CN103487456B - A method for detecting protein thermal stability in dairy products - Google Patents

Abstract

The invention relates to the technical field of dairy product processing, in particular to a method for detecting the thermal stability of protein in a dairy product. The detection method comprises the following steps: mixing a dairy product with water to obtain a first sample solution; treating the first sample solution at 100-135 ℃ for 10-40 min to obtain a second sample solution; and detecting the second sample solution to obtain the protein thermal stability of the second sample solution. The detection method provided by the invention can quickly and accurately detect the thermal stability of the protein in the dairy product, so that the dairy product with poor thermal stability of the protein is removed, the dairy product with excellent thermal stability of the protein is used for producing finished products, and the continuous production of ultrahigh-temperature sterilization equipment can be ensured for more than 6 hours, so that the production capacity of a production line is increased, the AIC times are reduced, the production cost is controlled, and the enterprise benefit is increased.

Description

A method for detecting protein thermal stability in dairy products

technical field

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

Background technique

Milk tea is a beverage that mixes tea and milk. The aroma of milk tea can be found in China, India, the United Kingdom, Singapore, Malaysia, Taiwan, Hong Kong, Macau and other parts of the world. Such as Indian milk tea, famous for adding the special spice of Marsala; Hong Kong milk tea is famous for silk stocking milk tea; Pearl milk tea of Taiwan is also unique. Milk tea has the double nutrition of both milk and tea. In addition to being rich in advanced nutrients such as protein and fat, it also contains caffeine, tannic acid, theophylline, aromatic oil, chlorophyll, amino acids, sugars, various minerals and many other nutrients. There are more than 300 kinds of vitamins (Vc, Vp, niacin, folic acid, etc.) and more than 300 chemical components that are beneficial to the human body. With the improvement of people's material living standards, milk tea is becoming more and more popular among consumers, and the market capacity is expanding year by year.

The preparation process of milk tea is generally made of fresh milk or dairy products and other raw materials through ultra-high temperature instantaneous sterilization (UHT). However, due to the regional nature of milk-producing livestock such as dairy cows, the production of fresh milk is also limited by the region, and because the shelf life of fresh milk products is short, corresponding processes must be carried out as soon as possible to complete the production of products. Therefore, non-fresh milk production areas Dairy product processing enterprises generally use dairy products such as whole milk powder, skimmed milk powder, condensed milk or milk protein concentrate as raw materials for processing milk tea, and these dairy products have their own taste characteristics and are loved by different consumer groups.

When dairy products are used as raw materials for UHT treatment during the processing process, the protein in them is volatile and forms precipitates, which gradually accumulate and adhere to the heating surface of the sterilization equipment to form scaling. The internal pressure of the sterilization equipment system will increase with the scaling degree of the heating surface. However, when the pressure in the system rises to a certain level, it will affect the heat transfer during the sterilization process, thereby affecting the sterilization effect of the product. At this time, it is necessary to perform intermediate cleaning (AIC) on the sterilization equipment. When dairy products with poor protein thermal stability are used as raw materials, the sterilization equipment can only run for 1.5-3 hours before AIC is required, while when dairy products with excellent protein thermal stability are used as raw materials, the sterilization equipment can run continuously for at least 6 hours. Therefore, milk The protein thermal stability of the product can directly affect the continuous operation time and sterilization conditions of the sterilization equipment. In actual production, the protein thermal stability of different brands or different batches of dairy products will vary. Therefore, how to quickly screen out dairy products with excellent protein thermal stability from different brands or different batches of dairy products for corresponding production, reduce the number of AIC, thereby reducing the corresponding production costs, has become an urgent need for dairy processing enterprises . However, there are no special regulations on protein thermal stability in the current relevant national standards for dairy products, and there is no published method for quickly detecting protein thermal stability in dairy products. Sexual methods have important practical significance.

Contents of the invention

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

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a method for detecting protein thermal stability in dairy products, 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 treated at 100°C to 135°C for 10min to 40min to obtain the second sample solution;

Detecting the second sample solution to obtain the protein thermal stability of the second sample solution;

The second sample solution has no stratification, no precipitation, no agglomeration, and its protein has excellent thermal stability;

The second sample solution is slightly wall-mounted, with small granular coagulation visible to the naked eye suspended in it, and its protein thermal stability is average;

The second sample solution has serious wall hanging and flocculation phenomenon, and its protein thermal stability is relatively poor;

The second sample solution had serious wall hanging and bean curd flower-like agglomeration, and its protein thermal stability was poor.

Preferably, the dairy product is selected from whole milk powder, skim milk powder, condensed milk or milk protein concentrate.

In some embodiments provided by the present invention, before step A, a step of detecting the protein content of dairy products is also included.

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

Preferably, a hydration step is also included between step A and step B.

Preferably, the hydration is stirred under the condition of 300 rpm to 700 rpm.

Preferably, the hydration time is 8 minutes to 20 minutes.

The present invention also provides a method for preparing milk-containing beverage, comprising the following steps:

Dairy products are detected by using the detection method provided by the invention to obtain dairy products with excellent protein thermal stability;

The milk product with excellent protein heat stability is taken, and the mixture is prepared and sterilized to obtain the product.

Preferably, the dairy product is selected from whole milk powder, skim milk powder, condensed milk or milk protein concentrate.

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 4s to 30s.

The invention provides a method for detecting protein thermal stability in dairy products. The detection method includes: mixing dairy products with water to obtain a first sample solution; treating the first sample solution at 100°C to 135°C for 10min to 40min to obtain a second sample solution; Test to obtain the protein thermal stability of the second sample solution; the second sample solution has no stratification, no precipitation, no agglomeration, and its protein thermal stability is excellent; the second sample solution has slight wall hanging and small particles visible to the naked eye The protein thermal stability is average; the second sample solution has serious wall hanging and flocculation phenomenon, and its protein thermal stability is poor; the second sample solution has serious wall hanging and appears tofu flower-like Caking, its protein thermal stability is poor. Utilize the detection method provided by the present invention to detect the dairy product standard product of known protein thermal stability, the result shows that the result of detection is consistent with reality; The dairy product of the different protein thermal stability that the present invention detects is put into actual production, the result It shows that the thermal stability of the protein detected by the detection method provided by the present invention is correlated with the continuous operation time of the ultra-high temperature sterilization equipment. When dairy products with excellent protein thermal stability are used for production, the ultra-high temperature sterilization equipment can be continuously operated The time is long; when dairy products with poor protein thermal stability are used for production, the continuous operation time of ultra-high temperature sterilization equipment is short; The thermal stability of protein in dairy products can be detected within 2 hours. It can be seen that the detection method provided by the present invention can quickly and accurately detect the thermal stability of proteins in dairy products, thereby eliminating dairy products with poor protein thermal stability, and using dairy products with excellent protein thermal stability to produce finished products, ensuring super The high-temperature sterilization equipment can produce continuously for more than 6 hours, thereby increasing the production capacity of the production line, reducing the number of AIC, controlling production costs, and increasing corporate benefits.

detailed description

The invention discloses a method for detecting the thermal stability of protein in dairy products. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to realize it. In particular, it should be pointed out that all similar replacements and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and the relevant personnel can obviously make changes or appropriate changes and combinations to the method and application described herein without departing from the content, spirit and scope of the present invention to realize and Apply the technology of the present invention.

The invention provides a method for detecting protein thermal stability in dairy products, 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 treated at 100°C to 135°C for 10min to 40min to obtain the second sample solution;

Detecting the second sample solution to obtain the protein thermal stability of the second sample solution;

The second sample solution has no stratification, no precipitation, no agglomeration, and its protein has excellent thermal stability;

The second sample solution is slightly wall-mounted, with small granular coagulation visible to the naked eye suspended in it, and its protein thermal stability is average;

The second sample solution has serious wall hanging and flocculation phenomenon, and its protein thermal stability is relatively poor;

The second sample solution had serious wall hanging and bean curd flower-like agglomeration, and its protein thermal stability was poor.

In some embodiments provided by the present invention, the dairy product is selected from whole milk powder, skimmed milk powder, condensed milk or milk protein concentrate.

In order to detect the thermal stability of the protein in the dairy product, the dairy product needs to be formulated into a certain concentration of the dairy product solution according to the protein content in the dairy product. Therefore, in some embodiments provided by the present invention, the detection of milk The protein content of the preparation step.

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

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

In order to ensure sufficient hydration, in some embodiments provided by the present invention, the hydration is stirring under the condition of 300rpm-700rpm.

In order to ensure sufficient hydration, in some embodiments provided by the present invention, the hydration time is 8 minutes to 20 minutes.

The present invention also provides a method for preparing milk-containing beverage, comprising the following steps:

Dairy products are detected by using the detection method provided by the invention to obtain dairy products with excellent protein thermal stability;

The milk product with excellent protein heat stability is taken, and the mixture is prepared and sterilized to obtain the product.

In some embodiments provided by the present invention, the dairy product is selected from whole milk powder, skimmed milk powder, condensed milk or milk protein concentrate.

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

In order to effectively kill most of the microorganisms in the milk-containing beverage and make the product have a longer shelf life, in some embodiments provided by the present invention, the sterilization temperature is 137°C-140°C.

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

The invention provides a method for detecting protein thermal stability in dairy products. The detection method includes: mixing dairy products with water to obtain a first sample solution; treating the first sample solution at 100°C to 135°C for 10min to 40min to obtain a second sample solution; Test to obtain the protein thermal stability of the second sample solution; the second sample solution has no stratification, no precipitation, no agglomeration, and its protein thermal stability is excellent; the second sample solution has slight wall hanging and small particles visible to the naked eye The protein thermal stability is average; the second sample solution has serious wall hanging and flocculation phenomenon, and its protein thermal stability is poor; the second sample solution has serious wall hanging and appears tofu flower-like Caking, its protein thermal stability is poor. Utilize the detection method provided by the present invention to detect the dairy product standard product of known protein thermal stability, the result shows that the result of detection is consistent with reality; The dairy product of the different protein thermal stability that the present invention detects is put into actual production, the result It shows that the thermal stability of the protein detected by the detection method provided by the present invention is correlated with the continuous operation time of the ultra-high temperature sterilization equipment. When dairy products with excellent protein thermal stability are used for production, the ultra-high temperature sterilization equipment can be continuously operated The time is long; when dairy products with poor protein thermal stability are used for production, the continuous operation time of ultra-high temperature sterilization equipment is short; The thermal stability of protein in dairy products can be detected within 2 hours. It can be seen that the detection method provided by the present invention can quickly and accurately detect the thermal stability of proteins in dairy products, thereby eliminating dairy products with poor protein thermal stability, and using dairy products with excellent protein thermal stability to produce finished products, ensuring super The high-temperature sterilization equipment can produce continuously for more than 6 hours, thereby increasing the production capacity of the production line, reducing the number of AIC, controlling production costs, and increasing corporate benefits.

The raw materials or auxiliary materials used in the method for detecting the thermal stability of protein in dairy products provided by the present invention can be purchased from the market.

Below in conjunction with embodiment, further set forth the present invention:

The protein thermostability detection of embodiment 1 whole milk powder standard product

Take 4 standard products of whole milk powder with known protein thermal stability, and the protein thermal stability is excellent, average, poor and poor respectively. Detect the content of protein in the standard product, the result shows that the mass percentage composition of protein in this standard product is 25%.

Prepare the whole milk powder solution (solution to be tested) respectively. The specific method is: weigh 80g of each of the above-mentioned standard products, weigh 320g of water at 50°C, and slowly add the weighed standard products into the water with an IKA mixer at 400rpm , after the standard substance was completely dissolved, a whole milk powder solution with a protein mass percentage content of 5% was obtained. The whole milk powder solution was hydrated for 10 min at 400 rpm. Pour 100g of the whole milk powder solution into three 250mL conical flasks respectively, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel whole milk powder solution standards for use .

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 121°C and 15 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. Three parallel whole milk powder solution standards were processed in a high-temperature and high-pressure sterilizer at 121°C for 15 minutes. When the high-temperature and high-pressure sterilizer is cooled to below 90°C, the standard product 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 protein thermal stability has no stratification, no precipitation, and no agglomeration; the standard solution with average protein thermal stability has slight wall hanging, and there are small granular coagulums visible to the naked eye suspended in it; The standard solution with poor thermal stability of protein had serious wall hanging and flocculation phenomenon; the standard solution with poor protein thermal stability had serious wall hanging and bean curd flower-like agglomeration. The test results were consistent with the actual results. It shows that the detection method provided by the present invention can accurately detect the protein thermal stability of whole milk powder.

The protein thermostability detection of embodiment 2 skimmed milk powder standard product

Take 4 standard products of skim milk powder with known protein thermal stability, and the protein thermal stability is excellent, average, poor and poor respectively. Detect the content of protein in the standard product, the result shows that the mass percentage composition of protein in this standard product is 32%.

Prepare skimmed milk powder solutions (solutions to be tested) respectively. The specific method is: weigh 62.5g of each of the above-mentioned standard products, weigh 337.5g of water at 50°C, and slowly add the weighed standard products with an IKA mixer at 400rpm In water, after the standard substance is completely dissolved, a skimmed milk powder solution with a protein mass percentage content of 5% is obtained. The skim milk powder solution was hydrated at 400 rpm for 10 min. Pour 100g each of the skim milk powder solution into three 250mL conical flasks, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel standard products of the skim milk powder solution for use.

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 121°C and 15 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. Three parallel skimmed milk powder solution standards were processed in a high-temperature and high-pressure sterilizer at 121°C for 15 minutes. When the high-temperature and high-pressure sterilizer is cooled to below 90°C, the standard product 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 protein thermal stability has no stratification, no precipitation, and no agglomeration; the standard solution with average protein thermal stability has slight wall hanging, and there are small granular coagulums visible to the naked eye suspended in it; The standard solution with poor thermal stability of protein had serious wall hanging and flocculation phenomenon; the standard solution with poor protein thermal stability had serious wall hanging and bean curd flower-like agglomeration. The test results were consistent with the actual results. It shows that the detection method provided by the present invention can accurately detect the protein thermal stability of skim milk powder.

The protein thermostability detection of embodiment 3 condensed milk standard products

Four condensed milk standard samples with known protein thermal stability were taken, and the protein thermal stability was excellent, average, poor, and poor, respectively. Detect the content of protein in the standard product, the result shows that the mass percentage composition of protein in this standard product is 8%.

Prepare the condensed milk solution (solution to be tested) respectively. The specific method is: weigh 250g of each of the above-mentioned standard products, weigh 150g of water at 50°C, and slowly add the weighed standard products into the water with an IKA mixer at 400rpm. After the standard substance was completely dissolved, a condensed milk solution with a protein mass percentage of 5% was obtained. The condensed milk solution was hydrated for 10 min at 400 rpm. Pour 100g of each condensed milk solution into three 250mL Erlenmeyer flasks, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel condensed milk solution standards for use.

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 121°C and 15 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. Three parallel condensed milk solution standards were processed in a high temperature and high pressure sterilizer at 121°C for 15 minutes. When the high-temperature and high-pressure sterilizer is cooled to below 90°C, the standard product 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 protein thermal stability has no stratification, no precipitation, and no agglomeration; the standard solution with average protein thermal stability has slight wall hanging, and there are small granular coagulums visible to the naked eye suspended in it; The standard solution with poor thermal stability of protein had serious wall hanging and flocculation phenomenon; the standard solution with poor protein thermal stability had serious wall hanging and bean curd flower-like agglomeration. The test results were consistent with the actual results. It shows that the detection method provided by the invention can accurately detect the protein thermal stability of condensed milk.

The protein thermostability detection of embodiment 4 milk protein concentrate standard substance

Take 4 milk protein concentrate standard products with known protein thermal stability, and the protein thermal stability is excellent, average, poor and poor respectively. The protein content in the standard product was detected, and the result showed that the protein mass percentage in the standard product was 80%.

Prepare the concentrated milk protein solution (solution to be tested) respectively. The specific method is: weigh 25g of the above-mentioned standard products, weigh 375g of water at 50°C, and slowly add the weighed standard products into the water with an IKA mixer at 400rpm , after the standard substance was completely dissolved, a milk protein concentrate solution with a protein mass percentage of 5% was obtained. The milk protein concentrate solution was hydrated at 400 rpm for 10 min. Pour 100g of the milk protein concentrate solution into three 250mL conical flasks respectively, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel milk protein concentrate solution standards for use .

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 121°C and 15 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. Three parallel milk protein concentrate solution standards were processed in a high-temperature and high-pressure sterilizer at 121°C for 15 minutes. When the high-temperature and high-pressure sterilizer is cooled to below 90°C, the standard product is taken out for observation to detect the protein thermal stability of the milk protein concentrate sample.

The test results show that the standard solution with excellent protein thermal stability has no stratification, no precipitation, and no agglomeration; the standard solution with average protein thermal stability has slight wall hanging, and there are small granular coagulums visible to the naked eye suspended in it; The standard solution with poor thermal stability of protein had serious wall hanging and flocculation phenomenon; the standard solution with poor protein thermal stability had serious wall hanging and bean curd flower-like agglomeration. The test results were consistent with the actual results. It shows that the detection method provided by the invention can accurately detect the protein thermal stability of milk protein concentrate.

The protein thermostability detection of embodiment 5 whole milk powder

Take four different brands of whole milk powder on the market, respectively brand A, brand B, brand C, and brand D, and detect the protein content in the whole milk powder. The results show that the protein content of brand A, brand B, brand C, and brand D The mass percentages of protein in whole milk powder were 25%, 24.8%, 24.5%, and 24%, respectively.

Weigh 80g of whole milk powder of each brand, weigh 320g, 316.8g, 312g, and 304g of water at 50°C respectively, and slowly add the weighed whole milk powder into the water with an IKA mixer at 400rpm, and wait until the whole milk powder is completely After dissolving, four parts of whole milk powder solutions with a protein mass percentage content of 5% were obtained. The whole milk powder solution was hydrated for 10 min at 400 rpm. Pour 100g of each whole milk powder solution into three 250mL conical flasks, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel whole milk powder solution samples. use.

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 121°C and 15 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. The whole milk powder solution sample was treated in a high temperature and high pressure sterilizer at 121°C for 15 minutes. When the high-temperature and high-pressure sterilizer is cooled below 90°C, the samples are taken out for observation, and the protein thermal stability of the whole milk powder samples is tested. The test standards are shown in Table 1, and the test results are shown in Table 2.

When dairy products are used as raw materials for UHT treatment during the processing process, the protein in them is volatile and forms precipitates, which gradually accumulate and adhere to the heating surface of the sterilization equipment to form scaling. The internal pressure of the sterilization equipment system will increase with the scaling degree of the heating surface. When the pressure in the system rises to a certain level, it indicates that the fouling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer during the sterilization process, thereby affecting the sterilization effect of the product. At this time, it is necessary to Perform intermediate cleaning (AIC) on the sterilizing equipment. Therefore, the continuous running time of sterilization equipment is directly related to the protein thermal stability of dairy products. In actual production, the thermal stability of protein in dairy products can be judged by measuring the continuous running time of sterilization equipment. Put the above four different brands of whole milk powder into the production of reconstituted milk with a protein content of 2.3%. When the temperature is less than 138°C, record the continuous operation time of the ultra-high temperature sterilization equipment, and the results are shown in Table 3.

Table 1 Standards for detection of protein thermal stability in dairy products

Table 2 Protein thermal stability test results of whole milk powder

Table 3 Continuous operation time of ultra-high temperature sterilization equipment

From the above test results, it can be seen that when the whole milk powder (brand A) with excellent protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can run continuously for 6.88 hours;

When the whole milk powder (brand B) with average protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can run continuously for 4.72 hours;

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

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

It can be seen that the protein thermal stability detected by the detection method provided by the present invention is correlated with the continuous operation time of the ultra-high temperature sterilization equipment. When using whole milk powder with excellent protein thermal stability for production, the ultra-high temperature sterilization The equipment can run continuously for a long time; when using whole milk powder with poor protein thermal stability for production, the ultra-high temperature sterilization equipment can continuously run for a short time, indicating that the detection method provided by the invention can accurately detect the protein thermal stability of whole milk powder sex.

The protein thermostability detection of embodiment 6 skimmed milk powder

Take four different brands of skim milk powder on the market, namely brand E, brand F, brand G, and brand H, and detect the protein content in the skim milk powder. The results show that the protein content in the skim milk powder of brand E, brand F, brand G, and brand H The mass percentages of protein were 34%, 33.8%, 33%, and 32%, respectively.

Weigh 60g of skimmed milk powder of each brand, weigh 450g, 447g, 435g, 420g of water at 50°C, and slowly add the weighed skimmed milk powder into water with an IKA mixer at 400rpm. After the skimmed milk powder is completely dissolved, four Part protein mass percentage content is the skim milk powder solution of 4%. Pour 100g of each skim milk powder solution into three 250mL conical flasks, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel skim milk powder solution samples for use.

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 100°C and 40 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. The skimmed milk powder solution samples were treated in a high temperature and high pressure sterilizer at 100°C for 40 minutes. When the high temperature and high pressure sterilizer was cooled below 90°C, the samples were taken out for observation, and the protein thermal stability of the skim milk powder sample was tested. The test standards are shown in Table 1, and the test results are shown in Table 4.

When dairy products are used as raw materials for UHT treatment during the processing process, the protein in them is volatile and forms precipitates, which gradually accumulate and adhere to the heating surface of the sterilization equipment to form scaling. The internal pressure of the sterilization equipment system will increase with the scaling degree of the heating surface. When the pressure in the system rises to a certain level, it indicates that the fouling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer during the sterilization process, thereby affecting the sterilization effect of the product. At this time, it is necessary to Perform intermediate cleaning (AIC) on the sterilizing equipment. Therefore, the continuous running time of sterilization equipment is directly related to the protein thermal stability of dairy products. In actual production, the thermal stability of protein in dairy products can be judged by measuring the continuous running time of sterilization equipment. The skim milk powder of the above four brands was put into the production of milk tea with a protein content of 0.8%. The ultra-high temperature sterilization equipment continuously sterilized at 138°C for 4s. °C, record the continuous operation time of the ultra-high temperature sterilization equipment, and the results are shown in Table 5.

Table 4 Protein thermal stability test results of skimmed milk powder

Table 5 Continuous operation time of ultra-high temperature sterilization equipment

From the above test results, it can be seen 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 run continuously for 8.95 hours;

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

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

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

It can be seen that the thermal stability of the protein detected by the detection method provided by the present invention is correlated with the continuous operation time of the ultra-high temperature sterilization equipment. When using skim milk powder with excellent protein thermal stability for production, the ultra-high temperature sterilization equipment The continuous operation time is long; when the skim milk powder with poor protein thermal stability is used for production, the ultra-high temperature sterilization equipment can continuously operate 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.

The protein thermostability detection of embodiment 7 condensed milk

Take four commercially available condensed milks of different brands, namely Brand I, Brand J, Brand K, and 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, and Brand L The mass percentage content is 8.8%, 8.4%, 8.2%, 8%.

Weigh 250g of condensed milk of each brand, respectively weigh 64.3g, 50g, 43g, 36g of water at 50°C, and slowly add the weighed condensed milk to the water with an IKA mixer at 400rpm. After the condensed milk is completely dissolved, four parts are obtained. A condensed milk solution with a protein mass percentage of 7%. The condensed milk solution was hydrated for 20 min at 300 rpm. Pour 100g of each condensed milk solution into three 250mL conical flasks, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel condensed milk solution samples for use.

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 135°C and 10 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. The condensed milk solution sample was treated in a high temperature and high pressure sterilizer at 135°C for 10 minutes. When the high-temperature and high-pressure sterilizer is cooled below 90°C, the samples are taken out for observation, and the protein thermal stability of the condensed milk samples is tested. The test standards are shown in Table 1, and the test results are shown in Table 6.

When dairy products are used as raw materials for UHT treatment during the processing process, the protein in them is volatile and forms precipitates, which gradually accumulate and adhere to the heating surface of the sterilization equipment to form scaling. The internal pressure of the sterilization equipment system will increase with the scaling degree of the heating surface. When the pressure in the system rises to a certain level, it indicates that the fouling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer during the sterilization process, thereby affecting the sterilization effect of the product. At this time, it is necessary to Perform intermediate cleaning (AIC) on the sterilizing equipment. Therefore, the continuous running time of sterilization equipment is directly related to the protein thermal stability of dairy products. In actual production, the thermal stability of protein in dairy products can be judged by measuring the continuous running time of sterilization equipment. The condensed milk of the above four brands is put into the production of milky coffee with a protein content of 1.1%. The ultra-high temperature sterilization equipment continuously sterilizes at 138°C for 4s. When the steam proportional valve is fully opened, the sterilization temperature cannot reach At 138°C, record the continuous operation time of the ultra-high temperature sterilization equipment, and the results are shown in Table 7.

Table 6 Protein thermal stability test results of condensed milk

Table 7 Continuous operation time of ultra-high temperature sterilization equipment

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

When condensed milk (brand J) with average protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can run continuously for 7.38 hours;

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

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

It can be seen that the thermal stability of the protein detected by the detection method provided by the present invention is correlated with the continuous operation time of the ultra-high temperature sterilization equipment. When condensed milk with excellent protein thermal stability is used for production, the ultra-high temperature sterilization equipment can The continuous operation time is long; when the condensed milk with poor protein thermal stability is used for production, the continuous operation time of the ultra-high temperature sterilization equipment is short, which shows that the detection method provided by the invention can accurately detect the protein thermal stability of the condensed milk.

The protein thermal stability detection of embodiment 8 milk protein concentrate

Take four different brands of milk protein concentrate on the market, namely brand M, brand N, brand O, and brand P, and detect the protein content in milk protein concentrate. The results show that brand M, brand N, brand O, and brand P are The mass percentage of protein in milk protein concentrate is 82%, 81.5%, 81%, 80%.

Weigh 25g of various brands of milk protein concentrate, weigh 385g, 382.5g, 380g, 375g of water at 50°C, and slowly add the weighed milk protein concentrate to water with an IKA mixer at 400rpm until the milk protein concentrate is completely dissolved Finally, four parts of milk protein concentrate solutions with a protein mass percentage content of 5% were obtained. The milk protein concentrate solution was hydrated at 700 rpm for 8 min. Pour 100g of each milk protein concentrate solution into three 250mL conical flasks, plug the corresponding rubber stoppers, cover with newspaper, and tie them with rubber bands to make three parallel milk protein concentrate solution samples. use.

Set the parameters of the experimental high-temperature and high-pressure sterilizer to 130°C and 12 minutes, and the model of the high-temperature and high-pressure sterilizer is: STURDYsa-300vl. The milk protein concentrate solution sample was treated in a high temperature and high pressure sterilizer at 130°C for 12 minutes. When the high temperature and high pressure sterilizer is cooled below 90°C, the samples are taken out for observation, and the protein thermal stability of the milk protein concentrate sample is tested. The test standards are shown in Table 1, and the test results are shown in Table 8.

When dairy products are used as raw materials for UHT treatment during processing, the protein in them is volatile and forms precipitates, which gradually accumulate and adhere to the heating surface of the sterilization equipment to form scaling. The pressure in the sterilization equipment system will increase with the scaling degree of the heating surface When the pressure in the system rises to a certain level, it indicates that the scaling rate of the heating surface of the sterilization equipment is high, which affects the heat transfer during the sterilization process, thereby affecting the sterilization effect of the product. At this time, it is necessary to Perform intermediate cleaning (AIC) on the sterilizing equipment. Therefore, the continuous running time of sterilization equipment is directly related to the protein thermal stability of dairy products. In actual production, the thermal stability of protein in dairy products can be judged by measuring the continuous running time of sterilization equipment.

Put the above four brands of concentrated milk protein into the production of milk tea with a protein content of 0.8%. The ultra-high temperature sterilization equipment continuously sterilizes at 138°C for 4s. When the steam proportional valve is fully opened, the sterilization temperature cannot reach At 138°C, record the continuous operation time of the ultra-high temperature sterilization equipment, and the results are shown in Table 9.

Table 8 Protein thermal stability test results of milk protein concentrate

Table 9 Continuous operation time of ultra-high temperature sterilization equipment

From the above test results, it can be seen that when the milk protein concentrate (brand M) with excellent protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can run continuously for 9.91 hours;

When the milk protein concentrate (brand N) with general protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can run continuously for 7.09 hours;

When the milk protein concentrate (brand O) with poor protein thermal stability detected by the detection method provided by the present invention is produced, the ultra-high temperature sterilization equipment can run continuously for 5.14 hours;

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

It can be seen that the protein thermal stability detected by the detection method provided by the present invention is correlated with the continuous operation time of the ultra-high temperature sterilization equipment. When using milk protein concentrate with excellent protein thermal stability for production, the ultra-high temperature sterilization The equipment can run continuously for a long time; when using milk protein concentrate with poor protein thermal stability for production, the ultra-high temperature sterilization equipment can run continuously for a short time, indicating that the detection method provided by the invention can accurately detect the protein heat stability of milk protein concentrate sex.

The preparation of embodiment 9 reconstituted milk

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

The preparation of embodiment 10 milk tea

Take skimmed milk powder (brand E) with excellent protein thermal stability detected in Example 6, mix it with conventional auxiliary materials, and sterilize it at 137°C for 30s to prepare milk tea with a protein content of 0.8%.

The preparation of embodiment 11 containing coffee with milk

Take the condensed milk (Brand I) with excellent protein thermal stability detected in Example 7, mix it with conventional auxiliary materials, and sterilize it at 140°C for 4s to prepare coffee with milk with a protein content of 1.1%.

The preparation of embodiment 12 milk tea

Take the milk protein concentrate (brand M) with excellent protein thermal stability detected in Example 8, mix it with conventional auxiliary materials, and sterilize it at 139°C for 10s to prepare milk tea with a protein content of 0.8%.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (6)

1. a detection method of protein thermostability in dairy products, is characterized in that, comprises the steps: Step A: mixing the dairy product with water to obtain a first sample solution; Step B: the first sample solution is treated at 100°C to 135°C for 10min to 40min to obtain a second sample solution; Detecting the second sample solution, and judging the thermal stability of the protein in the dairy product according to the homogeneity of the second sample solution; From the second sample solution without stratification, precipitation, and agglomeration, to slight wall hanging and small granular coagulation visible to the naked eye suspended in it, to serious wall hanging and flocculation, to the appearance of Severe hanging on the wall, and tofu flower-like agglomeration, which in turn indicates that the thermal stability of the protein is getting worse; The mass percentage of protein in the first sample solution is 4%-7%. 2. The detection method according to claim 1, wherein the dairy product is selected from whole milk powder, skimmed milk powder, condensed milk or milk protein concentrate. 3. The detection method according to claim 1, characterized in that, before step A, the step of detecting the protein content of the dairy product is also included. 4. The detection method according to claim 1, characterized in that, a hydration step is also included between step A and step B. 5. The detection method according to claim 4, characterized in that the hydration is stirring under the condition of 300rpm-700rpm. 6. The detection method according to claim 4, characterized in that, the hydration time is 8 minutes to 20 minutes.