Method for accelerating coagulation type yogurt curdling and enhancing water-holding capacity and hardness, black rice coagulation type yogurt, black rice leavening and application of black rice curdling type yogurt and black rice leavening

Abstract

The invention relates to the technical field of food, in particular to a method for accelerating coagulation of coagulated yoghurt and enhancing water-holding capacity and hardness, black rice coagulated yoghurt, black rice leavening and application. The preparation method of the solidified yoghurt capable of accelerating milk curding and enhancing water-holding capacity and hardness through black rice fermentation is characterized by comprising the following steps: preparing sterile pretreated black rice; preparing a fermentation seed solution; preparing fermented black rice: adding the fermented seed solution into the sterile pretreated black rice, uniformly mixing, and standing and fermenting for 60-96 hours at the temperature of 30-35 DEG C and the humidity of 70-80%; the preparation method comprises the following steps: preheating cow milk to 43 DEG C, adding fermented black rice (1: 7-1: 10, w / v), further adding a yoghurt fermentation inoculant (3: 1600, w / v), fully stirring and uniformly mixing, standing and fermenting at 42-44 DEG C for 4-6 hours, and refrigerating at 4 DEG C for 12 hours after the yoghurt is completely solidified, thereby obtaining the black rice step-by-step co-fermentation solidified yoghurt.

Description

Technical Field

[0001] The invention relates to the technical field of food, in particular to a method for accelerating the coagulation of coagulated yogurt and enhancing water holding capacity and hardness, as well as black rice coagulated yogurt and black rice fermented product and uses. Background Art

[0002] Yogurt is popular for its attractive flavor, texture and probiotic health effects, and has become one of the most common dairy products in people's daily consumption. Lactic acid bacteria fully consume the lactose in raw milk during the fermentation process, making it more suitable as a high-quality protein supplement for people with lactose intolerance. The State Council has previously issued the National Nutrition Plan (2017-2030) and other relevant documents, pointing out that it is necessary to "promote the dairy industry revitalization project, strengthen the construction of milk source bases, and optimize the structure of dairy products" and "establish a big food concept, build a diversified food supply system, and promote the key core technology research of agriculture", indicating that my country is currently continuing to promote the upgrading of the dairy industry structure and product diversification and characteristic processing technology innovation, which plays an important role in improving the overall health quality of the people and building modern agriculture.

[0003] At present, yogurt (coagulated type) often faces the problem of whey precipitation. The casein gel network mainly captures whey liquid through hydrogen bonding, that is, water holding capacity, which together with factors such as gel hardness and network porosity determine the anti-dehydration stability of yogurt. Poor stability can easily lead to whey precipitation in yogurt, resulting in the loss of soluble nutrients and deterioration of sensory properties, seriously affecting the quality and shelf life of yogurt. In addition, coagulation performance also has an important influence on the quality of yogurt. Poor coagulation can easily lead to prolonged fermentation and curdling time, as well as gel tissue destruction during slight collisions, vibrations, and decooling, resulting in whey precipitation and impaired appearance. The occurrence of these problems is jointly affected by multiple factors such as milk solid content, raw material composition, and fermentation conditions. Therefore, how to enhance water holding capacity and coagulation is a technical difficulty faced by yogurt production in the long term.

[0004] On November 28, 2024, a search was conducted in the Chinese Patent Publication Database with "yogurt and fermented milk and black rice" as the abstract keywords, and 36 related documents were found, namely: A black rice seed coat powder yogurt rich in anthocyanins and having the effect of lowering blood lipids and a preparation method thereof (CN202310305536.3); a method for processing high-stability yogurt by adsorbing black rice anthocyanins and polypeptides using starch (CN202110234670.X); a method and system for preparing black rice and highland barley yogurt (CN202111522218.X); yogurt purple rice dew and a preparation method thereof (CN201810500190.1); a black rice and white peach flavored yogurt and a preparation method thereof (CN2016 11019481.6); a blueberry black rice yogurt and a preparation method thereof (CN201610513898.1); a stirred black rice and highland barley yogurt and a preparation method thereof (CN201610412034.0); a black grain yogurt and a preparation method thereof (CN201710062735.0); a preparation method of sweet potato and black rice fermented milk (CN201210035034.5); avocado oatmeal and black rice flavored yogurt and a preparation method thereof (CN202010751321.0); A zero-added sucrose carbohydrate absorption-blocking yogurt and its preparation method (CN202411032334.7); a blood sugar-lowering yogurt and its preparation method and application (CN202410891325.7); a zero-added sweet mash yogurt and its preparation method (CN202410762844.3); a yam whole pulp yogurt rich in allantoin and total flavonoids and its preparation method (CN202410142520.X); a plant-based yogurt with the effects of calming the nerves, promoting sleep, and improving gastrointestinal function and its preparation method (CN202111681684.2); A composite bifidobacterium inoculum and its application in yogurt fermentation (CN202411148077.3); a plant lactobacillus STB9b and its application in preparing coconut-based yogurt (CN202411077973.5); a composition of Leuconostoc mesenteroides YM1 and Lactobacillus kefir NK1 and its application and a wire-drawing yogurt (CN202410822152.3); a method for preparing high-probiotic active yogurt (CN202410825237.7); a method for preparing microalgae plant yogurt using acid- and aroma-producing bacteria (CN202410601870.8); A processing system and method for solidified yogurt (CN202211479800.7); a solidified yogurt and a preparation method thereof (CN202110733512.9); a high-stringency yogurt drink and a preparation method thereof (CN202410911123.4); a method for preparing crispy yogurt blocks (CN202310082034.9); A sugar-free solidified whole oatmeal cereal beverage and its preparation method (CN202411103320.X); a blackberry yogurt and its preparation method (CN202211604104.4); a taro-based plant yogurt and its preparation method (CN202410776899.X); an oatmeal powder coconut milk yogurt and its preparation method (CN202310075015.3); a fruit and vegetable yogurt prepared from yogurt without additive preservatives and fruits, vegetables and nuts (CN202410342476.7); a preparation method for a solid whole matcha yogurt (CN202410615212.4); a preparation method for a blueberry jam soy milk yogurt (CN202410615212.4). N202410453707.1); a method for preparing cranberry jam yogurt (CN202410454264.8); a yogurt, an active lactic acid bacteria beverage and their preparation methods and the application of prickly pear cactus (CN202111430736.9); a compound extract of yam and dendrobium, yogurt and their preparation method and application (CN202410729048.X); a compound extract of yam and poria, yogurt and their preparation method and application (CN202410729054.5); the application of medicinal and edible substances in the preparation of fermented milk containing live bacteria and containing sugar alcohol substances with a prolonged shelf life (CN202111431211.7).

[0005] Among them, most of them add black rice or other plant-based raw materials to ferment and curd milk, and do not involve the step-by-step fermentation of black rice to accelerate the formation of yogurt gel and enhance the strength of the gel.

[0006] CN202310305536.3 discloses a method for preparing a functional yogurt rich in black rice seed coat anthocyanins and having the effect of lowering blood lipids, which is unrelated to the accelerated coagulation, enhanced water holding capacity and gel strength of this patent.

[0007] CN202110234670.X discloses a method for obtaining starch and polypeptides by enzymatic pretreatment of glutinous rice, and adsorbing black rice anthocyanins and polypeptides to obtain highly stable yogurt, which is different from the black rice step-by-step co-fermentation yogurt preparation process of this patent.

[0008] CN202111522218.X, CN201810500190.1, CN201611019481.6, CN201610513898.1, CN201610412034.0, CN201710062735.0, CN201210035034.5, CN202010751321.0, etc., all use black rice as raw material to make fermented yogurt, and mainly focus on enhancing the flavor, taste, and health benefits of yogurt. Their invention purposes are different from this patent.

[0009] CN202411148077.3, CN202411077973.5, CN202410822152.3, CN202410825237.7, CN202410601870.8 and the like use different lactic acid bacteria and their combinations to ferment yogurt to obtain fermented milk with different taste and nutritional properties, which is different from the strains used and the step-by-step fermentation method of this patent.

[0010] On November 28, 2024, an abstract search for "yogurt and fermented milk and black rice" was conducted on CNKI, and no relevant literature was found. Two papers were found, namely: "Development of low glycemic index whole grain fermented milk" published by Bao Yifeng; "Development of black rice fermented milk beverage" published by Chen Gang; Jian Suping; Wang Haili; Wu Ke. Among them, "Development of black rice fermented milk beverage" provides a reverse inspiration, that is, fermentation together.

[0011] On November 28, 2024, Yogurt with fermented milk with black rice with steaming with lactobacillus with Solid Body "A search on the US Patent and Trademark Office website did not find any relevant documents; the search URL is https: / / ppubs.uspto.gov / pubwebapp / .

[0012] On November 28, 2024, Yogurt and fermented milk and black rice "Searched on the Korean Patent Office; search URL http: / / eng.kipris.or.kr / enghome / main.jsp; found: Application number: 1020200027889; Antioxidant or anti-inflammatory functional food composition; An antioxidant and anti-inflammatory functional food composition containing black rice in whey protein isolated from Greek yogurt. When whey protein or black rice extract is used alone, the composition containing whey protein isolated from Greek yogurt of the present invention and black rice extract has an antioxidant effect by inhibiting ABTS free radical scavenging activity and DNA damage; and has nothing to do with yogurt products. Application number: 1020100071993; Advanced antioxidant rice containing spirulina and soybeans; Application number: 1020130030502; A method for preparing fermented chili juice and its use; On November 28, 2024, Yogurt and fermented milk and black rice "A search was conducted on WIPO's https: / / patentscope2.wipo.int / and the following was found: CN111742996 Avocado, oatmeal and black rice flavored yogurt and preparation method thereof, which provides a co-fermented oatmeal, black rice and apple flavored sauce, which is not co-fermented.

[0013] On November 28, 2024, Yogurt and fermented milk and black rice"A search on the Japan Patent Office website https: / / www.j-platpat.inpit.go.jp / did not find any relevant literature.

[0014] Completely different from the concept of this patent. Summary of the invention

[0015] Purpose of the invention: To provide a method for accelerating the coagulation of yogurt with better effects, enhancing water holding capacity and hardness, as well as black rice coagulated yogurt and black rice fermented product and uses. For specific purposes, see the multiple substantial technical effects in the specific implementation part.

[0016] In order to provide a preparation method and application of black rice step-by-step co-fermented yogurt with faster coagulation speed, stronger water holding capacity and gel texture hardness, the specific purpose can be seen in the multiple substantial technical effects of the specific implementation part.

[0017] In order to achieve the above purpose, the present invention adopts the following technical solutions: The method for preparing coagulated yogurt with accelerated coagulation by black rice fermentation and enhanced water holding capacity and hardness is characterized by comprising the following steps: Preparation of sterile pretreated black rice: black rice and distilled water were mixed in a mass-to-volume ratio of 1:2 (g / mL), soaked overnight (10-14 h) at 4 °C, steamed or sterilized at 121 °C with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice; Preparation of fermentation seed liquid: Inoculate Lactobacillus plantarum in culture liquid (using one or more of glucose, fructose, maltose, sucrose, and brown sugar as carbon sources, 0.5-5 wt %; using one or more of peptone, yeast extract, and beef extract as nitrogen sources, 0.5-5 wt %) or MRS broth culture liquid, and culture with shaking (30 ℃, 160 rpm / min) until the logarithmic growth phase. Determine the microbial concentration of the seed liquid by plate counting and OD600 ultraviolet spectrophotometry. Use a sterile pipette to absorb the culture liquid, centrifuge at 6000 rpm / min for 2 min, discard the supernatant, collect the bacterial precipitate, add sterile distilled water and mix well to obtain the fermentation seed liquid; Preparation of fermented black rice: Add the fermented seed liquid to the sterile pre-treated black rice at a ratio of 10 6 ~10 8 CFU / g black rice, stir and mix well, seal, and ferment in a solid state (30-35°C, humidity 70-80%) for 60-96 hours to obtain fermented black rice; Preparation of black rice step-by-step co-fermentation coagulated yogurt: preheat the milk to 43°C, add fermented black rice (1:7-1:10, w / v), further add yogurt fermentation agent (3:1600, w / v), stir and mix thoroughly, ferment at 42-44°C for 4-6 hours, and after the yogurt is completely coagulated, refrigerate at 4°C for 12 hours to obtain black rice step-by-step co-fermentation coagulated yogurt.

[0018] A further technical solution of the present invention is that the black rice is black glutinous rice.

[0019] A further technical solution of the present invention is that the black rice fermentation bacteria is Lactobacillus plantarum (ATCC 14917 or other commercially fermented Lactobacillus plantarum), and the milk is freshly obtained or pasteurized pure milk.

[0020] A further technical solution of the present invention is that the yogurt fermentation bacteria agent comprises thermophilic Streptococcus and bulgaricus, and any one or more of yogurt fermentation bacteria such as Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus plantarum are selectively added.

[0021] A further technical solution of the present invention is that the stepwise fermentation of black rice is divided into: 1. solid-state fermentation of black rice; 2. adding milk into the fermented black rice for co-fermentation.

[0022] A further technical solution of the present invention is that in the step of solid-state fermentation of black rice, the content of plant lactobacillus added is 10 6 ~10 8 CFU / g black rice, the fermentation temperature is 30-35 ℃, the humidity is maintained at 70-80%, and the time is 60-96 h.

[0023] A further technical solution of the present invention is that in the co-fermentation step after the fermented black rice is added to the milk, the milk preheating temperature is 40-45°C, the mass volume ratio of the fermented black rice to the milk is 1:7-1:10 (w / v), the fermentation temperature is 42-44°C, and the time is 4-6 h.

[0024] A further technical solution of the present invention is that the accelerated coagulation is to shorten the complete coagulation time of yogurt, the enhanced water holding capacity is to reduce the whey protein precipitation rate, and the enhanced hardness is to increase the hardness value of the gel texture characteristic.

[0025] The coagulated yogurt is prepared by the method for preparing coagulated yogurt with accelerated coagulation by step-by-step fermentation of black rice as described in any one of the above and with enhanced water holding capacity and hardness.

[0026] Use of the coagulated yogurt prepared by the method for preparing coagulated yogurt with accelerated coagulation by step-by-step fermentation of black rice as described in any one of the above and enhanced water holding capacity and hardness in the production of fermented yogurt food.

[0027] The present invention adopting the above technical solution has the following beneficial effects compared with the prior art: (1) The present invention proposes for the first time a method for preparing coagulated yogurt using black rice in step-by-step fermentation. By adjusting the fermentation process, a two-step black rice fermentation method can be used to effectively shorten the coagulation time of yogurt. The preparation method is simple, easy to scale up, and suitable for industrial application. It has great application potential in the preparation of fast-coagulating coagulated yogurt foods.

[0028] (2) The preparation method provided by the present invention can achieve multiple control of yogurt coagulation rate, water holding capacity, and gel texture hardness. While shortening the coagulation time of yogurt, it can enhance the water holding capacity and gel texture hardness of yogurt. It has great application potential in enhancing the production efficiency, shelf life quality stability, nutritional value and flavor of yogurt.

[0029] (3) The present invention has found through experiments that the fermentation degree of black rice significantly affects the coagulation speed, water holding capacity and texture characteristics of yogurt: Based on the method of the present invention, only when the black rice is moderately fermented and then involved in the coagulation-type yogurt fermentation, its coagulation rate, water holding capacity and gel texture hardness can be improved simultaneously, while the coagulation-type yogurt prepared by using unfermented, insufficiently fermented or over-fermented black rice as raw material cannot achieve the effects described in the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to further illustrate the present invention, the following is further described in conjunction with the accompanying drawings: Figure 1 The complete coagulation time, water holding capacity and gel hardness of yogurt of the examples and control examples are shown; Figure 2 It is the calculation formula in the yogurt water holding capacity test; DETAILED DESCRIPTION

[0031] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0032] In order to reduce the dependence on the use of different thickeners and stabilizers in yogurt production, reduce production costs and enhance flavor and nutritional quality, it is of great significance to develop yogurt processing technology that shortens yogurt coagulation time and enhances water holding capacity. Black rice, as a whole grain brown rice, has a variety of dietary health benefits. The use of black rice step-by-step fermentation process to enhance the texture, flavor and nutritional quality of yogurt has positive significance for promoting the coordinated development of whole grain diet and yogurt probiotic diet.

[0033] The purpose of the present invention is to overcome the shortcomings of the existing coagulated yogurt, such as low water holding capacity, whey protein precipitation leading to nutrient loss, and long yogurt fermentation coagulation time, and provide a method for preparing coagulated yogurt with accelerated coagulation and enhanced water holding capacity and hardness by step-by-step fermentation of black rice. First, black rice is modified by plant lactobacillus pre-fermentation treatment to promote the release of its protein, dietary fiber, anthocyanin, starch, etc., and then cow's milk is added and mixed by step-by-step fermentation treatment to obtain black rice coagulated yogurt. The black rice pre-fermentation treatment promotes the conversion and release of nutrients, changes the interaction force between protein and other macromolecules and the spatial distribution of the two in the subsequent yogurt fermentation process, and changes the spatial distribution of lactic acid bacteria in the coagulation process and its fermentation activity. The coagulated yogurt finally obtained has a shorter fermentation coagulation molding time, and higher water holding capacity and gel texture hardness.

[0034] The black rice and distilled water w / v in the embodiment are g / ml; Example 1

[0035] The black rice was mixed with distilled water in a mass-to-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 12 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Inoculate Lactobacillus plantarum ATCC 14917 into MRS broth culture medium and culture with shaking (30 ℃, 160 rpm / min) until the logarithmic growth phase. Use a sterile pipette to draw up the culture medium, centrifuge at 6000 rpm / min for 2 min, discard the supernatant, collect the bacterial precipitate, add sterile distilled water and mix well to obtain the fermentation seed liquid; Add the fermented seed liquid to the sterile pretreated black rice at a ratio of 10 6 CFU / g black rice, stir and mix well, seal, and ferment in a solid state (30 ℃, humidity 70%) for 60 h to obtain fermented black rice; The milk was preheated to 43°C, fermented black rice (1:7, w / v) was added, and yogurt fermentation agent (1:800, w / v) was further added, and the mixture was fully stirred and fermented at 43°C for 6 h. After the yogurt was completely solidified, it was refrigerated at 4°C for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which was recorded as Example 1. Example 2

[0036] The black rice was mixed with distilled water in a mass-to-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 12 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Inoculate Lactobacillus plantarum ATCC 14917 into MRS broth culture medium and culture with shaking (30 ℃, 160 rpm / min) until the logarithmic growth phase. Use a sterile pipette to draw up the culture medium, centrifuge at 6000 rpm / min for 2 min, discard the supernatant, collect the bacterial precipitate, add sterile distilled water and mix well to obtain the fermentation seed liquid; Add the fermented seed liquid to the sterile pretreated black rice at a ratio of 10 7 CFU / g black rice, stir and mix well, seal, and ferment in a solid state (33°C, humidity 75%) for 72 h to obtain fermented black rice; The milk was preheated to 43°C, fermented black rice (1:7, w / v) was added, and yogurt fermentation agent (1:800, w / v) was further added, and the mixture was fully stirred and fermented at 43°C for 6 h. After the yogurt was completely solidified, it was refrigerated at 4°C for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which was recorded as Example 2. Example 3

[0037] The black rice was mixed with distilled water in a mass-to-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 12 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Inoculate Lactobacillus plantarum ATCC 14917 into MRS broth culture medium and culture with shaking (30 ℃, 160 rpm / min) until the logarithmic growth phase. Use a sterile pipette to draw up the culture medium, centrifuge at 6000 rpm / min for 2 min, discard the supernatant, collect the bacterial precipitate, add sterile distilled water and mix well to obtain the fermentation seed liquid; Add the fermented seed liquid to the sterile pretreated black rice at a ratio of 10 8 CFU / g black rice, stir and mix well, seal, and ferment in a solid state (35°C, humidity 80%) for 96 h to obtain fermented black rice; The milk was preheated to 43°C, fermented black rice (1:7, w / v) was added, and yogurt fermentation agent (1:800, w / v) was further added, and the mixture was fully stirred and fermented at 43°C for 6 h. After the yogurt was completely solidified, it was refrigerated at 4°C for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which was recorded as Example 3. Example 4

[0038] The black rice was mixed with distilled water in a mass-to-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 12 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Inoculate Lactobacillus plantarum ATCC 14917 into MRS broth culture medium and culture with shaking (30 ℃, 160 rpm / min) until the logarithmic growth phase. Use a sterile pipette to draw up the culture medium, centrifuge at 6000 rpm / min for 2 min, discard the supernatant, collect the bacterial precipitate, add sterile distilled water and mix well to obtain the fermentation seed liquid; Add the fermented seed liquid to the sterile pretreated black rice at a ratio of 10 7 CFU / g black rice, stir and mix well, seal, and ferment in a solid state (33°C, humidity 75%) for 72 h to obtain fermented black rice; The milk was preheated to 43°C, fermented black rice (1:7, w / v) was added, and yogurt fermentation agent (3:1600, w / v) was further added, and the mixture was fully stirred and mixed. The mixture was allowed to stand and ferment at 43°C for 6 h. After the yogurt was completely solidified, it was refrigerated at 4°C for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which was recorded as Example 4. Example 5

[0039] The black rice was mixed with distilled water in a mass-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 10 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Lactobacillus plantarum ATCC 14917 was inoculated into a culture medium (glucose: fructose: maltose = 1:1:1 as a carbon source, 5wt%; peptone as a nitrogen source, 2wt%), and cultured with shaking (30°C, 160 rpm / min) until the logarithmic growth phase. The culture medium was aspirated using a sterile pipette, centrifuged at 6000 rpm / min for 2 min, the supernatant was discarded, the bacterial precipitate was collected, and sterile distilled water was added to mix to obtain the fermentation seed solution; Add the fermented seed liquid to the sterile pretreated black rice at a ratio of 10 7 CFU / g black rice, stir and mix well, seal, and ferment in a solid state (33°C, humidity 75%) for 72 h to obtain fermented black rice; The milk was preheated to 43°C, fermented black rice (1:10, w / v) was added, and yogurt fermentation agent (3:1600, w / v) was further added, and the mixture was fully stirred and fermented at 43°C for 6 h. After the yogurt was completely solidified, it was refrigerated at 4°C for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which was recorded as Example 5. Example 6

[0040] The black rice was mixed with distilled water in a mass-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 14 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Lactobacillus plantarum ATCC 14917 was inoculated into a culture medium (glucose: brown sugar = 1:1 as carbon source, 5 wt %; yeast extract as nitrogen source, 2 wt %) and cultured with shaking (30 ℃, 160 rpm / min) until the logarithmic growth phase. The culture medium was aspirated using a sterile pipette, centrifuged at 6000 rpm / min for 2 min, the supernatant was discarded, the bacterial precipitate was collected, and sterile distilled water was added to mix to obtain the fermentation seed solution; Add the fermented seed liquid to the sterile pretreated black rice at a ratio of 10 7 CFU / g black rice, stir and mix well, seal, and ferment in a solid state (33 ℃, humidity 80%) for 84 h to obtain fermented black rice; Preheat the milk to 43°C, add fermented black rice (1:9, w / v); further add yogurt fermentation agent (3:1600, w / v); fully stir and mix, ferment at 43°C for 6 h, and after the yogurt is completely solidified, refrigerate at 4°C for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which is recorded as Example 6. Comparative Example 1

[0041] The black rice was mixed with distilled water in a mass-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 14 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Preheat the milk to 43 ℃, add sterile pretreated black rice (1:8, w / v), further add yogurt fermentation agent (3:1600, w / v), stir and mix thoroughly, ferment at 43 ℃ for 6 h, and after the yogurt is completely solidified, refrigerate at 4 ℃ for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which is recorded as Control Example 1.

[0042] Add yogurt fermentation agent (3:1600, w / v) to preheated milk, stir and mix thoroughly, let stand and ferment at 43°C for 6 hours, and after the yogurt is completely solidified, refrigerate at 4°C for 12 hours to obtain solidified yogurt, and obtain control example 1-0. Comparative Example 2

[0043] The black rice was mixed with distilled water in a mass-volume ratio of 1:2 (w / v), soaked overnight at 4 °C for 10 h, sterilized with high-pressure steam for 15 min, and cooled naturally at room temperature to obtain sterile pretreated black rice. Preheat the milk to 43 °C, add sterile pretreated black rice (1:10, w / v), further add yogurt fermentation bacteria (1:800, w / v), stir and mix thoroughly, ferment at 43 °C for 6 h, and after the yogurt is completely solidified, refrigerate at 4 °C for 12 h to obtain black rice step-by-step co-fermentation solidified yogurt, which is recorded as Control Example 2.

[0044] Add yogurt fermentation agent (1:800, w / v) to preheated milk, stir and mix thoroughly, let stand and ferment at 43°C for 6 hours, and after the yogurt is completely solidified, refrigerate at 4°C for 12 hours to obtain solidified yogurt, obtaining Control Example 2-0.

[0045] 1. Methods (1) Yogurt coagulation time test Add the yogurt fermentation agent to the milk, stir it thoroughly, and ferment it at 43°C, which is recorded as the start of fermentation. During the fermentation, observe the coagulation state of the milk every 20 minutes, and determine the end of fermentation when the yogurt is completely coagulated. The time from the start of fermentation to the end of fermentation is the yogurt coagulation time.

[0046] (2) Yogurt water holding capacity test The water holding capacity of yogurt was tested by centrifugal precipitation method, i.e. the remaining mass ratio of the supernatant after the yogurt sample was centrifuged (1000 rpm, 10 min). The relevant calculation formula is:

[0047] (3) Yogurt gel texture hardness test 4 g of intact coagulated yogurt was cut and weighed, and the yogurt gel hardness was tested at 25 °C using a texture analyzer (P / 36R probe, TA-XT plus texture analyzer, Godalming, UK). The speed before the test was 2 mm / s, the speed during the test was 1 mm / s, the speed after the test was 2 mm / s, and the trigger force was 5 g. Each sample was tested at least 3 times in parallel.

[0048] 2. Results (1) Yogurt complete coagulation time The complete coagulation time of yogurt was measured for the samples of the embodiment and the control example. Figure 1 As shown, the complete solidification time of Examples 1 to 6 is 3.0 to 4.3 h, while the complete solidification time of Control Example 1 and Control Example 2 is 4.6 h and 4.7 h, respectively, and the complete solidification time of Control Example 1-0 and Control Example 2-0 is 5.1 h and 5.5 h, respectively.

[0049] The results of the measurement of the complete coagulation time of yogurt show that compared with the direct fermentation coagulation method, the black rice step-by-step fermentation method can significantly reduce the complete coagulation time of yogurt fermentation, improve the production efficiency of yogurt and reduce costs.

[0050] (2) Water holding capacity of yogurt The water holding capacity of the yogurt of Examples 1 to 6 was 89.6-93.1%, the water holding capacity of the yogurt of Control Examples 1 and 2 was 83.7% and 85.5%, respectively, and the water holding capacity of the yogurt of Control Examples 1-0 and 2-0 was 80.8% and 80.1%, respectively. The results show that the water holding capacity of the coagulated yogurt prepared without adding black rice is low, while the water holding capacity of the coagulated yogurt prepared by step-by-step co-fermentation of black rice is significantly better than the former, and changing the protein cross-linking structure of the yogurt helps to reduce the precipitation of whey protein and enhance the water holding capacity.

[0051] The water holding capacity of yogurt in the comparative example and the control example was compared. The results showed that the coagulated yogurt prepared with unfermented black rice as raw material could increase the water holding capacity of yogurt by 6.7%, while the coagulated yogurt prepared by step-by-step co-fermentation of black rice could increase the water holding capacity by 16.2%, which was significantly better than the former. This showed that the black rice fermentation treatment had a positive effect on enhancing the protein cross-linking of yogurt, further illustrating the uniqueness of the step-by-step fermentation of black rice in achieving the effect of the present invention.

[0052] (3) Yogurt gel hardness The gel hardness of the yogurt of Example 1 to Example 6 is 65.0-71.1 g, the gel hardness of Control Example 1 and Control Example 2 is 55.7 g and 54.4 g, respectively, and the gel hardness of Control Example 1-0 and Control Example 2-0 is 51.9 g and 51.5 g, respectively. The results show that the gel hardness of the coagulated yogurt prepared with unfermented black rice as raw material can be increased by 8.2%, and the gel hardness of the coagulated yogurt prepared by step-by-step co-fermentation of black rice can be increased by 38.1%, indicating that the co-fermentation treatment of black rice distribution can promote the cross-linking of proteins, effectively enhance the stability of the gel texture of yogurt, and enhance the taste of coagulated yogurt.

[0053] Through the above analysis, it can be known that the method for preparing coagulated yogurt with accelerated coagulation and enhanced water holding capacity and hardness by step-by-step fermentation of black rice of the present invention can effectively shorten the complete coagulation time of yogurt by adjusting the fermentation process and adopting the step-by-step fermentation method of black rice, and enhance the water holding capacity and gel texture hardness at the same time. The cross-linked morphology of protein molecules in yogurt is closely related to the spatial distribution and fermentation activity of lactic acid bacteria, and significantly affects the water holding capacity and gel texture of yogurt. Only by selecting moderately fermented black rice as raw material can the effect of the present invention be achieved.

[0054] Table 1 Complete coagulation time, water holding capacity and gel hardness of yogurt in Examples and Comparative Examples Further, different fermentation treatments lead to different changes in the black rice structure and different degrees of gelation of yogurt, resulting in differences in the interactions between proteins and between proteins and other molecules, affecting the formation of yogurt gel, and then there are differences in gel texture and coagulation rate. In the described embodiments, Embodiment 3 and Embodiment 5 are the best embodiments. Compared with the control example, the yogurt in Embodiment 3 has the shortest complete coagulation time, and Embodiment 5 has the highest water holding capacity and hardness value. The molecules of casein, whey protein, dietary fiber, anthocyanin, starch, etc. are cross-linked and aggregated to form a more stable gel network, which can provide a stronger spatial distribution support structure for lactic acid bacteria, resulting in a more uniform and efficient yogurt fermentation coagulation process, and the coagulation performance and texture improvement increase are most obvious, which can best reflect the effect of the present invention.

[0055] For fast-consuming and fast-produced products such as yogurt, improving production speed and stability can increase the stability and competitiveness of the industry and products; aggregation to form a more stable gel network can reduce the damage to the appearance quality of coagulated yogurt and the precipitation of whey, forming a denser structure, so that the quality can be guaranteed for a longer period of time.

[0056] The basic principle, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the protection required.

Claims

1. A method for accelerating the curdling of coagulated yogurt and enhancing water holding capacity and hardness, characterized in that: Co-fermentation is carried out using black rice fermentation product and milk.

2. The method for accelerating the coagulation type yogurt curd and enhancing the water holding capacity and hardness as claimed in claim 1, characterized in that: The co-fermentation is a step-by-step fermentation; the step-by-step fermentation of black rice is divided into:

1. solid-state fermentation of black rice; 2. co-fermentation after adding milk into the fermented black rice.

3. The method for accelerating the coagulation type yogurt curd and enhancing the water holding capacity and hardness as claimed in claim 2, characterized in that: The steps of the step-by-step fermentation are as follows: firstly, a fermented seed liquid is prepared, then fermented black rice is prepared, and then the fermented black rice and milk are fermented together.

4. The method for accelerating the coagulation type yogurt curd and enhancing the water holding capacity and hardness as claimed in claim 3, characterized in that: The steps include: Preparation of sterile pretreated black rice: black rice and distilled water were mixed in a mass-volume ratio of 1:2 (g / mL), soaked at 4°C for 10-14 h, steamed or sterilized at 121°C with high-pressure steam for 15 min, and naturally cooled at room temperature to obtain sterile pretreated black rice; Preparation of fermentation seed solution: inoculate Lactobacillus plantarum in culture solution (using one or more of glucose, fructose, maltose, sucrose, and brown sugar as carbon sources, with a content of 0.5-5 wt %; using one or more of peptone, yeast extract, and beef extract as nitrogen sources, with a content of 0.5-5 wt %) or MRS broth culture solution, and culture with shaking until the logarithmic growth phase; use a sterile pipette to absorb the culture solution and then centrifuge, discard the supernatant, collect the bacterial precipitate, add sterile distilled water and mix well to obtain fermentation seed solution; Preparation of fermented black rice: Add the fermented seed liquid to the sterile pre-treated black rice at a ratio of 10 6 ~10 8 CFU / g black rice, stirring and mixing, sealing, and standing in a solid state at a temperature of 30-35°C and a humidity of 70-80%, and fermenting for 60-96 hours to obtain fermented black rice; Preparation of black rice step-by-step co-fermentation coagulated yogurt: preheat the milk to 43°C, add fermented black rice, the fermented black rice g / milk volume ml is 1:7-1:10, further add yogurt fermentation bacteria, the volume ml ratio of yogurt fermentation bacteria g to fermented black rice milk mixture is 1:800-3:1600, stir and mix thoroughly, ferment at 42-44°C for 4-6 h, and after the yogurt is completely coagulated, refrigerate at 4°C for 12 h to obtain black rice step-by-step co-fermentation coagulated yogurt.

5. The method for accelerating the coagulation type yogurt curd and enhancing the water holding capacity and hardness as claimed in claim 4, characterized in that: The black rice is black glutinous rice, the black rice fermentation bacteria is Lactobacillus plantarum, and the cow's milk is freshly obtained or pasteurized pure cow's milk; the yogurt fermentation bacteria agent contains thermophilic streptococcus and bulgaricus, and selectively adds any one or more of yogurt fermentation bacteria such as Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus plantarum.

6. The method for accelerating the coagulation type yogurt curd and enhancing the water holding capacity and hardness as claimed in claim 1, characterized in that: Black rice is modified by pre-fermentation treatment with Lactobacillus plantarum to promote the release of its protein, dietary fiber, anthocyanin, starch, etc., and then cow's milk is added to the mixture for step-by-step fermentation to obtain black rice coagulated yogurt; the black rice pre-fermentation treatment promotes the transformation and release of nutrients, changes the interaction force between protein and other macromolecules and the spatial distribution of the two during the subsequent yogurt fermentation process, and also changes the spatial distribution of lactic acid bacteria in the coagulation process and its fermentation activity. The final coagulated yogurt has a shorter fermentation and coagulation time, and higher water holding capacity and gel texture hardness.

7. A black rice coagulated yogurt with high coagulation speed, strong water retention and high hardness, characterized in that: Coagulated yogurt prepared by using the method for accelerating coagulation yogurt curdling and enhancing water holding capacity and hardness as described in any one of claims 1 to 6.

8. A black rice fermented product for producing coagulated yogurt, characterized in that: The black rice fermentation product is produced by the following steps: The steps include: Preparation of sterile pretreated black rice: black rice and distilled water were mixed in a mass-volume ratio of 1:2 (g / mL), soaked at 4°C for 10-14 h, steamed or sterilized at 121°C with high-pressure steam for 15 min, and naturally cooled at room temperature to obtain sterile pretreated black rice; Preparation of fermentation seed solution: inoculate Lactobacillus plantarum in culture solution (using one or more of glucose, fructose, maltose, sucrose, and brown sugar as carbon sources, with a content of 0.5-5 wt %; using one or more of peptone, yeast extract, and beef extract as nitrogen sources, with a content of 0.5-5 wt %) or MRS broth culture solution, and culture with shaking until the logarithmic growth phase; use a sterile pipette to absorb the culture solution and then centrifuge, discard the supernatant, collect the bacterial precipitate, add sterile distilled water and mix well to obtain fermentation seed solution; Preparation of fermented black rice: Add the fermented seed liquid to the sterile pre-treated black rice at a ratio of 10 6 ~10 8 CFU / g black rice, stir and mix well, seal, and let stand in a solid state at a temperature of 30-35°C and a humidity of 70-80% for 60-96 h to obtain fermented black rice.

9. Use of black rice fermentation product in preparing coagulated yogurt or fermented yogurt food.

10. Use of black rice fermentation product in shortening the coagulation time of yogurt, enhancing water holding capacity and improving the hardness value of gel texture characteristics.

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