Method for preparing micro-endosperm corn plant-based yoghurt through enzymolysis debitterizing and product

Abstract

The invention discloses a method for preparing micro-endosperm corn plant-based yoghourt through enzymolysis and bitterness removal and a product, and belongs to the technical field of fermentation. According to the invention, flavourzyme, glutamine transaminase and alpha-amylase are combined to carry out enzymolysis treatment on a micro-endosperm corn fermentation base, and hydrophobic amino acids at the tail ends of proteins are removed by directionally hydrolyzing the proteins before fermentation, so that the bitter taste of the yoghourt product is effectively reduced; more importantly, the stability of a protein gel network structure is enhanced through a synergistic enzymolysis effect, energy is provided for subsequent strain fermentation, and the purposes of improving the fermentability of the strain and improving the yield of the microendosperm corn plant-based yoghurt are achieved by combining the subsequent optimization of a preparation process of the microendosperm corn plant-based yoghurt and determining the optimal sugar addition amount, the fermentation agent inoculation amount and the fermentation time. The purpose of improving the quality and the taste of the yoghourt is achieved, the brand-new high-quality micro-endosperm corn plant-based yoghourt is prepared, industrialization of micro-endosperm corn is promoted, and important data support is provided for research of the preparation technology of the plant yoghourt in China.

Description

Technical Field

[0001] The invention relates to the technical field of fermentation, and more particularly to a method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering and a product thereof. Background Art

[0002] In recent years, with the continuous iteration and upgrading of consumer demand, plant-based beverages have ushered in development opportunities, among which plant-based substitutes for dairy products have become the market leader. Compared with yogurt made from animal protein, plant-based yogurt products have lower cholesterol and lactose content, which reduces the occurrence of lactose intolerance and has functional characteristics such as preventing cardiovascular diseases. The development of plant-based yogurt products can effectively reduce the demand for raw cow milk and alleviate the pressure on milk sources, and has great development space in the future yogurt market.

[0003] At present, the plant-based yogurts sold in my country are mainly made from soybeans, coconuts, and almonds, and the protein sources are relatively single. High-protein "micro-endosperm corn" is a new type of non-GMO corn variety, the main feature of which is that the protein content of corn kernels can reach more than 20% during the mature stage. In view of the current situation of the plant yogurt market with a single taste and no innovation in raw materials, a new type of corn-based plant yogurt is developed. The product not only preserves the most nutritious active germ components of corn, but also meets the market's diversified consumption structure demand for plant protein and coarse grains, and has broad development prospects and economic value.

[0004] There are currently two main problems with micro-endosperm corn plant-based yogurt. One is that the product has a certain bitterness, and the other is that the product texture and stability are poor. This is mainly because the protein composition of micro-endosperm corn raw materials is rich in hydrophobic amino acids such as leucine, proline, and alanine. On the one hand, during the preparation of yogurt, the cooking and fermentation processes cause the structure of corn protein to denature and hydrolyze, exposing the hydrophobic amino acid ends wrapped inside, stimulating the taste buds to produce bitterness. Therefore, the improvement effects of methods such as adding aroma components to the raw materials or masking with acidulants are not ideal; on the other hand, plant protein has poor solubility and low bioavailability, resulting in incomplete microbial fermentation and rough and unstable gel structure, which in turn affects the texture and stability of the product, resulting in problems such as rough taste and heavy powdery feel.

[0005] Therefore, how to overcome the negative effects of plant-based products and develop a method and product for enzymatic debittering to prepare micro-endosperm corn plant-based yogurt is an urgent problem to be solved by technicians in this field. Summary of the invention

[0006] In view of this, the present invention provides a method and product for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering. The present invention uses flavor protease, glutamine transaminase and α-amylase to enzymatically hydrolyze the micro-endosperm corn fermentation base, directionally hydrolyze the protein before fermentation, remove the hydrophobic amino acids at the end of the protein, and reduce the bitterness of the product; more importantly, through the synergistic enzymatic hydrolysis, energy is provided for subsequent bacterial fermentation, the stability of the protein gel network structure is enhanced, and combined with the subsequent optimization of the preparation process of micro-endosperm corn plant-based yogurt, the optimal amount of sugar added, the amount of starter inoculation, and the fermentation time are determined, so as to achieve the purpose of improving the fermentability of the strain, improving the texture and taste of the yogurt, and preparing a new micro-endosperm corn plant-based yogurt with excellent quality, which provides a basis for the research and development of micro-endosperm corn plant-based yogurt.

[0007] One of the purposes of the present invention is to provide a method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering, the specific steps of which are as follows:

[0008] S1. Preparation of micro-endosperm corn fermentation medium

[0009] S11. Select dry corn kernels without moldy kernels, add water and boil for 30 minutes to hydrate and swell, remove and rinse, add 5 times the mass of pure water of dry corn kernels, wet grind with a colloid mill to obtain corn syrup, and set aside;

[0010] S12. Add flavor protease, glutamine transaminase and α-amylase, mix well, and perform enzymolysis at a constant temperature;

[0011] S13. After the enzymatic hydrolysis is completed, sterilization is performed for the first time, and the micro-endosperm corn fermentation base is obtained after cooling and filtration;

[0012] S2. Preparation of micro-endosperm corn plant-based yogurt

[0013] S21. Preparation: Weigh a certain amount of glucose, sugar, and inulin, add to the micro-endosperm corn fermentation base, high-speed shear for 2 minutes, and mix evenly;

[0014] S22. Homogenization: homogenize 3 times at 45 MPa;

[0015] S23. Sterilization: maintain at 95-100℃ for 15min, second sterilization;

[0016] S24. Cooling and inoculation: Cool naturally to 40-45°C, add direct-injection yogurt starter, and mix well;

[0017] S25. Fermentation: fermenting the inoculated mixed milk;

[0018] S26. Refrigerated post-ripening: After fermentation is completed, the micro-endosperm corn plant-based yogurt is quickly cooled to room temperature and then refrigerated at 4°C for 12 hours.

[0019] Preferably, in S12, the enzyme activity of the flavor protease is 5000-6000 U / g, the enzyme activity of the glutamine transaminase is 100-200 U / g, the flavor protease: glutamine transaminase = 2:1, and the total addition amount of the flavor protease and glutamine transaminase is 0.05-1.0% of the mass of the corn syrup; the enzyme activity of the α-amylase is 20000 U / g, and the addition amount is 0.1-0.3% of the mass of the corn syrup.

[0020] The beneficial effects of the above technical scheme are as follows: flavor protease and glutamine transaminase can be used to hydrolyze proteins and remove hydrophobic amino acids at the ends of proteins before fermentation, and the degree of protein cross-linking can be promoted through catalysis, thereby reducing the exposure of hydrophobic amino acids, effectively reducing bitterness, enhancing the gel network structure of proteins, and improving the texture of yogurt; on the other hand, the small molecule peptides and amino acids produced by enzymatic hydrolysis provide energy for subsequent fermentation, promote the reproduction and acid production of fermentation bacteria, improve the fermentability of yogurt, and shorten the time for yogurt to reach the end of fermentation; the macromolecular starch particles in micro-endosperm corn kernels will affect the taste and stability of yogurt, and the enzymatic hydrolysis and liquefaction of α-amylase hydrolyzes the starch in the raw materials into dextrin, maltose and glucose, removing the undesirable powdery feel of yogurt, increasing the delicate and smoothness of the product, and can also increase the sugar content in the corn fermentation base that can be used for fermentation, reduce the amount of exogenous sugar added, promote microbial acid production, and improve the utilization rate of raw materials.

[0021] More preferably, in S12, the enzymatic hydrolysis is performed at 45-65° C. for 20-60 min.

[0022] Preferably, in S12, the corn slurry is stirred 2 to 3 times during the enzymatic hydrolysis.

[0023] Preferably, in S13, the first sterilization is sterilization at 95° C. for 15 min.

[0024] Preferably, in S21, based on the mass of the micro-endosperm corn fermentation substrate: the glucose:white sugar=2:3, the added amount of the glucose and white sugar is 4-8%; the added amount of the inulin is 3%.

[0025] The beneficial effects of the above technical solution are as follows: the micro-endosperm corn fermentation base is hydrolyzed during the early enzymatic treatment to produce some glucose, which can be used for lactic acid fermentation. However, compared with the lactose content in cow's milk, the carbohydrates in the micro-endosperm corn raw materials that can be used by the bacteria for fermentation are still relatively small, which directly affects the fermentation speed of the micro-endosperm corn plant-based yogurt and the taste of the product, so additional carbon sources are required. Inulin has more hydrophilic groups and can form a good gel structure after combining with water. It can be used as a stabilizer and fat substitute for yogurt to increase the viscosity and water holding capacity of yogurt. Inulin also has prebiotic properties and can be added to yogurt as a prebiotic ingredient. It can not only increase the total number of lactic acid bacteria in yogurt but also enhance the survival time of probiotics during storage.

[0026] Further preferably, in S21, based on the mass of the micro-endosperm corn fermentation base: the added amount of the glucose and white sugar is 6%, and the glucose:white sugar=2:3; the added amount of the inulin is 3%.

[0027] The beneficial effect of adopting the above technical scheme is: when the amount of sugar added is too low, most of it is decomposed, absorbed and converted into lactic acid, resulting in insufficient overall sweetness of yogurt, and when the amount added is too high, the yogurt tastes too sweet and greasy, and the sensory score is reduced. Taking all factors into consideration, the most suitable amount of sugar added is 6%. Preferably, in S24, the direct-cast fermentation agent is selected from a combination of two or more of thermophilic Streptococcus, Lactobacillus acidophilus, Bifidobacterium lactis, Lactobacillus delbrueckii subspecies Bulgarian, Lactobacillus casei, and Lactococcus lactis diacetyl subspecies.

[0028] Preferably, the addition amount of the direct-injection starter is 0.1-0.5% based on the mass of the micro-endosperm corn fermentation base.

[0029] Further preferably, based on the mass of the micro-endosperm corn fermentation base, the addition amount of the direct-injection starter is 0.3%.

[0030] The beneficial effects of the above technical solution are as follows: if the inoculation amount of the starter is too low, the acid production rate of the yogurt is slow, the yogurt fermentation is incomplete, and the texture is loose; if the addition amount of the starter is too high, the acid production is too much, the protein denaturation is accelerated, the coagulation time is shortened, the whey precipitation is obvious, and the acidity is too high, the taste is not harmonious, and the sensory score is reduced. Based on the sensory score and acidity, the most suitable addition amount of the starter is 0.3%.

[0031] Preferably, in S25, the fermentation is performed at 43° C. for 3 to 7 hours.

[0032] Further preferably, in S25, the fermentation is carried out at 43° C. for 4 h.

[0033] The beneficial effects of adopting the above technical scheme are as follows: a large amount of aromatic substances will be produced in the yogurt during the fermentation process, but when the fermentation time is short, the accumulation of aromatic substances is insufficient and the flavor deteriorates; after the fermentation time lasts for 5 hours, the acidity continues to increase, but as time goes by, the whey precipitation phenomenon increases and the sensory quality decreases. Considering the production cost, the most suitable fermentation time is 4 hours.

[0034] The second object of the present invention is to provide a micro-endosperm corn plant-based yogurt.

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

[0036] (1) This paper uses the "Huajian No. 1" high-oil and high-protein micro-endosperm corn variety as raw material to develop plant-based yogurt products, and through research, a new micro-endosperm corn plant-based yogurt with good fermentation performance, uniform and stable texture, and delicate taste is prepared. While innovating, it meets the dual consumption needs of modern consumers for whole grains and plant protein food diets, conforms to the global concept of sustainable food development, reducing carbon emissions, and the general trend of the development of the healthy food market. It is the best breakthrough to promote the industrialization of micro-endosperm corn, and also provides important data support for the research on the preparation process of plant yogurt in my country.

[0037] (2) After enzymatic hydrolysis of micro-endosperm corn fermentation base, the content of free hydrophobic amino acids in corn pulp increased by 16.26 mg / mL compared with that before enzymatic hydrolysis, indicating that the hydrophobic amino acids at the end that cause bitterness after protein hydrolysis are removed and become free amino acids. The free amino acids will not have a significant effect on the product flavor, thereby significantly reducing the bitterness of yogurt; the time for the yogurt sample prepared after fermentation base enzymatic hydrolysis to reach the fermentation end point was shortened from 4h to 3h, and the acidity increased by 19.3°T when fermented to 6h. The yogurt sample prepared after fermentation base enzymatic hydrolysis had no obvious bitter taste, and the texture was delicate and smooth without powdery feeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0039] Figure 1 This is Example 2, the effect of the addition amount of flavor protease and glutamine transaminase on the sensory score of micro-endosperm corn plant-based yogurt.

[0040] Figure 2 This is Example 2, the effect of the addition amount of flavor protease and glutamine transaminase on the water holding capacity of micro-endosperm corn plant-based yogurt.

[0041] Figure 3 This is Example 3, the effect of the amount of α-amylase added on the quality of fermentation base and micro-endosperm corn plant-based yogurt.

[0042] Figure 4 This is Example 4, the effect of enzymatic hydrolysis time on the quality of fermentation base and micro-endosperm corn plant-based yogurt.

[0043] Figure 5 This is Example 5, the effect of enzymatic hydrolysis temperature on the quality of fermentation base and micro-endosperm corn plant-based yogurt.

[0044] Figure 6 To study the effect of enzymatic treatment of fermentation base on the fermentation performance of micro-endosperm corn plant-based yogurt.

[0045] Figure 7 Scanning electron micrographs of micro-endosperm corn plant-based yogurt prepared before (a) and after (b) fermentation-based enzymatic hydrolysis treatment. DETAILED DESCRIPTION The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0046] The micro-endosperm corn used in each embodiment is the "Huajian No. 1" corn commercially available from Guangxi Yibao Oil Corn Co., Ltd., and the total starch in the corn kernel dry basis is ≥25%, the protein is ≥20%, and the fat is ≥24%.

[0047] The starter is commercially available, such as direct-injection yogurt fermentation bacteria sold by DSM (China) Co., Ltd. and Danisco (China) Co., Ltd.

[0048] 1. Determination of water holding capacity:

[0049] Accurately weigh 10g of yogurt sample, place it in a 50mL centrifuge tube, centrifuge it at 5000r / min at 4℃ for 15min, discard the supernatant, weigh the remaining precipitate, and calculate the water holding capacity as follows:

[0050]

[0051] Where: WHC——water holding capacity of yogurt, %

[0052] m 0 ——Mass of centrifuge tube, g

[0053] m 1 ——Yogurt sample mass, g

[0054] m 2 ——Mass of the remaining sediment and centrifuge tube, g

[0055] 2. Determination of texture characteristics:

[0056] The TA11 / 1000 probe was used to analyze the hardness, elasticity, cohesion, chewiness and adhesiveness of yogurt. Test conditions: TPA mode, TA11 / 1000 probe, target value: 10mm, test speed: 1.0mm / s; trigger point load: 5g.

[0057] 3. Scanning electron microscope (SEM)

[0058] The central part of each group of yogurt samples was selected, frozen in a -80°C refrigerator overnight, and then vacuum freeze-dried. After gold plating, the microstructure of the yogurt was observed using a scanning electron microscope.

[0059] 4. Sensory evaluation:

[0060] The sensory evaluation method was optimized based on GB19302-2010 "National Food Safety Standard Fermented Milk". A sensory evaluation panel was composed of 10 food professionals (5 men and 5 women), and the panel members scored the yogurt samples item by item according to Table 1. The scoring content included the yogurt tissue state, taste, flavor and color, with a full score of 100 points, and the results were averaged.

[0061] Table 1 Sensory score table of micro-endosperm corn plant-based yogurt

[0062]

[0063]

[0064] 5. Determination of titratable acidity

[0065] Accurately weigh 5g of yogurt sample, add 20mL of distilled water that has been boiled and cooled to room temperature, then add 2 drops of 0.5% phenolphthalein indicator, mix well, and titrate it with 0.1mol / LNaOH standard solution until it turns slightly red, and keep it from fading within 30s. Read the volume of NaOH standard solution consumed, substitute it into the formula for calculation, and the acidity value of yogurt is expressed in Girner degrees (°T).

[0066]

[0067] Where: X——yogurt acidity, °T

[0068] C——Concentration of NaOH standard solution, mol / L

[0069] V——The volume of NaOH standard solution consumed during titration, mL

[0070] M——mass of yogurt sample, g

[0071] 0.1——Theoretical definition of acidity: NaOH molar concentration, mol / L

[0072] Example 1

[0073] In view of the quality problems existing in plant-based yogurt products, the present invention provides a method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering, comprising the following steps:

[0074] S1. Preparation of micro-endosperm corn fermentation medium

[0075] S11. Select dry corn kernels with micro-endosperm and no moldy kernels, add water and boil for 30 minutes to hydrate and swell, remove and rinse, add 5 times the mass of pure water of dry corn kernels, use a colloid mill to wet grind for 8 minutes to obtain corn syrup, and set aside;

[0076] S12. Add flavor protease, glutamine aminotransferase and α-amylase based on the mass of corn syrup, mix well, and perform enzymolysis at 45-65° C. for 20-50 min, stirring the corn syrup 2-3 times during the enzymolysis;

[0077] S13. After the enzymatic hydrolysis is completed, sterilize at 95°C for 15 min, cool and filter through 120 mesh to obtain micro-endosperm corn fermentation base;

[0078] S2. Preparation of micro-endosperm corn plant-based yogurt

[0079] S21. Preparation: Based on the mass of micro-endosperm corn fermentation base, weigh 6% glucose and white sugar, wherein glucose: white sugar = 2:3, 3% inulin, add to the micro-endosperm corn fermentation base, high-speed shear 2min mixing;

[0080] S22. Homogenization: homogenize 3 times at 45 MPa;

[0081] S23. Sterilization: Second sterilization at 95-100°C for 15 min;

[0082] S24. Cooling inoculation: Naturally cool to 40-45°C, add 0.3% starter culture to the micro-endosperm corn fermentation base, and mix well;

[0083] S25. Fermentation: fermenting the inoculated mixed milk at 43° C. for 4 h;

[0084] S26. Refrigerated post-ripening: After fermentation is completed, the micro-endosperm corn plant-based yogurt is quickly cooled to room temperature and then refrigerated at 4°C for 12 hours.

[0085] Example 2

[0086] The step S12 of Example 1 is replaced by "flavor protease: glutamine transaminase = 2:1, based on the mass of corn slurry, add 0%, 0.05%, 0.2%, 0.3%, 0.5%, and 1% of the complex enzyme respectively, mix well, and hydrolyze at 55°C for 30 minutes. Stir the corn slurry 2 to 3 times during the hydrolysis", and the rest is the same as Example 1.

[0087] like Figure 1 As shown in the figure, the water holding capacity of yogurt increases first and then decreases with the increase of enzyme addition. When the addition amount is 0.05% to 0.30%, the water holding capacity is higher than that of the group without addition. When the addition amount is 0.2%, the water holding capacity of yogurt reaches the highest of 59.88%, which is 2.65% higher than that of the control group. This is mainly due to the fact that under the action of the two enzymes, the raw protein undergoes directional hydrolysis and transfer cross-linking reaction, the protein cross-linking effect is enhanced, and the small molecular peptides and amino acids are generated. After being used by thermophilic streptococci and bulgaricus lactobacillus, the interaction between polysaccharide-polysaccharide and protein-polysaccharide in the yogurt system is enhanced, so that the gel structure of yogurt is strengthened, thereby improving the water holding capacity of yogurt. However, after excessive enzymatic hydrolysis, the molecular weight of protein decreases, which is not conducive to the formation of network structure, resulting in sparse texture of yogurt and reduced water holding capacity.

[0088] like Figure 2 As shown in the figure, with the increase of enzyme amount, the sensory score of yogurt shows a trend of increasing first and then decreasing. When the enzyme addition amount is 0.2% to 0.3%, the sensory score of yogurt increases significantly; when the addition amount is 0.2%, the sensory score of yogurt reaches the highest point of 76.9 points, at this time, the taste of yogurt is soft and there is no obvious bitter taste; when the addition amount is 0.5% and 1%, due to excessive enzymatic hydrolysis, the gel strength of yogurt is significantly reduced, the texture is loose, and the introduction of high content of composite enzyme makes the taste of yogurt uncoordinated, and the sensory score decreases significantly. The sensory score of yogurt is analyzed by the addition amount of composite enzyme. When the addition amount of composite enzyme is 0.2% and 0.3%, there is no significant difference in the sensory score of yogurt. Considering the production cost, 0.2% is selected as the appropriate addition amount of composite enzyme.

[0089] Example 3

[0090] Replace step S12 of Example 1 with "flavor protease: glutamine transaminase = 2:1, based on the mass of corn slurry, the total addition amount is 0.2%, on this basis, add 0.10%, 0.15%, 0.20%, 0.25%, 0.30% of α-amylase respectively, mix well, hydrolyze at 55°C for 30 minutes, and stir the corn slurry 2 to 3 times during the hydrolysis", and the rest is the same as Example 1.

[0091] like Figure 3, with the increase of amylase addition, the reducing sugar content in the fermentation base and the sensory score of yogurt both showed a trend of first rising and then falling. The greater the amount of enzyme added, the more starch was hydrolyzed and the higher the reducing sugar content. When the amylase addition was 0.2%, the sensory score of yogurt was as high as 83.6 points. At this time, the reducing sugar content in the fermentation base was 0.91%, which was 0.33% higher than that of the control group; when the enzyme addition was greater than 0.2%, the acid sensory score began to decrease. When the addition was 0.25% and 0.3%, the sensory score was lower than that of the control group without enzymatic hydrolysis. The high starch content in the fermentation base will cause the yogurt to have a heavy powdery feel, and the starch particles are easy to aggregate to form macromolecular aggregates, making the yogurt rough and not delicate. The appropriate amount of starch enzymatic hydrolysis can improve this problem. In addition, the dextrin produced by amylase enzymatic hydrolysis can mask the bitterness, help improve the taste and texture of yogurt, and improve the sensory score of yogurt. However, excessive enzymatic hydrolysis will make the yogurt thinner and darker in color. Adding more amylase may even introduce odor, affecting the sensory quality of yogurt. Based on the sensory score and reducing sugar content, 0.2% was selected as the appropriate addition amount of α-amylase.

[0092] Example 4

[0093] Replace step S12 of Example 1 with "flavor protease: glutamine transaminase = 2:1, based on the mass of corn slurry, the total addition amount is 0.2%, the addition amount of α-amylase is 0.2%, mix evenly, and enzymolyze at 55°C for 20min, 30min, 40min, 50min, and 60min respectively, and stir the corn slurry 2 to 3 times during the enzymolysis period", and the rest is the same as Example 1.

[0094] like Figure 4 , the reducing sugar content in the fermentation base and the sensory score of yogurt showed a trend of first increasing and then decreasing with the extension of enzymatic hydrolysis time. As the enzymatic hydrolysis time increased, the enzymatic reaction gradually became complete. When the enzymatic hydrolysis time reached 50 minutes, the reducing sugar content no longer increased; when the enzymatic hydrolysis time was 40 minutes, the sensory score of the yogurt obtained reached the maximum value and then began to decrease. If the enzymatic hydrolysis time is too long and the high temperature is maintained for a long time, it will cause the loss of some reducing sugars and even the deterioration of the fermentation base, which will affect the quality of the prepared yogurt, easily produce peculiar smell, and reduce the sensory score. Therefore, 40 minutes is a suitable enzymatic hydrolysis time for α-amylase.

[0095] Example 5

[0096] Replace step S12 of Example 1 with "flavor protease: glutamine transaminase = 2:1, based on the mass of corn slurry, the total addition amount is 0.2%, the addition amount of α-amylase is 0.2%, mix evenly, and hydrolyze at 45°C, 50°C, 55°C, 60°C, and 65°C for 30 minutes, respectively, and stir the corn slurry 2 to 3 times during the hydrolysis", and the rest is the same as Example 1.

[0097] like Figure 5 , the reducing sugar content in the fermentation base increases with the increase of enzymatic hydrolysis temperature. When the temperature reaches 55°C, the reducing sugar content reaches a maximum of 1.02%. As the temperature continues to rise, the enzyme activity is inhibited, and the reducing sugar content shows a downward trend. Too much starch in the fermentation base will cause the yogurt to have a rough texture and a sticky taste. With an appropriate amount of enzyme added, the better the enzymatic hydrolysis effect, the higher the sensory score of the yogurt. The sensory scores of yogurt at enzymatic hydrolysis temperatures of 50°C and 55°C were high and there was no significant difference, which were 83.8 points and 83 points respectively. Combined with the reducing sugar content in the fermentation base and the sensory score of yogurt, the suitable enzymatic hydrolysis temperature is 55°C.

[0098] On the basis of the total addition of flavor protease and glutamine transaminase of 0.2%, the optimal optimization process was screened out through orthogonal experiment with the reducing sugar content in the fermentation base and the sensory score of micro-endosperm corn plant-based yogurt as indicators, and it was determined that the optimal enzymatic hydrolysis process of micro-endosperm corn fermentation base was 0.2% α-amylase addition, 55°C enzymatic hydrolysis temperature, and 30 min enzymatic hydrolysis time.

[0099] Experiment 1: Effects of enzymatic hydrolysis on the types and contents of free amino acids in micro-endosperm corn fermentation base

[0100] The free amino acid composition and content in the corn fermentation base before and after enzymolysis were determined by high performance liquid chromatography, and the results are shown in Table 2. The total content of free amino acids in the corn fermentation base after enzymolysis was 103.5 mg / mL, an increase of 53.22 mg / mL compared with before enzymolysis. Among them, the content of valine, lysine, alanine, and tyrosine decreased compared with before enzymolysis, histidine did not change significantly, and the content of other amino acids increased significantly. Aspartic acid, proline, and glutamic acid increased significantly, increasing by 23.17 mg / mL, 15.72 mg / mL, and 4.19 mg / mL, respectively. The total amount of hydrophobic amino acids (valine, leucine, isoleucine, phenylalanine, tyrosine, and proline) after enzymolysis increased by 16.26 mg / mL compared with before enzymolysis. After the hydrophobic amino acids were hydrolyzed into free amino acids, it was shown that the enzymatic treatment could reduce the bitterness of the fermentation base liquid, thereby reducing the bitterness of micro-endosperm corn plant-based yogurt.

[0101] Table 2 Free amino acid composition of fermentation base before and after enzymatic hydrolysis

[0102]

[0103] Note: * indicates essential amino acid, “--” indicates not detected.

[0104] Experiment 2: Effect of enzymatic hydrolysis on the fermentation performance of micro-endosperm corn plant-based yogurt

[0105] The yogurt prepared before enzymatic hydrolysis of the fermentation base was used as a control to investigate the effect of the enzymatic hydrolysis fermentation base on the pH and acidity curves of micro-endosperm corn plant-based yogurt. Figure 6 As shown. Compared with the control group, the pH of the yogurt prepared after enzymatic hydrolysis and fermentation decreased significantly at a rate of 0 to 4 hours, and tended to be stable after 4 hours. The acidity of the yogurt increased significantly over time compared with that before enzymatic hydrolysis. The yogurt prepared by enzymatic hydrolysis and fermentation reached the fermentation end point at 3 hours (pH = 4.37, acidity = 63.32°T), while the yogurt prepared before enzymatic hydrolysis of the fermentation base had a pH of 4.51 at 3 hours and did not reach the fermentation end point. This is because the enzymatic hydrolysis increases the content of free amino acids and sugars available for fermentation in the system, promotes the growth and reproduction of lactic acid bacteria, accelerates the acid production rate, and shortens the fermentation time of yogurt.

[0106] Experiment 3: Effect of enzymatic treatment on scanning electron microscopy of micro-endosperm corn plant-based yogurt

[0107] Figure 7 The scanning electron microscope images of the micro-endosperm corn plant-based yogurt prepared before and after fermentation-based enzymatic hydrolysis were magnified 1000 times. As can be seen from the image (a), the surface structure of the sample before fermentation-based enzymatic hydrolysis showed multiple aggregates of different sizes, indicating that the gel structure was loose and the texture was rough; from (b), it can be seen that the surface aggregates of the sample after enzymatic hydrolysis were significantly reduced, and the structure was more compact. This shows that after enzymatic hydrolysis, the protein-protein micelles formed a compact and uniform three-dimensional network structure; in addition, after amylase hydrolysis, the macromolecular aggregates formed by protein-starch were reduced, and the yogurt surface was smoother and the texture was more delicate.

[0108] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

Claims

1. A method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering, characterized in that: The following steps are involved: S1. Preparation of micro-endosperm corn fermentation medium S11. Select dry corn kernels with micro-endosperm and no moldy kernels, boil them in water and swell them after 30 minutes, remove them and rinse them, add 5 times the mass of pure water of the dry corn kernels, wet grind them to obtain corn syrup, and set aside; S12. Add flavor protease, glutamine aminotransferase and α-amylase, mix well, and perform enzymolysis at a constant temperature; S13. After the enzymatic hydrolysis is completed, the first sterilization, cooling, and filtration are performed to obtain a micro-endosperm corn fermentation base; S2. Preparation of micro-endosperm corn plant-based yogurt S21. Preparation: Weigh a certain amount of glucose, sugar, and inulin, add them to the micro-endosperm corn fermentation base, and mix them evenly by high-speed shearing; S22. Homogenization: homogenize 3 times at 45 MPa; S23. Sterilization: Second sterilization at 95-100°C for 15 min; S24. Cooling and inoculation: cooling naturally, adding the fermentation agent, and mixing evenly; S25. Fermentation: fermenting the inoculated mixed milk; S26. Refrigerated post-ripening: After the fermentation is completed, the micro-endosperm corn plant-based yogurt is quickly cooled to room temperature, and then refrigerated and post-ripened at 4° C. for 12 hours to obtain the micro-endosperm corn plant-based yogurt.

2. The method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering according to claim 1, characterized in that: In S12, the enzyme activity of the flavor protease is 5000-6000 U / g, and the enzyme activity of the glutamine transaminase is 100-200 U / g; the flavor protease: glutamine transaminase = 2:1, and the total addition amount is 0.05-1.0% of the mass of the corn steep liquor; The enzyme activity of the alpha-amylase is 20000 U / g, and the added amount is 0.10-0.30% of the mass of the corn steep liquor.

3. The method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering according to claim 2, characterized in that: In S12, the enzymatic hydrolysis is carried out at a temperature of 45 to 60° C. for 20 to 50 minutes.

4. The method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering according to claim 3, characterized in that: In S12, the corn slurry is stirred 2 to 3 times during the enzymatic hydrolysis.

5. The method for preparing micro-endosperm corn plant-based stirred yogurt by enzymatic debittering according to claim 1, characterized in that: In S13, the first sterilization is performed at 95° C. for 15 min.

6. The method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering according to claim 1, characterized in that: In S21, based on the mass of micro-endosperm corn fermentation base: The glucose: white sugar = 2:3, the total added amount of the glucose and white sugar is 4-8%, and the added amount of the inulin is 3%.

7. The method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering according to claim 1, characterized in that: In S24, the temperature is naturally cooled to 40-45°C.

8. The method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering according to claim 1, characterized in that: In S24, the amount of the starter added is 0.1-0.5% based on the mass of the micro-endosperm corn fermentation base.

9. The method for preparing micro-endosperm corn plant-based yogurt by enzymatic debittering according to claim 1, characterized in that: In S25, the fermentation is carried out at 43° C. for 3 to 7 hours.

10. A micro-endosperm corn plant-based yogurt, characterized in that: A micro-endosperm corn plant-based yogurt prepared by the method according to any one of claims 1 to 9.

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