TWI498555B - Detection of Protein Thermal Stability in Dairy Products - Google Patents

Description

Method for detecting protein thermal stability in dairy products

The invention relates to the technical field of dairy product processing, in particular to a method for detecting the thermal stability of proteins in dairy products.

Milk tea is a kind of beverage that mixes tea and milk. It has the aroma of milk tea in China, India, Britain, Singapore, Malaysia, Taiwan, Hong Kong, Macao, etc. The way of making this beverage is different because of local characteristics, such as Indian milk tea is famous for its special spices added to Marsala; Hong Kong milk tea is famous for its stockings and milk tea; Taiwan's pearl milk tea is also unique. Milk tea has the dual nutrition of milk and tea. In addition to rich nutrients such as protein and fat, it also contains caffeine, tannic acid, theophylline, aromatic oil, chlorophyll, amino acids, sugars, various minerals and multivitamins. More than 300 kinds of chemical ingredients beneficial to the human body such as Vc, Vp, niacin, folic acid, etc., have the effects of removing greasy, helping digestion, refreshing, diuretic, detoxifying and eliminating fatigue. With the improvement of people's material living standards, milk tea has become more and more popular among consumers, and the market capacity has expanded year by year.

The preparation process of milk tea is generally prepared by ultra-high temperature transient sterilization (UHT) using raw materials such as fresh milk or dairy products. However, due to the regional nature of dairy cows and other dairy farms, the production of fresh milk is limited by geography. Because of the short shelf life of fresh milk products, it is necessary to carry out the corresponding process as soon as possible to complete the production of the products. Therefore, the non-fresh milk producing areas Dairy processing enterprises generally use dairy products such as whole milk powder, skim milk powder, condensed milk or milk concentrate protein as raw materials for processing milk tea, and these dairy products have their own taste characteristics and are loved by different consumers.

When the dairy product is used as a raw material for UHT treatment during processing, the protein is apt to form a precipitate, and gradually accumulates on the heated surface of the sterilization device to form scale. The pressure in the sterilization equipment system increases with the degree of fouling on the heated surface. Large, when the pressure in the system rises to a certain extent, it will affect the heat transfer during the sterilization process, thus affecting the sterilization effect of the product. At this time, the intermediate cleaning (AIC) of the sterilization equipment is required. When the dairy product with poor thermal stability of the protein is used as a raw material, the sterilization equipment generally only needs to perform AIC for 1.5 to 3 hours, and the sterilization equipment with excellent protein thermal stability as the raw material can be operated for at least 6 hours continuously. Therefore, the dairy product is The thermal stability of the protein directly affects the continuous running time and sterilization of the sterilization equipment. In actual production, the thermal stability of proteins in different brands or batches of dairy products may vary. Therefore, how to quickly screen out dairy products with excellent thermal stability of protein in different brands or different batches of dairy products, reduce the number of AICs, and reduce the corresponding production costs, thus becoming an urgent demand for dairy processing enterprises. . However, there is no special regulation on the thermal stability of proteins in the current national standards for dairy products, and there is no publicly available method for rapidly detecting the thermal stability of proteins in dairy products. Therefore, it provides a rapid detection of protein thermal stability in dairy products. The method has important practical significance.

In view of this, the present invention provides a method for detecting the thermal stability of proteins in dairy products. The detection method can quickly and accurately detect the thermal stability of proteins in dairy products.

In order to achieve the above object, the present invention provides the following technical solutions:

The invention provides a method for detecting the thermal stability of proteins in a dairy product, comprising the following steps: Step A: mixing the dairy product with water to obtain a first sample solution; Step B: the first sample solution is at 100 ° C to 135 The second sample solution is obtained by treating at a temperature of ° C for 10 min to 40 min; the second sample solution is detected to obtain a protein thermal stability of the second sample solution; the second sample solution has no delamination, no precipitation, no agglomeration, and The thermal stability of the protein is excellent; the second sample solution appears slightly wall-hanging, and the small granular coagulation visible to the naked eye is suspended therein, and the protein is thermally stable; the second sample solution appears to be more severely walled and flocculation occurs. The thermal stability of the protein is poor; the second sample solution is severely wall-hanging, and the tofu-like agglomeration appears, and the protein has poor thermal stability.

Preferably, the dairy product is selected from the group consisting of whole milk powder, skimmed milk powder, condensed milk or milk concentrated protein.

In some embodiments provided by the present invention, the step of detecting the protein content of the dairy product is also included prior to step A.

Preferably, the percentage of protein in the first sample solution is from 4% to 7% by mass.

Preferably, a step of hydrating is further included between step A and step B.

Preferably, the hydration is stirred at 300 rpm to 700 rpm.

Preferably, the hydration time is from 8 min to 20 min.

The invention also provides a preparation method of the milk-containing beverage, comprising the following steps: using the detection method provided by the invention to detect the dairy product, obtaining a dairy product with excellent protein thermal stability; taking the dairy product with excellent protein thermal stability, After the ingredients, sterilization, that is.

Preferably, the dairy product is selected from the group consisting of whole milk powder, skimmed milk powder, condensed milk or milk concentrated protein.

In some embodiments provided by the present invention, the milk-containing beverage is reconstituted milk, milk tea or milk-containing coffee.

Preferably, the sterilization temperature is 137 ° C to 140 ° C.

Preferably, the sterilization time is 4 s to 30 s.

The present invention provides a method for detecting the thermal stability of proteins in dairy products. The detecting method comprises: mixing the dairy product with water to obtain a first sample solution; the first sample solution is treated at 100 ° C to 135 ° C for 10 min to 40 min to obtain a second sample solution; and the second sample solution is performed Detecting, obtaining the thermal stability of the protein of the second sample solution; the second sample solution has no delamination, no precipitation, no agglomeration, and the protein has excellent thermal stability; the second sample solution is slightly wall-hanging, and there are small particles visible to the naked eye. When the condensate is suspended, the protein is thermally stable; the second sample solution is more severely walled and flocculation occurs, and the protein is less thermally stable; the second sample solution is severely wall-hanging, and the tofu flower-like knot appears. Block, its protein has poor thermal stability. The dairy product standard for detecting the thermal stability of the known protein is detected by the detection method provided by the present invention, and the results show that the detection result is consistent with the actual situation; the dairy products of different proteins thermally stable detected by the present invention are put into production practice, and the result is It is shown that the thermal stability of the protein detected by the detection method provided by the invention has a correlation with the continuous operation time of the ultra-high temperature sterilization equipment, and the continuous operation time of the ultra-high temperature sterilization equipment when the production is performed by using the dairy product with excellent thermal stability of the protein. Long; when using dairy products with poor thermal stability of protein, the ultra-high temperature sterilization equipment can run continuously for a short time; the detection method only needs to use ordinary experimental type sterilization pot to treat the dairy product samples in a constant temperature, within 1~2 hours. The thermal stability of the protein in the dairy product is measured. It can be seen that the detection method provided by the invention can quickly and accurately detect the thermal stability of the protein in the dairy product, thereby eliminating the dairy product with poor thermal stability of the protein, and using the dairy product with excellent thermal stability of the protein to produce the finished product, ensuring super High-temperature sterilization equipment can be continuously produced for more than 6 hours, thereby increasing production line capacity, reducing the number of AICs, controlling production costs, and increasing business efficiency.

The invention discloses a method for detecting the thermal stability of proteins in dairy products, and those skilled in the art can learn from the contents of the paper and appropriately improve the process parameters. It is to be understood that all such alternatives and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The method and the application of the present invention have been described by the preferred embodiments, and it is obvious that the method and application described herein may be modified or appropriately modified and combined without departing from the scope of the present invention. The technique of the present invention is applied.

The invention provides a method for detecting the thermal stability of proteins in a dairy product, comprising the following steps: Step A: mixing the dairy product with water to obtain a first sample solution; Step B: the first sample solution is at 100 ° C to 135 The second sample solution is obtained by treating at a temperature of ° C for 10 min to 40 min; the second sample solution is detected to obtain a protein thermal stability of the second sample solution; the second sample solution has no delamination, no precipitation, no agglomeration, and The thermal stability of the protein is excellent; the second sample solution appears slightly wall-hanging, and the small granular coagulation visible to the naked eye is suspended therein, and the protein is thermally stable; the second sample solution appears to be more severely walled and flocculation occurs. The thermal stability of the protein is poor; the second sample solution is severely wall-hanging, and the tofu-like agglomeration appears, and the protein has poor thermal stability.

In some embodiments provided by the invention, the dairy product is selected from the group consisting of whole milk powder, skim milk powder, condensed milk or milk concentrated protein.

In order to detect the thermal stability of the protein in the dairy product, it is necessary to formulate the dairy product to a concentration of the dairy product solution based on the protein content of the dairy product. Therefore, in some embodiments provided by the present invention, the step A includes detection before The step of the protein content of the dairy product.

In order to ensure the accuracy of the detection results, in some embodiments provided by the present invention, the protein content in the first sample solution is from 4% to 7% by mass.

In some embodiments provided by the present invention, in order to restore the protein in the dairy product to the hydrated state of the fresh milk, a step of hydrating is also included between step A and step B.

To ensure adequate hydration, in some embodiments provided herein, the hydration is agitation at 300 rpm to 700 rpm.

In order to ensure adequate hydration, in some embodiments provided by the present invention, the hydration time is from 8 min to 20 min.

The invention also provides a preparation method of the milk-containing beverage, comprising the following steps: using the detection method provided by the invention to detect the dairy product, obtaining a dairy product with excellent protein thermal stability; taking the dairy product with excellent protein thermal stability, After the ingredients, sterilization, that is.

In some embodiments provided by the invention, the dairy product is selected from the group consisting of whole milk powder, skim milk powder, condensed milk or milk concentrated protein.

In some embodiments provided by the present invention, the milk-containing beverage is reconstituted milk, milk tea or milk-containing coffee.

In order to ensure effective killing of most of the microorganisms in the milk-containing beverage, the product has a longer shelf life. In some embodiments provided by the invention, the sterilization temperature is from 137 °C to 140 °C.

In order to ensure maximum maintenance of nutrients in the milk-containing beverage, in some embodiments provided by the invention, the sterilization time is from 4 s to 30 s.

The present invention provides a method for detecting the thermal stability of proteins in dairy products. The detecting method comprises: mixing the dairy product with water to obtain a first sample solution; the first sample solution is treated at 100 ° C to 135 ° C for 10 min to 40 min to obtain a second sample solution; and the second sample solution is performed Detecting, obtaining the thermal stability of the protein of the second sample solution; the second sample solution has no delamination, no precipitation, no agglomeration, and the protein has excellent thermal stability; the second sample solution is slightly wall-hanging, and there are small particles visible to the naked eye. When the condensate is suspended, the protein is thermally stable; the second sample solution is more severely walled and flocculation occurs, and the protein is less thermally stable; the second sample solution is severely wall-hanging, and the tofu flower-like knot appears. Block, its protein has poor thermal stability. The dairy product standard for detecting the thermal stability of the known protein is detected by the detection method provided by the present invention, and the results show that the detection result is consistent with the actual situation; the dairy products of different proteins thermally stable detected by the present invention are put into production practice, and the result is It is shown that the thermal stability of the protein detected by the detection method provided by the invention has a correlation with the continuous operation time of the ultra-high temperature sterilization equipment, and the continuous operation time of the ultra-high temperature sterilization equipment when the production is performed by using the dairy product with excellent thermal stability of the protein. Long; when using dairy products with poor thermal stability of protein, the ultra-high temperature sterilization equipment can run continuously for a short time; the detection method only needs to use ordinary experimental type sterilization pot to treat the dairy product samples in a constant temperature, within 1~2 hours. The thermal stability of the protein in the dairy product is measured. It can be seen that the detection method provided by the invention can quickly and accurately detect the thermal stability of the protein in the dairy product, thereby eliminating the dairy product with poor thermal stability of the protein, and using the dairy product with excellent thermal stability of the protein to produce the finished product, ensuring super High-temperature sterilization equipment can be continuously produced for more than 6 hours, thereby increasing production line capacity, reducing the number of AICs, controlling production costs, and increasing business efficiency.

The raw materials or excipients used in the method for detecting the thermal stability of proteins in the dairy products provided by the present invention are commercially available.

The present invention is further illustrated below in conjunction with the embodiments:

Example 1 Protein Thermal Stability Test of Whole Milk Powder Standards

Four whole milk powder standards with known protein thermal stability were obtained, and the thermal stability of the protein was excellent, general, poor, and poor. The amount of protein in the standard was measured and the result showed that the protein had a quality content of 25%.

Prepare a whole milk powder solution (test solution to be tested) by weighing 80g of each of the above standards, weighing 320g, 50°C water, and using the IKA mixer at 400rpm to slowly weigh the standard. After adding water, after the standard product is completely dissolved, a whole milk powder solution having a protein quality percentage of 5% is obtained. The whole milk powder solution was hydrated at 400 rpm for 10 min. Pour 100g of whole milk powder solution into three 250mL triangle bottles, plug the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel whole milk powder solution standards. .

The parameters of the experimental high-temperature autoclave were set to 121 ° C, 15 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. Three parallel whole milk powder solution standards were processed in a high temperature autoclave at 121 ° C for 15 min. When the autoclave is cooled to below 90 °C, the standard is taken out for observation to detect the protein thermal stability of the whole milk powder sample.

The test results show that the standard solution with excellent thermal stability of protein has no delamination, no precipitation, no agglomeration; the standard solution of protein thermal stability is slightly wall-hanging, and small granular coagulation visible to the naked eye is suspended therein; The standard solution with poor thermal stability of the protein appeared to be severely walled and flocculated; the standard solution with poor thermal stability of the protein appeared severely walled, and the tofu was agglomerated, and the results were consistent with the actual results. The detection method provided by the invention can accurately detect the protein thermal stability of whole milk powder.

Example 2 Protein Thermal Stability Testing of Skim Milk Powder Standards

Take 4 standards of skim milk powder with known protein thermal stability, the protein thermal stability is excellent, general, poor, and poor. The amount of protein in the standard was measured and the result showed that the percentage of protein in the standard was 32%.

The skim milk powder solution (the solution to be tested) is prepared separately. The specific method is as follows: 62.5 g of each of the above standards is weighed, 337.5 g of water of 50 ° C is weighed, and the standard of the scale is slowly taken with an IKA mixer at 400 rpm. After adding water, after the standard product is completely dissolved, a skim milk powder solution having a protein quality percentage of 5% is obtained. The skim milk powder solution was hydrated at 400 rpm for 10 min. Pour 100g of the skimmed milk powder solution into three 250mL flasks, plug the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel skim milk powder solution standards.

The parameters of the experimental high-temperature autoclave were set to 121 ° C, 15 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. Three parallel skim milk powder solution standards were processed in a high temperature autoclave at 121 ° C for 15 min. When the autoclave is cooled to below 90 °C, the standard is taken out for observation to detect the protein thermal stability of the skim milk powder sample.

The test results show that the standard solution with excellent thermal stability of protein has no delamination, no precipitation, no agglomeration; the standard solution of protein thermal stability is slightly wall-hanging, and small granular coagulation visible to the naked eye is suspended therein; The standard solution with poor thermal stability of the protein appeared to be severely walled and flocculated; the standard solution with poor thermal stability of the protein appeared severely walled, and the tofu was agglomerated, and the results were consistent with the actual results. The detection method provided by the invention can accurately detect the protein thermal stability of skim milk powder.

Example 3 Protein Thermal Stability Testing of Condensed Milk Standards

Taking four condensed milk standards with known protein thermal stability, the protein thermal stability was excellent, general, poor, and poor. The content of the protein in the standard was measured, and the result showed that the content of the protein in the standard was 8%.

The condensed milk solution (solution to be tested) is separately prepared by weighing 250 g of each of the above standards, weighing 150 g of water at 50 ° C, and slowly adding the weighed standard to the water with an IKA mixer at 400 rpm. After the standard product is completely dissolved, a condensed milk solution having a protein quality percentage of 5% is obtained. The condensed milk solution was hydrated at 400 rpm for 10 min. Pour 100g of each condensed milk solution into three 250mL flasks, plug the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel condensed milk solution standards.

The parameters of the experimental high-temperature autoclave were set to 121 ° C, 15 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. Three parallel condensed milk solution standards were processed in a high temperature autoclave at 121 ° C for 15 min. When the autoclave is cooled to below 90 ° C, the standard is taken out for observation to detect the protein thermal stability of the condensed milk sample.

The test results show that the standard solution with excellent thermal stability of protein has no delamination, no precipitation, no agglomeration; the standard solution of protein thermal stability is slightly wall-hanging, and small granular coagulation visible to the naked eye is suspended therein; The standard solution with poor thermal stability of the protein appeared to be severely walled and flocculated; the standard solution with poor thermal stability of the protein appeared severely walled, and the tofu was agglomerated, and the results were consistent with the actual results. The detection method provided by the invention can accurately detect the protein thermal stability of condensed milk.

Example 4 Protein Thermal Stability Test of Milk Concentrated Protein Standard

Taking four milk-concentrated protein standards with known protein thermostability, the protein thermal stability was excellent, general, poor, and poor. The content of the protein in the standard was measured, and the result showed that the percentage of the protein in the standard was 80%.

The milk concentrated protein solution (the solution to be tested) is separately prepared by weighing 25 g of each of the above standards, weighing 375 g of water at 50 ° C, and slowly adding the standard product by using an IKA mixer at 400 rpm. In the water, after the standard product is completely dissolved, a milk concentrated protein solution having a protein quality percentage of 5% is obtained. The milk concentrated protein solution was hydrated at 400 rpm for 10 min. Pour 100g of milk concentrated protein solution into three 250mL flasks, plug the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel milk concentrated protein solution standards. .

The parameters of the experimental high-temperature autoclave were set to 121 ° C, 15 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. Three parallel milk concentrated protein solution standards were processed in a high temperature autoclave at 121 ° C for 15 min. When the autoclave is cooled to below 90 °C, the standard is taken out for observation to detect the protein thermal stability of the milk concentrated protein sample.

The test results show that the standard solution with excellent thermal stability of protein has no delamination, no precipitation, no agglomeration; the standard solution of protein thermal stability is slightly wall-hanging, and small granular coagulation visible to the naked eye is suspended therein; The standard solution with poor thermal stability of the protein appeared to be severely walled and flocculated; the standard solution with poor thermal stability of the protein appeared severely walled, and the tofu was agglomerated, and the results were consistent with the actual results. The detection method provided by the invention can accurately detect the protein thermal stability of milk concentrated protein.

Example 5 Protein Thermal Stability Test of Whole Milk Powder

Take four different brands of whole milk powder, which are brand A, brand B, brand C, brand D, and detect the protein content in whole milk powder. The results show that brand A, brand B, brand C, brand D The percentage of protein in whole milk powder was 25%, 24.8%, 24.5%, and 24%, respectively.

Weigh 80g of whole-fat milk powder of each brand, weigh 320g, 316.8g, 312g, 304g 50°C water separately, and slowly add the whole milk powder weighed to the water with IKA mixer at 400rpm, until the whole milk powder After complete dissolution, four portions of a whole milk powder solution having a protein content of 5% were obtained. The whole milk powder solution was hydrated at 400 rpm for 10 min. Pour 100g of each whole milk powder solution into three 250mL flasks, plug the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel samples of whole milk powder solution. use.

The parameters of the experimental high-temperature autoclave were set to 121 ° C, 15 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. The whole milk powder solution sample was treated in a high temperature autoclave at 121 ° C for 15 min. When the autoclave is cooled to below 90 °C, the sample is taken out for observation to detect the protein thermal stability of the whole milk powder sample. The detection standards are shown in Table 1, and the test results are shown in Table 2.

When the dairy product is used as a raw material for UHT treatment during processing, the protein is apt to form a precipitate, and gradually accumulates on the heated surface of the sterilization device to form scale. The pressure in the sterilization equipment system increases with the degree of fouling on the heated surface. Large, when the pressure in the system rises to a certain extent, it indicates that the fouling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer in the sterilization process, thereby affecting the sterilization effect of the product, and then the intermediate of the sterilization equipment is required. Cleaning (AIC). Therefore, the continuous execution time of the sterilization apparatus is directly related to the protein thermal stability of the dairy product, and in actual production, the thermal stability of the protein in the dairy product can be judged by measuring the continuous execution time of the sterilization apparatus. The above four different brands of whole milk powder were put into the production of reconstituted milk with a protein content of 2.3%, and the ultra-high temperature sterilization equipment was continuously sterilized at 138 ° C for 4 s. When the steam proportional valve was fully opened, the sterilization temperature was less than 138. At °C, the time of continuous operation of the ultra-high temperature sterilization equipment was recorded, and the results are shown in Table 3.

It can be seen from the above test results that the ultra-high temperature sterilization equipment can be continuously operated for 6.88 hours when the full-fat milk powder (brand A) having excellent protein thermal stability detected by the detection method provided by the present invention is produced.

When the whole-fat milk powder (brand B) which is detected by the detection method provided by the present invention is thermally stable, the ultra-high temperature sterilization equipment can be continuously operated for 4.72 hours.

When the whole milk powder (brand C) with poor thermal stability of the protein detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 3.13 hours.

When the whole milk powder (brand D) with poor thermal stability of the protein detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 1.57 hours.

It can be seen that the thermal stability of the protein detected by the detection method provided by the invention has a correlation with the continuous operation time of the ultra-high temperature sterilization equipment, and the ultra-high temperature sterilization equipment can be used when the whole-fat milk powder with excellent protein thermal stability is used for production. The continuous operation takes a long time; when the whole milk milk powder with poor thermal stability of protein is used for production, the ultra-high temperature sterilization equipment can be continuously operated for a short time, indicating that the detection method provided by the invention can accurately detect the protein thermal stability of the whole milk powder.

Example 6 Protein Thermal Stability Testing of Skim Milk Powder

Take four different brands of skimmed milk powder, brand E, brand F, brand G, brand H, and detect the protein content in skim milk powder. The results show that brand E, brand F, brand G, brand H skim milk powder The percentage of protein quality was 34%, 33.8%, 33%, and 32%, respectively.

Weigh 60g of skim milk powder of each brand, weigh 450g, 447g, 435g, 420g, 50°C water, and slowly add the skim milk powder weighed to the water with IKA mixer at 400rpm. After the skim milk powder is completely dissolved, Four portions of skim milk powder solution having a protein content of 4% were obtained. Pour 100g of each skimmed milk powder solution into three 250mL flasks, insert the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel samples of skim milk powder solution for use.

The parameters of the experimental high-temperature autoclave were set to 100 ° C, 40 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. The skim milk powder solution sample was treated in a high temperature autoclave at 100 ° C for 40 min. When the autoclave is cooled to below 90 °C, the sample is taken out for observation to detect the thermal stability of the protein of the skim milk powder sample. The detection standards are shown in Table 1. The test results are shown in Table 4.

When the dairy product is used as a raw material for UHT treatment during processing, the protein is apt to form a precipitate, and gradually accumulates on the heated surface of the sterilization device to form scale. The pressure in the sterilization equipment system increases with the degree of fouling on the heated surface. Large, when the pressure in the system rises to a certain extent, it indicates that the fouling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer in the sterilization process, thereby affecting the sterilization effect of the product, and then the intermediate of the sterilization equipment is required. Cleaning (AIC). Therefore, the continuous execution time of the sterilization apparatus is directly related to the protein thermal stability of the dairy product, and in actual production, the thermal stability of the protein in the dairy product can be judged by measuring the continuous execution time of the sterilization apparatus. The above four brands of skim milk powder were put into the production of milk tea with a protein content of 0.8%, and the ultra-high temperature sterilization equipment was continuously sterilized at 138 ° C for 4 s. When the steam proportional valve was fully opened and the sterilization temperature was less than 138 ° C, The time of continuous operation of the ultra-high temperature sterilization equipment was recorded, and the results are shown in Table 5.

It can be seen from the above test results that when the skim milk powder (brand E) with excellent protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 8.95 hours;

When the protein thermal stability of the general skim milk powder (brand F) detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 6.61 hours;

When the skim milk powder (brand G) with poor thermal stability of the protein detected by the detection method provided by the invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 5.13 h;

When the skim milk powder (brand H) having poor thermal stability of the protein detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 2.51 hours.

It can be seen that the thermal stability of the protein detected by the detection method provided by the invention has a correlation with the time when the ultra-high temperature sterilization equipment can be continuously operated, and the ultra-high temperature sterilization equipment can be continuously used when the protein thermal stability of the skim milk powder is excellent. The operation time is long; when using the skim milk powder with poor thermal stability of protein, the ultra-high temperature sterilization equipment can be continuously operated for a short time, indicating that the detection method provided by the invention can accurately detect the protein thermal stability of the skim milk powder.

Example 7 Protein Thermal Stability Test of Condensed Milk

Take four different brands of condensed milk on the market, namely brand I, brand J, brand K, brand L, and detect the protein content in the condensed milk. The results show that the protein in the condensed milk of brand I, brand J, brand K, brand L The percentage of quality is 8.8%, 8.4%, 8.2%, 8%.

Weigh 250g of various brands of condensed milk, weigh 64.3g, 50g, 43g, 36g of water at 50 °C, and slowly add the condensed milk to the water with an IKA mixer at 400 rpm. After the condensed milk is completely dissolved, we get four. A condensed milk solution having a protein content of 7% by weight. The condensed milk solution was hydrated at 300 rpm for 20 min. Pour 100g of each condensed milk solution into three 250mL flasks, insert the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel samples of condensed milk solution for use.

The parameters of the experimental high-temperature autoclave were set to 135 ° C, 10 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. The condensed milk solution sample was treated in a high temperature autoclave at 135 ° C for 10 min. When the autoclave is cooled to below 90 °C, the sample is taken out for observation to detect the thermal stability of the protein of the condensed milk sample. The detection standards are shown in Table 1. The test results are shown in Table 6.

When the dairy product is used as a raw material for UHT treatment during processing, the protein is apt to form a precipitate, and gradually accumulates on the heated surface of the sterilization device to form scale. The pressure in the sterilization equipment system increases with the degree of fouling on the heated surface. Large, when the pressure in the system rises to a certain extent, it indicates that the fouling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer in the sterilization process, thereby affecting the sterilization effect of the product, and then the intermediate of the sterilization equipment is required. Cleaning (AIC). Therefore, the continuous execution time of the sterilization apparatus is directly related to the protein thermal stability of the dairy product, and in actual production, the thermal stability of the protein in the dairy product can be judged by measuring the continuous execution time of the sterilization apparatus. The above four brands of condensed milk were put into the production of milk-containing coffee with a protein content of 1.1%, and the ultra-high temperature sterilization equipment was continuously sterilized at 138 ° C for 4 s. When the steam proportional valve was fully opened and the sterilization temperature was less than 138 ° C The time for continuous operation of the ultra-high temperature sterilization equipment was recorded, and the results are shown in Table 7.

From the above test results, it can be seen that the ultra-high temperature sterilization equipment can be continuously operated for 8.02 h when the condensed milk (brand I) having excellent thermal stability of the protein detected by the detection method provided by the present invention is produced.

When the heat stability of the protein (brand J) is detected by the detection method provided by the present invention, the ultra-high temperature sterilization equipment can be continuously operated for 7.38 hours.

When the condensed milk (brand K) having poor thermal stability of the protein detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 5.07 hours.

When the condensed milk (brand L) having poor thermal stability of the protein detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization apparatus can be continuously operated for 2.51 hours.

It can be seen that the thermal stability of the protein detected by the detection method provided by the invention has a correlation with the continuous operation time of the ultra-high temperature sterilization equipment, and the ultra-high temperature sterilization equipment can be continuously operated when the condensed milk with excellent thermal stability of the protein is used for production. The time is long; when the condensed milk with poor thermal stability of protein is used for production, the ultra-high temperature sterilization equipment can be continuously operated for a short time, indicating that the detection method provided by the invention can accurately detect the protein thermal stability of the condensed milk.

Example 8 Protein Thermal Stability Test of Milk Concentrate

Take four different brands of milk concentrated protein, which are brand M, brand N, brand O, brand P, and detect the protein content in milk concentrated protein. The results show that brand M, brand N, brand O, brand P The protein content of milk concentrated protein is 82%, 81.5%, 81%, 80%.

Weigh 25g of milk protein concentrate of each brand, weigh 385g, 382.5g, 380g, 375g, 50°C water, and slowly add the concentrated protein of milk to the water with IKA mixer at 400rpm, until the milk is concentrated. After the protein is completely dissolved, four milk concentrated protein solutions having a protein content of 5% are obtained. The milk concentrated protein solution was hydrated at 700 rpm for 8 min. Pour 100g of each milk concentrated protein solution into three 250mL flasks, plug the corresponding rubber stopper, cover the newspaper, and tie with rubber bands to make three parallel samples of milk concentrated protein solution. use.

The parameters of the experimental high-temperature autoclave were set to 130 ° C, 12 min, and the model of the high-temperature autoclave was: STURDY sa-300 vl. The milk concentrated protein solution sample was treated in a high temperature autoclave at 130 ° C for 12 min. When the autoclave is cooled to below 90 °C, the sample is taken out for observation to detect the thermal stability of the protein of the milk concentrated protein sample. The detection standards are shown in Table 1. The test results are shown in Table 8.

When the dairy product is used as a raw material for UHT treatment during processing, the protein is apt to form a precipitate, and gradually accumulates on the heated surface of the sterilization device to form scale. The pressure in the sterilization equipment system increases with the degree of fouling on the heated surface. Large, when the pressure in the system rises to a certain extent, it indicates that the fouling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer in the sterilization process, thereby affecting the sterilization effect of the product, and then the intermediate of the sterilization equipment is required. Cleaning (AIC). Therefore, the continuous execution time of the sterilization apparatus is directly related to the protein thermal stability of the dairy product, and in actual production, the thermal stability of the protein in the dairy product can be judged by measuring the continuous execution time of the sterilization apparatus.

The above four brands of milk protein concentrate were put into the production of milk tea with a protein content of 0.8%, and the ultra-high temperature sterilization equipment was continuously sterilized at 138 ° C for 4 s. When the steam proportional valve was fully opened and the sterilization temperature was less than 138 ° C The time for continuous operation of the ultra-high temperature sterilization equipment was recorded, and the results are shown in Table 9.

It can be seen from the above test results that when the milk concentrated protein (brand M) having excellent protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 9.91 h;

When the protein thermal stability protein (brand N) detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 7.09h.

When the milk concentrated protein (brand O) having poor thermal stability of the protein detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 5.14 hours.

When the milk concentrated protein (brand P) having poor thermal stability of the protein detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can be continuously operated for 2.55 hours.

It can be seen that the thermal stability of the protein detected by the detection method provided by the invention has a correlation with the continuous operation time of the ultra-high temperature sterilization equipment, and the ultra-high temperature sterilization equipment can be used when the protein is prepared by using the milk concentrated protein with excellent thermal stability of the protein. The continuous operation takes a long time; when the production of milk concentrated protein with poor thermal stability of protein is used, the ultra-high temperature sterilization equipment can be continuously operated for a short time, indicating that the detection method provided by the invention can accurately detect the protein thermal stability of milk concentrated protein.

Example 9 Preparation of reconstituted milk

The whole milk milk powder (brand A) having excellent protein thermal stability detected in Example 5 was mixed with a conventional auxiliary material, and sterilized at 138 ° C for 4 s to obtain a reconstituted milk having a protein content of 2.3%.

Example 10 Preparation of milk tea

The skim milk powder (brand E) having excellent thermal stability of the protein detected in Example 6 was mixed with a conventional auxiliary material, and sterilized at 137 ° C for 30 s to prepare a milk tea having a protein content of 0.8%.

Example 11 Preparation of milk-containing coffee

The condensed milk (brand I) having excellent thermal stability of the protein detected in Example 7 was mixed with a conventional auxiliary material, and sterilized at 140 ° C for 4 s to prepare a milk-containing coffee having a protein content of 1.1%.

Example 12 Preparation of milk tea

The milk concentrated protein (brand M) having excellent thermal stability of the protein detected in Example 8 was mixed with a conventional auxiliary material, and sterilized at 139 ° C for 10 s to prepare a milk tea having a protein content of 0.8%.

The above embodiments are intended to be illustrative only, and are not intended to limit the scope of the present invention. It is included in the scope of the following patent application.

Claims (9)

A method for detecting the thermal stability of a protein in a dairy product, comprising the steps of: step A: detecting a protein content of the dairy product, and mixing the dairy product with water to obtain a first sample solution, wherein the first The percentage of the protein in the product solution is 4% to 7%; Step B: the first sample solution is treated at 100 ° C to 135 ° C for 10 min to 40 min to obtain a second sample solution; The second sample solution is tested to obtain the protein thermal stability of the second sample solution; the second sample solution has no delamination, no precipitation, no agglomeration, and the protein thermal stability is excellent; the second sample solution appears Slightly hanging on the wall, there are small granular coagulations visible in the naked eye, the protein is thermally stable; the second sample solution appears to be more severely walled, and flocculation occurs, and the protein is less thermally stable; The two sample solutions are severely wall-hanging, and the tofu flower-like agglomeration occurs, and the protein is poor in thermal stability. The dairy product is selected from the group consisting of whole milk powder, skimmed milk powder, condensed milk or milk concentrated protein. The method for detecting the thermal stability of proteins in a dairy product according to claim 1, wherein the step of hydrating is further included between the steps A and B. The method for detecting the thermal stability of proteins in a dairy product according to the second aspect of the invention, wherein the step of hydrating is stirring at 300 rpm to 700 rpm. The method for detecting the thermal stability of a protein in a dairy product according to the second aspect of the invention, wherein the step of hydrating is from 8 min to 20 min. A preparation method of a milk-containing beverage, comprising the following steps: The dairy product is tested by the method for detecting the thermal stability of the protein in the dairy product according to any one of the claims 1 to 7 to obtain a dairy product having excellent protein thermal stability; and the protein is excellent in thermal stability. The dairy products are obtained by ingredients and sterilization. The method for preparing a milk-containing beverage according to claim 5, wherein the dairy product is selected from the group consisting of whole milk powder, skimmed milk powder, condensed milk or milk concentrated protein. The method for preparing a milk-containing beverage according to claim 5, wherein the milk-containing beverage is reconstituted milk, milk tea or milk-containing coffee. The method for preparing a milk-containing beverage according to claim 5, wherein the sterilization temperature is 137 ° C to 140 ° C. The method for preparing a milk-containing beverage according to claim 5, wherein the sterilization time is 4 s to 30 s.