Buffalo fresh milk based on ultrasonic homogenization and preparation method thereof

Abstract

The invention relates to the technical field of buffalo milk processing, in particular to buffalo fresh milk based on ultrasonic homogenization and a preparation method of the buffalo fresh milk, buffalo milk is used as a research object, and the optimal process conditions for different homogenization methods to influence the stability of pasteurized buffalo milk are determined. The influence of different ultrasonic power, time and temperature on buffalo milk fat floating rate, stability coefficient, homogeneous index and other indexes is screened out through single-factor experiment analysis, after the optimal single-factor ultrasonic condition is obtained, the single-factor experiment and the orthogonal experiment are combined, and the optimal buffalo milk ultrasonic process condition is screened out. Under the optimization condition, the influence of different homogenization methods on the stability of pasteurized buffalo milk fat is compared and analyzed, and in addition, the feasibility of the ultrasonic homogenization processing condition in the buffalo yogurt processing field is further determined through extended buffalo yogurt processing, so that a theoretical basis is provided for the improvement of a buffalo milk processing technology.

Description

[Technical field]

[0001] The invention relates to the technical field of buffalo milk processing, in particular to buffalo fresh milk based on ultrasonic homogenization and a preparation method thereof. [Background technology]

[0002] Buffalo milk is the second largest milk in the world after cow's milk. It contains more fat, protein, lactose and minerals, so it is more nutritious than cow's milk. In order to retain most of the active nutrients in cow's milk to a certain extent, pasteurization is often used to sterilize cow's milk during milk production and processing. Pasteurization is a traditional sterilization method in the dairy industry. It is becoming more and more popular due to its unique nutritional advantages. Since the fat globule size of ordinary cow's milk is 1-16μm (average 3.78μm), and the fat globule size of buffalo milk is between 2-18μm (average 8.7μm), the larger the fat globule diameter, the more obvious the fat floating rate, and the worse the stability of cow's milk. In addition, pasteurized milk needs to be stored at low temperature. As time goes by, the fat floating becomes more serious, resulting in a decrease in the sensory quality of the product, color changes, and the appearance of bad odor, which is not conducive to the preservation of the product and limits the development of the market. Ultrasonic wave is an emerging non-thermal sterilization technology in food processing. Studies have shown that ultrasound can destroy harmful microorganisms and enzymes in food, delay food spoilage, and effectively extend the shelf life of food. However, using ultrasound alone cannot achieve the ideal sterilization effect.

[0003] Domestic and foreign studies on the stability coefficient of cow's milk have shown that different homogenization methods have a significant effect on the stability of cow's milk. Homogenization is an important part of dairy processing. By changing the diameter of fat globules, the stability and nutritional value of the product can be improved. Currently, ultrasonic homogenization and high-pressure homogenization are mostly focused on ordinary cow's milk, and there are relatively few studies on buffalo milk. This is because different homogenization methods for dairy products with large fat globule diameters such as buffalo milk will have different effects on the stability of milk fat. Therefore, in-depth research on the effects of different homogenization methods on the stability of pasteurized buffalo milk fat and the selection of appropriate homogenization methods are crucial to improving buffalo milk processing technology and improving product quality.

[0004] Pasteurization is a key link in buffalo milk processing. The fat stability after treatment is directly related to the final quality of the product. In order to solve this problem, we need to find an effective sterilization method for buffalo milk, a dairy product with large fat globule diameter. This method can have a good sterilization effect and improve the texture quality of buffalo yogurt, thereby improving the quality of buffalo milk and achieving a good sterilization effect. [Summary of the invention]

[0005] In view of the above, it is necessary to find an effective sterilization method for buffalo milk, a dairy product with a large fat globule diameter. This method can have a good sterilization effect, while also improving the texture quality of buffalo yogurt, thereby improving the quality of buffalo milk and achieving a good sterilization effect.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing buffalo fresh milk based on ultrasonic homogenization, the method comprising the following steps:

[0008] (1) heating buffalo milk in a water bath;

[0009] (2) Ultrasonic homogenization after heating in a water bath;

[0010] (3) Ultrasonic homogenization and pasteurization are performed to obtain fresh buffalo milk.

[0011] Furthermore, the temperature of the ultrasonic homogenization treatment is 55°C-60°C, the time of the ultrasonic homogenization treatment is 10min-12min, and the power of the ultrasonic homogenization treatment is 500W-700W.

[0012] Furthermore, a high pressure treatment is performed before the ultrasonic treatment, wherein the temperature during the high pressure treatment is 60° C. and the pressure is 20 MP to 25 MP.

[0013] Furthermore, the water bath heating temperature is 60°C.

[0014] Furthermore, the ultrasonic frequency is 20 to 25 kHz.

[0015] Furthermore, the average particle size of the buffalo milk fat globules is 2000nm-4000nm.

[0016] The present invention also includes a method for preparing buffalo yogurt using the buffalo fresh milk prepared by the preparation method. The method comprises the following steps: cooling the pasteurized buffalo milk, inoculating, filling, fermenting, cooling and ripening to obtain the buffalo yogurt.

[0017] The present invention has the following beneficial effects:

[0018] This application takes buffalo milk as the research object, and determines the optimal process conditions for the influence of different homogenization methods on the stability of pasteurized buffalo milk for buffalo milk, a dairy product with a large fat globule diameter. Through single-factor experimental analysis, the influence of different ultrasonic powers, time and temperature on indicators such as the flotation rate, stability coefficient and homogeneity index of buffalo milk fat is screened out. After obtaining the optimal single-factor ultrasonic conditions, the single-factor experiment is combined with the orthogonal experiment to screen out the optimal process conditions for buffalo milk ultrasound. Under this optimized condition, the influence of different homogenization methods on the fat stability of pasteurized buffalo milk is compared and analyzed. In addition, the feasibility of ultrasonic homogenization processing conditions in the field of buffalo yogurt processing is further determined through the extended buffalo yogurt processing, providing a theoretical basis for the improvement of buffalo milk processing technology.

Brief Description of the Drawings

[0019] Figure 1-Figure 3 The results of the effects of different ultrasonic powers on the buoyancy rate, stability coefficient, and homogeneity index of buffalo milk fat are shown in the figure. Figure 1 is the fat buoyancy rate, Figure 2 is the stability coefficient, Figure 3 is the homogeneity index.

[0020] Figure 4-Figure 6 The results of the effects of different ultrasonic times on the flotation rate, stability coefficient, and homogeneity index of buffalo milk fat are shown in the figure. Figure 4 is the fat buoyancy rate, Figure 5 is the stability coefficient, Figure 6 is the homogeneity index.

[0021] Figure 7-Figure 9 This is the result diagram of the effect of different preheating temperatures on the flotation rate, stability coefficient and homogeneity index of buffalo milk fat; Figure 7 is the fat buoyancy rate, Figure 8 is the stability coefficient, Fig. 9 is the homogeneity index.

[0022] Figure 10-11 The results of the effects of different ultrasonic powers on the buoyancy rate and homogenization index of high-pressure homogenized buffalo milk; Fig.10 is the fat buoyancy rate, Fig.12 is the homogeneity index.

[0023] Fig.12 The effect of different ultrasonic time on the flotation rate of high-pressure homogenized buffalo milk fat.

[0024] Fig.13 The figure shows the effect of different ultrasonic time on the homogenization index after homogenization.

[0025] Fig.14The fluorescence scanning electron microscope was used to observe the morphological changes of milk fat globules of pasteurized buffalo milk under different homogenization treatment conditions after staining. In the figure, W is pasteurized milk without any homogenization treatment on the 1st, 3rd and 7th days, J is pasteurized milk with high pressure homogenization on the 1st, 3rd and 7th days, JC is pasteurized milk with high pressure homogenization and ultrasound on the 1st, 3rd and 7th days, and C is pasteurized milk with ultrasound on the 1st, 3rd and 7th days.

[0026] Figure 15-17 This is a diagram of the curd state of buffalo yogurt, where: Fig.15 The three types of fermented milk that were not treated by ultrasound and homogenization began to coagulate. Fig.16 The end-point status of fermented milk by three homogenization methods: ultrasound, homogenization, and untreated. Fig.17 The state of the fermented milk treated with ultrasound at the end of fermentation. In the figure, W is the control group without any homogenization treatment, JS is the high-pressure homogenization treatment group, and CS is the ultrasound treatment group.

[0027] Fig.18 Figure 1 is the effect of ultrasonic treatment on the quality of buffalo yogurt, where Figure 1 is the ultrasonic treatment group, Figures 2 and 3 are the high-pressure homogenization treatment groups, and Figure 4 is the untreated group.

[0028] Figure 19-20 This is the result of the effect of different fermentation time and different treatments on the acidity of buffalo yogurt; Fig.19 To titrate the acidity; Fig. 20 is the pH value.

[0029] Figure 21-23 The results of the different treatments on the texture of buffalo yogurt are shown in Figure 1. Fig.21 Ultrasonic homogenization treatment Fig. 22 For high pressure homogenization, Fig.23 Not homogenized.

[0030] Fig.24 The effect of different ultrasonic homogenization powers on buffalo yogurt fat. From left to right: normal treatment (without ultrasound and homogenization), 200w, 400w, 600w, 800w.

[0031] Fig.25 The effect of different preheating temperatures on buffalo yogurt fat: Figure ① shows ultrasonic treatment and non-ultrasonic treatment (normal) at 62°C, where the left picture of Figure ① is normal treatment and the right picture is ultrasonic treatment; Figure ② shows ultrasonic treatment and non-ultrasonic treatment (normal) at 65°C, where the left picture of Figure ① is normal treatment and the right picture is ultrasonic treatment. Figures ③ and ④ show ultrasonic treatment at different temperatures, Figure ③ is 60°C and 55°C, and Figure ④ is 65°C and 62°C.

[0032] Fig.26It is buffalo milk casein separated by ultra-high-speed centrifugation; the yellow one is the control group without ultrasonic treatment, and the white one is the experimental group after ultrasonic treatment. [Specific implementation method]

[0033] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0034] Any feature disclosed in this specification (including any appended claims and abstract), unless otherwise stated, is merely an example of a series of equivalent or similar features.

[0035] Example 1

[0036] This example studies the effect of ultrasound on the homogenization of buffalo milk, and the specific method is as follows:

[0037] 1. Effect of different ultrasonic powers on homogenization of buffalo milk: The processing volume of buffalo milk was 400 mL / time, the temperature of the electromagnetic cooker water bath was 60°C, the ultrasonic duration was 10 min, and the ultrasonic powers were 400 W, 500 W, 600 W, and 700 W. The homogenization effect of different ultrasonic powers on buffalo milk was evaluated by measuring the fat floating rate, stability coefficient, and homogenization index. The results are shown in Table 1 and Figure 1-Figure 3 .

[0038] Table 1 Effect of different ultrasonic powers on fat homogenization

[0039]

[0040] Note: Different lowercase letters in the table indicate significant differences among different treatments (P<0.05). (The same below)

[0041] From Table 1 and Figure 1 According to the data analysis, with the increase of ultrasonic power, the value of fat buoyancy rate of buffalo milk samples gradually decreased, and the value of fat buoyancy rate was the smallest when the ultrasonic power was 700W, which was better than other groups.

[0042] From Table 1 and Figure 2 Analysis shows that with the increase of ultrasonic power, the stability coefficient first decreases and then increases, but it is always close to 1. When the ultrasonic power is 600W, the stability coefficient is the lowest, which is better than other groups.

[0043] From Table 1 and Figure 3 The analysis shows that with the increase of power, the homogeneity index value of the sample first decreases and then increases, but the overall trend is downward. When the ultrasonic power is 600W, its homogeneity index result is the lowest compared with other groups, which is better than other groups.

[0044] Comprehensive Table 1 and Figure 1-Figure 3 The measured fat floating rate, stability coefficient and homogeneity index were used to analyze the effect of different ultrasonic powers on the homogenization effect of buffalo milk. It can be seen that with the increase of ultrasonic power, the fat floating rate gradually decreases, 500W is significantly smaller than 400W, but there is no significant difference between 600W and 700W. The effect on the stability coefficient is not significant. The homogeneity index value first decreases and then increases, and the overall trend is downward. The value is the smallest at 600W, and there is no significant difference between 500W and 700W. In the orthogonal experiment, 600W is selected as the intermediate factor.

[0045] 2. Effect of different ultrasonic time on homogenization of buffalo milk: Preheating temperature was 60℃, power was 600W, and ultrasonic time was 6min, 8min, 10min, and 12min. The effect of different ultrasonic time on homogenization of buffalo milk was evaluated by measuring fat floating rate, stability coefficient, and homogenization index. The results are shown in Table 2 and Figure 4 , Figure 5 , Figure 6 .

[0046] Table 2 Effect of different ultrasound time on fat homogenization effect

[0047]

[0048] From Table 2 and Figure 4 The analysis shows that when the ultrasonic treatment time increases from 6min to 10min, the value of the fat floating rate of the buffalo milk sample decreases, and the value of the fat floating rate begins to increase at 12min. When the ultrasonic treatment time is 10min, the fat floating rate data is the lowest, which is better than other groups.

[0049] From Table 2 and Figure 5 The analysis shows that the stability value of buffalo milk begins to rise as the ultrasound time increases from 6 minutes to 8 minutes, then decreases when the time increases to 10 minutes, and then increases again when it increases to 12 minutes. The stability coefficient is the lowest when the ultrasound time is 10 minutes, which is better than other groups.

[0050] From Table 2 and Figure 6 The analysis shows that with the increase of ultrasound time, the homogeneity index value gradually decreases. When the time is 12 minutes, the homogeneity index result is better than that of other groups, indicating that the stability of buffalo milk is good under this treatment time.

[0051] Comprehensive Table 2 and Figure 4 , Figure 5 , Figure 6The measured fat floating rate, stability coefficient and homogeneity index were used to analyze the effect of different ultrasonic times on the homogenization effect of buffalo milk. It was found that with the extension of ultrasonic time, fat floating first decreased and then increased. When the ultrasonic time was 10 minutes, the fat floating rate was significantly the lowest. After 8 minutes, there was no significant difference in the stability coefficient. With the increase of ultrasonic time, the homogeneity index first decreased. At 12 minutes, the mean index was the lowest. Based on the results of the three indicators, the ultrasonic time was determined to be 10 minutes.

[0052] Effect of different ultrasonic temperatures on the homogenization of buffalo milk: The ultrasonic power was 600W, the time was 10min, and the ultrasonic preheating temperatures were 50℃, 55℃, 60℃, and 65℃ respectively. The effect of different ultrasonic powers on the homogenization of buffalo milk was evaluated by fat floating rate, stability coefficient, and homogenization index. The results are shown in Table 3 and Figure 7 , Figure 8 , Fig. 9 .

[0053] Table 3 Effect of different ultrasonic temperatures on fat homogenization

[0054]

[0055] According to Table 3 and Figure 7 The analysis results showed that as the temperature increased from 50°C to 55°C, the fat floating rate began to decrease, and when it increased to 60°C, the fat floating rate began to increase, and at 65°C, the fat floating rate reached the highest value. When the ultrasound temperature was 55°C, the fat floating rate was the lowest, which was better than other groups.

[0056] According to Table 3 and Figure 8 From the data analysis, it can be seen that as the ultrasonic temperature increases from 50℃ to 55℃, the stability coefficient of buffalo milk decreases, and then when it increases to 60℃, the stability coefficient increases again, and at 65℃ the stability coefficient decreases again. At this time, the value of the stability coefficient is the lowest, which is better than other groups.

[0057] By comparing Table 3 and Fig. 9 From the analysis, it can be seen that when the temperature rises from 50℃ to 60℃, the homogeneity index shows a downward trend, and the difference between the homogeneity index values ​​is not large, indicating that the influence on the homogeneity index is not large within this temperature change range. However, when the temperature rises from 60℃ to 65℃, the homogeneity index value begins to rise, and the difference between the two values ​​increases significantly, indicating that the homogeneity index is greatly affected by temperature at this temperature. The homogeneity index value at 55℃ is the lowest, which is better than other groups.

[0058] The effect of different ultrasonic temperatures on the homogenization index of buffalo milk was studied. Figure 7 , Figure 8 , Fig. 9In summary, as the ultrasonic temperature increases, the fat floating rate and homogeneity index decrease first and then increase. At 55°C, the fat floating rate is the lowest, and at 65°C, the fat floating rate and homogeneity index increase significantly. The ultrasonic temperature has no significant effect on the stability coefficient. When the ultrasonic temperature is 55°C and 60°C, there is no significant difference in the homogeneity index, so 55°C is the best condition.

[0059] 4. Orthogonal test results:

[0060] The orthogonal test results and intuitive analysis of the optimization of buffalo milk ultrasonic homogenization process conditions are shown in Table 4.

[0061] Table 4 Orthogonal test results analysis table

[0062]

[0063] As shown in Table 4, in the effect of ultrasonic treatment on the floating rate of buffalo milk fat, ultrasonic temperature is the most important factor, followed by ultrasonic time, and ultrasonic power has the least effect. Through the range analysis, the best ultrasonic homogenization conditions are A1B3C3, that is, the ultrasonic temperature is 55℃, the ultrasonic time is 12min, and the ultrasonic power is 700W.

[0064] According to the analysis in Table 4, the main factor affecting the stability coefficient of buffalo milk under ultrasonic treatment conditions is ultrasonic power, followed by ultrasonic time, while ultrasonic temperature has the least effect. Through the range analysis, it is concluded that the best ultrasonic homogenization conditions are A1B2C3, that is, ultrasonic temperature is 55℃, ultrasonic time is 12min, and ultrasonic power is 700W.

[0065] Ultrasonic temperature has the greatest impact on the homogenization index of buffalo milk, followed by ultrasonic time, and ultrasonic power has the least impact. The best ultrasonic homogenization index A1B3C3 was obtained through range analysis, that is, ultrasonic temperature is 55℃, ultrasonic time is 12min, and ultrasonic power is 700W.

[0066] The data of fat floating rate, stability coefficient, homogeneity index and total colony count were analyzed by variance analysis. It was found that there was no significant difference in fat floating rate and stability coefficient. In the homogeneity index, there was no significant difference between 60℃ and 55℃. In the total colony count, the average total colony count of samples at 60℃ was 1.63×10 4 CFU / g(mL), the average total number of colonies at 55℃ was 2.3×10 4 CFU / g(mL), so the sterilization effect of 60℃ is better than that of 55℃. In the analysis of power and time, no significant difference was found, so 500W, 10min was selected. The temperature was combined with the total colony count results and the homogenization temperature of 60℃ in the actual production of the enterprise, and 60℃ was selected. Finally, combined with the single factor experiment, the best orthogonal conditions were obtained: preheating 60℃, 500W, 10min.

[0067] 5. Effect of high pressure homogenization and ultrasound on the homogenization of buffalo milk:

[0068] ① The effect of different ultrasonic powers on the homogenization effect of high-pressure homogenized buffalo milk: After the buffalo milk was homogenized using a high-pressure homogenizer, it was ultrasonically treated. The fat floating rate and homogenization index were used as measurement indicators to judge the effect of different ultrasonic powers on the homogenization of buffalo milk fat. The results are shown in Table 5.

[0069] Table 5 Effect of different ultrasonic powers on the homogenization effect of high-pressure homogenized buffalo milk

[0070]

[0071] Comprehensive Table 5 Fig.10 as well as Figure 3 The data analysis showed that the high-pressure homogenization combined with ultrasound treatment group showed a better effect on fat floating rate than the single ultrasound treatment group. In the same group comparison, the fat floating rate of the sample with 0 (high-pressure homogenization) was the highest, but with the increase of ultrasound power, the fat floating rate of each group of samples showed an overall downward trend. When the ultrasound power was 600W, the fat floating rate of the sample treated with high-pressure homogenization combined with ultrasound reached the lowest value, indicating that its effect was better than that of the sample treated with only high-pressure homogenization.

[0072] From Table 5 and Fig.11 From the analysis of Table 1 and Figure 1, it can be seen that the homogenization index of buffalo milk samples treated with ultrasound at high pressure is significantly lower than that of samples treated with ultrasound alone. As the power increases, the homogenization index shows a downward trend. When the ultrasound power is 600W, the homogenization index of the high pressure homogenized sample is better than that of other groups.

[0073] Comprehensive Table 5 and Fig.10 , Fig.11 Comprehensive analysis shows that with the increase of power, the fat floating rate and homogeneity index decrease significantly. Combined with the results of orthogonal experiments, the optimal ultrasonic power is 500W.

[0074] 6. Effect of different ultrasonic time on the homogenization effect of high-pressure homogenized buffalo milk

[0075] The buffalo milk was first subjected to high pressure homogenization and then to ultrasound. The fat floating rate and homogenization index were used as indicators to evaluate the effect of different ultrasound times on the homogenization of buffalo milk fat. The results are shown in Table 6.

[0076] Table 6 Effect of different ultrasonic time on the homogenization effect of high pressure homogenized buffalo milk

[0077]

[0078] From Table 6 and Fig.13 and Table 2 and Figure 4Comprehensive analysis shows that the high-pressure homogenization combined with ultrasound treatment group showed better fat floating rate than the single ultrasound treatment group. In the same group comparison, the fat floating rate of the buffalo milk sample 0 (homogenized) had the weakest homogenization effect compared with other groups. As the ultrasound time increased, the fat floating rate gradually decreased. The treatment group with the best fat floating rate was 10 minutes.

[0079] From Table 6 and Fig.13 The analysis shows that the homogeneity index of buffalo milk samples at 0 (high pressure homogenization) is the highest among the four groups. As the ultrasonic time increases, the homogeneity index shows a downward trend. When the ultrasonic time is 12 minutes, the homogeneity index value of buffalo milk is better than that of other groups.

[0080] Comprehensive Table 6 and Fig.12 , Fig.13 Analysis shows that as time goes by, the fat floating rate and homogeneity index decrease significantly, so 10 minutes is the best condition.

[0081] 7. Effects of different homogenization methods on the homogenization effect of pasteurized buffalo milk

[0082] ① Effect of storage time on the homogenization effect of pasteurized buffalo milk under different homogenization treatment conditions: Four conditions were used: ultrasound (500W, 10min, 60℃), high-pressure homogenization (preheating 60℃, pressure 20-25MP), high-pressure homogenization followed by ultrasound, and ultrasound followed by high-pressure homogenization. The effects of different treatment methods on the homogenization of buffalo milk fat were evaluated by fat floating rate and homogenization index. The results are shown in Tables 7 and 8. The titratable acidity of buffalo milk samples was measured to determine the effect of storage time on titratable acidity under different homogenization conditions, as shown in Table 9, where J is high-pressure homogenized pasteurized milk, JC is high-pressure homogenization + ultrasound pasteurized milk, and C is ultrasound pasteurized milk.

[0083] Table 7 Effect of storage time on the fat floating rate of pasteurized buffalo milk under different homogenization methods Unit: %

[0084]

[0085] Note: Different lowercase letters in the table indicate significant differences between groups, and different uppercase letters indicate significant differences within groups (P<0.05) (the same below).

[0086] From the analysis in Table 7, it can be seen that on the 0th day, the fat floating rate of high-pressure homogenization and ultrasound (JC) is better than that of ultrasound pasteurized milk (C) and high-pressure homogenization pasteurized milk (J). The smaller the fat floating rate, the more complete the crushing of large fat globules and the better the homogenization effect. With the increase of storage time, the fat floating rate first increased and then decreased, and then decreased again. Until the 11th day, the fat floating rate of the three groups of samples increased, but the value of high-pressure homogenization + ultrasound pasteurized milk (JC) was better than the other two groups.

[0087] Table 8 Effect of different homogenization methods on the homogenization index of pasteurized buffalo milk stored for 48 h

[0088]

[0089] From the analysis in Table 8, it can be seen that the homogenization index of the samples in the three groups was below 10 after 48 hours of low temperature storage, indicating that the homogenization effect of milk was good. The homogenization index of pasteurized milk (J) with high pressure homogenization was the highest, followed by ultrasound (C), and finally high pressure homogenization + ultrasound (JC). The higher the homogenization index, the larger the fat globule particles, which are easy to cause aggregation and floating. The lower the homogenization index, the smaller the fat globule particles, and the better the homogenization effect. Therefore, the homogenization effect of high pressure homogenization combined with ultrasound (JC) is better than that of the other two groups.

[0090] ② Effect of storage time on titer acidity of pasteurized buffalo milk under different homogenization conditions

[0091] Table 9 Effect of storage time on titer acidity of pasteurized buffalo milk under different homogenization methods Unit: °T

[0092]

[0093] According to the observation and analysis in Table 9, on the 0th day, the titrated acidity of the three groups of samples was within the normal range of the national standard, and no deterioration occurred. As the storage time increased, the titrated acidity began to rise. On the 5th day, the titrated acidity of the three groups of samples increased significantly. The titrated acidity results were ranked as ultrasonic pasteurized milk (C), followed by homogenized pasteurized milk (J), and finally high-pressure homogenization + ultrasonic pasteurized milk (JC), but the titrated acidity was still within the qualified range. According to GB 4789.2-2022 National Food Safety Standard Food Microbiology Test Colony Count Determination of the total number of colonies in pasteurized buffalo milk samples, on the 7th day, the total number of colonies in each group of samples exceeded 50,000, which did not meet the standard. When the titrated acidity was in the range of 10-18°T, no flocs were produced when the ninth-day sample was boiled, while flocs appeared in the 11th-day sample, indicating that the sample had completely deteriorated.

[0094] ③ Effect of storage time under different homogenization conditions on the microstructure of pasteurized buffalo milk fat

[0095] The morphological changes of milk fat globules in pasteurized buffalo milk with different homogenization conditions after dyeing were observed by fluorescence scanning electron microscopy. Fig.14 As shown in the figure, W is pasteurized milk without any homogenization treatment on the 1st day, the 3rd day and the 7th day, J is high-pressure homogenized pasteurized milk on the 1st day, the 3rd day and the 7th day, JC is high-pressure homogenized ultrasonic pasteurized milk on the 1st day, the 3rd day and the 7th day, and C is ultrasonic pasteurized milk on the 1st day, the 3rd day and the 7th day.

[0096] As can be seen from the figure, with the extension of storage time, on the first day, both W and I had large fat globules, and the fat crushing effect of JC and C groups was obvious, the fat globules were evenly dispersed, and no agglomeration occurred. There was no significant difference in the size of the fat globules between the two groups. On the third day, fat globules began to appear in W, J, and C groups, indicating that small fat globules began to agglomerate and the homogenization effect began to decline. On the seventh day, the fat globules in W group were the most seriously aggregated, and fat globules appeared in J and C, while no fat globules agglomerated in JC group.

[0097] In summary, the coagulation phenomenon occurred in group JC, and the fat globule coagulation phenomenon was the weakest, indicating that the homogenization effect was better than that of other groups. Then, the homogenization effects of group C, group J, and group W were the least ideal.

[0098] Based on the above experimental results, this experiment studied the effects of ultrasonic power, time and temperature on the homogenization effect of buffalo milk at an ultrasonic frequency of 20-25kHz. Through single-factor experimental analysis, the results showed that when the ultrasonic power was 600W, the ultrasonic time was 10min and the ultrasonic temperature was 55℃, there was no significant difference in the fat floating rate, stability coefficient and homogenization index of buffalo milk (P>0.05), which was considered to be the best single-factor condition. Further combined with single-factor experiment and orthogonal test optimization, the optimal process conditions for ultrasonic homogenization of bovine milk were determined to be ultrasonic power 500W, ultrasonic time 10min and preheating temperature 60℃. Under this optimized condition, high-pressure homogenization composite ultrasonic pasteurized milk was prepared. The conditions for high-pressure homogenization were: preheating 60℃, pressure 20-25MP; through comparative experiments, it was found that high-pressure homogenization composite ultrasound performed better in fat stability and could significantly reduce fat floating. During storage, the titrated acidity began to increase significantly on the 7th day, indicating that the sample began to become rancid. Comprehensive analysis showed that high-pressure homogenization combined with ultrasound technology is an ideal method for milk homogenization, which helps pasteurized buffalo milk maintain fat stability during low-temperature storage, and this homogenization technology can be given priority in actual production.

[0099] Example 2

[0100] This embodiment is a preparation scheme of buffalo yogurt:

[0101] The preparation method of the yogurt of group W is as follows: the pasteurized buffalo milk is cooled, inoculated, filled, fermented, cooled and ripened to obtain buffalo yogurt (without high pressure and ultrasonic homogenization treatment).

[0102] The preparation method of CS group yogurt is: ultrasonic homogenization of buffalo milk, pasteurization of buffalo milk, inoculation after cooling, filling, fermentation, cooling and ripening to obtain buffalo yogurt (without high pressure treatment). The ultrasonic conditions are: preheating at 60℃, 500w, and time for 10min.

[0103] The preparation method of JS group yogurt is as follows: preheating buffalo milk, high pressure homogenization, cooling the pasteurized buffalo milk, inoculating, filling, fermenting, cooling and ripening to obtain buffalo yogurt. The high pressure conditions are: preheating at 60℃, pressure 20-25MP,

[0104] The coagulation state, texture and acidity changes of the coagulated yogurt made from homogenized and unhomogenized buffalo milk in the above experimental groups were investigated. The fermentation pH was determined to be 4.6 as the end point.

[0105] 1. Observe the curd state:

[0106] By observing the fermentation and curdling process, Figure 15-18 As shown: Among them, Figure 15-17 This is a diagram of the curd state of buffalo yogurt, where: Fig.15 The three types of fermented milk that were not treated by ultrasound and homogenization began to coagulate. Fig.16 The end-point status of fermented milk by three homogenization methods: ultrasound, homogenization, and untreated. Fig.17 The fermented milk treated with ultrasound is in the state at the end of fermentation, W is the control group without any homogenization treatment, JS is the high-pressure homogenization and ultrasound treatment group, and CS is the ultrasound treatment group. Fig.18 The effect of ultrasonic treatment on the quality of buffalo yogurt, where Figure 1 is the ultrasonic treatment group, Figures 2 and 3 are the high-pressure homogenization treatment groups, and Figure 4 is the untreated group. As can be seen from the figure, the unhomogenized yogurt (W group) has a thick layer of fat on it, and after fermentation, the product has serious whey precipitation, and the curd is relatively loose. The high-pressure homogenized yogurt (JS group) also has a small amount of fat on the upper layer, and a small amount of whey precipitation. Vibration will cause more whey precipitation and the structure is also destroyed. The yogurt made under ultrasonic conditions (CS group) has a relatively intact structure and no whey precipitation. Slight vibration has little effect on curd.

[0107] 2. The changes in acidity during yogurt fermentation are shown in Table 10 and Figure 19-20 As shown:

[0108] Table 10 Changes in acidity during fermentation under different homogenization conditions

[0109]

[0110]

[0111] As shown in Table 10, the fermentation endpoint is determined by pH 4.6 or so, the fermentation time is 7h, the ultrasonic homogenization condition is reached first, and the yogurt coagulation state is the best. However, for the yogurt homogenized by high pressure, a small amount of whey has been precipitated at this time, and the whey has been seriously precipitated in the unhomogenized yogurt, affecting the properties and appearance of the product. In the late fermentation period, the pH change rate under the two homogenization conditions is almost overlapping, and there is no obvious change, which is better than the unhomogenized condition.

[0112] like Figure 19-20 As shown: By titrating the acidity, it can be seen that in the early stage of fermentation, the average acidity change rate under ultrasonic homogenization conditions is 14.23°T / h, 10.9°T / h under high pressure homogenization, and 15.39°T / h under ordinary conditions. In the middle stage of fermentation, the average acidity change rate under ultrasonic conditions is 25.85°T / h, 24.77°T / h under high pressure homogenization, and 19.87°T / h under ordinary conditions. In the late stage of fermentation, the average acidity change rate under ultrasonic conditions is 6.46°T / h, 9.78°T / h under high pressure homogenization, and 8.36°T / h under ordinary conditions. Although the fermentation speed is fastest under ultrasonic homogenization conditions, its product stability is the best.

[0113] 3. Effects of different treatment conditions on yogurt texture:

[0114] The specific results are shown in Table 11 and Figure 21-26 As shown:

[0115] Table 11 Effect of different homogenization conditions on yogurt texture

[0116]

[0117] It can be seen from the above table that the hardness, viscosity and chewiness of yogurt under ultrasonic homogenization conditions are significantly the greatest. Although the elasticity does not change significantly, the elasticity under ultrasonic homogenization conditions is also the greatest. The cohesion of unhomogenized yogurt is significantly higher than that of the two homogenization conditions.

[0118] Figure 21-23 The texture images of yogurt homogenized by ultrasound, homogenized by high pressure, and homogenized by yogurt without high pressure and ultrasound are shown in Table 11. The hardness, viscosity, and chewiness of yogurt under ultrasound homogenization are significantly greater. Although the elasticity does not change significantly, the elasticity under ultrasound homogenization is also the greatest. The cohesion of yogurt without homogenization is significantly higher than that of the two homogenization conditions. Therefore, ultrasound treatment can improve the texture and taste of yogurt and is a better homogenization and emulsification method.

[0119] Depend on Fig.24It can be seen that the pasteurized milk that has not been ultrasonically homogenized has a thick layer of fat on top, while the pasteurized milk that has been ultrasonically homogenized has less fat on the top.

[0120] Depend on Fig.25 It can be seen that Fig.25 Figure ① shows ultrasonic treatment and non-ultrasonic treatment (normal) at 62°C, where the left picture of Figure ① shows normal treatment and the right picture shows ultrasonic treatment; Figure ② shows ultrasonic treatment and non-ultrasonic treatment (normal) at 65°C, where the left picture of Figure ① shows normal treatment and the right picture shows ultrasonic treatment. It can be seen from the two figures that the pasteurized milk that has not been ultrasonically homogenized has a thick layer of fat on top under the same temperature conditions, while the pasteurized milk that has been ultrasonically homogenized has less fat on the top.

[0121] Fig.25 Figures ③ and ④ show pasteurized milk treated with ultrasound at different temperatures, Figure ③ at 60°C and 55°C, and Figure ④ at 65°C and 62°C.

[0122] Depend on Fig.26 It can be seen that from the casein obtained after ultra-high-speed centrifugation of buffalo milk, after ultrasonic homogenization, the fat and protein are tightly combined. When casein and whey are separated by ultra-high-speed centrifugation, there is a layer of fat on the surface of the casein. However, when casein is separated by ultra-high-speed centrifugation from buffalo milk without ultrasonic homogenization, the casein is relatively pure and has no fat on the surface. This shows that ultrasonic treatment makes the casein and fat globules in the milk more evenly distributed, avoids the agglomeration of fat globules, promotes the adsorption of casein on the surface of fat globules, increases the stability of the milk emulsion, prevents the separation of fat, thereby reducing the fat floating rate during the storage period of pasteurized milk and improving the stability of the product.

[0123] In summary, this application uses buffalo milk as the research object to determine the optimal process conditions for the effects of different homogenization methods on the stability of pasteurized buffalo milk. Through single-factor experimental analysis, the effects of different ultrasonic powers, time and temperature on indicators such as the flotation rate, stability coefficient and homogeneity index of buffalo milk were screened out, and the optimal ultrasonic process conditions for buffalo milk were optimized. In addition, the feasibility of ultrasonic homogenization processing conditions in the field of buffalo yogurt processing was further determined through extended buffalo yogurt processing, providing a theoretical basis for the improvement of buffalo milk processing technology.

[0124] The above-described embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications 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 present invention shall be subject to the attached claims.

Claims

1. A method for preparing buffalo fresh milk based on ultrasonic homogenization, characterized in that: The method comprises the following steps: (1) heating buffalo milk in a water bath; (2) Ultrasonic homogenization after heating in a water bath; (3) Ultrasonic homogenization and pasteurization are performed to obtain fresh buffalo milk.

2. The preparation method according to claim 1, characterized in that: The temperature of the ultrasonic homogenization treatment is 55° C.-60° C., the time of the ultrasonic homogenization treatment is 10 min-12 min, and the power of the ultrasonic homogenization treatment is 500W-700W.

3. The preparation method according to claim 1, characterized in that: The high pressure treatment is also performed before the ultrasonic treatment, the temperature during the high pressure treatment is 60° C., and the pressure is 20 MP to 25 MP.

4. The preparation method according to claim 1, characterized in that: The water bath heating temperature is 60°C.

5. The preparation method according to claim 1, characterized in that: The ultrasonic frequency is 20-25 kHz.

6. The preparation method according to claim 1, characterized in that: The average particle size of the fat globules of the buffalo milk is 2000nm-4000nm.

7. A method for preparing buffalo yogurt using buffalo fresh milk prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: cooling the pasteurized buffalo milk, inoculating, filling, fermenting, cooling and ripening to obtain buffalo yogurt.

Images