Stabilization method of fermented buffalo milk

Abstract

The invention provides a method for stabilizing fermented buffalo milk, which comprises the following steps: firstly, adjusting the pH value of buffalo milk before thermal sterilization to 7.4 from about 6.7 in a natural state, so that the chemical environment of the product in a high-temperature sterilization process can be effectively improved; secondly, TG enzyme is added while the white granulated sugar is added into the buffalo milk system, the TG enzyme can catalyze cross-linking reaction in protein molecules or among the molecules, and in the fermented buffalo milk system, the protein is promoted to form a more stable and ordered network structure. According to the invention, the two key problems of mouth feel and shelf life in the production process of the normal-temperature fermented buffalo milk are fundamentally solved, the market competitiveness of the product is greatly improved, and the preparation method has extremely high application value and economic benefit.

Description

Technical Field

[0001] The invention belongs to the technical field of dairy product processing, and particularly relates to a method for stabilizing fermented buffalo milk. Background Art

[0002] Fermented buffalo milk is highly favored in the market due to its unique flavor and taste. At present, the production of buffalo milk in my country is mainly concentrated in southern regions such as Guangxi and Yunnan. However, low-temperature fermented buffalo milk has a short shelf life, usually within 21 days, which greatly limits its expansion into the northern market. Converting low-temperature fermented buffalo milk to room-temperature fermented buffalo milk has become an effective way to solve this dilemma.

[0003] The significant difference between room temperature fermented buffalo milk and low temperature fermented buffalo milk is that after fermentation, room temperature fermented milk needs to be homogenized and sterilized to completely inactivate the microorganisms in the fermented milk, thereby achieving stable storage of the product at room temperature.

[0004] However, after high-temperature sterilization, the fermented buffalo milk has a rough taste and loses the delicate and smooth feeling of low-temperature fermented buffalo milk, which seriously affects the product quality. Therefore, exploring technical methods to improve the quality of room-temperature fermented buffalo milk products has become a technical problem that needs to be overcome urgently. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a method for stabilizing fermented buffalo milk, which can effectively reduce the roughness of buffalo milk fermented at room temperature and improve the smoothness and sensory quality.

[0006] The objective of the present invention is achieved through the following technical solutions: The first aspect of the present invention provides a method for stabilizing fermented buffalo milk, comprising the following steps: (1) adjusting the pH value of buffalo milk to 7.0-7.5, and then performing UHT sterilization to obtain UHT buffalo milk; (2) UHT buffalo milk is heated to 45°C-50°C in a fermentation tank, white sugar and pectin are mixed and added to the buffalo milk system, and glutamine aminotransferase is added and stirred to make the materials evenly mixed to prepare a buffalo milk-based material, which is heated to 35°C-45°C in a water bath for 30 min-45 min, and then the buffalo milk-based material is homogenized; (3) After homogenization, the substrate is sterilized and then cooled to 42 ± 1°C through the cooling water circulation system in the fermentation tank for inoculation and fermentation. The fermentation is terminated when the pH end point is 4.50 ± 0.04. After demulsification, the sample is sterilized again to finally obtain stabilized room temperature fermented buffalo milk.

[0007] Furthermore, in step (1), the pH value of the buffalo milk is adjusted to 7.4 using a sodium hydroxide solution.

[0008] Furthermore, in step (2), the amounts of the white sugar and pectin added to the UHT buffalo milk by mass percentage are 5% to 10% and 0.5% to 1%, respectively; preferably, the amounts of the white sugar and pectin added to the UHT buffalo milk by mass percentage are 6% and 0.6%, respectively.

[0009] Furthermore, in step (2), the amount of transglutaminase added is 1-10 U / g buffalo milk protein; preferably, the amount of transglutaminase added is 10 U / g buffalo milk protein.

[0010] Furthermore, in step (2), the specific process of homogenization includes: the first-stage homogenization pressure is 40 bar, and the second-stage homogenization pressure is 150 bar.

[0011] Furthermore, in step (3), the specific process of the demulsification treatment includes: stirring and demulsifying at a rotation speed of 500-600 rpm.

[0012] The second aspect of the present invention provides stabilized room-temperature fermented buffalo milk prepared by the method described in the first aspect.

[0013] The third aspect of the present invention provides application of the stabilization method described in the first aspect in preparing fermented buffalo milk.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention brings about significant beneficial effects by adjusting the pH value to 7.4 and adding glutamine aminotransferase (TG enzyme) before heat sterilization of buffalo milk.

[0015] First, adjusting the pH value of buffalo milk from about 6.7 in its natural state to 7.4 before heat sterilization can effectively improve the chemical environment of the product during high-temperature sterilization. This adjustment helps to alleviate the damage of high temperature to the structure of milk proteins, reduce the occurrence of protein denaturation and aggregation, and thus avoid the problem of rough taste caused by changes in protein structure. After sterilization, room temperature fermented buffalo milk can be closer to the delicate and smooth taste of low temperature fermented buffalo milk, significantly improving product quality.

[0016] Secondly, TG enzyme was added to the buffalo milk system at the same time as white sugar, and the dosage of TG enzyme was 1-10U / g buffalo milk protein, which played a positive role in many aspects. TG enzyme can catalyze the cross-linking reaction within or between protein molecules, and in the fermented buffalo milk system, it promotes the formation of a more stable and orderly network structure of protein. This not only enhances the stability of the product, effectively prolongs the shelf life of room temperature fermented buffalo milk, and solves the dilemma of low temperature fermented buffalo milk with a short shelf life and difficulty in entering the northern market; it also further optimizes the texture and taste of the product, making the product more delicate and elastic, bringing consumers a better eating experience.

[0017] In summary, the method of adjusting pH value and adding TG enzyme adopted in the present invention fundamentally solves the two key problems of taste and shelf life faced by room temperature fermented buffalo milk in the production process, greatly improves the market competitiveness of the product, and has extremely high application value and economic benefits. DETAILED DESCRIPTION

[0018] The implementation of the present invention is not limited to the following embodiments, and any form of modification and / or change made to the present invention will fall within the scope of protection of the present invention. In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. Unless otherwise specified, the methods used in the embodiments are common techniques in the art.

[0019] For numerical ranges, the endpoints of each range, the endpoints of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be deemed to be specifically disclosed herein.

[0020] Example 1 This embodiment provides a method for stabilizing fermented buffalo milk, comprising the following steps: (1) The pH value of buffalo milk was adjusted to 7.4 with 0.1 M sodium hydroxide, and then UHT buffalo milk was sterilized at 147 °C for 3 s to obtain UHT buffalo milk.

[0021] (2) UHT buffalo milk was heated to 45°C-50°C in a fermentation tank, 6% white sugar and 0.6% pectin were mixed and added to the buffalo milk system, and glutamine aminotransferase (TGase) was added, and the TGase dosage was 10U / g buffalo milk protein. The materials were uniformly mixed by stirring and shearing at a rate of 700 rpm with a mechanical stirrer to prepare a buffalo milk-based material, which was heated to 40°C in a water bath for 40 min, and then the buffalo milk-based material was homogenized.

[0022] Among them, the specific process of homogenization includes: the first-level homogenization pressure is 40 bar, and the second-level homogenization pressure is 150 bar.

[0023] (3) After homogenization, the substrate was sterilized (85°C for 20 min), and then cooled to 42 ± 1°C through the cooling water circulation system in the fermentation tank for inoculation and fermentation (0.03% (w / w), thermophilic Streptococcus). The fermentation was terminated when the pH end point was 4.50 ± 0.04 (about 5-6 h). After the emulsion was broken by stirring at 550 rpm, the sample was sterilized again at 85°C for 25 s to finally obtain stable room temperature fermented buffalo milk.

[0024] Comparative Example 1 This comparative example provides a method for fermenting buffalo milk with reference to Example 1, except that no TG enzyme is added to the buffalo milk system. Specifically, the method comprises the following steps: (1) The pH value of buffalo milk was adjusted to 7.4 with 0.1 M sodium hydroxide, and then UHT buffalo milk was sterilized at 147 °C for 3 s to obtain UHT buffalo milk.

[0025] (2) UHT buffalo milk was heated to 45°C-50°C in a fermentation tank, and 6% white sugar and 0.6% pectin were mixed and added to the buffalo milk system. The materials were uniformly mixed by stirring and shearing at 700 rpm with a mechanical stirrer to prepare a buffalo milk-based material, which was heated to 40°C in a water bath for 40 min, and then the buffalo milk-based material was homogenized.

[0026] Among them, the specific process of homogenization includes: the first-level homogenization pressure is 40 bar, and the second-level homogenization pressure is 150 bar.

[0027] (3) After homogenization, the substrate was sterilized (85°C for 20 min), and then cooled to 42 ± 1°C through the cooling water circulation system in the fermentation tank for inoculation and fermentation (0.03% (w / w), thermophilic Streptococcus). The fermentation was terminated when the pH end point was 4.50 ± 0.04 (about 5-6 h), and the sample was sterilized again at 85°C for 25 s to obtain room temperature fermented buffalo milk.

[0028] Comparative Example 2 This comparative example provides a method for fermenting buffalo milk with reference to Example 1, except that the pH is not adjusted before UHT sterilization. Specifically, the method comprises the following steps: (1) Buffalo milk was sterilized by UHT at 147°C for 3 seconds to obtain UHT buffalo milk.

[0029] (2) UHT buffalo milk was heated to 45°C-50°C in a fermentation tank, 6% white sugar and 0.6% pectin were mixed and added to the buffalo milk system, and glutamine aminotransferase (TGase) was added, and the TGase dosage was 10U / g buffalo milk protein. The materials were uniformly mixed by stirring and shearing at a rate of 700 rpm with a mechanical stirrer to prepare a buffalo milk-based material, which was heated to 40°C in a water bath for 40 min, and then the buffalo milk-based material was homogenized.

[0030] Among them, the specific process of homogenization includes: the first-level homogenization pressure is 40 bar, and the second-level homogenization pressure is 150 bar.

[0031] (3) After homogenization, the substrate was sterilized (85°C for 20 min), and then cooled to 42 ± 1°C through the cooling water circulation system in the fermentation tank for inoculation and fermentation (0.03% (w / w), thermophilic Streptococcus). The fermentation was terminated when the pH end point was 4.50 ± 0.04 (about 5-6 h), and the sample was sterilized again at 85°C for 25 s to obtain room temperature fermented buffalo milk.

[0032] Comparative Example 3 This comparative example provides a conventional method for fermenting buffalo milk, which specifically comprises the following steps: (1) Buffalo milk was sterilized by UHT at 147°C for 3 seconds to obtain UHT buffalo milk.

[0033] (2) UHT buffalo milk was heated to 45°C-50°C in a fermentation tank, and 6% white sugar and 0.6% pectin were mixed and added to the buffalo milk system. The materials were uniformly mixed by stirring and shearing at 700 rpm with a mechanical stirrer to prepare a buffalo milk-based material, which was heated to 40°C in a water bath for 40 min, and then the buffalo milk-based material was homogenized.

[0034] Among them, the specific process of homogenization includes: the first-level homogenization pressure is 40 bar, and the second-level homogenization pressure is 150 bar.

[0035] (3) After homogenization, the substrate was sterilized (85°C for 20 min), and then cooled to 42 ± 1°C through the cooling water circulation system in the fermentation tank for inoculation and fermentation (0.03% (w / w), thermophilic Streptococcus). The fermentation was terminated when the pH end point was 4.50 ± 0.04 (about 5-6 h), and the sample was sterilized again at 85°C for 25 s to obtain room temperature fermented buffalo milk.

[0036] Test Case In order to explore the effect of different preparation methods on the quality of fermented buffalo milk products, this test example evaluated the sensory properties and tested the sample friction coefficient of the room temperature fermented buffalo milk prepared in the above Example 1 and Comparative Examples 1 to 3.

[0037] Sensory evaluation: The sensory properties of the room temperature fermented buffalo milk samples prepared in the above Example 1 and Comparative Examples 1 to 3 were evaluated by a consumer preference test. The test was conducted by 100 randomly hired consumers. After all the subpackaged samples were equilibrated at room temperature for 30 minutes, the sensory evaluation was conducted. In between the sensory evaluations of each sample, "taste bud cleansing water" was provided for the subjects to rinse their mouths to avoid possible cross-influence between samples. 0-10 points indicate that the degree of roughness increases in sequence.

[0038] The sensory evaluation results are shown in Table 1. The fermented buffalo milk prepared by combining the pH adjustment and TG enzyme addition treatments significantly reduced the roughness intensity of the product and improved the smoothness and sensory quality.

[0039] Table 1 Consumers’ evaluation results on the roughness of fermented buffalo milk Group Roughness intensity Example 1 <![CDATA[0.47±0.36 a ]]> Comparative Example 1 <![CDATA[1.75±0.92 b ]]> Comparative Example 2 <![CDATA[2.42±1.21 b ]]> Comparative Example 3 <![CDATA[70.57±2.59 c ]]> Note: Different superscript letters in the same column indicate significant differences ( p ≤ 0.05) Method for testing the friction coefficient of the sample: The friction mechanical properties of the room temperature fermented buffalo milk samples prepared in the above-mentioned Example 1 and Comparative Examples 1 to 3 were tested by a pressure-controlled rheometer equipped with a ring-plate fixture. Cover the plate with 3M Transpore surgical medical transparent tape. Before the test, the sample was pre-balanced for 30 s at 37°C; during the test, an appropriate amount of fermented milk sample was gently spread and covered on the surface of the plate, and the thickness was maintained at about 2 mm; then, at 37°C, a constant normal force was set to 2 N to obtain a friction coefficient within the speed range of 0.15-300 mm / s. After each measurement, the transparent tape was replaced and the friction rheometer plate was cleaned and dried. The test results are shown in Table 2. The fermented buffalo milk prepared by the combination of adjusting the pH value and adding TG enzyme significantly reduced the friction coefficient of the product.

[0040] Table 2 Friction coefficient test results Group Friction coefficient Example 1 <![CDATA[0.12±0.07 a ]]> Comparative Example 1 <![CDATA[0.27±0.02 b ]]> Comparative Example 2 <![CDATA[0.24±0.04 b ]]> Comparative Example 3 <![CDATA[0.52±0.12 c ]]> Note: Different superscript letters in the same column indicate significant differences ( p ≤ 0.05) Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred arrangement scheme, a person skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for stabilizing fermented buffalo milk, characterized in that: The method comprises the following steps: (1) adjusting the pH value of buffalo milk to 7.0-7.5, and then performing UHT sterilization to obtain UHT buffalo milk; (2) UHT buffalo milk is heated to 45°C-50°C in a fermentation tank, white sugar and pectin are mixed and added to the buffalo milk system, and glutamine aminotransferase is added and stirred to make the materials evenly mixed to prepare a buffalo milk-based material, which is heated to 35°C-45°C in a water bath for 30 min-45 min, and then the buffalo milk-based material is homogenized; (3) After homogenization, the substrate is sterilized and then cooled to 42 ± 1°C through the cooling water circulation system in the fermentation tank for inoculation and fermentation. The fermentation is terminated when the pH end point is 4.50 ± 0.

04. After demulsification, the sample is sterilized again to finally obtain stabilized room temperature fermented buffalo milk.

2. The method for stabilizing fermented buffalo milk according to claim 1, characterized in that: In step (1), the pH value of buffalo milk is adjusted to 7.4 using sodium hydroxide solution.

3. The method for stabilizing fermented buffalo milk according to claim 1, characterized in that: In step (2), the amounts of white sugar and pectin added to UHT buffalo milk are 5%-10% and 0.5%-1% respectively by mass percentage.

4. The method for stabilizing fermented buffalo milk according to claim 3, characterized in that: In step (2), the amounts of white sugar and pectin added to the UHT buffalo milk are 6% and 0.6% respectively by mass percentage.

5. The method for stabilizing fermented buffalo milk according to claim 1, characterized in that: In step (2), the amount of glutamine transaminase added is 1-10 U / g buffalo milk protein.

6. The method for stabilizing fermented buffalo milk according to claim 5, characterized in that: In step (2), the amount of glutamine transaminase added is 10 U / g buffalo milk protein.

7. The method for stabilizing fermented buffalo milk according to claim 1, characterized in that: In step (2), the specific process of homogenization includes: the first-stage homogenization pressure is 40 bar, and the second-stage homogenization pressure is 150 bar.

8. The method for stabilizing fermented buffalo milk according to claim 1, characterized in that: In step (3), the specific process of the demulsification treatment includes: stirring and demulsifying at a rotation speed of 500-600 rpm.

9. Stabilized room temperature fermented buffalo milk prepared by the stabilization method according to any one of claims 1 to 8.

10. Use of the stabilization method according to any one of claims 1 to 8 in the preparation of fermented buffalo milk.