Method for preparing mung bean sour pulp based on freeze drying

Abstract

The invention provides a freeze-drying-based method for more conveniently and quickly preparing mung bean sour slurry with better taste and better flora, which comprises the following steps of: centrifuging the traditionally fermented mung bean sour slurry at a high speed, removing supernatant, taking precipitate, freezing at the temperature of 80 DEG C below zero for 3 hours, and drying into powder (freeze-dried powder) in a freeze dryer. And adding the freeze-dried powder into the unfermented mung bean sour pulp raw stock according to a certain proportion, and carrying out closed fermentation to obtain the newly prepared mung bean sour pulp. The method has the advantages of mellower and richer smell, high content of effective microbial communities, simplicity in operation, short fermentation period and convenience in popularization and application in actual production.

Description

Technical Field

[0001] The invention relates to the field of food processing, and in particular to a method for preparing mung bean physalis based on freeze drying. Background Art

[0002] Mung bean physalis is a traditional beverage with a unique sour and fermented flavor. It is prepared through liquid fermentation of mung bean powder, which involves processes such as mung bean processing, fermentation, and subsequent processing. Microorganisms play a key role in the production of mung bean physalis. Through fermentation, they convert the starch in the mung beans into easily digestible sugars, which also produces the unique sour flavor. In addition, the lactic acid bacteria in mung bean physalis not only provide sourness but also have health benefits such as regulating the intestines and promoting digestion. Therefore, mung bean physalis is not only a delicacy but also a healthy beverage. The production process of mung bean physalis may vary from region to region, but the basic principles are similar, all achieved through mung bean processing and microbial fermentation.

[0003] The traditional mung bean paste production method typically involves soaking, beating, and fermenting the beans. The quality of the mung beans during this process directly impacts the quality of the final product, making the selection of high-quality beans crucial. While traditional, the mung bean paste production process also has limitations, such as long fermentation cycles, low efficiency, and substandard hygiene. With the advancement of technology, new processing techniques, such as freeze-drying, are being applied to mung bean paste production in the hope of improving production efficiency while maintaining the nutritional and sensory qualities of the product.

[0004] Freeze-drying technology is a method that rapidly dries food while preserving its original structure and nutrients. By rapidly freezing the food and then drying it under low pressure, it effectively reduces its moisture content and extends its shelf life. For mung bean physalis, freeze-drying not only significantly shortens its production cycle but also helps preserve its unique taste and nutritional profile. Furthermore, freeze-dried mung bean physalis can be enjoyed as a new healthy food or ready-to-drink beverage, making it convenient for consumers to enjoy on a variety of occasions. Summary of the Invention

[0005] The purpose of the present invention is to develop a method for preparing mung bean paste using freeze-drying technology, so as to improve the production efficiency and quality of mung bean paste, solve the problem of long production cycle of traditional mung bean paste, stabilize the proportion of dominant bacteria, and improve it, enhance the taste and content of beneficial bacteria, make the taste softer, and at the same time utilize the damage during the freeze-drying process to significantly eliminate harmful bacteria, making the paste more stable and suitable for more people.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing mung bean pulp based on freeze drying, comprising the following steps: Step 1: 0.75 kg of mung bean powder and 6 L of water were mixed, stirred for 10 minutes using a low-speed mixer, filtered through a 100-mesh sieve and the residue was discarded, 6 L of water was added to the slurry, and the mixture was covered with plastic film and fermented for 60 hours. The upper white foam was scooped off every 12 hours to obtain mung bean paste made by traditional technology; Step 2: Take 4 L of fermented mung bean pulp, put it into a centrifuge tube and balance it, each weighing 400 g, put it into a centrifuge and centrifuge it at 15°C and 3000 rpm for 15 minutes, remove the supernatant, put the precipitate into a bag, freeze it at -80°C for 24 hours, and then put it into a freeze dryer, freeze-dry it for 48 hours into powder, and store it in a refrigerator; Step 3: Mix 0.5 kg of mung bean powder with 6 L of water, weigh 65 g of the freeze-dried powder in step 2, mix it with mung bean milk, stir it with a low-speed mixer for 10 minutes, filter it through a 100-mesh sieve, discard the residue, add 2 L of water to the slurry, cover it with plastic film, and ferment it for 48 hours. Scoop off the upper white foam every 12 hours to obtain fresh mung bean slurry; Step 4: Take 2L of the mung bean paste fermented in step 3, take another 0.375kg of mung bean powder and 6L of water, stir them with a low-speed mixer for 10 minutes, pass them through a 100-mesh sieve and discard the residue, add 2L of the mung bean paste fermented in step 3 to the paste, seal it with plastic film and ferment it for 24 hours, and scoop off the upper white foam every 12 hours to obtain mung bean paste (expanded culture).

[0007] Preferably, the ratio of mung bean powder to clean water in step 1 should be 1kg:16L.

[0008] Preferably, the upper white foam is continuously scooped off during the 60 hours of fermentation in step 1. The upper white foam is mainly composed of protein, which can prevent the protein from deteriorating and releasing ammonia during the fermentation process, thereby affecting the smell and final taste of the Physalis.

[0009] Preferably, the freezing time in step 2 is 24 hours, and the refrigerated freeze-drying time is 48 hours.

[0010] Preferably, the centrifugation temperature in step 2 should not be too high, and the supernatant should be completely discarded, otherwise the freeze-dried powder will be impure and the freezing time will be increased.

[0011] Preferably, the ratio of the mung bean powder content to the freeze-dried powder content in step 3 should be 1kg:130g.

[0012] Preferably, the fermentation time in step 3 is shortened to 48 hours, reducing the fermentation cycle.

[0013] Preferably, the ratio of old pulp to new pulp in the expansion culture of the winter pulp in step 4 is 1:3.

[0014] Preferably, the fermentation time in step 4 is shortened to 24 hours, greatly reducing the fermentation cycle.

[0015] Beneficial effects of the present invention: The present invention utilizes freeze-dried powder to produce mung bean milk, reversing the traditional mung bean milk production process. Traditional mung bean milk production has a long fermentation cycle, requiring significant manpower and resources, and resulting in long waiting times and a short shelf life, making it difficult to meet market demand in a timely manner. The present invention significantly shortens the production cycle and delivers the product to consumers in the shortest possible time, reducing waste. Furthermore, the present invention boasts a richer dominant bacterial community, with Lactococcus, Leuconostoc, Lactobacillus plantarum, Leuconostoc citracoids, and Bifidobacterium mongoliae significantly performing better than traditional mung bean milk fermentation cycles. Lactococcus and Leuconostoc are dominant strains in the early stages of freeze-dried fermentation, enabling rapid sugar metabolism and creating a low pH environment. Subsequently, Lactobacillus plantarum, which tolerates low pH, takes over as the dominant bacterial community. Its proportion increases continuously during fermentation and remains stable (>60%) after H36. Leuconostoc citracoids initially increases and then decreases. Finally, in the later stages, the proportion of beneficial bacteria, such as Bifidobacterium mongoliae, remains stable, while the proportion of Lactobacillus brevis increases to 2.3%.

[0016] Therefore, the new method for preparing mung bean paste can prepare mung bean paste with better taste and more stable and reasonable bacterial composition more precisely and quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 This is a pH comparison chart of different fermentation methods; Figure 2 This is a comparison chart of TTA in different fermentation methods; Figure 3 This is the change chart of the number of colonies in the fermentation of freeze-dried powder; Figure 4 Schematic diagram of sensory scoring for different fermentation methods; Figure 5 Schematic diagram of total sensory scores for different fermentation methods; Figure 6 A diagram showing product preferences for different genders; Figure 7 The Venn diagram for the composition of freeze-dried powder fermentation bacteria; Figure 8 This is a bar chart of the composition of the freeze-dried powder fermentation flora; Figure 9 Schematic diagram of PCoA_(bacteria) composition of freeze-dried powder fermentation flora. DETAILED DESCRIPTION

[0019] The present invention provides a method for preparing mung bean pulp based on freeze drying, comprising the following steps: Step 1: Take 0.75 kg of mung bean powder and mix it with 6 L of clean water, stir it with a low-speed mixer for 10 minutes, discard the residue after passing it through a 100-mesh sieve, add 6 L of clean water to the slurry, add plastic film and ferment it for 60 hours, and scoop off the upper white foam every 12 hours to obtain mung bean paste made by traditional technology.

[0020] Step 2: Take 4 L of fermented mung bean pulp, put it into a centrifuge tube and balance it, each weighing 400 g, put it into a centrifuge and centrifuge it at 15°C and 3000 rpm for 15 minutes, remove the supernatant, put the precipitate into a bag, put it into a -4°C freezer for 24 hours, then put it into a freeze dryer, freeze-dry it for 48 hours into powder, and store it in a refrigerator.

[0021] Step 3: Mix 0.5 kg of mung bean powder with 6 L of water, weigh 65 g of the freeze-dried powder in step 2, mix it with mung bean milk, stir it with a low-speed mixer for 10 minutes, pass it through a 100-mesh sieve and discard the residue, add 2 L of water to the slurry, add plastic film and ferment for 48 hours, and scoop off the upper white foam every 12 hours to obtain fresh mung bean slurry.

[0022] Step 4: Take 2L of mung bean paste fermented in step 3, take another 0.375kg of mung bean powder and 6L of water, stir with a low-speed mixer for 10 minutes to mix, pass through a 100-mesh sieve and discard the residue, add 2L of mung bean paste fermented in step 3 to the paste, seal with plastic film and ferment for 24 hours, and scoop off the upper white foam every 12 hours to obtain expanded mung bean paste.

[0023] In the present invention, when the traditional mung bean soya bean is initially prepared, the ratio of mung bean powder to clean water should be 1kg:16L. At the same time, the upper white foam needs to be continuously scooped off within 60h or 24h of fermentation in different time periods. The upper white foam, whose main component is protein, can prevent the protein from deteriorating and releasing ammonia during the fermentation process, which affects the smell and final taste of the soya bean.

[0024] In the present invention, the centrifugation temperature cannot be too high and the supernatant should be completely discarded, otherwise the powder after freeze-drying will be impure and the freezing time will be increased. Figure 3 This is a graph showing the changes in the number of colonies during the fermentation of freeze-dried powder.

[0025] In the present invention, when preparing freeze-dried powder, the freezing time should be 24 hours or more to prevent the precipitate after centrifugation from not being completely frozen into a solid state. The refrigerated freeze-drying time is 48 hours until all solid objects are freeze-dried into powder. Otherwise, it needs to be frozen and freeze-dried again.

[0026] In the present invention, the ratio of mung bean powder content to freeze-dried powder content in the preparation of newly prepared mung bean paste should be 1kg:130g, and the fermentation time at this time will be shortened to 48h, which is less than the fermentation time of traditional mung bean paste.

[0027] In the present invention, the ratio of old pulp to new pulp in the newly prepared mung bean pulp is 1:3, and the subsequent fermentation time is shortened to 24 hours. At this time, the pH has tended to be stable, which greatly reduces the fermentation cycle.

[0028] After fermentation, the present invention collects samples of the mung bean physalis for observation and measurement of various quality indicators. The quality indicators include color difference comparison of the mung bean physalis, determination of the fermentation flora, physical and chemical properties, and sensory evaluation. The sensory evaluation includes evaluating the exterior and interior of the physalis. The exterior includes indicators such as specific volume and appearance, and the interior includes indicators such as color, structure, elasticity, toughness, tooth adhesion, and odor. The measurement method is not particularly limited, and a measurement method familiar to those skilled in the art can be used.

[0029] The following provides a clear and complete description of the technical solutions of the present invention, in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only a portion of the embodiments of the present invention, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention. Example 1

[0030] Step 1: Mix 0.75 kg of mung bean powder with 6 L of clean water, stir with a low-speed mixer for 10 minutes to mix, pass through a 100-mesh sieve and discard the residue, add 6 L of clean water to the slurry, cover with plastic film and ferment for 60 hours, scoop off the upper white foam every 12 hours, sample 12-15 ml every 6 hours into a centrifuge tube, and take a total of 6 tubes for measuring pH and microorganisms. Store 2 tubes of samples at 4°C and 4 tubes at -18°C.

[0031] Step 2: Take 4 L of fermented traditional mung bean paste, 0.5 kg of mung bean powder and 6 L of water, stir them for 10 minutes with a low-speed mixer, pass them through a 100-mesh sieve and discard the residue, add 4 L of fermented traditional mung bean paste to the paste, seal it with plastic film and ferment it for 60 hours, remove the upper white foam every 12 hours, sample 12-15 ml into a centrifuge tube every 6 hours, and take a total of 6 tubes for measuring pH and microorganisms. Store 2 tubes of samples at 4°C and 4 tubes at -18°C.

[0032] Step 3: Mix 0.5 kg of mung bean powder with 6 L of water, weigh 65 g of freeze-dried powder, mix it with mung bean milk, stir it with a low-speed mixer for 10 minutes, pass it through a 100-mesh sieve and discard the residue, add 2 L of water to the slurry, cover it with plastic film and ferment it for 60 hours, scoop out the upper white foam every 12 hours, sample 12-15 ml every 6 hours into a centrifuge tube, and take a total of 6 tubes for measuring pH and microorganisms. Store 2 tubes of samples at 4°C and 4 tubes at -18°C.

[0033] Step 4: Take 2L of freshly fermented mung bean pulp, 0.375kg of mung bean powder and 6L of clean water, stir with a low-speed mixer for 10 minutes, filter through a 100-mesh sieve and discard the residue, add 2L of freshly fermented mung bean pulp to the pulp, seal with plastic film and ferment for 60 hours, remove the upper white foam every 12 hours, sample 12-15ml every 6 hours into a centrifuge tube, and take 6 tubes in total for measuring pH and microorganisms. Store 2 tubes of samples at 4°C and 4 tubes at -18°C. Figure 1 This is a pH comparison chart for different fermentation methods. Example 2

[0034] Step 1: Take 1 tube of sample, take out 1 ml of sample and add it to 15 ml of distilled water, mix well, and repeat three times.

[0035] Step 2: Titrate the diluted acid slurry with 0.1 mol / L NaOH to pH 8.3, and record the amount of 0.1 mol / L NaOH used to measure TTA. Figure 2 This is a comparison chart of TTA in different fermentation methods. Example 3

[0036] The quality of the various mung bean pulps prepared in Example 1 was evaluated, including color difference comparison, textural properties determination, and sensory evaluation.

[0037] Sensory evaluation The two types of Physalis in step 2 and step 4 of Example 1 and the Physalis sold on the market were made into edible Physalis noodles without adding any seasoning. Six people were recruited to conduct sensory evaluation and fill in the sensory evaluation form. The consumed Physalis noodles were then stored at 4°C. Figure 4 Schematic diagram of sensory scoring for different fermentation methods. Figure 5 Schematic diagram of total sensory scores for different fermentation methods. Figure 6 A diagram showing product preferences of different genders.

[0038] (2) Color difference comparison The cooled Physalis noodles were placed under a colorimeter to measure the color difference of the different types of Physalis noodles. The evaluation data is shown in Table 1.

[0039] (3) Determination of texture characteristics After cooling, the noodles solidified into a colloid and were placed in a cup to form a cylindrical shape. The texture characteristics of the noodles were then measured. The texture analyzer parameters were: TPA mode, P / 36R aluminum probe, pre-test speed of 1.0 mm / s, test speed of 1.0 mm / s, post-test speed of 3.0 mm / s, compression level of 50%, trigger force of 5 g, and a 5-second interval between compressions. The evaluation data is shown in Table 2.

[0040] Table 1 Comparison of color difference of freeze-dried powder fermented mung bean paste

[0041] SS: Commercially available Physalis LJ: old pulp expansion stage FD: Physalis lyophilized powder Table 2 Sensory scores of freeze-dried powder fermented mung bean syrup

[0042] There is no significant difference in the a and b values ​​in Table 1, but the L value LJ is greater than that of FD and SS.

[0043] In the texture results in Table 2, the hardness of LJ and FD is much higher than that of SS, while there is no significant difference in adhesiveness and springiness. At the same time, the cohesiveness is significantly improved, and the gumminess of LJ is significantly higher than that of FD and SS. Example 4

[0044] Step 1: Take 100 ml of each sample and divide it into two 50 ml centrifuge tubes. After balancing, place them in a centrifuge and centrifuge at 3000 rpm for 15 minutes at 16°C. Remove the supernatant and protein and transfer the remaining sample to a centrifuge tube. Add water to the centrifuge tube to 30 ml and centrifuge at 3000 rpm for 15 minutes. Discard the supernatant and protein.

[0045] Step 2: After balancing the supernatant and protein in step 1, centrifuge at 3000 rpm for 15 minutes and retain.

[0046] Step 3: Combine the starch in step 1 into one tube using two tubes, balance the mixture, centrifuge at 3000 rpm for 15 minutes, and discard the supernatant.

[0047] Step 4: Pool the proteins from the two tubes in step 2 into one tube, balance the mixture, centrifuge at 3000 rpm for 15 minutes, and discard the supernatant.

[0048] Step 5) The starch was dried at 40°C for 24 h, and the protein was freeze-dried at -18°C. The bacterial content was determined. The data are shown in Tables 3, 4, 5, and 6.

[0049] Table 3 Alpha diversity analysis of freeze-dried powder fermentation bacteria

[0050] From the Ace, Chao and other indices, it can be seen that the richness of the bacterial community decreased between 0h and 12h, and the Sob index indicated that the position of the dominant bacterial genus was consolidating.

[0051] There are three levels of Venn, with 3, 11, and 15 species in total. The number of unique bacterial species at 0h is up to 16, which may be related to the bacterial species in the material itself. Figure 7 The Venn diagram of the composition of freeze-dried powder fermentation bacteria is shown below. Figure 8 This is a bar chart of the composition of the freeze-dried powder fermentation flora. Figure 9 Schematic diagram of PCoA_(bacteria) composition of freeze-dried powder fermentation flora.

[0052] Table 4. Composition of dominant bacterial flora in freeze-dried powder fermentation of Physalis graminis (%)_bacteria genus level

[0053] Lactococcus and Leuconostoc are the dominant strains in the early stages of freeze-dried fermentation, rapidly metabolizing sugars and creating a low pH environment. Subsequently, Lactobacillus plantarum takes over as the dominant bacterial community, as it can tolerate low pH.

[0054] Table 5 Dominant bacterial composition of lyophilized powder fermented mung bean Physalis (%) _ bacteria species level

[0055] The proportion of Lactobacillus plantarum continued to increase during the fermentation process and remained stable after H36 (>60%), followed by Leuconostoc citrate, which first increased and then decreased. In the later period, the proportion of beneficial bacteria such as Bifidobacterium nemergonicum remained stable, while the proportion of Lactobacillus brevis increased to 2.3%.

[0056] Table 6 Analysis of freeze-dried fermented fungi composition_fungus_genus

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing mung bean pulp based on freeze drying, characterized in that: The method comprises the following steps: Step 1: 0.75 kg of mung bean powder and 6 L of water were mixed, stirred for 10 min using a low-speed mixer, filtered through a 100-mesh sieve and the residue was discarded, and then 6 L of water was added. The mixture was covered with plastic film and fermented for 60 h, and the upper white foam was removed every 12 h to obtain mung bean paste made by traditional process; Step 2: Take 4 L of fermented mung bean pulp, put it into a centrifuge tube and balance it, each weighing 400 g, put it into a centrifuge at 15°C and 3000 rpm for 15 minutes, remove the supernatant, put the precipitate into a ziplock bag, freeze it at -80°C for 12 hours, put it into a freeze dryer, freeze-dry it for 48 hours into powder, and store it in a refrigerator; Step 3: Mix 0.5 kg of mung bean powder with 6 L of water, weigh 65 g of the freeze-dried powder in step 2, mix it with mung bean milk, stir it with a low-speed mixer for 10 minutes, filter it through a 100-mesh sieve, discard the residue, add 2 L of water to the slurry, cover it with plastic wrap, and ferment it for 48 hours. Scoop off the upper white foam every 12 hours to obtain mung bean slurry (freeze-dried powder method); Step 4: Take 2L of the mung bean paste fermented in step 3, take another 0.375kg of mung bean powder and 6L of water, stir them with a low-speed mixer for 10 minutes, pass them through a 100-mesh sieve and discard the residue, add 2L of the mung bean paste fermented in step 3 to the paste, seal it with plastic film and ferment it for 24 hours, and scoop off the upper white foam every 12 hours to obtain mung bean paste (continuous expansion culture).

2. The method according to claim 1, characterized in that In step 1, the ratio of mung bean powder to clean water should be 1kg:16L.

3. The method according to claim 1, characterized in that During the 60 hours of fermentation in step 1, the upper white foam is continuously scooped off. The main component of the foam is protein, which can prevent the protein from deteriorating and releasing ammonia during the fermentation process, affecting the smell and final taste of the fruit.

4. The method according to claim 1, wherein The freezing time in step 2 is 12 hours, and the refrigeration and freeze-drying time is 48 hours.

5. The method according to claim 1, wherein The centrifugation temperature in step 2 should not be too high, and the supernatant should be completely discarded, otherwise the freeze-dried powder will be impure and the freezing time will be increased.

6. The method according to claim 1, wherein The ratio of mung bean powder content to freeze-dried powder content in step 3 should be 1kg:130g.

7. The method according to claim 1, characterized in that The fermentation time in step 3 can be shortened to 48 hours, reducing the fermentation cycle.

8. The method according to claim 1, characterized in that The volume ratio of the old pulp to the new pulp in step 4 is 1:

3.

9. The method according to claim 1, characterized in that The fermentation time in step 4 can be shortened to 24 hours, greatly reducing the fermentation cycle.

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