Solid plant yoghourt as well as preparation method and application thereof

Abstract

The invention belongs to the field of yoghourt preparation, and discloses solid plant yoghourt as well as a preparation method and application thereof. Adding fruit raw materials into the bean matrix, mixing to obtain a plant-based emulsion, sterilizing, inoculating a direct vat set yoghurt starter, and fermenting; after fermentation, refrigerating and after-ripening, freeze-drying to obtain plant yoghourt freeze-dried powder, and mixing the plant yoghourt freeze-dried powder with a thickening agent to prepare the solid plant yoghourt. Substances such as starch and lipid in the fruit raw materials can effectively enhance the gel network strength and reduce the damage of freeze-drying to a protein structure; through the flavor masking effect, the beany flavor of the bean matrix is obviously weakened, and the bean matrix is endowed with the characteristic fruity flavor. On the basis, plant yoghourt freeze-dried powder and a thickening agent are matched to prepare solid plant yoghourt, the solid plant yoghourt can have the texture and taste close to those of fresh yoghourt after being brewed with cold water or normal-temperature water, and the thickening agent can reconstruct part of protein gel network by increasing hydrophobic interaction and ionic bond proportion in a system, so that the solid plant yoghourt has the advantages that the solid plant yoghourt can be used for preparing the solid plant yoghourt; the water-holding capacity and the viscosity of the recovered yoghourt are improved.

Description

Technical Field

[0001] The present invention belongs to the field of yogurt preparation, and particularly relates to a solid plant yogurt, a preparation method thereof and an application thereof. Background Art

[0002] Plant-based yogurt is a plant protein beverage product made from plants containing a certain amount of protein and / or their products as raw materials, through processes such as sterilization and fermentation to reduce the pH value, and adding or not adding non-animal-derived ingredients before or after fermentation. Driven by the deepening of the concept of healthy diet and the demand for sustainable development, in recent years, plant-based yogurt has been attracting the attention of capital and the market as an ideal substitute for traditional animal yogurt.

[0003] Liquid plant yogurt products, like ordinary yogurt, generally need to be stored at 4°C for 21 days, and the quality needs to be maintained by relying on the cold chain system during storage and transportation. This not only increases the cost of the entire industrial chain, but also limits the market radiation radius, and fails to fully meet the current market demand for convenient consumption. Therefore, this demand in the current market encourages the improvement of existing methods or the creation of new methods for producing solid plant yogurt. The plant acid milk powder transformed by dehydration engineering shows unique advantages in breaking through the boundaries of traditional consumption scenarios, and its application fields can be extended to functional foods (such as candies, baked products, beverages, ice creams, etc.). In the existing dehydration technology system, freeze-drying is regarded as the preferred process solution because it can maintain the volatile flavor components, heat-sensitive nutrients and probiotic activity to the greatest extent. However, this technology has other limitations: the protein conformational changes caused by ice crystal nucleation-growth, and the gel network reconstruction caused by the synergistic effect of dehydration phase change, resulting in significant attenuation of rheological properties such as gel strength attenuation, viscosity reduction and water-holding capacity weakening in the rehydration system. Most studies focus on the protection of probiotics in acid milk powder, such as "Preparation of Probiotic Fermented Sea Buckthorn Acid Milk Powder and Evaluation of Its Product Characteristics" and "Spray Drying Process of Lychee Yogurt and Application of Trehalose as a Protective Agent". Different from animal yogurt, plant yogurt generally shows greater viscosity, but the protein gel structure of plant yogurt is damaged during the freeze-drying process, resulting in problems such as low viscosity, thin taste, lack of flavor and poor stability in the reconstituted yogurt after reconstitution. Summary of the Invention

[0004] In order to overcome the disadvantages of low viscosity, poor flavor and instability of the plant yogurt freeze-dried powder after being reconstituted with water in the above-mentioned existing technologies, the object of the present invention is to provide a preparation method of solid plant yogurt: the preparation method is simple to operate. By adding fruit raw materials to the soybean matrix emulsion, after fermentation, the plant yogurt freeze-dried powder is prepared by dehydration through the freeze-drying process, and then the freeze-dried powder is mixed with a thickener to prepare the solid plant yogurt. The addition of fruit raw materials not only significantly improves the water-holding capacity and viscosity of the reconstituted yogurt, but also can endow it with a unique fruity flavor; and the addition of the thickener further improves the problems of low viscosity and poor stability of the reconstituted plant yogurt. However, the thickeners suitable for animal yogurt are not suitable for plant yogurt. Selecting a thickener suitable for solid plant yogurt is a key problem to be solved in the present invention.

[0005] Another object of the present invention is to provide a solid plant yogurt prepared by the above preparation method: the solid plant yogurt prepared by mixing the plant yogurt freeze-dried powder with a thickener has a small volume and is easy to package and transport; it has good instant solubility (fast dissolution speed in normal temperature or cold water); after being reconstituted with water, the sourness and consistency are both moderate; it has a unique fruity aroma.

[0006] Another object of the present invention is to provide the application of the above solid plant yogurt: the reconstituted plant yogurt obtained by reconstituting the solid plant yogurt with cold water or normal temperature water has been significantly improved in terms of viscosity, texture, taste and stability, can restore the flavor and taste of fresh plant yogurt, and can be directly drunk without fermentation. In addition, the solid plant yogurt is rich in high protein, has a strong sour taste and contains probiotics, so it can play an important role as a flavor enhancer, nutritional supplement and texture improver in the product formula.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A preparation method of solid plant yogurt includes the following operating steps: adding fruit raw materials to the soybean matrix, mixing with drinking water to obtain a plant-based emulsion, and after sterilization, inoculating a direct-to-vat yogurt starter for fermentation; after the fermentation is completed, refrigerating for after-ripening, obtaining the plant yogurt freeze-dried powder through freeze-drying, and then mixing the plant yogurt freeze-dried powder with a thickener to prepare the solid plant yogurt.

[0009] The above-mentioned preparation method of solid plant yogurt specifically follows the following operating steps:

[0010] S1: Stir and dissolve the soybean matrix and fruit raw materials with heated drinking water, and then make up the volume with drinking water to obtain a plant-based emulsion;

[0011] S2: Heat the central temperature of the plant-based emulsion obtained in S1 to 85±0.5°C, and then maintain the temperature for 20 minutes for sterilization;

[0012] S3: Cool the sterilized plant-based emulsion to below 45°C, inoculate with a direct vat set yogurt starter, and carry out static fermentation. After refrigerating and ripening at 4°C for more than 12 h, plant yogurt is obtained;

[0013] S4: Demulsify the plant yogurt obtained in S3 and then pre-freeze it. After freeze-drying, plant yogurt freeze-dried powder is obtained;

[0014] S5: Mix the plant yogurt freeze-dried powder obtained in S4 with a thickener to prepare solid plant yogurt.

[0015] The bean matrix described in step S1 is fresh soy milk and / or pure soy flour, preferably fresh soy milk and / or pure soy flour of soybeans;

[0016] The plant-based emulsion described in step S1 also contains sucrose;

[0017] The fruit raw material described in step S1 is not limited to fruit juice or fruit powder. Specifically, fruit juice or fruit powder of durian, litchi, coconut, banana, green grape, avocado, mango or pineapple is used, preferably banana powder and avocado powder, and more preferably avocado powder.

[0018] The formula of the plant-based emulsion described in step S1 is that each 1000 mL of the plant-based emulsion contains the following raw materials: 60 - 100 g of pure soy flour, 5 - 40 g of fruit powder, 60 - 90 g of sucrose, and the balance is drinking water.

[0019] Preferably, the formula of the plant-based emulsion is that each 1000 mL of the plant-based emulsion contains: 80 - 90 g of pure soy flour, 20 - 30 g of fruit powder, 65 - 75 g of granulated sugar, and the balance is drinking water.

[0020] The inoculation amount of the direct vat set yogurt starter described in step S3 is 0.01% - 0.1%, and the bacterial content in the plant-based emulsion after inoculation is 2×10 9 ~2×10 10 CFU / L;

[0021] The fermentation temperature is 30 - 42°C, and the fermentation time is 8 - 18 h.

[0022] The pre-freezing temperature described in step S4 is -20 - -80°C, and the pre-freezing time is 2 - 8 h; the freeze-drying time is 24 - 48 h.

[0023] The above-mentioned plant yogurt freeze-dried powder is mixed with a thickener to prepare solid plant yogurt. When in use, it is directly drunk after being diluted with drinking water.

[0024] The thickener includes a low-ester pectin single preparation, or a mixed preparation of any one or more of guar gum and carrageenan.

[0025] The addition amount of the thickener is 0.2%-2% of the mass of the plant yogurt freeze-dried powder, preferably 0.5%-1.68%.

[0026] A solid plant yogurt obtained by the above preparation method is small in volume, easy to package and transport; has good instant solubility (fast dissolution rate at normal temperature or in cold water); has moderate sour-sweet taste and consistency after being brewed; and has a unique fruity aroma.

[0027] When the above solid plant yogurt is used, it is reconstituted by brewing with drinking water at 0-45°C according to the mass ratio of powder to water of 1:10-1:3 to obtain a reconstituted plant yogurt, which can be directly drunk without fermentation. The flavor is better after refrigerating at 0-4°C for 1-2 hours after brewing.

[0028] The application of the above solid plant yogurt as a flavor enhancer, nutritional supplement or texture improver in the food field.

[0029] The principle of the present invention:

[0030] Aiming at the problems of low viscosity, poor flavor and instability of the plant yogurt freeze-dried powder after being reconstituted with water, the present invention adds fruit raw materials to the plant-based emulsion, performs co-fermentation and then freeze-dries it into powder, endowing the yogurt freeze-dried powder with characteristic fruity aroma and having a certain improvement effect on the gel properties of the reconstituted plant yogurt after its reconstitution with water; the solid plant yogurt prepared by mixing the freeze-dried powder with a thickener has excellent rehydration performance, can be directly brewed with cold water or normal-temperature water, quickly restores to a partial gel state, restores the flavor and taste of the plant yogurt, and the thickener therein can significantly improve the viscosity, texture, taste and stability of the reconstituted plant yogurt, etc., and can be directly drunk without fermentation. The solid plant yogurt of the present invention can also be used as a formulation component of various products.

[0031] The present invention has the following advantages and beneficial effects compared with the prior art:

[0032] (1) In the present invention, by adding flavor fruit powder to the soybean matrix for co-fermentation, substances such as starch, lipids and dietary fiber rich in the fruit powder can be used to fill the gel network structure, effectively enhance the mechanical strength of the gel network, reduce the damage of ice crystal growth and dehydration to proteins during the freeze-drying process, and play a certain protective role.

[0033] (2) The natural volatile components (such as esters and aldehydes) in the fruit powder used in the preparation process of the present invention significantly weaken the soybean odor existing in the soybean matrix itself and the odor of the thickener introduced through the flavor masking effect of the flavor substances, endowing the solid plant yogurt with characteristic fruity aroma, and the active substances therein can also realize the synergistic optimization of nutritional fortification and sensory quality.

[0034] (3) The present invention uses freeze-drying technology to prepare plant yogurt freeze-dried powder, which can maximize the preservation of the activity of lactic acid bacteria and the biological functions of various metabolites, providing a strong guarantee for long-term storage and transportation. By mixing the freeze-dried powder with a thickener to obtain solid plant yogurt, after reconstitution with water, part of the gel structure can be reconstructed, improving the taste and stability after reconstitution. At the same time, it is found that increasing the proportion of hydrophobic interactions in the reconstitution system can increase the viscosity of the reconstituted yogurt. Description of the Drawings

[0035] Figure 1 It is a comparison chart of the water-holding capacity of different fruit powder additions to plant yogurt and reconstituted plant yogurt in Example 1, Example 2, and Example 5 of the present invention.

[0036] Figure 2 It is a comparison chart of the viscosity of different fruit powder additions to plant yogurt and reconstituted plant yogurt in Example 1, Example 2, and Example 5 of the present invention.

[0037] Figure 3 It is a comparison chart of the viscosity of adding banana powder before and after fermentation to reconstituted plant yogurt in Comparative Example 1 and Comparative Example 2 of the present invention.

[0038] Figure 4 It is a comparison chart of the viscosity of reconstituted plant yogurt with different reconstitution water temperatures in Example 3 of the present invention.

[0039] Figure 5 It is a comparison chart of the viscosity of reconstituted plant yogurt with different powder-to-water ratios in Example 4 of the present invention.

[0040] Figure 6 It is a comparison chart of the molecular forces in the reconstitution system of reconstituted plant yogurt with different powder-to-water ratios in Example 4 of the present invention.

[0041] Figure 7 It is a comparison chart of the viscosity of reconstituted plant yogurt with different amounts of low-ester pectin added in Example 6 of the present invention.

[0042] Figure 8 It is a comparison chart of the molecular forces in the reconstitution system of reconstituted plant yogurt with different amounts of low-ester pectin added in Example 6 of the present invention. Detailed Embodiments

[0043] The following further illustrates the content of the present invention with specific embodiments, but should not be construed as a limitation to the present invention.

[0044] Example 1

[0045] The method of this example is used to prepare plant yogurt freeze-dried powder, including the following steps:

[0046] (1) Take 2.8 kg of banana powder, 7 kg of granulated sugar, and 9 kg of pure soy flour. After mixing the powders evenly, stir and completely dissolve them with warm drinking water, and make up to 100 L with drinking water to obtain a plant-based emulsion; perform pasteurization on the plant-based emulsion. After its central temperature reaches 85 ± 0.5 °C, maintain the temperature for 20 min continuously;

[0047] (2) Cool the sterilized plant-based emulsion to below 42 °C, and inoculate with a direct vat set yogurt starter to make the bacterial content in the plant-based emulsion 2×10 9 CFU / L; Let the inoculated emulsion stand and ferment at a constant temperature of 30 ± 0.5 °C for 18 h, and after the fermentation is completed, refrigerate and ripen at below 4 °C for more than 12 h to obtain plant yogurt;

[0048] (3) After demulsifying the ripened plant yogurt above, spread it flat on a tray and pre-freeze it at -80 °C for 2 h to ensure that the yogurt sample freezes quickly and completely; After the cold trap temperature of the vacuum freeze dryer drops below -50 °C, place the tray containing the pre-frozen yogurt into it and dry for 24 h; After drying, crush the freeze-dried blocks and powder them to obtain plant yogurt freeze-dried powder.

[0049] Example 2

[0050] Other steps are the same as in Example 1, the difference is only that: the banana powder in step (1) is replaced with durian powder, litchi powder, coconut powder, green grape powder, avocado powder, mango powder or pineapple powder.

[0051] Example 3

[0052] This example refers to the method for preparing plant yogurt freeze-dried powder in Example 1 and performs reconstitution on the obtained plant yogurt freeze-dried powder, including the following steps:

[0053] Take 17.8 g of the freeze-dried powder, and separately stir and dissolve it with 82.2 g of drinking water at 4 °C, 25 °C, 45 °C, 55 °C, and 65 °C (the total weight of one portion of reconstituted plant yogurt is 100 g). After observing no obvious lumps, refrigerate at 0 - 4 °C for 1 - 2 h (the purpose is to stabilize the reconstituted plant yogurt) to obtain reconstituted plant yogurt.

[0054] Example 4

[0055] This example refers to the method for preparing plant yogurt freeze-dried powder in Example 1 and performs reconstitution on the obtained plant yogurt freeze-dried powder, including the following steps:

[0056] Weigh out 14.3 g, 16.7 g, 17.8 g, 20 g, and 25 g of the freeze-dried powder respectively, and dissolve it while stirring with drinking water at 25°C (the total weight of one portion of the reconstituted plant yogurt is 100 g). After observing no obvious lumps, refrigerate it at 0 - 4°C for 1 - 2 h (this is to stabilize the reconstituted plant yogurt), and obtain the reconstituted plant yogurt.

[0057] Example 5

[0058] In this example, referring to the optimal rehydration method obtained in Examples 3 and 4, the plant yogurt freeze-dried powder obtained in Examples 1 and 2 is rehydrated, including the following steps:

[0059] Weigh out 17.8 g of the freeze-dried powder, and dissolve it while stirring with 82.2 g of drinking water at 25°C (the total weight of one portion of the reconstituted plant yogurt is 100 g). After observing no obvious lumps, refrigerate it at 0 - 4°C for 1 - 2 h (this is to stabilize the reconstituted plant yogurt), and obtain the reconstituted plant yogurt.

[0060] Example 6

[0061] In this example, referring to the method for preparing the plant yogurt freeze-dried powder in Example 1, the freeze-dried powder is mixed with low-ester pectin to prepare a solid plant yogurt, and then rehydrated, including the following steps:

[0062] Weigh out 5 portions of 17.8 g of the freeze-dried powder, mix them evenly with 0.1 g, 0.15 g, 0.2 g, 0.25 g, and 0.3 g of low-ester pectin respectively to prepare solid plant yogurt, and then dissolve them while stirring with 82.2 g of drinking water at 25°C respectively. After observing no obvious lumps, refrigerate them at 0 - 4°C for 1 - 2 h (this is to stabilize the reconstituted plant yogurt), and obtain the reconstituted plant yogurt.

[0063] Example 7

[0064] Other steps are the same as in Example 6, except that: replace the low-ester pectin with guar gum, soluble soybean polysaccharide, carrageenan, sodium alginate, or sodium caseinate, and the addition amounts are 0.1 g (low addition) and 0.3 g (high addition) respectively.

[0065] Example 8

[0066] In this example, referring to the method for preparing the plant yogurt freeze-dried powder in Example 1, the freeze-dried powder is mixed with various thickeners to prepare a solid plant yogurt, and then rehydrated, including the following steps:

[0067] Take 17.8 g of freeze-dried powder, mix it evenly with 0.1 g of low-ester pectin and 0.1 g of guar gum to prepare a solid plant yogurt. Then, while stirring, dissolve it separately with 82.2 g of drinking water at 25 °C. After observing no obvious lumps, refrigerate it at 0 - 4 °C for 1 - 2 h (the purpose is to stabilize the reconstituted plant yogurt) to obtain the reconstituted plant yogurt.

[0068] Example 9

[0069] In this example, referring to the method for preparing the freeze-dried powder of plant yogurt in Example 1, the freeze-dried powder is mixed with various thickeners to prepare a solid plant yogurt, and then it is reconstituted, including the following steps:

[0070] Take 17.8 g of freeze-dried powder, mix it evenly with 0.1 g of low-ester pectin and 0.1 g of carrageenan to prepare a solid plant yogurt. Then, while stirring, dissolve it separately with 82.2 g of drinking water at 25 °C. After observing no obvious lumps, refrigerate it at 0 - 4 °C for 1 - 2 h (the purpose is to stabilize the reconstituted plant yogurt) to obtain the reconstituted plant yogurt.

[0071] Example 10

[0072] In this example, referring to the method for preparing the freeze-dried powder of plant yogurt in Example 1, the freeze-dried powder is mixed with various thickeners to prepare a solid plant yogurt, and then it is reconstituted, including the following steps:

[0073] Take 17.8 g of freeze-dried powder, mix it evenly with 0.1 g of low-ester pectin, 0.05 g of guar gum and 0.05 g of carrageenan to prepare a solid plant yogurt. Then, while stirring, dissolve it separately with 82.2 g of drinking water at 25 °C. After observing no obvious lumps, refrigerate it at 0 - 4 °C for 1 - 2 h (the purpose is to stabilize the reconstituted plant yogurt) to obtain the reconstituted plant yogurt.

[0074] Comparative Example 1

[0075] The difference from Example 1 is only that no fruit powder is added to the plant-based emulsion. The freeze-dried powder of plant yogurt obtained in this comparative example is reconstituted, including the following steps:

[0076] Take 15.0 g of freeze-dried powder, while stirring, dissolve it with 85.0 g of drinking water at 25 °C (the total weight of one portion of reconstituted plant yogurt is 100 g). After observing no obvious lumps, refrigerate it at 0 - 4 °C for 1 - 2 h (the purpose is to stabilize the reconstituted plant yogurt) to obtain the reconstituted plant yogurt.

[0077] Comparative Example 2

[0078] The difference from Comparative Example 1 is only that banana powder is added during the reconstitution process. It includes the following steps:

[0079] Take 15.0 g of freeze-dried plant yogurt powder and 2.8 g of banana powder, and while stirring, dissolve them in 82.2 g of drinking water at 25 °C (the total weight of one portion of reconstituted plant yogurt is 100 g). After observing that there are no obvious lumps, refrigerate it at 0 - 4 °C for 1 - 2 h (the purpose is to stabilize the reconstituted plant yogurt), and obtain the reconstituted plant yogurt.

[0080] Comparative Example 3

[0081] The difference from Example 6 is only that no thickener is added during the preparation process.

[0082] Experimental Example 1

[0083] In Experimental Example 1, the plant yogurt obtained from Example 1, Example 2, and Comparative Example 1 and the reconstituted plant yogurt obtained from Example 5 and Comparative Example 1 were used as samples for water-holding capacity and viscosity tests. The test methods are as follows:

[0084] Water-holding capacity: Take 5 g of plant yogurt and reconstituted plant yogurt respectively in a 10 mL centrifuge tube, centrifuge at 4000 r / min for 20 min in a centrifuge, remove the supernatant, and measure the mass of the residue and the centrifuge tube. Water-holding capacity = m 1 / (m 2 -m 0 ). In the formula, m 0 is the mass of the 10 mL centrifuge tube (g), m 1 is the mass of the soy yogurt before centrifugation (g), and m 2 is the mass of the soy yogurt and the centrifuge tube after centrifugation (g).

[0085] Viscosity: Measure 30 mL of plant yogurt and reconstituted plant yogurt (temperature restored to room temperature) and pour them into a 50 mL centrifuge tube. Use a viscometer to measure their viscosities at different rotational speeds of the same rotor. Calculate the viscosity coefficient C according to the following formula, and use the viscosity coefficient C to represent the viscosity of the yogurt.

[0086] V = 2wR c 2 / (R c 2 -R b 2 ) = Aw (rpm → rad / s, w = rotational speed / 2π)

[0087] η = C * V n-1

[0088] In the formula:

[0089] V is the shear rate measured by the viscometer, s -1 ;

[0090] w is the angular velocity of the rotor during viscometer measurement, in rad / s;

[0091] R b is the radius of the rotor, in mm;

[0092] R c is the inner diameter of the container, in mm;

[0093] A is the constant for converting angular velocity to shear rate;

[0094] η is the viscosity, in mPa·s;

[0095] C is the viscosity coefficient.

[0096] As Figure 1 shown, where Comparative Example 1 represents a plant yogurt or reconstituted plant yogurt without adding any fruit powder. It can be concluded that: ① After freeze-drying and reconstitution, the water-holding capacity of plant yogurt all shows a significant decrease; ② Adding fruit powder can effectively improve the water-holding capacity of reconstituted plant yogurt; ③ Taking the water-holding capacity of reconstituted plant yogurt reaching more than 60% (at this time, the yogurt has strong stability) as the evaluation criterion, durian powder, coconut oil powder, banana powder, avocado powder, mango powder and pineapple powder show the best improvement effect.

[0097] As Figure 2 shown, it can be concluded that: ① After freeze-drying and reconstitution treatment, the viscosity of plant yogurt all shows a significant decrease; ② Adding fruit powder can effectively increase the viscosity of reconstituted plant yogurt; ③ Taking the viscosity of reconstituted plant yogurt reaching 4000 mPa·s as the evaluation criterion (at this time, the yogurt can sense an obvious consistency), litchi powder, banana powder and avocado powder show the best improvement effect.

[0098] In the present invention, by adding fruit powder into plant yogurt for co-fermentation and then freeze-drying into powder, the water-holding capacity and viscosity of reconstituted plant yogurt after being reconstituted with water can be effectively improved, thereby enhancing its taste and quality. Among them, banana powder and avocado powder have the most significant improvement effect on the water-holding capacity and viscosity of reconstituted plant yogurt.

[0099] Experimental Example 2

[0100] In Experimental Example 2, the reconstituted plant yogurt obtained from Example 5, Comparative Example 1 and Comparative Example 2 was used as a sample for viscosity testing. The testing method is the same as that in Experimental Example 1.

[0101] As Figure 3As shown, Comparative Example 1 represents a reconstituted plant yogurt without adding any fruit powder, Comparative Example 2 represents a reconstituted yogurt prepared by mixing a solid plant yogurt without adding any fruit powder with banana powder, and Example 5 represents a reconstituted yogurt obtained by adding banana powder to the emulsion, fermenting, and freeze-drying to obtain a solid plant yogurt and then reconstituting it. It can be concluded that adding banana powder to the emulsion and then fermenting and freeze-drying can improve the viscosity of the reconstituted plant yogurt, while adding it later does not have a significant improvement effect.

[0102] Experimental Example 3

[0103] In Experimental Example 3, the reconstituted plant yogurt obtained in Example 3 was used as a sample for viscosity testing. The testing method was the same as that in Experimental Example 1.

[0104] Figure 4 Among them, CK represents plant yogurt. As the reconstitution temperature increases, the viscosity of the reconstituted yogurt decreases. At high temperatures, the molecular kinetic energy increases, resulting in a relatively loose reconstituted tissue structure, and high temperatures also have a certain destructive effect on the protein structure in the system. Among them, the viscosity of the reconstituted yogurt is higher under low-temperature rehydration conditions, and at the same time, the survival rate of lactic acid bacteria can be maintained.

[0105] Experimental Example 4

[0106] In Experimental Example 4, the reconstituted plant yogurt obtained in Example 4 was used as a sample for viscosity and molecular force measurement, as specifically shown in Figure 5 and Figure 6 . The viscosity measurement method was the same as that in Experimental Example 1, and the molecular force measurement method was as follows:

[0107] Molecular force: Accurately weigh 1.0 g of each sample (plant yogurt or reconstituted plant yogurt) and place it in a 50 ml centrifuge tube. Add 19 mL of S 1 (0.6 M NaCl), S 2 (0.6 M NaCl + 1.5 M Urea), S 3 (0.6 M NaCl + 8 M Urea), S 4 (1 mol / L NaOH) four solutions, vortex for 15 - 20 s (maximum power), mix well, place at 4°C for 30 min, then vortex evenly, take 1 mL of the sample solution, centrifuge at 12000 r / min for 10 min, take the supernatant, and measure its protein concentration by the Folin-phenol method. Their solubilities are respectively recorded as C 1 、C 2 、C 3 、C 4 .

[0108] Ionic bond = C 1 / C 4 (%)

[0109] Hydrogen bond = (C2 -C 1 ) / C 4 (%)

[0110] Hydrophobic interaction = (C 3 -C 2 ) / C 4 (%)

[0111] Covalent bond = (C 4 -C 3 ) / C 4 (%)

[0112] Figure 4 It is revealed that the viscosity of the reconstituted plant yogurt shows a significant dependence on the powder - water ratio. When the solid concentration reaches 25% (powder - water mass ratio is 1:3), the viscosity reaches 8852.69 ± 125 mPa·s, far exceeding that of plant yogurt. It is worth noting that Figure 5 shows that the proportion of hydrophobic interaction first increases and then decreases with the increase of the powder - water ratio. It is speculated that the increase in viscosity may be due to the volume exclusion effect rather than the reconstruction of intermolecular forces.

[0113] Experimental Example 5

[0114] In Experimental Example 5, the reconstituted plant yogurt obtained in Example 6 was used as a sample to measure the viscosity and molecular forces of the reconstituted plant yogurt. The methods for measuring viscosity and molecular forces were the same as those in Experimental Example 3.

[0115] As an anionic polysaccharide, low - methoxyl pectin is adsorbed on the surface of protein micelles through electrostatic complexation to form a network gel system, which can retain the free aqueous phase and improve the gel stability of the system. As Figure 7 can be seen, the viscosity of the reconstituted plant yogurt shows a dose - dependent relationship. When the addition amount reaches 0.2 g, the water - holding capacity and apparent viscosity have exceeded those of fresh yogurt. Figure 8 The data of molecular forces in [[ ]] show that the proportions of hydrophobic interaction and ionic bond increase with the increase of the addition amount of low - methoxyl pectin, indicating that low - methoxyl pectin can enhance the viscosity of the system by increasing the proportions of hydrophobic interaction and ionic bond in the reconstituted plant yogurt.

[0116] Experimental Example 6

[0117] In Experimental Example 6, the reconstituted plant yogurts obtained in Example 6, Experimental Example 7 and Comparative Example 3 were used as samples for viscosity measurement. The method for measuring viscosity was the same as that in Experimental Example 3.

[0118] The viscosity of the plant yogurt is 6784.39±207.09 mPa·s. Comparative Example 3 is the reconstituted plant yogurt without any thickener added, and its viscosity is 4043.68±180.08 mPa·s. As can be seen from Table 1, different thickeners and their addition amounts have an impact on the viscosity of the reconstituted plant yogurt. Among them, the addition of sodium alginate will cause the appearance of the reconstituted yogurt to show a multi-porous structure. Although the thickening effect is the best, it has a certain damage to the texture of the reconstituted yogurt. The texture and smoothness of the reconstituted yogurt added with low-ester pectin, carrageenan and guar gum are the closest to those of the plant yogurt, and the effect of low-ester pectin is the most obvious.

[0119] Table 1 Comparison of the types and addition amounts of thickeners on the viscosity of reconstituted plant yogurt

[0120]

[0121] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing solid vegetable yogurt, characterized in that The steps include: S1: stirring and dissolving the bean matrix and the fruit raw material with heated drinking water, and then fixing the volume with drinking water to obtain a plant-based emulsion; S2: After heating the central temperature of the plant-based emulsion obtained in S1 to 85±0.5°C, maintain the temperature for 20 minutes for sterilization; S3: Cooling the sterilized plant-based emulsion to below 45° C., adding a direct-injection yogurt starter, allowing it to ferment, and refrigerating it at 4° C. for more than 12 hours to obtain plant yogurt; S4: demulsifying the plant yogurt obtained in S3, pre-freezing the plant yogurt, and freeze-drying the plant yogurt to obtain a freeze-dried plant yogurt powder; S5: The plant yogurt freeze-dried powder obtained in S4 is mixed with a thickener to prepare solid plant yogurt.

2. The method for preparing a solid vegetable yogurt according to claim 1, characterized in that: In step S1, the bean matrix is ​​fresh soy milk and / or pure soy powder; the fruit raw material is juice or fruit powder of durian, lychee, coconut, banana, green grape, avocado, mango or pineapple; and the plant-based emulsion also contains sucrose.

3. The method for preparing a solid vegetable yogurt according to claim 2, characterized in that: The bean matrix is ​​fresh soybean milk and / or pure soybean powder; the fruit raw material is banana powder or avocado powder.

4. The method for preparing a solid vegetable yogurt according to claim 1, characterized in that: The formula of the plant-based emulsion in step S1 is that every 1000 mL of the plant-based emulsion contains the following raw materials: 60-100 g of pure soy powder, 5-40 g of fruit powder, 60-90 g of sucrose, and the balance is drinking water.

5. The method for preparing a solid vegetable yogurt according to claim 1, characterized in that: The inoculation amount of the direct-injection yogurt starter in step S3 is 0.01% to 0.1%, and the bacterial content in the plant-based emulsion after inoculation is 2×10 9 ~2×10 10 CFU / L; the temperature of the static fermentation is 30-42°C, and the fermentation time is 8-18h.

6. The method for preparing a solid vegetable yogurt according to claim 1, characterized in that: The pre-freezing temperature in step S4 is -20 to -80°C, the pre-freezing time is 2 to 8 hours, and the freeze-drying time is 24 to 48 hours.

7. The method for preparing a solid vegetable yogurt according to claim 1, characterized in that: In step S5, the thickener is a single preparation of low-ester pectin, or a mixed preparation of low-ester pectin with any one or more of guar gum and carrageenan; the added amount of the thickener is 0.2%-2% of the mass of the plant yogurt freeze-dried powder.

8. A solid vegetable yogurt prepared by the preparation method according to any one of claims 1 to 7.

9. The solid plant yogurt according to claim 8, characterized in that: When the solid plant yogurt is used, it is mixed with drinking water at 0 to 45° C. in a powder-to-water mass ratio of 1:10 to 1:3 and then directly drunk.

10. Use of the solid vegetable yogurt according to claim 8 as a flavor enhancer, nutritional supplement or texture improver in the food field.

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