Preparation method of low-temperature yoghurt with long shelf life
The preparation of low-temperature yogurt through low-temperature fermentation and low-temperature plasma sterilization solves the problem of short shelf life of existing yogurts, extends the shelf life and improves the market competitiveness of the products.
Patent Information
- Application Number
- CN202411950927.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-03-14
AI Technical Summary
The shelf life of existing low-temperature yogurt is relatively short, resulting in limited product sales scope.
Yogurt is prepared by low-temperature fermentation and low-temperature plasma sterilization. The specific steps include pasteurization, low-temperature fermentation, homogenization treatment, low-temperature plasma sterilization, filling and sealing, and refrigeration storage.
It effectively extends the shelf life of yogurt to 32 days to 35 days, improves the market competitiveness of the product, and reduces the risk of food waste.
Smart Images
Figure BDA0005214855440000121
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of yogurt preparation, and in particular relates to a method for preparing low-temperature yogurt with a long shelf life. Background Art
[0002] Yogurt is a food obtained by fermenting milk with lactic acid bacteria. It is divided into low-temperature yogurt and room-temperature yogurt according to storage conditions. Low-temperature yogurt has a unique taste and rich nutritional value, and its texture is delicate. It contains live lactic acid bacteria, which can improve health by regulating human metabolism. However, at present, the preparation process of low-temperature yogurt sold on the market usually involves pasteurizing the raw materials, and then fermenting them at high temperature with Lactobacillus bulgaricus and Streptococcus thermophilus. The fermentation time is 2h to 4h, and the fermentation temperature is 40℃ to 42℃. After fermentation, no sterilization treatment is performed, and the yogurt is directly filled and stored at low temperature for sale. This method has a short production cycle. However, data show that the yogurt prepared by this method has too strong acidification after the presence of yogurt, which makes the shelf life of yogurt relatively short, generally 18 to 21 days, which greatly limits the sales scope of the product. Summary of the invention
[0003] In order to solve the above problems, the present invention provides a method for preparing low-temperature yogurt with a long shelf life, so as to improve the shelf life of the low-temperature yogurt.
[0004] The present invention is achieved through the following technical solutions:
[0005] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0006] Raw material processing: Choose raw milk as the raw material, add white sugar, stir evenly and then pasteurize;
[0007] Low-temperature fermentation: Lactic acid bacteria are inoculated into pasteurized raw milk for fermentation at a temperature of 4°C to 10°C for 12 to 24 hours to obtain a semi-finished product.
[0008] Homogenization: Homogenize the semi-finished product.
[0009] Low-temperature plasma sterilization: The semi-finished product after homogenization is sterilized by low-temperature plasma, the sterilization temperature is 10℃~20℃, the electric field strength is 5kV / cm~50kV / cm, and the processing time is 1min~10min.
[0010] Filling and sealing: The semi-finished products sterilized by low-temperature plasma are filled into sterile cups through aseptic filling equipment and sealed.
[0011] Preferably, the pasteurization temperature is 62° C. to 65° C. and the time is 30 min to 35 min, so as to kill most of the harmful bacteria while retaining the beneficial microorganisms and nutrients in the food as much as possible.
[0012] Preferably, the fermentation temperature is 6°C and the fermentation time is 18 hours, so that the growth and fermentation speed of lactic acid bacteria slow down, thereby extending the shelf life of yogurt. At a lower temperature, the growth rate of lactic acid bacteria slows down, and the fermentation process also slows down accordingly, so that the yogurt can be kept fresh for a longer time. At the same time, a longer fermentation time helps lactic acid bacteria to fully ferment, making the taste of yogurt more sweet and sour.
[0013] Preferably, the temperature of the homogenization treatment is 5°C to 10°C, and the rotation speed is 10,000 rpm to 20,000 rpm, so as to improve the uniformity of the yogurt and avoid over-fermentation during the homogenization process. Homogenization at a lower temperature can effectively prevent the lactic acid bacteria from over-breeding during the homogenization process, thereby avoiding over-fermentation of the yogurt. At the same time, a higher rotation speed can make the fat globules in the yogurt more evenly distributed, improving the texture and taste of the yogurt.
[0014] Preferably, the low-temperature plasma sterilization temperature is 15°C, the electric field strength is 25kV / cm, and the treatment time is 5min, which effectively kills the remaining harmful bacteria in the yogurt and ensures the safety and shelf life of the product. Sterilization at a lower temperature can minimize the impact on the beneficial microorganisms in the yogurt. At the same time, the appropriate electric field strength and treatment time can ensure the sterilization effect.
[0015] Preferably, the refrigeration temperature is 4° C. to 10° C., which maintains the quality of the yogurt, slows down the growth of microorganisms, and prolongs the shelf life of the yogurt. Within this temperature range, the taste, texture, and nutritional components of the yogurt can be effectively maintained.
[0016] Preferably, the weight-to-volume ratio of the white sugar to the raw milk is 1:15-16, ensuring that the yogurt has a moderate sweet and sour taste.
[0017] Preferably, 1×10 7 CFU to 1 × 10 8 CFU of lactic acid bacteria to obtain a yogurt with medium acidity.
[0018] Preferably, the lactic acid bacteria is at least one of Lactococcus lactis lactis, Lactococcus lactis cremoris, Bifidobacterium lactis, Lactobacillus acidophilus, and Lactobacillus paracasei, and the lactic acid bacteria have good fermentation performance during the fermentation of yogurt, and can make the yogurt produce rich taste and nutritional value. At the same time, these lactic acid bacteria also have physiological functions such as regulating intestinal health and enhancing immunity.
[0019] Compared with the prior art, the present invention has the following beneficial effects:
[0020] The invention provides a method for preparing a low-temperature yogurt with a long shelf life, comprising the following specific steps: selecting raw milk as a raw material, adding white sugar, stirring evenly and then pasteurizing; inoculating lactic acid bacteria into the pasteurized raw milk for fermentation, the fermentation temperature is 4°C to 10°C, the time is 12 hours to 24 hours, and a semi-finished product is obtained; the semi-finished product after low-temperature plasma sterilization is homogenized; the semi-finished product after homogenization is sterilized by low-temperature plasma, the sterilization temperature is 10°C to 20°C, the electric field strength is 5kV / cm to 50kV / cm, and the processing time is 1min to 10min; the semi-finished product is filled into a sterile cup by an aseptic filling machine, and sealed; after sealing, it is placed in a refrigeration device for storage. The method can slow down the continued fermentation and acid production of lactic acid bacteria, effectively prolong the shelf life of yogurt, and increase the shelf life of yogurt to 32 days to 35 days. The mild taste and rich aroma mean that the product has a longer time window during transportation, storage and sales, reduces the risk of food waste, and improves economic benefits. In addition, low-temperature fermentation and low-temperature plasma sterilization technology are easy to control and operate, and are suitable for large-scale production. This helps to improve production efficiency and reduce production costs, making low-temperature yogurt more competitive in the market. DETAILED DESCRIPTION
[0021] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.
[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.
[0023] The purchase sources of the lactic acid bacteria used in the present invention are:
[0024] The lactic acid bacteria included Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Bifidobacterium lactis, Lactobacillus acidophilus, and Lactobacillus paracasei, all of which were purchased from Hebei Yiran Biotechnology Co., Ltd.
[0025] In the preparation process, traditional low-temperature yogurt is only sterilized once in the raw milk state, and then lactic acid bacteria are added for fermentation. After fermentation, no sterilization is performed. After fermentation, it is stored and transported at low temperatures. However, during transportation and storage, the lactic acid bacteria in the yogurt will continue to ferment and produce acid. Excessive acidification affects the quality of the yogurt and causes it to deteriorate. It also shortens the shelf life of low-temperature yogurt and makes it difficult to meet people's storage time requirements.
[0026] The present invention provides a method for preparing low-temperature yogurt with a long shelf life, comprising the following specific steps:
[0027] Raw material processing: Choose raw milk as the raw material, add white sugar, stir evenly and then pasteurize.
[0028] Low-temperature fermentation: Lactic acid bacteria are inoculated into pasteurized raw milk for fermentation at a temperature of 4°C to 10°C for 12 to 24 hours to obtain a semi-finished product.
[0029] Homogenization: Homogenize the semi-finished product.
[0030] Low-temperature plasma sterilization: The semi-finished product after homogenization is sterilized by low-temperature plasma, the sterilization temperature is 10℃~20℃, the electric field strength is 5kV / cm~50kV / cm, and the processing time is 1min~10min.
[0031] Filling and sealing: The semi-finished product sterilized by low-temperature plasma is filled into a sterile cup through an aseptic filling machine and sealed.
[0032] Refrigerated storage: Store in a refrigerator after sealing.
[0033] Low-temperature fermentation is a fermentation process carried out at a lower temperature, which can inhibit the growth of harmful microorganisms, thereby extending the shelf life of food and reducing food waste. It also slowly changes the physical and chemical properties of food, thereby improving its taste, texture and flavor, increasing nutritional value and nutrient content.
[0034] Low-temperature plasma sterilization is a method of disinfection and sterilization using low-temperature plasma. Plasma is a state of matter composed of charged particles, such as electrons, ions and free radicals, which exists in gaseous substances. In the low-temperature plasma sterilization process, microorganisms are killed quickly and efficiently by generating a plasma area under specific conditions. Compared with the traditional high-temperature and high-pressure sterilization method, this method is faster, more convenient and energy-saving. At the same time, it can better protect the quality and effect of the sterilized items and avoid problems such as product damage and deterioration caused by high temperature and high pressure. Low-temperature plasma sterilization can reduce the survival rate of harmful microorganisms and slow down the continued fermentation and acid production of lactic acid bacteria, thereby inhibiting acidification and extending the shelf life of yogurt. The present invention uses low-temperature fermentation, and after the fermentation is completed, low-temperature plasma sterilization is used to prepare low-temperature yogurt, which effectively solves the problem of short shelf life of low-temperature yogurt.
[0035] The technical solution of the present invention will be further described below in conjunction with specific embodiments.
[0036] Example 1
[0037] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0038] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0039] (2) Low temperature fermentation: 1×10 6 The fermentation is carried out with CFU of Lactococcus lactis subspecies lactic acid bacteria at a fermentation temperature of 4° C. and a fermentation time of 12 hours to obtain a semi-finished product.
[0040] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform; the homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 5°C to make the texture of the semi-finished product uniform.
[0041] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 10°C, the electric field strength to 5 kV / cm, and the processing time to 1 min for sterilization.
[0042] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0043] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0044] Example 2
[0045] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0046] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0047] (2) Low temperature fermentation: 1×10 8 The CFU Lactococcus lactis subspecies cremoris is fermented at a temperature of 4° C. for 12 hours to obtain a semi-finished product.
[0048] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform; the homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 5°C to make the texture of the semi-finished product uniform.
[0049] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 10°C, the electric field strength to 5 kV / cm, and the processing time to 1 min for sterilization.
[0050] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0051] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0052] Example 3
[0053] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0054] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:16, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0055] (2) Low temperature fermentation: 1×10 8CFU Bifidobacterium lactis lactic acid bacteria are fermented at a temperature of 4° C. for 12 hours to obtain a semi-finished product.
[0056] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform; the homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 5°C to make the texture of the semi-finished product uniform.
[0057] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 10°C, the electric field strength to 5 kV / cm, and the processing time to 1 min for sterilization.
[0058] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0059] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0060] Example 4
[0061] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0062] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0063] (2) Low temperature fermentation: 1×10 6 The CFU Lactobacillus acidophilus lactic acid bacteria is fermented at a temperature of 4° C. for 12 hours to obtain a semi-finished product.
[0064] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform; the homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 5°C to make the texture of the semi-finished product uniform.
[0065] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 10°C, the electric field strength to 5 kV / cm, and the processing time to 1 min for sterilization.
[0066] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0067] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0068] Example 5
[0069] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0070] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0071] (2) Low temperature fermentation: 1×10 6 The CFU Lactobacillus paracasei lactic acid bacteria are fermented at a temperature of 4° C. for 12 hours to obtain a semi-finished product.
[0072] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform; the homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 5°C to make the texture of the semi-finished product uniform.
[0073] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 10°C, the electric field strength to 5 kV / cm, and the processing time to 1 min for sterilization.
[0074] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0075] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0076] Example 6
[0077] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0078] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 63°C and keep for 32 minutes for pasteurization.
[0079] (2) Low temperature fermentation: 1×10 6 The CFU lactic acid bacteria are fermented at a temperature of 6°C for 18 hours to obtain a semi-finished product.
[0080] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform. The homogenization process is: stirring at a speed of 15,000 rpm for 15 minutes at a temperature of 8°C to make the texture of the semi-finished product uniform.
[0081] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 15°C, the electric field strength to 25 kV / cm, and the processing time to 5 min for sterilization.
[0082] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0083] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 8°C.
[0084] Example 7
[0085] A method for preparing low-temperature yogurt with a long shelf life comprises the following specific steps:
[0086] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 65°C and keep for 35 minutes for pasteurization.
[0087] (2) Low temperature fermentation: 1×10 6 The CFU lactic acid bacteria are fermented at a temperature of 10°C for 24 hours to obtain a semi-finished product.
[0088] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform. The homogenization process is: stirring at a speed of 20,000 rpm for 20 minutes at a temperature of 10°C to make the texture of the semi-finished product uniform.
[0089] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 20°C, the electric field strength to 50 kV / cm, and the processing time to 10 min for sterilization.
[0090] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0091] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 10°C.
[0092] Comparative Example 1
[0093] This comparative example uses only a low-temperature fermentation method to prepare low-temperature yogurt, including the following specific steps:
[0094] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0095] (2) Low temperature fermentation: 1×10 6 The CFU lactic acid bacteria are fermented at a temperature of 4° C. for 12 hours to obtain a semi-finished product.
[0096] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform. The homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 8°C to make the texture of the semi-finished product uniform.
[0097] (4) Filling and sealing: Use a sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0098] (5) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0099] The lactic acid bacteria is at least one of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Bifidobacterium lactis, Lactobacillus acidophilus and Lactobacillus paracasei.
[0100] Comparative Example 2
[0101] This comparative example uses a method of low-temperature fermentation combined with high-temperature sterilization to prepare low-temperature yogurt, including the following specific steps:
[0102] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0103] (2) Low temperature fermentation: 1×10 6 The CFU lactic acid bacteria are fermented at a temperature of 4° C. for 12 hours to obtain a semi-finished product.
[0104] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform. The homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 8°C to make the texture of the semi-finished product uniform.
[0105] (4) High temperature sterilization: sterilize at 90℃ for 15 minutes and cool rapidly.
[0106] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0107] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0108] The lactic acid bacteria is at least one of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Bifidobacterium lactis, Lactobacillus acidophilus and Lactobacillus paracasei.
[0109] Comparative Example 3
[0110] This comparative example uses a method of high temperature fermentation combined with high temperature sterilization to prepare low temperature yogurt, including the following specific steps:
[0111] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0112] (2) High temperature fermentation: 1×10 6 The CFU lactic acid bacteria are fermented at a temperature of 42° C. for 3 hours to obtain a semi-finished product.
[0113] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform. The homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 8°C to make the texture of the semi-finished product uniform.
[0114] (4) High temperature sterilization: sterilize at 90℃ for 15 minutes and cool rapidly.
[0115] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0116] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0117] The lactic acid bacteria is at least one of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Bifidobacterium lactis, Lactobacillus acidophilus and Lactobacillus paracasei.
[0118] Comparative Example 4
[0119] This comparative example uses a method of high temperature fermentation combined with low temperature plasma sterilization to prepare low temperature yogurt, including the following specific steps:
[0120] (1) Raw material processing: Select raw milk as the raw material, add the raw milk into the mixing tank, add white sugar, the weight volume ratio of white sugar to raw milk is 1:15, stir evenly at 40°C, then heat to 62°C and keep for 30 minutes for pasteurization.
[0121] (2) High temperature fermentation: 1×10 6 The CFU lactic acid bacteria are fermented at a temperature of 42° C. for 3 hours to obtain a semi-finished product.
[0122] (3) Homogenization: The semi-finished product is homogenized to make the texture of the semi-finished product uniform. The homogenization process is: stirring at a speed of 10,000 rpm for 10 minutes at a temperature of 8°C to make the texture of the semi-finished product uniform.
[0123] (4) Low-temperature plasma sterilization: Set the temperature of the plasma sterilizer to 15°C, the electric field strength to 5 kV / cm, and the processing time to 1 min for sterilization.
[0124] (5) Filling and sealing: Use the sterile chamber to spray hydrogen peroxide to sterilize the aseptic filling machine, and after sterilization, it enters the production state; the surface of the packaging material sterile cup is disinfected by spraying quantitative atomized hydrogen peroxide, and the residual hydrogen peroxide in the cup is dried by hot air to achieve a sterile state; then the semi-finished product is filled into the sterile cup through the aseptic filling machine and sealed.
[0125] (6) Refrigerated storage: After sealing, place in a refrigerator at a temperature of 4°C.
[0126] The lactic acid bacteria is at least one of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Bifidobacterium lactis, Lactobacillus acidophilus and Lactobacillus paracasei.
[0127] The pH values of the yogurts prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were tested to determine the degree of acidification of each yogurt. The results are shown in the following table:
[0128] Table 1 The relationship between pH value of yogurt and time
[0129]
[0130] As can be seen from Table 1, the pH value of the yogurt prepared by the method of low-temperature fermentation combined with low-temperature plasma sterilization in Examples 1 to 7 decreased slowly during the detection process, and the pH value was still greater than 4.0 at 30 days; while the pH value of the yogurt prepared by the method in Comparative Examples 1 to 4 decreased rapidly during the detection process, and the pH value was less than 3.5 at 30 days. This indicates that the method of low-temperature fermentation combined with low-temperature plasma sterilization in the present invention effectively inhibits the late acidification of yogurt.
[0131] In addition, the shelf life of the yogurts prepared in Examples 1 to 7 and Comparative Examples 1 to 4 was tested respectively. The test results showed that the shelf life of the low-temperature yogurt prepared by the method of low-temperature fermentation combined with low-temperature plasma sterilization in Examples 1 to 7 was 32 to 35 days; the shelf life of the low-temperature yogurt prepared by only the low-temperature fermentation method in Comparative Example 1 was 23 days; the shelf life of the low-temperature yogurt prepared by the method of low-temperature fermentation combined with high-temperature sterilization in Comparative Example 2 was 26 days; the shelf life of the low-temperature yogurt prepared by the method of high-temperature fermentation combined with high-temperature sterilization in Comparative Example 3 was 24 days; the shelf life of the low-temperature yogurt prepared by the method of high-temperature fermentation combined with low-temperature plasma sterilization in Comparative Example 4 was 25 days. The shelf life of the low-temperature yogurts prepared in Examples 1 to 7 is higher than that of the low-temperature yogurts prepared in Comparative Examples 1 to 4.
[0132] In summary, the present invention provides a method for preparing low-temperature yogurt with a long shelf life, which uses a method of combining low-temperature fermentation with low-temperature plasma sterilization to prepare low-temperature yogurt, inhibits the late acidification of yogurt, and effectively extends the shelf life of yogurt.
[0133] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0134] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A method for preparing low-temperature yogurt with a long shelf life, characterized in that: The specific steps include: Raw material processing: Choose raw milk as the raw material, add white sugar, stir evenly and then pasteurize; Low-temperature fermentation: inoculate lactic acid bacteria into pasteurized raw milk for fermentation at a temperature of 4°C to 10°C for 12 to 24 hours to obtain a semi-finished product; Homogenization: homogenize the semi-finished product; Low-temperature plasma sterilization: The semi-finished product after homogenization is sterilized by low-temperature plasma, the sterilization temperature is 10℃~20℃, the electric field strength is 5kV / cm~50kV / cm, and the processing time is 1min~10min; Filling and sealing: The semi-finished product sterilized by low-temperature plasma is filled into a sterile cup through aseptic filling equipment and sealed.
2. The method for preparing the long-shelf-life low-temperature yogurt according to claim 1, characterized in that: The pasteurization temperature is 62° C. to 65° C., and the time is 30 min to 35 min.
3. The method for preparing the long-shelf-life low-temperature yogurt according to claim 1, characterized in that: The fermentation temperature is 6°C and the fermentation time is 18 hours.
4. The method for preparing the long-shelf-life low-temperature yogurt as described in claim 1, characterized in that: The temperature of the homogenization treatment is 5° C. to 10° C., and the rotation speed is 10,000 rpm to 20,000 rpm.
5. The method for preparing the long-shelf-life low-temperature yogurt as described in claim 1, characterized in that: The low-temperature plasma sterilization is performed at a temperature of 15° C., an electric field strength of 25 kV / cm, and a treatment time of 5 minutes.
6. The method for preparing the long-shelf-life low-temperature yogurt as described in claim 1, characterized in that: The refrigeration temperature is 4°C to 10°C.
7. The method for preparing the long-shelf-life low-temperature yogurt as claimed in claim 1, characterized in that: The weight volume ratio of the white sugar to the raw milk is 1:15-16.
8. The method for preparing the long-shelf-life low-temperature yogurt as described in claim 1, characterized in that: Inoculate 1×10 7 CFU to 1 × 10 8 CFU of lactic acid bacteria.
9. The method for preparing the long-shelf-life low-temperature yogurt as claimed in claim 1, characterized in that: The lactic acid bacteria is at least one of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Bifidobacterium lactis, Lactobacillus acidophilus, and Lactobacillus paracasei.