Preparation method of soybean-based charcoal-fired fermented plant milk

Abstract

The invention discloses a preparation method of soybean-based charcoal-roasted fermented plant milk, and belongs to the technical field of food fermentation. The invention provides a preparation method of fermented plant milk. The taste smoothness and stability of the fermented plant milk can be effectively improved. The main process comprises the following steps: cleaning, soaking, pulping, blending, homogenizing, Maillard treatment, inoculating and fermenting. The obtained fermented plant milk does not contain any animal raw material, is fermented from whole plant raw materials, optimizes the rough taste and low water binding capacity of a bean fermented product, and has rich and unique charcoal-roasted fermented soybean milk flavor; after Maillard treatment, the texture of the soybean yoghurt is obviously improved, the gel is fine and uniform, and the taste is fine, smooth and soft.

Description

Technical Field

[0001] The invention belongs to the field of food fermentation processing, and in particular relates to a method for preparing soybean-based charcoal-roasted fermented plant milk. Background Art

[0002] Fermented soy milk is a popular high-quality plant protein beverage made from soybeans. With the continuous increase in public consumption demand, beverages with health, pure plants and probiotics as keywords are pushed into the market. At present, the main factors limiting fermented soy milk products come from the rough taste and poor water retention, which seriously affect consumers' sensory experience.

[0003] In order to overcome this shortcoming, the products on the market at this stage mainly use technologies such as ultrasound and high-pressure homogenization or add additives such as animal milk powder and stabilizers to enhance the taste and flavor of fermented soy milk. Under the premise of keeping costs low, there is still no effective large-scale production solution to improve the rough taste and low water holding capacity of fermented soy milk. Summary of the invention

[0004] The purpose of the present invention is to effectively improve the rough taste and low water holding capacity of fermented soy milk. In order to solve the above technical problems, the present invention provides a charcoal-roasted fermented soy milk with a stable structure, a thick texture and a strong water holding capacity. The fermented soy milk is obtained by directly inoculating Lactobacillus casei powder into pure soy milk for fermentation.

[0005] The present invention also provides a method for preparing the soybean-based charcoal-roasted fermented vegetable milk, and the preparation method is as follows:

[0006] (1) Weigh 100 g of clean and dry soybeans, remove the skin and embryo, and soak them in 800 ml of water at 90°C for 10 min.

[0007] (2) The soybeans fully soaked in step (1) are pulped to separate the product and waste residue, and finally 5% by mass of glucose is added to the pure soy milk without impurities. Then, high-pressure homogenization (50 MPa, 5 min) is performed.

[0008] (3) The pure soy milk without impurities treated in step (2) is subjected to Maillard treatment (95° C., 6 h) and cooled to obtain the treated sterile pre-fermented soy milk.

[0009] (4) Adding 1.5% by mass of Lactobacillus casei powder starter to the aseptic pre-fermented soymilk treated in step (3), fermenting at a constant temperature of 40° C. for 12 hours, and stopping the fermentation when the termination acidity reaches pH=4.2.

[0010] It is further defined that the peeling in step (1) means that the volume fraction of the remaining soybean skin is less than 1% of the total soybean skin, and the germ removal means that the volume fraction of the remaining soybean embryo is less than 0.2% of the whole soybean.

[0011] Beneficial effects: The fermented plant milk obtained by the present invention does not contain any animal raw materials, is fermented from all plant raw materials, optimizes the rough taste and low water holding capacity of fermented soy products, and contains a strong and unique charcoal-roasted fermented soy milk flavor; after Maillard treatment, the texture of soy yogurt is significantly improved, the gel is delicate and uniform, and the taste is delicate and smooth. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Scanning electron microscope (SEM) images of the fermented soymilk gel structure; (A) is the sample treated with Maillard for 6 hours (MFP6), (B) is the control sample (FP0), and (C) is the sample treated with heat for 6 hours (FP6).

[0013] Figure 2 This is a rheological temperature scanning change diagram of fermented soymilk gel; wherein the abscissa is time, and the ordinate is elastic modulus, viscous modulus and real-time temperature.

[0014] Figure 3 These are actual samples of soybean-based charcoal-grilled fermented plant milk; from left to right are samples that were processed with Maillard for 2 to 8 hours (MFP2 to MFP8).

[0015] Figure 4 These are actual photos of samples of high-hardness and chewy charcoal-roasted soy yogurt. From the top left to the bottom right are samples that were processed by Maillard for 2 to 8 hours (MFP2 to MFP8). Specific embodiments

[0016] The Lactobacillus casei powder starter selected by the present invention is commercially purchased from Taobao.

[0017] The soybeans were Longken soybeans purchased commercially and offline.

[0018] The specific embodiments of the present invention are described in detail below.

[0019] Example 1

[0020] A method for preparing soybean-based charcoal-roasted fermented vegetable milk, the specific steps are as follows:

[0021] (1) Weigh 100 g of clean and dry soybeans, remove the husks and germs, and soak them in 800 ml of water at 90° C. for 10 min. Husk removal means that the volume fraction of the remaining soybean husks is less than 1% of the total soybean husks, and germ removal means that the volume fraction of the remaining soybean germs is less than 0.2% of the whole soybeans.

[0022] (2) The soybeans fully soaked in step (1) are pulped to separate the product and waste residue, and finally 5% by mass of glucose is added to the pure soy milk without impurities. Then, high-pressure homogenization (50 MPa, 5 min) is performed.

[0023] (3) The pure soy milk without impurities treated in step (2) is subjected to Maillard treatment (95° C., 6 h) and cooled to obtain the treated sterile pre-fermented soy milk.

[0024] (4) Adding 1.5% by mass of Lactobacillus casei powder starter to the aseptic pre-fermented soymilk treated in step (3), fermenting at a constant temperature of 40° C. for 12 hours, and stopping the fermentation when the termination acidity reaches pH=4.2.

[0025] (5) Stir every 2-3 hours during fermentation to prevent solid precipitation.

[0026] Example 2

[0027] A method for preparing high-hardness chewable charcoal-roasted soybean yogurt, the specific steps are as follows:

[0028] (1) Weigh 100 g of clean and dry soybeans, remove the husks and germs, and soak them in 600 ml of water at 90° C. for 10 min. Husk removal means that the volume fraction of the remaining soybean husks is less than 1% of the total soybean husks, and germ removal means that the volume fraction of the remaining soybean germs is less than 0.2% of the whole soybeans.

[0029] (2) The soybeans fully soaked in step (1) are pulped to separate the product and waste residue, and finally 5% by mass of glucose is added to the pure soy milk without impurities. Then, high-pressure homogenization (50 MPa, 5 min) is performed.

[0030] (3) The pure soy milk without impurities treated in step (2) is subjected to Maillard treatment (75° C., 24 h) and cooled to obtain the treated sterile pre-fermented soy milk.

[0031] (4) Add 1.5% by mass of Lactobacillus casei powder starter to the aseptic pre-fermented soymilk treated in step (3), divide the mixture into 10 ml sub-packaging boxes, and ferment at a constant temperature of 40° C. for 12 hours. When the end acidity reaches pH=4.2, the fermentation is stopped and the soymilk is refrigerated at 4° C.

[0032] The experimental results are verified by the following experiments:.

[0033] The impurity-free soymilk was heated for 2, 4, 6, and 8 hours and then fermented with Maillard treatment to obtain heating group samples (FP2, FP4, FP6, FP8) and Maillard treatment group samples (MFP2, MFP4, MFP6, MFP8). The fermented soymilk without heating was used as the blank control (FP0).

[0034] 1. Analysis of the texture and water holding properties of fermented soymilk gel As shown in Table 1, Maillard treatment significantly increased the hardness of the fermentation-induced gel. This indicates that Maillard treatment can promote the formation of gel networks. The viscosity of the fermented soymilk samples increased with the increase in the degree of treatment, indicating that heating is the root cause of this phenomenon. The change in adhesion is mainly caused by the formation of high molecular weight protein polymers and protein micelles. Overall, the fermented soymilk samples treated with Maillard for 6 hours showed stronger solid properties, higher hardness and elasticity, and the smaller change in viscosity made it less greasy than the pure heating treatment group.

[0035] The gel has a porous structure that can retain water, nutrients and other components, and WHC is closely related to its internal network structure. Gel foods with high water holding capacity can effectively resist structural shrinkage caused by water loss, which is a reflection of gel strength and stability. The more stable the gel structure, the stronger the ability to absorb water, and the less likely the water is to be squeezed out by external forces. As shown in Table 1, the water holding capacity of fermented soy protein gel decreases with the extension of heating time. The WHC of MFP6 is significantly higher than that of other samples (83.99%), indicating that moderate Maillard reaction will cross-link the network structure inside the gel, resulting in higher WHC. However, excessive treatment will lead to a loose protein network structure and a decrease in WHC (MFP8, 82.83%).

[0036] In summary, the texture properties and water holding capacity of soy protein gel after 6 hours of Maillard treatment are better, and it has a better taste and better structural stability when used in food.

[0037] 2. Analysis of the Gel Structure of Fermented Soymilk The microstructure of the gel was observed by SEM at 1000× to 5000× magnification. At 1000× magnification, prolonged heating time caused the protein gel structure to become looser and cracks to appear on the surface ( Figure 1C, FP6). This phenomenon may be related to the weakening of the interaction between protein molecules, resulting in a decrease in the stability of the gel network. The stronger Maillard reaction causes more structural changes and changes the tertiary structure of the protein. The arrangement between protein molecules becomes loose, and the pores in the gel network structure increase. Observed at 5000×, MFP6 gel presents an obvious honeycomb structure. The structure of FP6 ( Figure 1 C) is more like a "ball and stick" structure connected together. The formation of this structure may be related to the cross-linked soy protein isolate (SPI) aggregates produced by microbial fermentation. Although its structure is dense and its skeleton is coarse, its distribution is uneven. In contrast, MFP8 ( Figure 1 A) It presents a "spider web" polymer cross-linking morphology, with a loose network, regular pores, and a more stable network skeleton. It shows stronger continuity and uniformity, while showing strong water binding ability, reducing water analysis during compression. The formation of this structure may be related to the hydrolysis and reorganization of proteins during fermentation. A three-dimensional gel network structure composed of stable protein micro-micelles is formed.

[0038] In summary, the SEM observation results show that the heating time has a significant effect on the microstructure of protein gel. Prolonging the heating time will lead to loose gel structure and cracks on the surface. Maillard reaction synergistic fermentation forms a stable three-dimensional gel network structure through the cross-linking of reaction intermediates and extracellular polysaccharide filaments, which has stronger water binding capacity and better structural stability. These microstructural changes directly affect the functional properties of protein gel, such as hydration capacity, mechanical strength and taste. Therefore, in the process of food processing, it is of great significance to reasonably control the heating time, Maillard reaction degree and fermentation conditions for regulating the microstructure and functional properties of protein gel.

[0039] 3. Temperature scanning property analysis of fermented soy milk like Figure 2As shown in the figure, the two fermented soymilk samples exhibited typical rheological characteristics of protein gel during the temperature scanning process. When the ambient temperature increased linearly from 25°C to 75°C, both G' (storage modulus) and G" (loss modulus) showed a significant downward trend. This change pattern is consistent with the typical characteristics of heat-induced relaxation of the protein gel network structure. It is worth noting that in the entire temperature change range, G' is always higher than G", and the modulus ratio (G' / G") is maintained between 1.5-2.8, indicating that the sample system always maintains a viscoelastic characteristic dominated by elasticity. This mechanical response characteristic shows that the fermented soymilk system has formed a three-dimensional network structure, in which the elastic structure formed by the interaction of soy protein-protein occupies a dominant position. As the heating temperature increases and then decreases, the fermented soymilk undergoes a structural reorganization process in which protein molecules unfold and aggregate to form a gel network. This leads to an increase in the viscoelasticity of the Maillard-treated sample (MFP6), showing stronger elasticity or curing properties. Compared with the Maillard-treated sample, the changes in the fermented soymilk sample simply heated are not so obvious. The results show that this Maillard treatment method can control The viscoelasticity of Lactobacillus casei fermented soy milk under drastic temperature changes, and the viscoelasticity of MFP6 changed the most, with a stronger gel structure. These samples have good thermal stability or strong gelation at high temperatures, and the tissue state is more stable. Therefore, Maillard treatment is more likely to promote the formation of a stronger cross-linked network in fermented soy milk, and it has better stability at high temperatures. The results of this experiment have important guiding significance for the process optimization of plant-based fermented products: the Maillard treatment temperature is controlled at 75-95℃ and the reaction time is within 4-6 hours, which can produce the most appropriate Maillard reaction system. This Maillard-modified fermented soy milk gel system has multiple application values ​​in the field of food innovation: (1) As a texture improver for plant-based yogurt, it can solve the technical problem of easy water precipitation of traditional products; (2) In the field of 3D food printing, its rheological properties that resist large temperature changes are suitable as food printing consumables; (3) As a probiotic delivery carrier, combined with the control of the degree of Maillard reaction and the kinetics of flavor substance formation, its synergistic mechanism with probiotic metabolism is explored.

[0040] Table 1 Texture characteristics and WHC of Maillard reaction modified SPI gels with different treatment times (2-8 h) Note: The results are expressed as mean ± standard deviation (n = 3). Different letters (ae) in the same column indicate that the means of different samples under the same indicator are significantly different (P<0.05).

Claims

1. A method for preparing soybean-based charcoal-roasted fermented vegetable milk, characterized in that: The fermented soybean milk is obtained by inoculating Lactobacillus casei powder into pre-fermented soybean milk for fermentation.

2. The method for preparing the soybean-based charcoal-roasted fermented vegetable milk according to claim 1, characterized in that: The preparation method is as follows: (1) Weigh 100 g of clean and dry soybeans, remove the skin and embryo, and soak them in 800 ml of water at 90°C for 10 min; (2) The soybeans fully soaked in step (1) are pulped to separate the product and waste residue, and finally 5% by mass of glucose is added to the pure soy milk without impurities. Then, high-pressure homogenization (50 MPa, 5 min) is performed; (3) subjecting the pure soy milk without impurities treated in step (2) to Maillard treatment (95° C., 6 h) and cooling the treated sterile pre-fermented soy milk; (4) adding 1.5% by mass of Lactobacillus casei powder starter to the aseptic pre-fermented soymilk treated in step (3), fermenting at a constant temperature of 40° C. for 12 h, and stopping the fermentation when the termination acidity reaches pH = 4.2; It is further defined that the peeling in step (1) means that the volume fraction of the remaining soybean skin is less than 1% of the total soybean skin, and the germ removal means that the volume fraction of the remaining soybean embryo is less than 0.2% of the whole soybean.

Images