Yoghourt and preparation method thereof

Abstract

The invention relates to the technical field of food, in particular to yoghourt and a preparation method thereof. The yoghourt disclosed by the invention is prepared from the following raw materials in parts by weight: 7 to 15 parts of hydrolyzed millet liquid powder, 85 to 93 parts of liquid milk, 0.03 to 0.5 part of lactic acid bacteria starter and 0.005 to 0.012 part of saccharifying enzyme, or 30 to 60 parts of hydrolyzed millet liquid, 22 to 58 parts of water, 12 to 18 parts of milk powder, 0.03 to 0.5 part of lactic acid bacteria starter and 0.005 to 0.012 part of saccharifying enzyme. According to the invention, the hydrolyzed millet liquid or the hydrolyzed millet liquid powder is added into the yoghurt as a thickening agent and a stabilizing agent, so that the texture characteristics of the yoghurt are improved, and the viscosity and the water-holding capacity of the yoghurt are improved. The saccharifying enzyme and the lactic acid bacteria are added for synchronous enzymolysis and fermentation, so that the sweetness of the yoghourt is remarkably improved, the sucrose can be partially or completely replaced, the number of the lactic acid bacteria is increased, the fermentation time is shortened, and the yoghourt is endowed with good antioxidant and anti-inflammatory functions.

Description

Technical Field

[0001] This invention relates to the field of food technology, and in particular to a yogurt with added millet and its preparation method. Background Technology

[0002] Fermented milk is a product with a lower pH, made from one or more of the following raw materials: raw cow (or sheep) milk, concentrated milk for the food industry, and milk powder, through sterilization and fermentation. Flavored fermented milk uses at least 80% raw cow (or sheep) milk, concentrated milk for the food industry, or milk powder as its main raw material. Products made with added ingredients, sterilized and fermented to lower pH, and with or without the addition of food additives, nutritional fortifiers, fruits, vegetables, grains, etc., before or after fermentation, are usually called yogurt.

[0003] The texture of yogurt primarily relies on the gel formed by the electrostatic interactions between casein micelles in milk under acidic conditions. This gel is typically susceptible to damage from mechanical forces during processing and transportation, leading to issues such as thinning and whey separation. To improve taste and texture, stabilizers and thickeners are usually used, and sucrose is added to neutralize the yogurt's acidity and enhance its flavor. With increasing health awareness, consumers are paying more attention to the use of exogenous synthetic additives and refined sugars, making clean labels a top priority for many. However, stabilizers and thickeners used in yogurt, such as hydroxypropyl distarch phosphate, diacetyl tartaric acid mono- and diglycerides, gelatin, pectin, and carrageenan, may have adverse effects on gut health, such as causing constipation and intestinal inflammation, and may also trigger allergic reactions. Long-term, excessive consumption is detrimental to health. Summary of the Invention

[0004] This invention provides a method for preparing yogurt, which addresses the problems of the adverse effects on human health caused by the use of stabilizers, thickeners, and refined sugar in existing yogurts.

[0005] Furthermore, the saccharifying enzyme treatment is carried out simultaneously with the lactic acid bacteria fermentation, which helps to promote the growth rate of lactic acid bacteria, improve fermentation efficiency, shorten fermentation time, and increase the number of lactic acid bacteria.

[0006] According to a first aspect of the present invention, the present invention provides a yogurt with added millet, prepared from raw materials comprising the following components in parts by weight: 7-15 parts hydrolyzed millet powder, 90-93 parts liquid milk, 0.03-0.5 parts lactic acid bacteria starter, and 0.005-0.012 parts saccharifying enzyme; Alternatively, the mixture may contain 30-60 parts of hydrolyzed millet liquid, 22-58 parts of water, 12-18 parts of milk powder, 0.03-0.5 parts of lactic acid bacteria starter, and 0.005-0.012 parts of saccharifying enzyme.

[0007] This invention provides a novel yogurt formula that replaces thickeners and stabilizers used in traditional yogurt by adding hydrolyzed millet powder or hydrolyzed millet liquid. This solves the problem of potential adverse health effects from exogenous synthetic additives in existing yogurts and meets consumer demand for clean-label products. The addition of hydrolyzed millet powder or hydrolyzed millet liquid improves the texture of the yogurt, including increasing viscosity, water-holding capacity, and rheological properties, resulting in a better taste and texture, reducing whey separation, and further enhancing the sweetness of the yogurt through simultaneous enzymatic fermentation with the addition of saccharifying enzymes. This partially or completely replaces sucrose, improves the efficiency of lactic acid bacteria growth, and enhances the overall quality of the product. Simultaneously, the enzymatically hydrolyzed millet is rich in polyphenols, vitamins, polysaccharides, and many other bioactive components, which can improve the nutritional and functional properties of the yogurt.

[0008] Furthermore, the milk powder is selected from one or more of whole milk powder, skim milk powder, semi-skim milk powder, concentrated milk protein powder, and whey protein powder; the liquid milk is selected from one or more of whole milk, skim milk, semi-skim milk, and concentrated milk.

[0009] Furthermore, the hydrolyzed millet liquid powder is obtained by drying the hydrolyzed millet liquid. This processing method allows for convenient storage and transportation of the hydrolyzed millet liquid, improving the flexibility of raw material use and reducing production costs. Simultaneously, the dried hydrolyzed millet liquid powder disperses and dissolves better when mixed with liquid milk, further optimizing the yogurt production process and improving production stability and product quality consistency.

[0010] Furthermore, the yogurt has a pH of 4.5-4.6 and a lactic acid bacteria count greater than 10 × 10⁻⁶. 8 The yogurt exhibits the following characteristics: CFU / g, viscosity greater than or equal to 6500 cP (preferably 6500-9000 cP), whey separation rate less than 40% (preferably 30-38.5%), free phenol content of 30-50 mg GAE / 100g, DPPH free radical scavenging rate of 20-30%, and ABTS free radical scavenging rate of 4-7%. Furthermore, this yogurt possesses potential anti-inflammatory effects, inhibiting the high expression of inflammatory factors induced by DSS in Caco-2 cells. The inhibition rates of TNF-α, IL-6, and IL-1β high expression reach 75%-100%, 90%-100%, and 70%-86%, respectively. TNF-α, IL-6, and IL-1β are common inflammatory factors, and their abnormally high expression is closely related to various inflammatory and autoimmune diseases. The use of millet extract (powder) in the yogurt can promote the growth of lactic acid bacteria, increase the content of polyphenol components, and enhance the antioxidant, free radical scavenging, and anti-inflammatory effects of the yogurt.

[0011] The above-mentioned scheme sets limits on key indicators of yogurt, including pH value, lactic acid bacteria count, viscosity, free phenol content, DPPH and ABTS free radical scavenging rates, and the inhibition rate of DSS-induced high expression of inflammatory factors in Caco-2 cells. This ensures that the product's quality and functionality meet specific standards. Limiting the pH value ensures the yogurt has a moderate acidity, which is conducive to the growth and fermentation of lactic acid bacteria and also meets consumer taste preferences. Limiting the lactic acid bacteria count ensures the yogurt has sufficient active lactic acid bacteria, which helps maintain intestinal health. Limiting the viscosity gives the yogurt a good taste and texture, and reduces the likelihood of whey separation. Limiting the free phenol content, DPPH and ABTS free radical scavenging rates, and the inhibition rate of DSS-induced high expression of inflammatory factors in Caco-2 cells demonstrates the yogurt's antioxidant and anti-inflammatory functions, increasing the product's added value and enhancing its market competitiveness.

[0012] According to a second aspect of the present invention, the present invention also provides a method for preparing the above-mentioned yogurt with added millet, comprising the following steps: Step (1): Mix millet and water at a weight ratio of 1:(3-4) to prepare a mixture; after gelatinization, add amylase to the mixture, treat at 70-90℃ for 90-110 min, and then pass through a 100-200 mesh sieve to obtain hydrolyzed millet liquid; Step (2): Mix the prepared hydrolyzed millet liquid with water and milk powder and then homogenize it to obtain a homogenized liquid; or, dry the prepared hydrolyzed millet liquid to obtain hydrolyzed millet liquid powder; mix the obtained hydrolyzed millet liquid powder with liquid milk and then homogenize it to obtain a homogenized liquid. Step (3): Heat-treat the homogenized liquid obtained in step (2) and then cool it to 40-45℃; add saccharifying enzyme and inoculate with lactic acid bacteria starter; keep warm at 40-45℃ for simultaneous enzymatic hydrolysis and fermentation until the pH is below 4.6 (preferably 4.5-4.6); stir to break the emulsion and cool it to 3-5℃; and mature it at 3-5℃.

[0013] The yogurt preparation method of the present invention covers the entire process from raw material preparation to final product shaping, including key steps such as preparation of hydrolyzed millet liquid, homogenization treatment, heat treatment, simultaneous saccharification and enzymatic hydrolysis fermentation treatment, and ripening. Through the rational combination and optimization of these steps, the efficient production of yogurt with added millet is achieved, improving production efficiency, reducing production costs, and ensuring product quality and functionality.

[0014] Furthermore, in step (1), the preparation method of the hydrolyzed millet liquid is as follows: A mixture was prepared by mixing millet and water at a weight ratio of 1:(3-4); After gelatinizing the obtained mixture, amylase was added, and the mixture was treated at 70-90℃ for 90-110 minutes. The mixture was then sieved to obtain hydrolyzed millet liquid.

[0015] The preparation method of hydrolyzed millet liquid includes specific parameters such as the mixing ratio of millet and water, gelatinization conditions, the amount of amylase added, and the processing temperature and time. These parameters ensure a more precise and controllable preparation process, guaranteeing the quality and characteristics of the hydrolyzed millet liquid and providing a high-quality raw material foundation for subsequent yogurt production. By optimizing these preparation conditions, the degree of hydrolysis of starch and polysaccharides in millet can be increased, releasing more effective components such as oligosaccharides, dextrins, and maltose, thus better leveraging the thickening and stabilizing effects of millet and improving yogurt quality. Simultaneously, it facilitates the release of polyphenols and flavonoids, further enhancing the antioxidant and anti-inflammatory properties of the yogurt.

[0016] Furthermore, the preparation method of the mixture is as follows: millet is pulverized and passed through an 80-mesh sieve to obtain millet flour; the millet flour is mixed with water and then soaked at 40-60℃ for 20-40 minutes; or, millet is mixed with water and soaked at 40-60℃ for 20-40 minutes, and then pulped. By specifying the particle size requirements of the millet flour (passing through an 80-mesh sieve) and the soaking conditions (soaking at 40-60℃ for 20-40 minutes), it can be ensured that the millet flour fully absorbs water and swells, creating favorable conditions for subsequent gelatinization and enzymatic hydrolysis reactions.

[0017] Furthermore, the gelatinization process is carried out at 85-95°C for 50-70 minutes. Optimizing the temperature and time range of the gelatinization process ensures that the starch in the millet is fully gelatinized, thereby improving the enzymatic hydrolysis efficiency.

[0018] Furthermore, the amount of amylase added is 0.02-0.04% of the mass of the millet; Precise control over the amount of amylase added helps to achieve efficient hydrolysis of starch in millet, resulting in better quality and functionality of the hydrolyzed millet liquid, thereby improving the quality and nutritional value of the final yogurt product.

[0019] Furthermore, in step (3), the heat treatment is performed at 90-98°C for 3-8 minutes.

[0020] The aforementioned conditions are crucial for ensuring the quality and safety of yogurt. Heat treatment effectively kills harmful microorganisms in raw materials and inactivates enzymes, preventing microbial contamination and extending the product's shelf life. Simultaneously, a reasonable range of heat treatment temperature and time can prevent overheating from damaging the nutrients and flavor compounds in the raw materials, thus preserving the nutritional and flavor qualities of the yogurt. These limitations make the yogurt production process more scientific and rational, resulting in more reliable product quality.

[0021] Further, in step (3), the amount of saccharifying enzyme added is 0.005-0.012% of the mass of the homogenized liquid in step (2).

[0022] The aforementioned conditions facilitate the simultaneous hydrolysis of carbohydrates in the millet liquid by saccharifying enzymes during lactic acid bacteria fermentation. This releases components such as glucose, maltose, and polysaccharides, neutralizing lactic acid, improving the sweetness of yogurt, and reducing or replacing the use of sucrose. Simultaneously, the release of hydrolyzed components promotes the proliferation of lactic acid bacteria, thereby increasing fermentation efficiency, shortening fermentation time, and increasing the number of lactic acid bacteria.

[0023] Further, in step (3), the lactic acid bacteria starter includes one or more of Streptococcus thermophilus starter, Lactobacillus bulgaricus starter, Bifidobacterium starter and Lactococcus lactis starter; Further, in step (3), the amount of lactic acid bacteria starter added is 0.03-0.5% of the mass of the homogenized liquid in step (2).

[0024] Preferably, the lactic acid bacteria starter culture includes Streptococcus thermophilus starter culture and Lactobacillus bulgaricus starter culture; more preferably, the weight ratio of Streptococcus thermophilus starter culture to Lactobacillus bulgaricus starter culture in the lactic acid bacteria starter culture is (1~10):1. Different lactic acid bacteria starter cultures have different fermentation characteristics and functions. By rationally selecting and combining starter cultures, the fermentation process of yogurt can be better controlled to achieve ideal acidity, flavor, and texture. For example, Streptococcus thermophilus and Lactobacillus bulgaricus are common combinations of yogurt starter cultures. They work synergistically to produce rich flavor compounds and lactic acid, promoting gel formation in yogurt. The addition of other starter cultures, such as Bifidobacterium and Lactococcus lactis, can further enhance the nutritional value and functionality of yogurt, such as promoting gut health.

[0025] Furthermore, in step (3), the fermentation treatment time is 3-3.5 hours; Furthermore, the ripening time is 12-24 hours.

[0026] The use of millet liquid in yogurt and the simultaneous enzymatic fermentation process can shorten the fermentation time to within 3.5 hours. By limiting the fermentation and maturation times, the fermentation degree of yogurt can be ensured to be moderate, giving it a good taste and flavor. At the same time, the activity and quantity of lactic acid bacteria are guaranteed, thereby improving the nutritional value and market competitiveness of the product.

[0027] Furthermore, in step (2), the homogenization process is carried out at a temperature of 50-70°C and a pressure of 15-25 MPa.

[0028] Homogenization is a crucial step in yogurt production. Its purpose is to evenly disperse fat globules and protein particles in the raw materials, preventing fat from rising to the surface and protein from agglomerating and settling. This improves the yogurt's texture and mouthfeel, making it smoother and more uniform. A suitable range of homogenization temperature and pressure ensures effective homogenization while avoiding excessive damage to the nutrients and flavor compounds in the raw materials. By adhering to these limits, ideal homogenization results can be achieved during yogurt production, enhancing product quality and market competitiveness.

[0029] The beneficial effects of this invention are: This invention provides a yogurt that successfully replaces the thickeners and stabilizers used in traditional yogurt by adding hydrolyzed millet liquid or hydrolyzed millet liquid powder. This solves the problem of potential adverse health effects from exogenous synthetic additives in existing yogurts and meets consumer demand for clean-label products. Simultaneously, by adding saccharifying enzymes and starter cultures for simultaneous enzymatic fermentation, the natural sweetness of the yogurt is further enhanced, reducing the use of sucrose and sweeteners. This also helps increase the number of lactic acid bacteria, shortens fermentation time, and further improves the nutritional value and health properties of the yogurt. Through formula and process optimization, this invention significantly improves the textural properties of the yogurt, increasing its viscosity and water-holding capacity, enhancing its taste and the number of lactic acid bacteria, shortening fermentation time, improving production efficiency and product quality, and endowing the yogurt with good antioxidant and anti-inflammatory functions. This enhances the market competitiveness of yogurt and provides consumers with a healthy, delicious, and functional new yogurt product. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 The following are state diagrams of millet liquid obtained under different hydrolysis conditions for experimental examples of the present invention: Figure a shows the millet liquid without amylase hydrolysis treatment; Figure b shows the millet liquid after amylase hydrolysis treatment for 30 min; Figure c shows the millet liquid after amylase hydrolysis treatment for 90 min.

[0032] Figure 2 The following are state diagrams of millet liquid obtained under different weight ratios of millet and water provided for experimental examples of the present invention: Figure a shows the weight ratio of millet and water as 1:15; Figure b shows the weight ratio of millet and water as 1:4; and Figure c shows the weight ratio of millet and water as 1:3.

[0033] Figure 3The viscosity comparison charts are of the yogurts provided in Examples 1-4 and Comparative Examples 1-3 of the present invention.

[0034] Figure 4 This is a comparison chart of the whey separation rate of the yogurts provided in Examples 1-4 and Comparative Examples 1-3 of the present invention.

[0035] Figure 5 The above are sensory analysis comparison charts of the yogurts provided in Examples 1-4 and Comparative Examples 1, 2, and 4 of this invention.

[0036] Figure 6 This is a comparison chart of the free phenol content of yogurts provided in Examples 1-4 and Comparative Examples 1-2 of the present invention.

[0037] Figure 7 The above are comparison charts showing the DPPH removal effect of yogurt provided in Examples 1-4 and Comparative Examples 1-2 of this invention.

[0038] Figure 8 The above are comparison charts showing the ABTs removal effects of yogurt provided in Examples 1-4 and Comparative Examples 1-2 of this invention.

[0039] Figure 9 The image shows the effect of yogurt provided in Examples 2, 4, and Comparative Example 2 of this invention on DSS-induced inflammation in Caco-2 cells using IL-1β.

[0040] Figure 10 The TNF-α diagram shows the effect of yogurt provided in Examples 2, 4, and Comparative Example 2 of this invention on DSS-induced inflammation in Caco-2 cells.

[0041] Figure 11 The IL-6 graph shows the effect of yogurt provided in Examples 2, 4, and Comparative Example 2 of this invention on DSS-induced inflammation in Caco-2 cells.

[0042] Figure 12 This is a comparison chart of lactic acid bacteria counts in yogurts stored for different times, provided in Example 2 and Comparative Example 2 of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0044] The sources of raw materials used in the following examples and comparative examples are as follows: Whole milk powder: derived from Anchor whole milk powder.

[0045] Whole milk: derived from Sanyuan whole milk.

[0046] Thickener: Yogurt stabilizer sourced from Shengfa Biotechnology Co., Ltd.

[0047] White sugar: sourced from Fulinmen premium white sugar.

[0048] Millet: Jingu No. 21 millet, Jinzhong Fengyuan Planting Professional Cooperative.

[0049] Amylase: α-amylase from Xiasheng (Beijing) Biotechnology Development Co., Ltd.

[0050] Glycoamylase: Food-grade glucoamylase from Xiasheng (Beijing) Biotechnology Development Co., Ltd.

[0051] Mixed lactic acid bacteria starter culture: Chr. Hansen YC380, which includes Streptococcus thermophilus and Lactobacillus bulgaricus starter culture.

[0052] Example 1 This embodiment provides a yogurt with added millet, comprising the ingredients in the following parts by weight as shown in Table 1.

[0053] This embodiment also provides a method for preparing the yogurt, including the following steps: Hulled millet was ground in a mill at 3200 r / min and then passed through an 80-mesh sieve to obtain millet flour. The millet flour was mixed with distilled water at a ratio of 1:3 and soaked at 50℃ for 30 min. After gelatinization treatment (held at 90℃ for 60 min), α-amylase (0.3 g / kg millet flour) was added and treated at 80℃ for 90 min. The mixture was then passed through a 200-mesh sieve to obtain hydrolyzed millet liquid.

[0054] 12g of whole milk powder was mixed with 58g of distilled water, and 30g of hydrolyzed millet liquid was added. The mixture was preheated to 60℃ and homogenized at 20MPa. The homogenate was then heated at 95℃ for 5 minutes, cooled to 40-42℃, and inoculated with 0.05g of mixed lactic acid bacteria starter culture, along with 0.008g of saccharifying enzyme. The inoculated milk was fermented at 42℃±1℃ until the pH reached 4.6. The mixture was then stirred to break the emulsion and rapidly cooled, followed by post-fermentation at 4℃ for 12 hours.

[0055] Example 2 This embodiment provides a yogurt with added millet, which differs from Embodiment 1 in that the amounts of water, whole milk powder, and hydrolyzed millet liquid used in the preparation are different, as shown in Table 1 below by weight. The preparation method is the same as in Embodiment 1.

[0056] Example 3 This embodiment provides a yogurt with added millet, comprising the ingredients in the parts by weight shown in Table 1 below. The preparation method includes the following steps: Hulled millet is ground in a mill at 3200 r / min and then passed through an 80-mesh sieve to obtain millet flour. The millet flour is mixed with distilled water at a ratio of 1:3 and soaked at 50℃ for 30 min. After gelatinization treatment (maintained at 90℃ for 60 min), α-amylase (0.3 g / kg millet flour) is added and treated at 60-80℃ for 90 min. The mixture is then passed through a 200-mesh sieve to obtain hydrolyzed millet liquid.

[0057] Hydrolyzed millet liquid is dried to obtain hydrolyzed millet liquid powder.

[0058] Add 7g of hydrolyzed millet powder to 93g of whole milk, preheat to 60℃, and homogenize at 20MPa. Then heat the mixture at 95℃ for 5 minutes, cool to 40-42℃, inoculate with 0.05g of mixed lactic acid bacteria starter, and add 0.008g of saccharifying enzyme. Ferment the inoculated milk at 42℃±1℃ until the pH reaches 4.6, then stir to break the emulsion and rapidly cool at 4℃ for 12 hours for post-fermentation.

[0059] Example 4 This embodiment provides a yogurt with added millet, comprising the ingredients in the parts by weight shown in Table 1 below. The preparation method is the same as in Embodiment 3.

[0060] Example 5 This embodiment provides a yogurt with added millet. The only difference between this yogurt and the one in embodiment 1 is that the amount of α-amylase added is 0.4 g / kg of millet flour, and the treatment time is 80°C for 90 min.

[0061] Example 6 This embodiment provides a yogurt with added millet. The only difference between this yogurt and the one in embodiment 5 is that millet powder and distilled water are mixed at a ratio of 1:3 and then soaked at 60°C for 20 minutes.

[0062] Example 7 This embodiment provides a yogurt with added millet, the only difference between its preparation method and that of Embodiment 5 is that the amount of saccharifying enzyme added to the mixture is 0.01g.

[0063] Example 8 This embodiment provides a yogurt with added millet, which differs from Embodiment 1 only in that: millet and distilled water are mixed in a 1:4 ratio and soaked at 50°C for 30 minutes, then blended into a uniform slurry using a blender (5000 rpm), gelatinized (held at 90°C for 60 minutes), α-amylase (0.3 g / kg millet) is added, and the mixture is treated at 80°C for 90 minutes. Finally, the mixture is passed through a 200-mesh sieve to obtain hydrolyzed millet liquid.

[0064] Comparative Example 1 Comparative Example 1 provides a yogurt comprising the ingredients in parts by weight as shown in Table 1 below. Its preparation method differs from Example 1 only in that: hydrolyzed millet liquid is not added, and saccharifying enzyme is not added simultaneously when inoculating with lactic acid bacteria starter.

[0065] Comparative Example 2 Comparative Example 2 provides a yogurt comprising the ingredients in parts by weight as shown in Table 1 below. Its preparation method differs from Example 1 only in that: hydrolyzed millet liquid is not added, thickener and white sugar are added, and saccharifying enzyme is not added simultaneously when inoculating with lactic acid bacteria starter.

[0066] Comparative Example 3 Comparative Example 3 provides a yogurt comprising the ingredients in the parts by weight shown in Table 1 below. Its preparation method is the same as in Example 1.

[0067] Comparative Example 4 This comparative example provides a yogurt with added millet, which differs from Example 1 only in that it does not contain saccharifying enzymes. The preparation method differs from Example 1 in that saccharifying enzymes are not added during the inoculation of lactic acid bacteria starter.

[0068] Comparative Example 5 Comparative Example 5 provides a yogurt that differs from Example 1 in that the method for preparing the hydrolyzed millet liquid is as follows: Hulled millet was ground in a mill at 3200 r / min and then passed through an 80-mesh sieve to obtain millet flour. The millet flour was mixed with distilled water at a ratio of 1:3 and soaked at 50℃ for 30 min. After gelatinization treatment (held at 90℃ for 60 min), amylase (0.2 g / kg millet flour) was added and treated at 50℃ for 100 min. The mixture was then passed through a 200-mesh sieve to obtain hydrolyzed millet liquid.

[0069] Comparative Example 6 Comparative Example 6 provides a yogurt that differs from Example 1 in that the method for preparing the hydrolyzed millet liquid is as follows: Millet and distilled water were mixed in a 1:3 ratio and soaked at 50°C for 30 minutes. After gelatinization (maintained at 90°C for 60 minutes), amylase (0.3 g / kg millet flour) was added and treated at 80°C for 60 minutes. The mixture was then passed through a 200-mesh sieve to obtain hydrolyzed millet liquid.

[0070] Table 1

[0071] Experimental Example Millet liquid treatment condition test To explore suitable conditions for preparing hydrolyzed millet extract, experiments were conducted in comparison with Example 1, including experiments with no amylase hydrolysis and experiments with amylase hydrolysis for 30 minutes. Figure 1 As shown, millet liquid that has not been hydrolyzed with amylase or has been hydrolyzed for 30 minutes is too coarse and precipitates, and is not suitable for adding to milk to prepare yogurt.

[0072] In the preparation of millet liquid, the weight ratio of millet to water was set to 1:15, 1:4, and 1:3, respectively. Using the method described in Example 1, the millet liquid was prepared. Experiments showed that, as... Figure 2 As shown, if the ratio is too low (1:15), the resulting millet paste will be too thin and unsuitable for adding to milk to prepare yogurt. A millet-to-liquid ratio of 1:3 to 1:4, followed by treatment with α-amylase for 90-110 minutes, will yield a uniform and smooth millet paste.

[0073] The following performance tests were conducted on the yogurts from Examples 1-4 and Comparative Examples 1-4: 1. pH value The pH value of the yogurt samples was measured using a pH meter (Corning Scientific Products, New York, USA). The test results are shown in Table 2 below.

[0074] Table 2

[0075] As can be seen from the experimental data in Table 2, under the condition of controlling the pH value at the fermentation endpoint, the fermentation time of Examples 1-4 of the present invention is significantly shorter than that of Comparative Examples 1 and 2, and the number of lactic acid bacteria in Examples 1-4 is significantly higher than that in Comparative Examples 1 and 2, indicating that the conditions of the present invention are conducive to the proliferation and survival of lactic acid bacteria, thus shortening the yogurt fermentation time. The number of lactic acid bacteria in Comparative Example 4, which did not have the addition of saccharifying enzymes for co-fermentation, is lower than that in Example 1, indicating that adding saccharifying enzymes for co-fermentation with lactic acid bacteria is very important for promoting the proliferation of lactic acid bacteria. The fermentation time of Comparative Example 3 is longer than that of Examples 1-4, and the number of lactic acid bacteria is also lower than that of Examples 1-4, indicating that a low amount of hydrolyzed millet liquid is not very effective.

[0076] 2. Apparent viscosity The apparent viscosity of a yogurt sample was determined at 5°C according to the operating instructions of the Brookfield DV-III viscometer (Brookfield Engineering Laboratories Inc.). Measurements were taken using a V-63 spindle at 5 rpm along a spiral path for 60 seconds.

[0077] like Figure 3As shown, the viscosity of the yogurt in Examples 1-4 and Comparative Example 2 is significantly higher than that in Comparative Example 1, indicating that adding millet liquid or powder and using thickeners can improve the quality and increase the viscosity of yogurt. The viscosity of the yogurt in Examples 1-4 is higher than that in Comparative Example 2, indicating that adding hydrolyzed millet liquid or hydrolyzed millet liquid powder can replace thickeners and better achieve the thickening effect, thus improving the viscosity of fermented milk.

[0078] 3. Whey separation rate Take 25 g of yogurt and centrifuge it at 2900×g for 20 min at 4℃. Take the supernatant (whey) and weigh it. Calculate the whey separation rate according to formula (1).

[0079] Whey separation rate (%) = (Whey weight (g) / Yogurt weight (g)) × 100 (1) like Figure 4 As shown, the whey separation rate of the yogurts in Examples 1-4 and Comparative Example 2 was significantly lower than that in Comparative Example 1, indicating that adding millet components and using thickeners can improve the quality of yogurt, increase water-holding capacity, and reduce whey separation. The whey separation rate of the yogurts in Examples 1 and 3 was no different from that in Comparative Example 2, while the whey separation rate in Examples 2 and 4 was significantly lower than that in Comparative Example 2, indicating that adding hydrolyzed millet liquid or hydrolyzed millet liquid powder can replace thickeners, improve the water-holding capacity of yogurt, and reduce whey separation.

[0080] 4. Lactic acid bacteria count The microbial survival rate in yogurt was determined using the serial dilution method and the spread plate technique, and expressed as log cfu / g yogurt.

[0081] 5. Sensory analysis Appearance, texture, taste, and flavor were scored using a 10-point strength scale (weak: 0-2; medium: 3-6; strong: 7-10) (Table 3).

[0082] Table 3 Sensory evaluation scoring indicators and standards for yogurt samples

[0083] like Figure 5As shown, the sensory evaluation scores of Examples 1-4 and Comparative Example 2 were higher than those of Comparative Example 1 in terms of milky aroma, richness, smoothness, fineness, and viscosity. This indicates that adding hydrolyzed millet liquid or hydrolyzed millet liquid powder and adding thickeners both improve the quality of fermented yogurt. Furthermore, the scores of yogurt from Examples 1-4 were higher than those from Comparative Example 2, suggesting that adding hydrolyzed millet liquid or hydrolyzed millet liquid powder is more effective than adding thickeners. In terms of sweet and sour taste, Examples 1-4 scored higher than Comparative Example 2. The sweetness of Comparative Example 4 was significantly lower than that of Examples 1-4 and also lower than that of Comparative Example 2. This indicates that compared to not adding saccharifying enzymes, adding saccharifying enzymes during fermentation can promote the release of sweetness from the millet liquid, acting as a substitute for sweeteners and providing a good sweet and sour taste for the yogurt.

[0084] 6. Determination of free phenols and antioxidant activity Determination of free phenol content The free phenol content was determined using the Folin-Ciocalteu method, with gallic acid used as a reference for polyphenol determination, and a calibration curve was established. The results are expressed as milligrams of gallic acid equivalent (GAE) per 100g of yogurt sample (mg GAE / 100g).

[0085] like Figure 6 As shown, compared with Comparative Examples 1 and 2, Examples 1-4 all had higher free phenol content. The higher the proportion of hydrolyzed millet liquid or hydrolyzed millet flour added, the higher the free phenol content in the yogurt.

[0086] Furthermore, in Comparative Examples 2 and 4, the free phenol content in the yogurt significantly increased after fermentation compared to before fermentation. This indicates that the fermentation process promoted the release of phenolic substances from the bound state in millet into the yogurt. The free phenols in MPY60, belonging to the millet liquid itself, amounted to 26.75 mg GAE. After fermentation, excluding the free phenols from CY itself, the free phenol content in MPY60 was 33.10 mg GAE. This shows that fermentation significantly increased the free phenol content in MY60, but had no significant effect on the free phenol content in MY40. This indicates that the interaction between proteins and polyphenols changed during fermentation, and fermentation promoted the release of bound phenols from millet. Whether fermentation can significantly change the free phenol content in millet liquid may be related to the amount of millet liquid added.

[0087] ABTS free radical scavenging activity Take 5.0 mL of 7 mmol / L ABTS solution, add 88.0 μL of 140 mmol / L potassium persulfate, and react in the dark at room temperature for 12–16 h to form an ABTS radical stock solution. Dilute the ABTS radical stock solution with 70% ethanol (by dilution to an absorbance of 0.6–0.7) at 734 nm for later use. Accurately measure 0.1 mL of the sample solution, add 3.9 mL of the diluted ABTS radical stock solution with an absorbance of 0.6–0.7, mix well, react at room temperature for 6 min (in the dark), and measure the absorbance A at 734 nm. sample Simultaneously, 3.9 mL of diluted ABTS radical stock solution with an absorbance of 0.6–0.7 was taken, and 0.1 mL of a 1:1 (v / v) methanol-acetonitrile solution was added. The absorbance A was measured at 734 nm. control The ABTS radical scavenging rate is calculated using the following formula: Free radical scavenging rate (2) Among them, A sample It is the absorbance of the supernatant sample, A. control It is the absorbance of a methanol-acetonitrile solution containing a volume ratio of 1:1.

[0088] like Figure 7 As shown, compared with Comparative Examples 1 and 2, Examples 1-4 all showed higher ABTs removal effects. The higher the proportion of hydrolyzed millet liquid or hydrolyzed millet liquid powder added, the higher the ABTs removal ability in yogurt.

[0089] DPPH free radical scavenging activity The method for measuring DPPH radical scavenging activity was described by Sabeena Farvin et al. 100 μL of supernatant was mixed with 100 μL of DPPH solution (0.2 mM, 95% methanol) and then incubated at 37 °C in the dark for 30 min. The absorbance was measured at 517 nm, and the DPPH radical scavenging rate was calculated as follows: (3) Among them, A sample It is the absorbance of the supernatant sample; A control It is the absorbance of a methanol-acetonitrile solution containing a volume ratio of 1:1.

[0090] like Figure 8 As shown, compared with Comparative Examples 1 and 2, Examples 1-4 all showed higher DPPH removal effects. The higher the proportion of hydrolyzed millet liquid or hydrolyzed millet liquid powder added, the higher the DPPH removal ability in yogurt.

[0091] 7. Anti-inflammatory activity Human epithelial colorectal adenocarcinoma cell line (Caco-2) (Shanghai Fuheng Biotechnology Co., Ltd.) was cultured in Roswell Park Memorial Institute (RPMI)-1640 medium (YiAobang, Beijing) containing 15% fetal bovine serum (Fuheng Biotechnology, Shanghai) and 1% penicillin / streptomycin (YiAobang, Beijing) in a humidified incubator at 37°C with 5% CO2. Cells were passaged when they reached 80% confluence.

[0092] Caco-2 cells (3×10) 6 Cells were seeded at a concentration of 1 / mL in 60 mm diameter cell culture dishes for 24 h, reaching approximately 70% confluence. Cells were treated with serum-free medium containing 2% DSS and 100 μL / mL yogurt supernatant. Total RNA was extracted using an RNA extraction kit (TransGen Biotech, Beijing) according to the manufacturer's instructions, and the 260 / 280 RNA ratio was determined using a q3000 spectrophotometer. 0.5 mg of isolated RNA was used to synthesize cDNA using a reverse transcription kit (Beyotime Biotech, Shanghai). cDNA was detected using SYBR Green Master Mix (Toyobo Biotech, Shanghai), with β-actin as an internal control, to quantitatively detect the expression levels of TNF-α, IL-6, and IL-1β. -ΔΔCt The expression levels of target genes were calculated by normalizing β-actin.

[0093] like Figure 9-11 As shown, compared with the blank control, treatment with 2% DSS significantly induced increased mRNA expression levels of TNF-α, IL-1β, and IL-6. Comparative Example 2, Example 2, and Example 4 all inhibited DSS-induced expression of the inflammatory cytokines TNF-α, IL-6, and IL-1β. Compared with Comparative Example 2, Examples 2 and 4 showed stronger inhibition of inflammatory cytokine expression and more significantly downregulated the expression of TNF-α, IL-6, and IL-1β. The examples showed the best remission effect, almost reaching the level of the blank control. This indicates that the examples of adding millet to fermented yogurt effectively improved the anti-inflammatory effect of the yogurt. TNF-α, IL-6, and IL-1β are common inflammatory cytokines, and their abnormally high expression is closely related to various inflammatory and autoimmune diseases. The addition of millet may exert an anti-colitis effect by inhibiting the expression of inflammatory cytokines.

[0094] 8. Storage Experiment The yogurts from Example 2 and Comparative Example 2 were stored for 1 day, 7 days, 14 days, and 21 days, respectively, and the changes in the number of lactic acid bacteria during storage were tested. Figure 12 As shown, the number of lactic acid bacteria in the yogurt of Example 2 is significantly higher than that of Comparative Example 2, and the number of active lactic acid bacteria remains higher than that of the Comparative Example throughout the 21-day storage period.

[0095] The viscosity, whey separation rate, and sweetness of the yogurts in Examples 1-8 and Comparative Examples 1-5 are compared in Table 4 below.

[0096] Table 4

[0097] Note: "-" indicates no obvious sweetness, while "+", "++", and "+++" indicate increasing sweetness in that order. The experimental data in Table 4 show that the viscosity of the yogurt in Examples 1-8 and Comparative Example 2 is significantly higher than that in Comparative Example 1, indicating that adding millet liquid or powder and using thickeners can improve the quality and increase the viscosity of yogurt. The viscosity of the yogurt in Examples 1-8 is higher than that in Comparative Example 2, indicating that adding hydrolyzed millet liquid or hydrolyzed millet liquid powder can replace thickeners and better thicken the yogurt, thus improving the viscosity of the fermented milk. The sweetness of the yogurt in Comparative Example 4 is higher than that in Comparative Example 1 but lower than that in Comparative Example 2, indicating that adding millet liquid has a certain effect on increasing the sweetness of yogurt, but it is not enough to completely replace the amount of sucrose used. The sweetness of the yogurt in Examples 1-8 is higher than that in Comparative Example 2, indicating that during the fermentation process of yogurt with added millet liquid, the simultaneous addition of saccharifying enzymes can significantly increase the sweetness of the yogurt. The higher the content of millet liquid or millet liquid powder, the higher the sweetness, which can reduce or completely replace the amount of sucrose used in the yogurt.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A yoghurt, characterized in that, Prepared from raw materials comprising the following components by weight: hydrolyzed millet liquid powder 7-15 parts, liquid milk 85-93 parts, lactic acid bacteria starter 0.03-0.5 parts, and saccharifying enzyme 0.005-0.012 parts; or, the hydrolyzed millet liquid 30-60 parts, water 22-58 parts, milk powder 12-18 parts, lactic acid bacteria starter 0.03-0.5 parts, and saccharifying enzyme 0.005-0.012 parts.

2. The yoghurt according to claim 1, characterized in that, The milk powder is selected from one or more of whole milk powder, skim milk powder, semi-skim milk powder, concentrated milk protein powder, and whey protein powder; and the liquid milk is selected from one or more of whole milk, skim milk, semi-skim milk, and concentrated milk.

3. The yoghurt according to claim 1 or 2, characterized in that, The hydrolyzed millet liquid powder is obtained by drying the hydrolyzed millet liquid.

4. The yoghurt according to any one of claims 1 to 3, characterized in that, The pH value of the yogurt is 4.5-4.6, the number of lactic acid bacteria is greater than 10×10 8 CFU / g, the viscosity is greater than or equal to 6500 cP, the whey separation rate is less than 40%, the free phenol content is 30-50 mg GAE / 100 g, the DPPH free radical scavenging rate is 20-30%, and the ABTS free radical scavenging rate is 4-7%.

5. Process for the preparation of a yoghurt according to any one of claims 1 to 4, characterized in that, comprising the following steps: Step (1): mixing millet and water at a weight ratio of 1:(3-4) to obtain a mixed liquid; adding amylase to the obtained mixed liquid after gelatinization treatment, treating at 70-90℃ for 90-110min, and then passing through a 100-200 mesh sieve to obtain a hydrolyzed millet liquid; Step (2): mixing the prepared hydrolyzed millet liquid with water and milk powder to obtain a homogenized liquid; or drying the prepared hydrolyzed millet liquid to obtain hydrolyzed millet liquid powder; mixing the obtained hydrolyzed millet liquid powder with liquid milk to obtain a homogenized liquid; Step (3): heat treating the homogenized liquid obtained in step (2), and then cooling to 40-45℃; adding saccharifying enzyme and inoculating lactic acid bacteria starter, incubating at 40-45℃ to simultaneously perform enzyme hydrolysis and fermentation until the pH is below 4.6, stirring to break the emulsion, and cooling to 3-5℃, and then aging at 3-5℃.

6. The method of preparing a yogurt according to claim 5, characterized in that, In step (1), the amylase is alpha amylase, and in step (3), the saccharifying enzyme is glucoamylase.

7. The method of preparing a yoghurt according to claim 5 or 6, characterized in that, The preparation method of the mixed liquid is as follows: crushing millet to pass through an 80 mesh sieve to obtain millet powder; mixing the millet powder with water, and then soaking at 40-60℃ for 20-40min; or mixing millet with water, soaking at 40-60℃ for 20-40min, and then performing beating treatment; and / or, the gelatinization treatment is at 85-95℃ for 50-70min; and / or, the addition amount of amylase is 0.02-0.04% of the mass of millet; and / or, the addition amount of saccharifying enzyme is 0.005-0.012% of the mass of the homogenized liquid in step (2); and / or, the addition amount of lactic acid bacteria starter is 0.03-0.5% of the mass of the homogenized liquid in step (2).

8. The method of preparing a yoghurt according to any one of claims 5-7, characterized in that, In step (3), the heat treatment is at 90-98℃ for 3-8min.

9. The method of preparing a yoghurt according to any one of claims 5-8, characterized in that, In step (3), the lactic acid bacteria starter comprises one or more of Streptococcus thermophilus starter, Lactobacillus bulgaricus starter, Bifidobacterium starter, and Lactococcus lactis starter; Preferably, the lactic acid bacteria starter comprises Streptococcus thermophilus starter and Lactobacillus bulgaricus starter; more preferably, in the lactic acid bacteria starter, the weight ratio of Streptococcus thermophilus starter to Lactobacillus bulgaricus starter is (1-10):

1. And / or, in the step (3), the fermentation treatment time is 3-3.5h; And / or, the aging time is 12-24h.

10. The method of preparing a yoghurt according to any one of claims 5-9, characterized in that, In the step (2), the homogenization treatment temperature is 50-70℃, and the pressure is 15-25MPa.

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