Method for preparing yak yoghourt by using frozen yak milk as raw material

Abstract

The invention provides a method for preparing yak yoghourt by using frozen yak milk as a raw material, and belongs to the technical field of food processing. The method comprises the following steps: by taking frozen yak milk as a raw material, carrying out water bath thawing on the frozen yak milk at 0-10 DEG C, and sequentially adding a sweetening agent, shearing, sterilizing, inoculating a fermentation strain and fermenting to obtain the yak yoghourt. Compared with the traditional black-white cattle yoghurt, the yak yoghurt disclosed by the invention is higher in calcium content, iron content and zinc content, richer in taste, mellower in mouthfeel and easier to digest, does not need to be added with thickening and other additives, and is suitable for being eaten by people with relatively sensitive digestive systems. Meanwhile, compared with the traditional Tibetan yak yoghourt, the yak yoghourt disclosed by the invention solves the problem of seasonal supply, the manufacturing method is scientific, the operation is simple, the batch production can be realized, and the majority of consumers can eat the yak yoghourt from the snow plateau throughout the year.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to a method for making yak yogurt by taking frozen yak milk as a raw material. Background Art

[0002] Yaks are mammals of the genus Bovis in the family Bovidae, order Artiodactyla. They mainly live in high-altitude plateaus, generally above 3,000 meters above sea level. Plateaus have low temperatures, thin oxygen, short sunshine hours, little precipitation, and extremely harsh environments. However, yaks are able to adapt to the plateau environment and have become an important livestock animal in the region. The good ecological environment of yaks ensures the natural and green quality of yak milk.

[0003] Due to the special growth environment of yaks and their free-range characteristics, each lactating yak produces only about 3 kilograms of usable milk per day, and the milking season is only 100 to 120 days per year.

[0004] Yak yogurt is a very traditional cold milk drink. The yogurt in pastoral areas is made from yak milk. The surface of this yogurt is a yellow hard fat skin containing cream. When the skin is peeled off, the soft and sticky yogurt is as white as snow and fragrant as tofu brain. There are two types of traditional yak yogurt in Tibetan areas. People distinguish them according to whether they contain ghee or not. Yogurt with ghee is yogurt made directly without extracting ghee. This yogurt is milky yellow in color and has a suitable acidity. Yogurt without ghee is yogurt that extracts ghee from yak milk first and then processes it. Unlike yogurt with ghee, yogurt without ghee is snow-white and crystal clear with a suitable acidity. Traditional yak yogurt has a long history in Tibetan areas. People living on the plateau have always treated this delicacy with a long and clean attitude. Therefore, to this day, we can still taste the most original yak yogurt. Yak yogurt can not only effectively improve the function of the human immune system, but also contains a large number of probiotics, which can regulate the balance of intestinal flora, improve immunity, and prevent intestinal diseases.

[0005] In the prior art, the milk used to make yak yogurt is fresh yak milk, because fresh yak milk contains active lactic acid bacteria, which can multiply and produce lactic acid in a large number under suitable temperature and humidity conditions, so that yak milk is fermented into yogurt. However, when yak milk is frozen, the water therein will form ice crystals, resulting in the destruction of cell structure, protein denaturation and coagulation, oxidation of milk fat, and destruction of nutrients. At the same time, microorganisms such as lactic acid bacteria will lose their activity in a frozen state, so frozen yak milk can no longer be used to ferment and make yogurt. Although in theory, the activity of lactic acid bacteria can be restored by some technical means, doing so is not only costly, but also not ideal. Therefore, there is currently no precedent for making yak yogurt with frozen yak milk. Summary of the invention

[0006] The purpose of the invention is to provide a method for preparing yak yogurt by using frozen yak milk as a raw material, which can solve the problem of seasonal drinking of yak yogurt.

[0007] The present invention provides a method for making yak yogurt using frozen yak milk as a raw material, comprising the following steps: thawing the frozen yak milk in a water bath to obtain thawed yak milk; mixing the thawed yak milk with a sweetener to obtain a mixture; shearing the mixture; sterilizing the sheared liquid; inoculating fermentation bacteria and fermenting to obtain yak yogurt; the temperature of the water bath thawing is 0-10°C 。

[0008] Preferably, the mass ratio of the thawed yak milk to the sweetener is 100:5; and the sweetener includes white sugar.

[0009] Preferably, the shearing includes high-speed shearing; the shearing rotation speed is 1000-50000 rpm; and the shearing time is 30 min.

[0010] Preferably, the sterilization includes water bath sterilization; the temperature of the water bath sterilization is 80-90° C.; and the water bath sterilization time is 10-15 minutes.

[0011] Preferably, the fermentation bacteria include traditional yogurt fermentation bacteria in the Tibetan plateau or yak yogurt made with traditional yogurt fermentation bacteria in the Tibetan plateau.

[0012] Preferably, the effective viable count of the fermentation bacteria is ≥ 10 7 CFU / g or ≥10 7 CFU / ml.

[0013] Preferably, the fermentation temperature is 42° C. and the fermentation time is 8 to 10 hours.

[0014] Preferably, after the sterilization and before the inoculation of the fermentation bacteria, the sterilized material is further cooled to below 43°C.

[0015] Preferably, after inoculating the fermentation bacteria and before fermentation, the process further includes filling 5 the material inoculated with the fermentation bacteria.

[0016] Preferably, the water bath thawing process also includes stirring the frozen yak milk.

[0017] The present invention provides a method for making yak yogurt using frozen yak milk as a raw material. The method of the present invention uses frozen yak milk as a raw material, thaws the frozen yak milk in a water bath at 0 to 10°C, then sequentially adds a sweetener, shears, sterilizes, inoculates a fermentation strain, and ferments to obtain yak yogurt. The method of the present invention uses frozen yak milk to obtain yak yogurt, which solves the problem of seasonal supply of yak yogurt in the Qinghai-Tibet Plateau. The manufacturing method is scientific and simple to operate, and batch production can be achieved, so that consumers can eat yak yogurt from the snowy plateau all year round. Compared with traditional black and white spotted cattle yogurt, the yak yogurt produced by the method of the present invention has higher calcium content, iron content, and zinc content, and has a richer taste, a mellower taste, and is easier to digest. It does not require the addition of additives such as thickeners, and is suitable for people with sensitive digestive systems. DETAILED DESCRIPTION

[0018] The present invention provides a method for preparing yak yogurt by using frozen yak milk as raw material, comprising the following steps:

[0019] Thawing the frozen yak milk in a water bath to obtain thawed yak milk;

[0020] Mixing the thawed yak milk and a sweetener to obtain a mixture;

[0021] The mixture is sequentially sheared, sterilized, inoculated with fermentation bacteria and fermented to obtain yak yogurt;

[0022] The temperature of the water bath thawing is 0-10°C.

[0023] The invention firstly thaws frozen yak milk in a water bath to obtain thawed yak milk.

[0024] In the present invention, the frozen yak milk is preferably derived from fresh yak milk in high-altitude cold areas and is processed through a series of processes. In the specific implementation of the present invention, the frozen yak milk is purchased from Kangding Lanyi Plateau Food Co., Ltd. in Ganzi Tibetan Autonomous Prefecture. In the present invention, the frozen yak milk is inspected and used for subsequent production after the quality is qualified. In the present invention, the inspection preferably includes: appearance inspection, component analysis, microbial inspection, food additive inspection, nutrition label inspection, food contact material inspection, storage and transportation conditions inspection, and safety assessment of yak milk in accordance with national frozen food inspection standards. After inspection, the quality and safety of yak yogurt can be effectively controlled to ensure the safety of yak yogurt.

[0025] Before thawing the frozen yak milk in a water bath, the present invention preferably further comprises crushing the frozen yak milk into crushed ice cubes to shorten the thawing time while retaining the nutrients in the yak milk; the crushing is preferably performed by using a hard object, such as a hammer.

[0026] During the water bath thawing process, the present invention preferably further comprises changing the water every 20 minutes until the milk is completely thawed. During the water bath thawing process, the present invention preferably further comprises stirring the frozen yak milk to accelerate the thawing process.

[0027] Yak milk contains free water, crystal water and bound water. In frozen yak milk, free water freezes first, and yak milk freezes from the outside to the inside, but calcium, fat and protein in yak milk are usually not frozen. As the freezing time increases, the content of calcium, fat and the like will increase. At this time, if the frozen yak milk is thawed with hot water or thawed for a long time, the protein may coagulate and precipitate, thereby causing the yak milk to deteriorate. In the present invention, the frozen yak milk is thawed in a water bath, which can shorten the thawing time and retain the nutrients in the yak milk.

[0028] After obtaining the thawed yak milk, the present invention mixes the thawed yak milk and a sweetener to obtain a mixture. In the present invention, the mixing is preferably stirring and mixing; and the stirring and mixing time is preferably 10 minutes.

[0029] In the present invention, the mass ratio of the thawed yak milk to the sweetener is preferably 100:5. The main ingredient of the yak yogurt of the present invention is frozen yak milk, and the auxiliary ingredient is the sweetener. In the present invention, the sweetener includes white sugar.

[0030] After obtaining the mixture, the present invention sequentially shears, sterilizes, inoculates fermentation bacteria and ferments the mixture to obtain yak yogurt.

[0031] In the present invention, the shearing preferably includes high-speed shearing; the rotation speed of the shearing is preferably 1000-50000rpm; the shearing time is preferably 30min; the high-speed shearing is preferably performed using a high-speed shearing emulsifier. The present invention generates a strong shearing force through the high-speed rotating blades, rotors and other working elements of the high-speed shearing emulsifier, and refines the protein, fat and other phase particles dispersed in the yak milk, so that they are evenly dispersed in the continuous phase, which can improve the stability and delicate taste of yak yogurt. The shearing step is an important step in the production of yogurt with frozen yak milk in the present invention, and it is also a step that distinguishes it from the production of other ordinary yogurts and yak yogurt.

[0032] In the present invention, the fermentation bacteria include traditional Tibetan plateau yogurt fermentation bacteria or yak yogurt made from traditional Tibetan plateau yogurt fermentation bacteria; the traditional Tibetan plateau yogurt fermentation bacteria are preferably purchased from the Animal Products Processing Institute of Sichuan Food Fermentation Industry Research and Design Institute Co., Ltd.; the effective viable count of the fermentation bacteria is preferably ≥10 7 CFU / g or ≥10 7CFU / ml; In the specific implementation of the present invention, the traditional yogurt fermentation agent of the plateau Tibetan area is a solid dosage form, and the traditional yogurt fermentation agent of the plateau Tibetan area is dissolved in water or milk for dilution before inoculation; after dilution, the concentration of the traditional yogurt fermentation agent of the plateau Tibetan area is 0.2-0.3g / 10ml. In the specific implementation of the present invention, the fermentation strain can also be selected according to personal taste.

[0033] In the present invention, the sterilization preferably includes water bath sterilization; the temperature of the water bath sterilization is preferably 80-90° C.; and the water bath sterilization time is preferably 10-15 min.

[0034] After the sterilization and before inoculating the fermentation bacteria, the present invention preferably further comprises cooling the sterilized material to below 43°C.

[0035] In the present invention, after inoculating the fermentation bacteria, stirring is further performed until the bacteria are fully dissolved; the stirring time is preferably 6 to 10 minutes.

[0036] After the fermentation bacteria are inoculated and before fermentation, the present invention preferably further comprises filling the material after the fermentation bacteria are inoculated.

[0037] In the present invention, the fermentation temperature is preferably 42°C; the fermentation time is preferably 8 to 10 hours; and the fermentation is preferably carried out in a yogurt machine. The fermentation conditions of the present invention can ensure the taste and nutritional value of yak yogurt.

[0038] In the present invention, the packaged yak yogurt is preferably refrigerated and stored at 2-6° C., and has a shelf life of 20-25 days.

[0039] In the present invention, the yak yogurt prepared by the method does not add any gelling agent or thickener, and has the same taste as the traditional yak yogurt prepared by using fresh yak milk.

[0040] In order to further illustrate the present invention, a method for preparing yak yogurt using frozen yak milk as a raw material provided by the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] The traditional yogurt starter used in the embodiments of the present invention was purchased from the Animal Products Processing Institute of Sichuan Food Fermentation Industry Research and Design Institute Co., Ltd.

[0042] Example 1

[0043] (1) Inspection of frozen yak milk: In accordance with national frozen food inspection standards, yak milk is inspected for appearance, ingredient analysis, microbiological testing, food additive testing, nutrition labeling, food contact materials testing, storage and transportation conditions testing, and safety assessment.

[0044] (2) Thawing: Mash the qualified frozen yak milk and thaw it in a cold water bath (temperature 0-10°C), changing the water every 20 minutes until it is completely thawed.

[0045] (3) Adding auxiliary materials: adding 5% by mass of white sugar to the thawed yak milk and stirring for 10 min;

[0046] (4) Shearing: the yak milk after adding white sugar was sheared for 30 min using a high-speed shear emulsifier;

[0047] (5) Sterilization: sterilize the cut yak milk in a water bath at a temperature of 90°C and a sterilization time of 10 min;

[0048] (6) Cooling: The sterilized yak milk is cooled to below 43°C;

[0049] (7) Adding bacteria: After cooling to 43°C, add yogurt ("old yogurt") made with traditional yogurt starter culture from the Tibetan plateau the day before as the bacteria, and stir for 6 min until the bacteria are fully dissolved;

[0050] (8) Canning: canning the yak milk after adding the bacteria;

[0051] (9) Fermentation: The canned yak milk was placed in a yogurt machine for fermentation at 42°C for 8 h;

[0052] (10) Refrigerated storage: Packaged yak yogurt should be stored at 2-6°C and has a shelf life of 20-25 days.

[0053] The quality of the yak yogurt prepared in this embodiment is as follows:

[0054] Taste: Yak yogurt has a mellow texture, delicate taste, and melts in the mouth. Consumers report that the taste of yak yogurt is smoother than 90%, with almost no graininess. From the parameters, its viscosity reaches 9065mPa-s and its hardness is 45.219, showing its rich and delicate texture. In addition, the water holding capacity of yak yogurt is 57.53%, which means it has a good taste and taste persistence.

[0055] Taste: 1. Rich milk flavor: Yak yogurt is rich in protein and fat, and after fermentation, it presents a rich milk flavor. In the rating of 1 to 10, the average score of yak yogurt's milk flavor is more than 8 points.

[0056] 2. Rich aftertaste: Yak yogurt leaves a long aftertaste in the mouth, which is mainly due to its rich nutrients such as amino acids, minerals and vitamins. In the rating of 1 to 10, the average score of the mellow aftertaste is between 7 and 9.

[0057] 3. Moderate sweetness and sourness: The acidity and sweetness of yak yogurt are moderate, neither too sour nor too sweet. Most consumers may think that its sweetness and sourness are just right and give positive comments. From the specific parameters, the acidity of yak yogurt is 95.41°T, showing a moderate sour taste. At the same time, due to the addition of 5% sugar, yak yogurt also has a certain sweetness, but it is not too sweet. This moderate sweetness and sourness makes yak yogurt more delicious.

[0058] 4. Rich in nutrients:

[0059] 1) The protein content reaches 4.7g / 100ml: The protein content in yak yogurt is high. This protein contains complete amino acids, is easy to digest and absorb, and is beneficial to muscle growth and maintenance.

[0060] 2) The number of lactic acid bacteria reaches 2.0×10 9 CFU / ml: Yak yogurt contains a large amount of lactic acid bacteria. These beneficial bacteria help enhance the balance of intestinal flora and promote intestinal health.

[0061] 3) Calcium content reaches 129mg / 100ml: Yak yogurt is rich in calcium, which helps maintain the body's normal metabolism and health, and has a positive effect on bone health and immunity.

[0062] Example 2

[0063] (1) Inspection of frozen yak milk: In accordance with national frozen food inspection standards, yak milk is inspected for appearance, ingredient analysis, microbiological testing, food additive testing, nutrition labeling, food contact materials testing, storage and transportation conditions testing, and safety assessment.

[0064] (2) Thawing: Mash the qualified frozen yak milk and thaw it in a cold water bath (temperature 0-10°C), changing the water every 20 minutes until it is completely thawed.

[0065] (3) Adding auxiliary materials: adding 5% by mass of white sugar to the thawed yak milk and stirring for 10 min;

[0066] (4) Shearing: the yak milk after adding white sugar was sheared for 30 min using a high-speed shear emulsifier;

[0067] (5) Sterilization: sterilize the cut yak milk in a water bath at a temperature of 80°C and a sterilization time of 15 min;

[0068] (6) Cooling: The sterilized yak milk is cooled to below 43°C;

[0069] (7) Adding bacteria: After cooling to 43°C, add yogurt ("old yogurt") made with traditional yogurt starter culture from the Tibetan plateau the day before as bacteria, and stir for 10 min until the bacteria are fully dissolved;

[0070] (8) Canning: canning the yak milk after adding the bacteria;

[0071] (9) Fermentation: The canned yak milk was placed in a yogurt machine for fermentation at 42°C for 10 h;

[0072] (10) Refrigerated storage: Packaged yak yogurt should be stored at 2-6°C and has a shelf life of 20-25 days.

[0073] Comparative Example 1

[0074] The preparation method of ordinary yogurt is as follows:

[0075] 1. Add an appropriate amount of fresh whole milk into the sterilized container. The temperature of the milk should be controlled at around 40°C.

[0076] 2. According to the instructions of the purchased yogurt fermentation powder, pour an appropriate amount of powder into the milk and stir evenly with a spoon or blender.

[0077] 3. Pour the mixed milk into a yogurt machine or incubator, and make sure the temperature remains constant between 40 and 42°C.

[0078] 4. Set the fermentation time according to the instructions of the purchased bacteria powder, usually 6 to 8 hours.

[0079] 5. After fermentation is completed, open the yogurt machine or incubator and observe the coagulation state of the yogurt. Normally fermented yogurt should be semi-solid, with a smooth surface and no liquid precipitation.

[0080] 6. If you find that the yogurt is not completely solidified or liquid has precipitated, you can extend the fermentation time appropriately.

[0081] Test Example 1

[0082] The nutritional components of the yak yogurt of Example 1 and the ordinary yogurt prepared in Comparative Example 1 were tested, and the testing process was as follows:

[0083] 1. In terms of sensory requirements, the main thing is to observe and evaluate the product. The product should have a delicate and uniform texture, and a small amount of whey should be allowed to drip out. At the same time, the fermented milk should have a uniform color, milky white or slightly yellow, and have the unique taste and smell of fermented milk. The evaluation of these sensory characteristics is an important step in judging the quality of yak yogurt.

[0084] 2. The detection of physical and chemical indicators is more specific and quantitative. Among them, acidity is an important detection indicator, and its determination method follows the relevant provisions of the national food safety standards. By measuring the acidity, the fermentation degree and taste of the yogurt can be understood. The protein detection of yak yogurt can mainly adopt the Kjeldahl method. This method is based on the fact that when heated, sulfuric acid decomposes into sulfurous anhydride, water and oxygen, organic matter is oxidized into carbon dioxide and water, and the ammonia nitrogen of protein reacts with excess sulfuric acid to convert into ammonium sulfate, which is distilled in an alkaline solution to perform quantitative determination of protein. The detection of calcium content in yak yogurt is usually carried out using atomic absorption spectroscopy or inductively coupled plasma optical emission spectroscopy (ICP-OES). These methods are all based on quantitative analysis of the specific spectral properties of elements.

[0085] The test results are shown in Table 1. As can be seen from Table 1, compared with ordinary yogurt, yak yogurt has more superior nutritional components in terms of protein, lactic acid bacteria and calcium. These characteristics make yak yogurt have better effects in maintaining human health, promoting growth and development, and enhancing immunity.

[0086] Table 1 Comparison of nutritional components between yak yogurt and ordinary yogurt

[0087]

[0088] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for making yak yogurt using frozen yak milk as raw material, characterized in that: The following steps are involved: Thawing the frozen yak milk in a water bath to obtain thawed yak milk; Mixing the thawed yak milk and a sweetener to obtain a mixture; shearing the mixture; Sterilize the sheared liquid; Inoculating fermentation bacteria and fermenting to obtain yak yogurt; The temperature of the water bath thawing is 0-10°C.

2. The method according to claim 1, characterized in that The mass ratio of the thawed yak milk to the sweetener is 100:5; the sweetener includes white sugar.

3. The method according to claim 1, characterized in that The shearing includes high-speed shearing; the shearing rotation speed is 1000-50000 rpm; and the shearing time is 30 minutes.

4. The method according to claim 1, characterized in that: The sterilization includes water bath sterilization; the temperature of the water bath sterilization is 80-90° C.; the water bath sterilization time is 10-15 minutes.

5. The method according to claim 1, characterized in that The fermentation bacteria include traditional yogurt fermentation bacteria in plateau Tibetan areas or yak yogurt made with traditional yogurt fermentation bacteria in plateau Tibetan areas.

6. The method according to claim 1 or 5, characterized in that: The effective viable count of the fermentation strain is ≥10 7 CFU / g or ≥10 7 CFU / ml.

7. The method according to claim 1, characterized in that The fermentation temperature is 42° C. and the fermentation time is 8 to 10 hours.

8. The method according to claim 1, characterized in that After the sterilization and before the inoculation of the fermentation bacteria, the sterilized material is cooled to below 43°C.

9. The method according to claim 1, characterized in that: After the fermentation bacteria are inoculated and before fermentation, the process also includes filling 5 the material after the fermentation bacteria are inoculated.

10. The method according to claim 1, characterized in that The water bath thawing process also includes stirring the frozen yak milk.

Images