A high-stability whole-grain mung bean milk based on staged ultrasound and its preparation method and application

Abstract

The invention discloses a high-stability whole-grain mung bean milk based on staged ultrasound, a preparation method and an application thereof. After the mung beans are processed by beating, enzymolysis, staged ultrasound, homogenization, sterilization and the like, the mung bean milk is obtained. The staged ultrasound treatment reduces the particle size in the mung bean milk, increases the ζ-potential value of the mung bean milk, improves the flavor quality of the mung bean milk, increases the stability of the mung bean milk, and provides a new method for the application of ultrasound in food processing.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to a high-stability whole-grain mung bean milk based on staged ultrasound, and a preparation method and application thereof. Background Art

[0002] Mung beans have been cultivated and eaten in China for more than 2,000 years and are one of the main grain beans. Mung beans are widely planted in poor land areas due to their short growth period, high flexibility in sowing period, wide adaptability, favorable land use and protection, high economic benefits, and strong pesticide resistance. Not only that, mung beans are rich in nutrients, and their protein content is between 19% and 33%, which is two to three times that of ordinary crops. Mung beans also contain nutrients such as dietary fiber, β-carotene, vitamin E, calcium, potassium, magnesium, iron, zinc, selenium, as well as functional ingredients such as functional oligosaccharides, flavonoids, and stigmasterols. Chinese people often drink mung bean soup in summer to relieve heat and cool down. At the same time, mung beans also have the effects of clearing heat and detoxifying and protecting the liver, and are known as "the best food, the long-term valley of saving the world".

[0003] However, there is a lack of deep-processing products of mung beans in my country, resulting in low added value. In recent years, with the development of my country's society and the improvement of people's living standards, the plant-based alternative milk industry is rapidly developing into a mainstream industry of future food. According to surveys, the growth rate in Europe, the United States, Australia and other regions is between 8% and 15%, which reflects that plant milk substitutes are becoming more and more popular around the world. Therefore, the development of plant-based milk substitutes using mung beans as raw materials can not only increase the added value of mung beans and increase farmers' income, but also make full use of the health benefits of mung beans. Compared with mung bean soup, whole-grain mung bean milk fully preserves the active ingredients of mung beans during the processing process, avoids the waste of nutritional components, and is easier to achieve the nutritional benefits of mung beans.

[0004] However, insoluble proteins and solid particles are often produced during the production of mung bean milk, resulting in problems such as rough taste, liquid stratification, and poor stability. At the same time, the beany and astringent taste unique to legumes also need to be solved urgently. These problems directly affect the production and promotion of mung bean milk products.

[0005] Ultrasound is a physical processing technology with the advantages of being simple, safe, efficient and environmentally friendly. The use of ultrasound has been widely used in many fields such as food and beverage processing, processing in the dairy industry, and processing of milk protein concentrates. However, the application of ultrasound in the processing of mung bean milk has not been reported. In addition, during the research on mung bean milk processing, the inventors found that traditional ultrasound would produce a thermal effect, leading to the denaturation and even aggregation of proteins in mung bean milk, which is not conducive to the stability of the product. In order to avoid the adverse effects of ultrasonic thermal effects, it is usually necessary to control the temperature of the ultrasonic equipment, but the conventional temperature control methods such as electric energy or circulating water have high energy consumption and serious energy waste. Summary of the invention

[0006] In order to solve the above technical problems, improve the flavor and stability of mung bean milk, and realize the effective application of ultrasonic technology in the processing of mung bean milk, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides a method for preparing high-stability whole-seed mung bean milk based on staged ultrasound, comprising beating mung beans and sterilizing the mung beans. The preparation method further comprises the step of performing staged ultrasound treatment after beating the mung beans.

[0008] Preferably, the number of staged ultrasounds is ≥ 3, for example: 3 times, 4 times, 5 times.

[0009] Preferably, the interval between two adjacent ultrasounds is ≥5 min, more preferably 5-10 min, for example: 5 min, 6 min, 7 min, 8 min, 9 min, 10 min.

[0010] Preferably, the ultrasonic power of each ultrasound is 200-600W, for example: 200W, 250W, 300W, 350W, 400W, 450W, 500W, 550W, 600W.

[0011] Preferably, the duration of each ultrasound treatment is less than 10 min, for example: 4 min, 5 min, 6 min, 7 min, 8 min, 9 min.

[0012] In a specific embodiment of the present invention, the number of ultrasonic treatments is 3 times, and the ultrasonic powers are 200-500W, 300-400W and 300-600W respectively.

[0013] Preferably, the ultrasonic powers are different for two consecutive times.

[0014] Furthermore, the ultrasonic power increases in sequence, for example, the ultrasonic power is 300W, 400W and 500W in sequence; or the ultrasonic power is 200W, 300W and 600W in sequence.

[0015] Furthermore, the ultrasonic power decreases in sequence, for example, the ultrasonic power is 500W, 400W and 300W in sequence.

[0016] Preferably, the temperature of the staged ultrasound is ≤35°C, for example: 15°C, 20°C, 25°C, 30°C, 35°C.

[0017] Preferably, the preparation method further comprises the step of enzymatic hydrolysis before the staged ultrasound.

[0018] Preferably, the enzyme for enzymolysis comprises one or more combinations of protease, amylase, saccharifying enzyme or cellulase.

[0019] Preferably, the enzymatic hydrolysis is a two-step enzymatic hydrolysis, and more preferably, an enzyme inactivation step is included between the two steps of enzymatic hydrolysis.

[0020] Preferably, the enzymes used in the two-step enzymolysis are different, wherein the enzymes used in the first-step enzymolysis are protease and amylase, and the enzymes used in the second-step enzymolysis are saccharifying enzyme and cellulase.

[0021] Preferably, the added amount of the protease is 0.002-0.008% of the mung bean milk, for example: 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%.

[0022] Preferably, the amount of amylase added is 0.15-0.3% of mung bean milk, for example: 0.15%, 0.17%, 0.2%, 0.22%, 0.25%, 0.27%, 0.3%.

[0023] Preferably, the added amount of the saccharifying enzyme is 0.2-0.5% of the mung bean milk, for example: 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%.

[0024] Preferably, the added amount of the cellulase is 0.15-0.3% of the mung bean milk, for example: 0.15%, 0.17%, 0.2%, 0.22%, 0.25%, 0.27%, 0.3%.

[0025] Preferably, the preparation method further comprises a homogenization step before sterilization.

[0026] In a specific embodiment of the present invention, mung beans are sequentially subjected to pulping, enzymolysis, staged ultrasound, homogenization, and sterilization to obtain mung bean milk.

[0027] In a second aspect, the present invention provides a mung bean milk prepared according to the preparation method described in the first aspect.

[0028] In a third aspect, the present invention provides a composition comprising the mung bean milk described in the second aspect.

[0029] Preferably, the composition is a food or a medicine.

[0030] In a fourth aspect, the present invention provides application of the preparation method described in the first aspect in improving the stability of whole-grain mung bean milk.

[0031] In a fifth aspect, the present invention provides the use of the mung bean milk described in the second aspect in the preparation of food, feed, health products, cosmetics or medicines.

[0032] Preferably, the food further comprises auxiliary materials allowed to be added to food.

[0033] Preferably, the medicine further comprises excipients allowed to be added to drugs.

[0034] Beneficial effects of the present invention:

[0035] The invention adopts staged ultrasonic treatment of mung bean milk, reduces the particle size in the mung bean milk, increases the ζ-potential value of the mung bean milk, improves the flavor quality of the mung bean milk, increases the stability of the mung bean milk, and provides a new method for the application of ultrasound in food processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Shown is the effect of staged ultrasound on the particle size distribution of mung bean milk;

[0037] Figure 2 Shown is the effect of staged ultrasound on the sensory quality of mung bean milk;

[0038] Figure 3 The following are the appearances of mung bean milk samples, where (a) to (e) are comparative examples 1-5, and (f) to (h) are examples 1-3;

[0039] Figure 4 Shown is the effect of staged ultrasound on the amount of flavor substances in mung bean milk. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below in conjunction with the embodiments and drawings, and the advantages and features of the present invention will become clearer as the description proceeds. However, it should be understood that the embodiments are merely exemplary and do not limit the scope of the present invention.

[0041] It should be noted that the experimental methods used in the following examples are all conventional methods in the art unless otherwise specified. Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention relates.

[0042] Example 1

[0043] 1.1 Pulping: Take 50g of mung bean seeds, wash, dry and crush them, dissolve them in 90℃ pure water with a mass ratio of 1:8 to mung bean and keep for 3 minutes, then cool to 60℃.

[0044] 1.2 One-step enzymatic hydrolysis: add alkaline protease (0.005%) to the sample, and then stir at 60°C for 20 minutes. Then add α-amylase (0.2%) and stir for another 10 minutes. Then raise the temperature to 95°C and keep it for 10 minutes to inactivate the enzyme.

[0045] 1.3 Two-step enzymatic hydrolysis: Add saccharifying enzyme (0.3%) and cellulase (0.2%) to the sample and hydrolyze at 55°C for 1 hour. Then filter with 200 mesh filter cloth and add 1.5% rice oil to the filtrate.

[0046] 1.4 Ultrasound: Disperse the mixture obtained in 1.3 at 6000 rpm for 2 minutes, and perform staged ultrasound at room temperature (20-25°C) (first stage 5 min, 300 W, stand for 5 min; second stage 5 min, 400 W, stand for 5 min; third stage 5 min, 500 W).

[0047] 1.5 Homogenization and sterilization: The mixture after ultrasonic treatment was homogenized twice under a pressure of 40 MPa, and then sterilized at 135°C for 5 seconds to obtain a mung bean milk sample.

[0048] Example 2

[0049] The preparation process of mung bean milk is the same as that of Example 1, except that the ultrasonic process is as follows: the first stage is 5 min 500 W, standing for 5 min, the second stage is 5 min, 400 W, standing for 5 min; the third stage is 5 min, 300 W.

[0050] Example 3

[0051] The preparation process of mung bean milk is the same as that of Example 1, except that the ultrasonic process is as follows: the first stage is 5 min, 200 W, and standing for 5 min; the second stage is 5 min, 300 W, and standing for 5 min; the third stage is 5 min, 600 W.

[0052] Comparative Example 1

[0053] The preparation process of mung bean milk is the same as that of Example 1, except that there is no ultrasonic treatment step.

[0054] Comparative Example 2

[0055] The preparation process of mung bean milk is the same as that of Example 1, except that the ultrasonic process is: 300W, 15min.

[0056] Comparative Example 3

[0057] The preparation process of mung bean milk is the same as that of Example 1, except that the ultrasonic process is: 400W, 15min.

[0058] Comparative Example 4

[0059] The preparation process of mung bean milk is the same as that of Example 1, except that the ultrasonic process is: 500W, 15min.

[0060] Comparative Example 5

[0061] The preparation process of mung bean milk is the same as that of Example 1, except that the ultrasonic process is: 300 W, 7.5 min, let stand for 5 min; 500 W, 7.5 min.

[0062] Mung bean milk sample testing

[0063] 1. Particle size of mung bean milk: The particle size of the sample of Example 1 and the sample of Comparative Example 1 was tested. The results are shown in Figure 1 .

[0064] like Figure 1 As shown, the particle size distribution of all mung bean milk samples is between 0.1 and 100 μm. Both samples show a bimodal distribution. The average particle size of mung bean milk in Comparative Example 1 is 1.998 μm, and the average particle size of mung bean milk in Example 1 is 1.447 μm. The smaller the particle size in the plant beverage, the better the stability of the plant beverage. Figure 1 The results showed that the step-by-step ultrasonic treatment significantly reduced the particle size of mung bean milk, which was beneficial to maintaining the stability of mung bean milk.

[0065] 2. Zeta potential value of mung bean milk

[0066] The ζ-potential values ​​of the mung bean milk samples of Example 1 and Comparative Example 1 were measured. The results are shown in Table 1.

[0067] Table 1 ζ-potential values ​​of mung bean milk samples

[0068]

[0069] It can be seen from Table 1 that the ζ-potential value of the sample in Example 1 is -26.5 mV, and the ζ-potential value of the sample in Comparative Example 1 is -22.3 mV. The absolute value of the ζ-potential value of Example 1 is 18.8% higher than that of Comparative Example 1, and the difference between the two is significant.

[0070] Zeta potential is a key parameter for evaluating the stability of plant-based beverages. The larger the absolute value of the Zeta potential, the stronger the repulsion between particles, the smaller the probability of aggregation between particles, and the more stable the emulsion. The results in Table 1 show that the mung bean milk treated with staged ultrasound has a higher surface charge and a higher absolute value of zeta potential. This indicates that staged ultrasound treatment can enhance electrostatic repulsion, inhibit the aggregation of particles, and significantly improve the stability of mung bean milk.

[0071] 3. Sedimentation rate of mung bean milk

[0072] Add 10 mL of mung bean milk to a 15 mL centrifuge tube and centrifuge at 4000 r / min for 30 min. After discarding the supernatant, accurately weigh the centrifuge tube and the precipitate mass, and calculate the centrifugal sedimentation rate. Perform three parallel measurements for each sample and take the average value.

[0073]

[0074] The above method was used to measure the precipitation rate of the mung bean milk samples of Examples 1-3 and Comparative Examples 1-5. The results are shown in Tables 2 and Figure 3 .

[0075] Table 2 Sedimentation rate of mung bean milk samples

[0076]

[0077] As can be seen from Table 2, compared with Comparative Example 1, the precipitation rates of Examples 1-3 were reduced by 5.75%, 3.26%, and 2.16%, respectively, and the differences reached the significance level, and the difference between Example 1 and Examples 2-3 also reached the significance level, indicating that staged ultrasound improved the stability of mung bean milk. Compared with Comparative Example 1, the precipitation rates of Comparative Examples 2-5 were increased by 9.18%, 10.4%, 4.07%, and 3.37%, respectively, and the differences reached the significance level. This indicates that due to the long time of the first stage of ultrasound, the thermal effect of ultrasound caused the denaturation and even aggregation of proteins in the mung bean milk, reducing the stability of the product; and due to the low degree of particle fragmentation in the mung bean milk caused by the second stage of ultrasound, the stability of the mung bean milk was poor.

[0078] 4. Sensory evaluation of mung bean milk

[0079] The color, aroma, taste, texture and overall acceptance of the mung bean milk samples of Examples 1-3 and Comparative Examples 1-5 were evaluated according to Table 3. The panel consisted of 10 personnel trained in sensory evaluation. A 9-point rating system was used, where 1 = very dislike, 5 = average, and 9 = very like. The results are shown in Table 3. Figure 2 , Figure 3 and Table 4.

[0080] Table 3 Sensory evaluation table of mung bean milk

[0081]

[0082] Table 4 Sensory evaluation of mung bean milk samples

[0083]

[0084] Depend on Figure 2 As can be seen from Table 4, compared with Comparative Example 1, the sensory scores of Examples 1-3 increased by 39.3%, 21.4%, and 14.3%, indicating that staged ultrasound significantly improved the quality of mung bean milk. Compared with Comparative Example 1, the sensory scores of Comparative Examples 2-5 decreased by 37.5%, 50%, 35.7%, and 0%, respectively, indicating that one-stage ultrasound or two-stage ultrasound reduced the quality of mung bean milk.

[0085] like Figure 3As shown, Examples 1-3 ((f) to (h)) have good uniformity and no stratification, while the mung bean milk of Comparative Example 1 has stratification and flocculation, and the stratification of Comparative Examples 2-5 ((a) to (e)) is more obvious. This further illustrates that staged ultrasound significantly improves the quality of mung bean milk, while one-stage ultrasound or two-stage ultrasound easily leads to denaturation or even aggregation of proteins in mung bean milk, which is not conducive to product stability and reduces the quality of mung bean milk.

[0086] 5. Determination of volatile flavor substances in mung bean milk

[0087] The volatile flavor substances in the samples of Example 1 and Comparative Example 1 were determined by GC-MS method. The results are shown in Tables 5 and Figure 4 .

[0088] Table 5 Volatile flavor substances content in mung bean milk (μg / kg)

[0089]

[0090]

[0091] From Table 5 and Figure 4 It can be seen that compared with the sample of Comparative Example 1, the contents of undesirable flavor substances such as 1-pentanol, 1-hexanol, 1-octen-3-ol, hexanal, octanal, nonanal, trans, trans-2,4-decadienal, and 2-pentylfuran in Example 1 are significantly reduced, and pleasant ethyl acetate is produced, indicating that staged ultrasound significantly improves the flavor of mung bean milk and enhances the quality of mung bean milk.

[0092] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A method for preparing high-stability whole-grain mung bean milk based on staged ultrasound, characterized in that: The following steps are involved: Pulp mung beans; Primary enzymatic hydrolysis: add 0.002-0.008% alkaline protease to the mung bean slurry for enzymatic hydrolysis, then add 0.15-0.3% α-amylase for stirring enzymatic hydrolysis to inactivate the enzyme; Secondary enzymolysis: adding 0.2-0.5% saccharifying enzyme and 0.15-0.3% cellulase to the primary enzymolysis solution for secondary enzymolysis and filtering to obtain a filtrate; Ultrasound: the filtrate is subjected to staged ultrasonic treatment at room temperature, the number of staged ultrasonic treatment is 3 times, the ultrasonic power is 200-500W, 300-400W and 300-600W respectively, and the ultrasonic power of two adjacent ultrasonic treatments is different; After homogenization and sterilization, mung bean milk is obtained.

2. The preparation method according to claim 1, characterized in that: Each ultrasound session lasted less than 10 minutes.

3. The preparation method according to claim 1, characterized in that: The ultrasonic powers are 300W, 400W and 500W respectively.

4. The preparation method according to claim 1, characterized in that: The method also includes the step of adding rice oil to the filtrate.

5. Use of the method according to any one of claims 1 to 4 in improving the stability of whole-grain mung bean milk.

6. A mung bean milk, characterized in that: The mung bean milk is prepared according to any one of the preparation methods described in claims 1-4.

7. Use of the mung bean milk according to claim 6 in the preparation of food, feed, health products, cosmetics or medicines.

Images