the step (3). Steaming with high pressure steam sterilizing pot under 0.1MPa at 121 deg.C for 15-20 min. The cooked beans should be yellow brown to be cooked without rotting. Cooling to prepare for fermentation.

(5) Preparing a bacillus natto seed culture solution: bacillus natto is used as a fermentation strain of natto, and is subjected to amplification culture firstly, and a liquid seed amplification culture method is adopted. The culture medium is beef extract peptone culture medium, and a loopful of the strain is inoculated into a 250mL triangular flask containing 50mL seed culture medium with initial pH of 7.0-7.5, and subjected to shake cultivation at 37 ℃ and 180r/min for 16h to prepare the bacillus natto seed culture solution.

(6) Fermentation culture: and (3) putting the raw material obtained by the treatment in the step (4) into a sterile room, cooling to room temperature, inoculating, adding sterile water and 6% (W/V) of inoculating amount according to the water content of 6% (W/V) into the seed culture solution obtained by shake cultivation in the step (5) for 16h, uniformly mixing, putting the expanded soybean treated according to the step into a constant-temperature incubator at 37 ℃ for constant-temperature fermentation for 24h, putting the fermented soybean into a refrigerator at 4 ℃ for 24h, and performing after-ripening.

The natto product obtained by the steps is yellow brown and glossy; the natto sauce has strong fragrance, has the peculiar flavor of natto, and has light ammonia taste; the bean particles are moderate in hardness, crisp and soft in taste and moderate in wet and slippery; the adhesion is better, the wire drawing is dense, the wire drawing is long, and the wire drawing is not easy to break. The physical and chemical indexes and sanitary indexes of the product meet the relevant standards.

Example 2

A method for producing soybean paste comprises the following steps:

(1) pretreatment of raw materials: selecting small-sized soybeans which are full in grains, uniform in granularity, free of broken skins, folds, mildew and worm damage. Removing dust from semen glycines, cleaning, and soaking for 4 hr.

(2) And (3) finishing the grains with microwaves: and (3) performing size grading treatment on the raw materials treated in the step (1) by adopting a microwave method, and filling the raw materials in a special preservation box for a microwave oven. The method comprises the steps of firstly carrying out microwave for 50min under the power of 100W and then carrying out microwave for 35min under the power of 400W, so that the soybeans are not completely expanded and have moderate denaturation with certain volume expansion degree, the moisture content of the soybeans is reduced, the soybeans are crisp to eat, cooling to room temperature, and sealing for later use. When the puffing is carried out, local overheating is avoided, so that the puffing is not uniform.

(3) Soaking: and (3) soaking the raw materials treated in the step (2) with water three times of the mass of the raw materials for 1.5 hours at a constant temperature of 25 ℃ to ensure that the puffed soybeans fully absorb water as much as possible.

(5) And (3) starter propagation culture: cooling the raw materials obtained by the treatment in the step (4), and mixing with flour, wherein the mass ratio of the added flour to the beans is 1: 3, the flour is dry steamed flour, and the function of the flour is to provide a carbon source required by the fermentation of the soybean paste. Inoculating Aspergillus oryzae, inoculating with the amount of 0.2% of the raw material, and mixing. The starter propagation adopts 2 day starter, and the starter is cultured in an incubator at 32-35 ℃. Culturing for about 12h, and turning over the yeast for the first time when the yeast material turns white. And turning over for the second time when the green villi grow on the surface.

(6) Fermentation culture: adopts a solid-state low-salt heat preservation quick brewing method. Mixing the raw materials obtained by the step (5) with 60-65 ℃ saline water to obtain solid soy sauce mash, carrying out heat preservation fermentation in a 45-50 ℃ water bath kettle, sealing with a cotton plug, and preparing the low-salt solid fermented soy sauce.

The soybean paste product obtained by the steps is dark brown and glossy; the sauce has strong flavor and no other bad smell; the salt taste is moderate and has no bitter taste; moderate thickness and no lumps.

Example 3

A method for producing fermented soya beans comprises the following specific steps:

(2) And (3) finishing the grains with microwaves: and (3) performing size grading treatment on the raw materials treated in the step (1) by adopting a microwave method, and filling the raw materials in a special preservation box for a microwave oven. The method comprises the following steps of firstly carrying out microwave for 30min under the power of 150W and then carrying out microwave for 15min under the power of 500W, so that the soybeans are not completely expanded and have moderate denaturation with certain volume expansion degree, the moisture content of the soybeans is reduced, the soybeans are crisp to eat, cooling to room temperature, and sealing for later use. When the puffing is carried out, local overheating is avoided, so that the puffing is not uniform.

(3) Soaking: and (3) soaking the raw materials treated in the step (2) with water three times of the mass of the raw materials for 1 hour at a constant temperature of 27 ℃ to ensure that the puffed soybeans fully absorb water as much as possible.

(5) And (3) starter propagation culture: cooling the raw material obtained by the step (4), uniformly spraying 0.2% (W/V) of mucor powder in the clinker, uniformly stirring, keeping the product temperature at 21-25 ℃, draining water at the later stage, and turning over the yeast twice during the yeast making period for 56-72 hours. The surface is full of white villi with the length of about 2 cm. During the period, the bean koji should not be soaked in water for a long time to avoid the increase of water content.

(6) Fermentation culture: adding seasonings into the yeast material treated in the step (5), putting the yeast material into a constant-temperature incubator at 45 ℃, and sealing and fermenting in a jar. The specific seasoning proportion is added as follows: 100g of soybeans, 8g of salt, 3g of white spirit, 4g of rice wine and 5-10g of cold boiled water, and the total amount is 165-170 g.

The wet fermented soya bean product obtained by the steps is dark brown and is oily and bright; the fermented soya beans are rich in fragrance and have no bad smell; the taste is delicious, the salty taste is moderate, and the peculiar smell such as bitter and astringent taste is avoided; the fermented soya bean has complete shape and loose granules; the physical and chemical indexes of the product and the sanitary indexes meet the relevant standards.

Example 4

Comparison experiment of molecular weight distribution of microwave-treated soybeans and non-microwave-treated soybeans

(1) Analyzing the molecular weight of the protein of the microwave-treated soybean material and the protein of the non-microwave-treated soybean material by SDS-PAGE electrophoresis

Assembling an electrophoresis device → preparing and separating, concentrating glue → loading sample → electrifying → fixing → dyeing → decolorizing → analyzing.

TABLE 1 concentrated gel and separation gel formulations

(2) Analyzing molecular weight of puffed soybean and soybean protein by gel filtration chromatography

The chromatographic column is G-25 gel chromatographic column (phi 0.8 × 90 cm); the mobile phase is distilled water passing through the membrane (0.2 μm); the standard protein solution comprises 2mg/mL blue glucan solution, 2mg/mL bacitracin solution, 3mg/mL oxidized glutathione solution and 3mg/mL reduced glutathione solution, the sample solution is used for preparing a sample solution with the protein content of 2mg/mL, and all the solutions are ultrasonically degassed for standby.

And drawing a gel chromatography standard curve, washing the column by using a mobile phase, wherein the liquid loading amount of a sample is 2mL, the flow rate is 2mL/min, the pressure is 0.3MPa, and the detection wavelength is 280 nm. And (3) drawing a standard protein molecular weight curve map, as shown in figure 1.

And (3) determination of a sample:

diluting the sample liquid to protein content concentration of 2mg/mL, filtering with 0.2 μm microporous membrane, degassing, and loading at flow rate of 2mL/min and pressure of 0.3MPa and detection wavelength of 280 nm.

As shown in FIG. 2 and Table 2, SDS-PAGE of the microwave-treated soybeans and the untreated soybeans is shown in FIG. 2, and gel filtration analysis is shown in Table 2.

TABLE 2 analysis of the distribution of small molecular weight proteins in gel filtration chromatography of microwave treated and non-microwave treated soy materials

In the second figure,

lanes

1, 2 and 3 show the raw material of soybean without microwave treatment,

lanes

4, 5 and 6 show the raw material of soybean after microwave treatment, and it is evident from the electrophoresis pattern of figure 2 that most of the soybean protein is above 30kDa and a plurality of distinct bands are evident; the soybean protein treated by microwave is mostly 14.4-30 kDa. As can be seen from the figure, under the condition of ensuring the consistent loading amount, the microwave-treated soybean material has more small-molecule peptides than the non-microwave-treated soybean material, and the molecular weight of the protein of the microwave-treated soybean material is mainly concentrated below 400Da in combination with the table 2, but the protein below 400Da runs out of the gel strip in SDS-PAGE electrophoresis, so that

lanes

4, 5 and 6 are lighter than

lanes

1, 2 and 3.

The molecular weight of the microwave-treated soybean raw material is less than 416.87Da and accounts for 74.5 percent according to the analysis of a gel chromatography table 2; the molecular weight of the soybean raw material which is not subjected to microwave treatment is less than 660.69Da and accounts for 18.63%, the macromolecular protein can be degraded into micromolecules by the microwave treatment process, and the content of the micromolecule peptide of the soybean raw material which is subjected to microwave treatment is obviously higher than that of the micromolecule peptide of the soybean raw material which is not subjected to microwave treatment. Therefore, the content of the micromolecule of the soybeans subjected to the whole grain microwave treatment in the step (2) is higher than that of the soybeans not subjected to the microwave treatment, and the distribution of the micromolecule peptide is increased.

Example 5

Fermented soybeans were fermented with microwave-treated soybeans and non-microwave-treated soybeans as raw materials with reference to the above examples 1 to 3 to obtain natto, soybean paste and fermented soybeans. Wherein the product not subjected to microwave treatment is the same as the example except for the steps (2) and (3). Wherein: the non-microwave treatment means that the step (2) is not carried out after the step (1), and then the mixture is statically soaked for 4 hours at the constant temperature of 25 ℃. After fermentation, the physical and chemical indexes of the finished product are measured and compared.

TABLE 3 influence of different raw materials on the quality of fermented Soy products

As can be seen from the results in Table 3, whether the microwave operation of the whole grain in step (2) has a great influence on the product quality, the activity of protease, saccharifying enzyme and amylase is improved when soybeans are treated by microwaves for fermentation, the content of amino acid nitrogen is also improved, which has a great effect on the product quality, and the water content is slightly improved. The total acid content of the microwave-treated fermented soybean product is greater than that of the non-microwave-treated fermented soybean product. In summary, the finished products of natto, soybean paste and fermented soybean obtained by using microwave-treated soybean as raw material have better indexes.

Example 6

Examples 1-3 functional Studies of fermented Bean products

Three fermented bean products (natto, fermented soya beans and bean paste) prepared by fermenting in examples 1-3 are respectively frozen, drained and ground, after ICR mice are adaptively fed for one week, the three fermented bean products are randomly divided into 12 groups and 8 animals in each group, the animals are fed according to clean grades, the environmental sanitation of a laboratory is kept, the animals are freely eaten and eaten, the animals are fed in cages and are fed for 3 weeks, and the animals are gavaged twice a day. The feeding method comprises the following steps:

TABLE 4 feeding methods

Weighing and recording the body mass of each group of mice every day, after the last gastric lavage, fasting the mice for 12h without water prohibition, weighing the body mass the next day, taking blood from the orbit, standing, centrifuging at 3000r/min for 10min at 4 ℃, separating serum, and temporarily storing the serum in a refrigerator at-20 ℃. The mice were sacrificed, the organs were dissected out, the surface blood was washed away with pre-cooled physiological saline, and the mass was weighed out by blotting with filter paper. Wrapping the liver with tinfoil paper, and storing in a refrigerator at-80 deg.C. Determination of Total Cholesterol (TC), Triglycerides (TG), Low Density lipoprotein (LDL-C), high Density lipoprotein (HDL-C) in mouse serum was performed according to the kit instructions. Liver index determination: cutting a certain mass of liver, mechanically grinding the liver by using normal saline under the ice bath condition to obtain liver tissue homogenate with the mass fraction of 10%, and then centrifuging the liver tissue homogenate for 10min at 3000r/min at 4 ℃ to obtain supernatant. Measuring the MDA content and SOD activity in liver tissue. And calculating the organ index according to the mouse body mass and the organ mass.

As can be seen from table 5, after the hyperlipidemia model group was fed with the high-fat diet for 3 weeks, compared with the blank control group, the contents of Triglyceride (TG), Total Cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) in the serum of the mice were all significantly different (P <0.01), the difference of high-density lipoprotein cholesterol (HDL-C) was not significant (P >0.05), and the success of constructing the hyperlipidemia model was determined.

TABLE 5 modeling of hyperlipidemic mice

Note: "#" indicates significant difference from the blank control group (P <0.05), "# #" indicates significant difference from the blank control group (P < 0.01). "+" indicates significant difference from the high fat model group (P <0.05), "+" indicates significant difference from the high fat model group (P < 0.01).

1. Influence of natto, fermented soybean and soybean paste on blood lipid level of mouse

Hyperlipidemia is a common and frequent metabolic disease characterized by an increase in Total Cholesterol (TC) and Triglycerides (TG), an increase in low-density lipoprotein (LDL-C) and a decrease in high-density lipoprotein (HDL-C), which are one or more lipids in plasma higher than normal due to abnormal fat metabolism or movement. The blood lipid levels of the mice in each group are shown in Table 6.

TABLE 6 influence of Natto, fermented soya beans, and Soybean paste on blood lipid level of mice

As can be seen from Table 6, after feeding 3 weeks of high-fat diet, the levels of TC, TG and LDL-C in the serum of the high-fat model group were significantly higher than those of the blank control group (P < 0.01). Compared with a high-fat model group, the positive control group, the low, medium and high dose natto and soybean paste can remarkably reduce the contents of TC, TG and LDL-C (P is less than 0.01) of the mice with the hyperlipidemia, and the low, medium and high dose fermented soybean group can remarkably reduce the contents of TC and LDL-C (P is less than 0.05) of the mice with the hyperlipidemia, but has no remarkable influence on HDL-C (P is more than 0.05). The results show that the flavor natto, the low-salt fermented soybean and the soybean paste have a prevention effect on the experimental hyperlipidemia of mice.

2. Influence of natto, fermented soybean and soybean paste on MDA and T-SOD levels of mouse liver

Free radicals in the MDA organism attack polyunsaturated fatty acids in the biofilm, initiating a stable end product of lipid peroxidation. And thus is a sensitive indicator of lipid peroxidation levels in vivo. T-SOD is one of the free radical scavengers of enzymes of the body, has the function of eliminating the damage of the excessive accumulated free radicals in the body to biological membranes and other tissues, and the content of the T-SOD can indicate the functional level of an antioxidant system of the body. Liver MDA and SOD levels in mice of each group are shown in Table 7.

TABLE 7 Effect of Natto, fermented soya beans, Soy paste on mouse liver MDA and T-SOD levels

As shown in Table 7, the concentration of MDA in liver was significantly higher in the high-lipid model group than in the blank control group (P <0.05), and the activity of T-SOD in liver was significantly lower than that in the normal control group (P < 0.05). Compared with the high-fat model group, the positive control group, the high, medium and low dosage of the low-salt fermented soya beans and the soybean paste can obviously reduce the MDA level in the liver and improve the SOD activity in the liver (P is less than 0.05). The flavor natto, the less-salt fermented soya beans and the soybean paste can reduce the peroxidation of the organism of the hyperlipidemic mouse and have certain protection effect on the damage of the liver.

3. Influence of natto, fermented soybean and soybean paste on mouse body quality

The body mass of each group of mice after 3 weeks of continuous feeding is shown in table 8.

TABLE 8 influence of Natto, fermented soya beans, Soybean paste on mouse body quality

As can be seen from Table 8, the body mass of each group of mice increased to various degrees by continuous feeding for 3 weeks. Meanwhile, under the condition of feeding high-fat feed, the increase of the body mass of the positive control group and the low, medium and high dose groups of the flavored natto, the low-salt fermented soybeans and the soybean paste is less than that of the high-fat model group, and the flavored natto, the low-salt fermented soybeans and the soybean paste have certain control effect on the increase of the body mass of the mice with the hyperlipidemia.

4. Influence of natto, fermented soybean and soybean paste on organ index of mouse

The organ index of each group of mice is shown in table 9.

TABLE 9 Effect of Natto, fermented soya beans and Soy paste on mouse organ index

As can be seen from table 9, compared with the normal group, the high-fat model group not only changed the heart, spleen and liver indices, but also significantly decreased the kidney index, indicating that the heart, spleen, liver and kidney of the mice in the high-fat model group were damaged to some extent. Compared with a high-fat model group, the positive control group and the flavored natto, the low-salt fermented soybean, the soybean paste low, medium and high dose groups basically improve the heart index, spleen index and kidney index of the mice and reduce the liver index, thereby indicating that the positive control group has relieving and protecting effects on the damage caused by the hyperlipidemia.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of fermented bean products is characterized by comprising the following steps:

(1) soaking soybeans;

(2) performing microwave treatment on the soaked soybeans;

(3) soaking the microwave-treated soybean again to absorb enough water;

(4) the soybeans processed in the step (3) are steamed under pressure;

2. The method according to claim 1, characterized in that the microwave treatment is carried out by: the microwave is firstly carried out for 30-50 min under the power of 100-150W, and then the microwave is carried out for 15-35 min under the power of 400-500W.

3. The method according to claim 1, wherein the soaking time in the step (1) is 4-24 h.

4. The method according to claim 1, wherein the mass ratio of the soybeans to the water in the soaking in the step (3) is 1: 2-4.

5. The method according to claim 1 or 4, wherein the soaking temperature in the step (3) is 20-28 ℃, and the soaking time is 0.5-2 h.

6. The method of claim 1, wherein the pressure cooking conditions are: pressurizing to 0.1MPa, and decocting at 121 deg.C for 15-20 min.

7. The method of claim 1 wherein the soybeans are selected from the group consisting of full, uniform size, no dehulling, no wrinkling, no molding, and no worm damage soybeans.

8. A fermented soybean product produced by the method according to any one of claims 1 to 7.

9. The fermented soybean product according to claim 7, wherein the fermented soybean product is natto, fermented soybeans, soy sauce or fermented bean curd.

10. Use of the fermented soybean product of claim 8 or 9 for the preparation of a composition for preventing hyperlipidemia.