A cooling agent and its application, and food freezing method

Abstract

The present invention discloses a refrigerant and its application, and a food freezing method. The refrigerant comprises, by mass percentage, 16% to 37% of amino acids, 10.5% to 15% of sodium chloride, and the remainder comprises water. The present invention provides the application of the above-mentioned refrigerant in food freezing. The food freezing method provided by the present invention comprises: preparing the refrigerant described in the above-mentioned technical solution, immersing the food to be frozen in the refrigerant for freezing, and the solid-liquid mass ratio of the food to be frozen to the refrigerant is 1:6 to 1:20. The refrigerant provided by the present invention can significantly reduce the freezing time and freezing energy consumption of food when used for immersion freezing. The amino acids used can not only lower the freezing point, but also improve the quality or water retention properties of meat products; the infiltration of amino acids and sodium chloride into meat products together can not only realize the integrated freezing and pickling of meat products and reduce the processing procedures, but also increase the product yield and improve the nutritional quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of refrigerants, and in particular relates to a refrigerant and its application, and a food freezing method. Background Art

[0002] Freezing is a crucial preservation technique in the meat industry. It inhibits the growth and reproduction of microorganisms, reduces enzyme activity, and delays the oxidative degradation of lipids and proteins, thereby extending the shelf life of products. The meat industry typically uses temperatures below -18°C for frozen storage. Additionally, some meat products are also partially frozen at temperatures above -10°C.

[0003] Traditional freezing technologies such as air freezing and plate freezing have low freezing efficiency and poor freezing uniformity, which will cause large and unevenly distributed ice crystals to form in meat products, leading to damage to the tissue structure of meat products and protein denaturation, greatly reducing the food quality and processing performance such as product texture and flavor. Immersion freezing is a method that utilizes the efficient thermal conductivity of a liquid medium to immerse the sample directly in a liquid refrigerant for heat exchange, so that the sample is quickly frozen. Rapid freezing can produce smaller and more evenly distributed ice crystals during the freezing process of meat products, reduce the damage of ice crystals to the tissue structure of meat products, and achieve high-quality preservation of the product. The refrigerant, as the heat conduction medium for immersion freezing, is a key component of this freezing method. The appropriate components and ratios of the refrigerant are crucial for freezing equipment and frozen samples.

[0004] Current refrigerants primarily use high-purity alcohols such as ethanol, ethylene glycol, and propylene glycol as a means of lowering the freezing point. These are highly volatile and flammable, posing significant safety risks. Furthermore, alcohols like ethylene glycol are slightly toxic, making them unsuitable for long-term immersion of food.

[0005] Some refrigerants lower the freezing point by adding sugars such as fructose, xylitol, and trehalose. However, these sugars usually need to be added in higher concentrations to produce the effect of lowering the freezing point. The resulting high viscosity may not only affect the preservation and flavor of food, but also have an adverse effect on the performance and life of the refrigeration equipment.

[0006] During use, refrigerants containing calcium chloride can easily cause calcium carbonate precipitation on the surface of the equipment, forming scale, thereby reducing the heat exchange efficiency of the refrigeration system.

[0007] Some brine agents are optimized by adding proteins with specific properties. However, these proteins present challenges in extraction purity and yield, leading to high costs. Many existing brine agents have complex compositions, complicated preparation processes, and are difficult to control.

[0008] Acids, alkalis, esters and other components in the refrigerant cannot come into direct contact with food and can only be used for packaged food. If the food packaging is not sealed enough or is damaged, quality problems or even safety problems will arise. Summary of the Invention

[0009] One of the objectives of the present invention is to provide a refrigerant that utilizes sodium chloride and amino acids to synergistically lower the freezing point. That is, the solubilizing effect of sodium chloride on amino acids is utilized to form a large number of hydrogen bonds between amino acids and water molecules, thereby forming a supramolecular network structure in the solution system, blocking the molecular movement and redirection of free water in the system, inhibiting the formation of ice nuclei, and thereby lowering the freezing point of the solution.

[0010] A second object of the present invention is to provide the use of the above-mentioned coolant in food freezing.

[0011] A third object of the present invention is to provide a food freezing method using the refrigerant of the above technical solution.

[0012] In order to solve all or part of the above technical problems, the present invention provides the following technical solutions:

[0013] The invention provides a cooling agent. Calculated by mass percentage, the cooling agent comprises 16% to 37% of amino acid, 10.5% to 15% of sodium chloride, and the remainder comprises water.

[0014] The present invention provides application of the above-mentioned coolant in freezing food.

[0015] The present invention also provides a food freezing method, comprising: preparing the coolant described in the above technical solution; immersing pre-packaged or unpackaged food to be frozen in the coolant for freezing, wherein the solid-liquid mass ratio of the food to be frozen to the coolant is 1:6 to 1:20.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] (1) The coolant provided by the present invention utilizes the solubilizing effect of sodium chloride at the above concentration on amino acids, so that a large number of hydrogen bonds are formed between the amino acids at the above concentration and water molecules, so that the solution system forms a supramolecular network structure, which blocks the molecular movement and reorientation of free water in the system, inhibits the formation of ice nuclei, and thus synergistically lowers the freezing point of the coolant;

[0018] (2) The present invention provides three preferred amino acids, which have a relatively excellent synergistic freezing point lowering effect with sodium chloride;

[0019] (3) The coolant provided by the present invention has a simple composition, is easy to control, has low cost, and has good industrial and commercial value. It does not require the addition of traditional freezing point depressing substances such as alcohols, thus solving the potential safety hazards such as volatility, flammability, and explosion caused by alcohols. It does not require the addition of substances such as acids, alkalis, and ethers, is non-toxic, and can directly contact food.

[0020] (4) The coolant provided by the present invention can significantly reduce the freezing time and freezing energy consumption of food when used for immersion freezing. The amino acids used can not only lower the freezing point, but also improve the quality or water retention properties of meat products. The infiltration of amino acids and sodium chloride into meat products can not only realize the integrated freezing and marinating of meat products, reduce the processing procedures, but also increase the product yield and improve the nutritional quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a cooling curve when the longissimus dorsi muscle of pig is frozen according to the food freezing method of Examples 33 and 34 and Comparative Example 16.

[0023] Figure 2 It is the freezing time required for freezing the longissimus dorsi muscle of pig according to the food freezing method of Examples 33, 34 and Comparative Example 16.

[0024] Figure 3 It is the freezing energy consumption required for freezing the longissimus dorsi muscle of pig according to the food freezing method of Examples 33, 34 and Comparative Example 16. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solution of the present invention. The specific functional details disclosed herein should not be interpreted as limiting.

[0026] The invention provides a cooling agent. Calculated by mass percentage, the cooling agent comprises 16% to 37% of amino acid, 10.5% to 15% of sodium chloride, and the remainder comprises water.

[0027] In some embodiments, the coolant comprises the following components: 16% to 37% amino acid, 10.5% to 15% sodium chloride, and the remainder water.

[0028] In some embodiments, the amino acids include one or more of glycine, L-lysine, and L-proline.

[0029] According to the temperature requirements of different frozen storage methods of food, the inventors further designed coolants suitable for different temperature ranges.

[0030] In some embodiments, when the coolant is suitable for temperatures above -20°C, its components include 16% to 25% amino acids, 10.5% to 15% sodium chloride, and the rest include water; when the coolant is suitable for temperatures between -20°C and -30°C, its components include 24% to 30% amino acids, 11.5% to 15% sodium chloride, and the rest include water; when the coolant is suitable for temperatures between -30°C and -40°C, its components include 30% to 37% amino acids, 11.5% to 15% sodium chloride, and the rest include water.

[0031] In some embodiments, the coolant is suitable for temperatures above -20°C, and its components include 16% to 20% glycine, 10.5% to 14.5% sodium chloride, and the remainder is water; alternatively, the coolant includes 17% to 24% L-lysine, 11.5% to 15% sodium chloride, and the remainder is water; alternatively, the coolant includes 21% to 25% L-proline, 11.5% to 15% sodium chloride, and the remainder is water.

[0032] In some embodiments, the coolant is suitable for temperatures between -20°C and -30°C, and its components include 24% to 30% L-lysine, 11.5% to 15% sodium chloride, and the remainder is water; or, the coolant includes 25% to 30% L-proline, 11.5% to 15% sodium chloride, and the remainder is water.

[0033] In some embodiments, the coolant is suitable for temperatures between -30°C and -40°C, and its components include 30% to 37% L-lysine, 11.5% to 15% sodium chloride, and the remainder is water; or, the coolant includes 30% to 35% L-proline, 11.5% to 15% sodium chloride, and the remainder is water.

[0034] In some embodiments, the coolant components are all food grade.

[0035] The present invention provides the use of the coolant in the above technical solution in freezing food.

[0036] The present invention also provides a food freezing method, comprising: preparing the coolant described in the above technical solution; immersing pre-packaged or unpackaged food to be frozen in the coolant for freezing, wherein the solid-liquid mass ratio of the food to be frozen to the coolant is 1:6 to 1:20.

[0037] In some embodiments, the pre-packaged food is skin packaging or vacuum packaging, and the food includes but is not limited to fresh meat and meat products, fresh aquatic products and aquatic products, fruits and vegetables, etc.

[0038] In some embodiments, when the working temperature is above -20°C, the coolant includes 16% to 25% amino acids, 10.5% to 15% sodium chloride, and the balance is water; when the working temperature is -20°C to -30°C, the coolant includes 24% to 30% amino acids, 11.5% to 15% sodium chloride, and the balance is water; when the working temperature is -30°C to -40°C, the coolant includes 30% to 37% amino acids, 11.5% to 15% sodium chloride, and the balance is water.

[0039] In some embodiments, specifically: when the operating temperature is above -20°C, the coolant includes 16% to 20% glycine, 10.5% to 14.5% sodium chloride and the balance is water; or, the coolant includes 17% to 24% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; or, the coolant includes 21% to 25% L-proline, 11.5% to 15% sodium chloride, and the balance is water; when the operating temperature is -20°C to -30°C, the coolant includes 16% to 20% glycine, 10.5% to 14.5% sodium chloride and the balance is water; The coolant comprises 24% to 30% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; or, the coolant comprises 25% to 30% L-proline, 11.5% to 15% sodium chloride, and the balance is water; when the operating temperature is -30°C to -40°C, the coolant comprises 30% to 37% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; or, the coolant comprises 30% to 35% L-proline, 11.5% to 15% sodium chloride, and the balance is water.

[0040] The experimental materials used in the examples provided by the present invention are as follows. Unless otherwise specified, they can all be purchased from conventional biochemical reagent companies.

[0041] Sodium chloride, CAS number: 7647-14-5, food grade, was purchased from Zhejiang Yinuo Biotechnology Co., Ltd.;

[0042] Glycine, CAS number: 56-40-6, food grade, purchased from Zhejiang Yinuo Biotechnology Co., Ltd.;

[0043] L-lysine, CAS number: 56-87-1, food grade, purchased from Zhejiang Yinuo Biotechnology Co., Ltd.;

[0044] L-Proline, CAS number: 147-85-3, food grade, purchased from Zhejiang Yinuo Biotechnology Co., Ltd.;

[0045] L-Alanine, CAS number: 56-41-7, food grade, purchased from Zhejiang Yinuo Biotechnology Co., Ltd.;

[0046] Histidine, CAS number: 71-00-1, food grade, was purchased from Zhejiang Yinuo Biotechnology Co., Ltd.;

[0047] L-cysteine, CAS number: 52-90-4, food grade, was purchased from Zhejiang Yinuo Biotechnology Co., Ltd.

[0048] Example 1:

[0049] The coolant provided in Example 1 is composed of 18.75% glycine, 14.1% sodium chloride, and the balance water.

[0050] Freezing point test: 10 ml of the prepared coolant was added to a 20 ml glass test tube. A thermocouple for temperature data acquisition was placed at the geometric center of the test tube and secured with a stopper. The test tube was then placed in a refrigerator and frozen. Temperature data was collected every 5 seconds to obtain a freezing time-temperature curve for the coolant. The freezing points of the coolants are shown in Table 1.

[0051] Examples 2 to 32:

[0052] The only difference between Examples 2 to 32 and Example 1 is that the amino acid species and mass concentrations used in Examples 2 to 32 are different, as is the mass concentration of sodium chloride. The coolant compositions and freezing point test results of Examples 2 to 32 are shown in Table 1.

[0053] Comparative Examples 1 to 15:

[0054] The only difference between Comparative Examples 1 to 15 and Example 1 is that the amino acid types and mass concentrations used in Comparative Examples 1 to 15 are different, and the mass concentration of sodium chloride is different. The compositions and freezing point test results of Comparative Examples 1 to 15 are shown in Table 1.

[0055]

[0056]

[0057] Note: The measured freezing points in the table represent the actual freezing points of the refrigerants in each Example and Comparative Example. The freezing points of the amino acid solutions represent the actual freezing points of amino acid solutions of the same mass concentration in the same group. The freezing points of the sodium chloride solutions represent the actual freezing points of sodium chloride solutions of the same mass concentration in the same group. "Not Detected" indicates that the solute in this group was difficult to dissolve and freezing point testing was not performed. "" indicates that freezing point testing was not performed for this group.

[0058] Table 1 shows the freezing points of the coolants prepared in Examples 1-32 and Comparative Examples 1-15. The results in Table 1 are analyzed below:

[0059] (1) As can be seen from Table 1, the freezing point of Example 1 is -19.5°C. Further addition of glycine will make the solution difficult to dissolve. Therefore, the refrigerant with glycine and sodium chloride as the main components is suitable for samples stored in a slightly frozen state, that is, suitable for operating temperatures above -20°C.

[0060] (2) From Examples 2-18 and 19-30, it can be seen that the addition of L-lysine or L-proline can synergize with sodium chloride to significantly reduce the freezing point of the coolant, and this synergistic effect shows a dose-effect effect, which can increase with the increase in the amount of the two amino acids added. L-lysine and L-proline in the solution can form a large number of hydrogen bonds with water molecules, and the solution system forms a supramolecular network structure, which blocks the molecular movement and reorientation of free water in the solution, inhibits the formation of ice nuclei, and thus reduces the freezing point of the solution. The presence of sodium chloride promotes the solubility of L-lysine and L-proline in water, so that the freezing point of the system is synergistically reduced. Therefore, the coolant with L-lysine, L-proline and sodium chloride as the main components is suitable for working temperatures below -20°C, especially working temperatures of -20°C to -40°C. According to Examples 31 and 32, the freezing point of the coolant compounded with L-lysine and L-proline is basically the same as that of the corresponding coolant with the same mass concentration of a single amino acid. It can be seen that the amino acids provided by the present invention have substantially the same effects when used alone or in combination.

[0061] (3) The freezing points of the coolants described in Comparative Examples 1, 3, and 5 are all above -13.6°C. Since further addition of the same amino acids in each comparative example will make them difficult to dissolve, it is difficult to further lower their freezing points. Therefore, the coolants described in Comparative Examples 1, 3, and 5 are not suitable for use in immersion freezing. The solubility of amino acids is closely related to their side chain groups. At the same temperature, the solubility of glycine, L-alanine, histidine, and L-cysteine ​​in water is much lower than that of L-lysine or L-proline. Therefore, glycine, L-alanine, histidine, and L-cysteine ​​have limited ability to form hydrogen bonds with water and cannot significantly lower the freezing point of the solution. That is, the glycine, L-lysine, and L-proline provided by the present invention are the three more preferred amino acids suitable for immersion freezing of food.

[0062] (4) Comparative Examples 7-15 show that low concentrations of amino acids and sodium chloride do not synergistically lower the freezing point. That is, within the concentration ranges provided by the present invention, the amino acids and sodium chloride produce a synergistic effect.

[0063] Example 33:

[0064] This embodiment provides a food freezing method, comprising:

[0065] Prepare the coolant described in Example 25 by dissolving 14.10% by mass of sodium chloride in water. After complete dissolution, add 23.03% by mass of L-proline to completely dissolve the mixture.

[0066] The coolant described in Example 25 was added to a freezer, and the refrigeration unit was turned on to reduce the temperature of the coolant to -18°C. Then, the pig longissimus dorsi muscle (thickness 2 cm, weight 100±1 g) treated with skin packaging (0.05 mm thick PE film) was immersed in the coolant (solid-liquid mass ratio of 1:20) and frozen until the center temperature of the sample reached -17°C. After freezing, the sample was stored in a -20°C refrigerator.

[0067] Example 34:

[0068] This embodiment provides a food freezing method, comprising:

[0069] The coolant described in Example 25 was prepared by dissolving 14.10% by mass of sodium chloride in water. After the sodium chloride was completely dissolved, 23.03% by mass of L-proline was added to completely dissolve the sodium chloride.

[0070] The coolant described in Example 25 was added to a freezer, and the refrigeration unit was turned on to reduce the temperature of the coolant to -18°C. Unpackaged pig longissimus dorsi muscle (thickness 2 cm, weight 100±1 g) was then immersed in the coolant (solid-liquid mass ratio of 1:20) for freezing. The freezing was completed until the center temperature of the sample reached -17°C. After freezing, the sample was stored in a -20°C refrigerator.

[0071] Comparative Example 16:

[0072] The only difference from Example 33 is that no refrigerant is used, and the pig longissimus dorsi muscle (thickness 2 cm, weight 100±1 g) is air-frozen.

[0073] To verify the effectiveness of the food freezing method provided by the present invention in reducing freezing time and freezing energy consumption, cooling curve tests, freezing time tests, and power consumption tests were conducted on Example 33, Example 34, and Comparative Example 16. The measurement methods and results are described in detail below.

[0074] (1) Cooling curve measurement method:

[0075] Before freezing the longissimus dorsi muscles of the pigs in Example 33, Example 34 and Comparative Example 16, a thermocouple for detecting temperature was inserted into the geometric center of the sample, and temperature data was collected every 5 seconds to obtain the cooling curves of the longissimus dorsi muscles of the pigs in Example 33, Example 34 and Comparative Example 16. The results are shown in FIG. Figure 1 shown.

[0076] (2) Freezing time determination method:

[0077] The total freezing time of the longissimus dorsi muscle of the pig in Example 33, Example 34 and Comparative Example 16 is the time required for the sample to cool from the initial temperature (7°C) to -17°C; the freezing phase transition time of the longissimus dorsi muscle of the pig in Example 33, Example 34 and Comparative Example 16 is the time required for the sample to cool from -1°C to -7°C. Figure 2 shown.

[0078] (3) Method for measuring power consumption during cooling process:

[0079] Before freezing, the electric energy meter was connected to the freezing equipment. The power consumption of the longissimus dorsi muscle of the pig in Example 33, Example 34 and Comparative Example 16 was the value change of the electric energy meter during the process of the sample dropping from the initial temperature (7°C) to -17°C. The results are as follows: Figure 3 shown.

[0080] Combine Figure 1-3 As can be seen, the high thermal conductivity of the refrigerant described in Example 25 significantly reduces the total freezing time and freezing phase transition time in Examples 33 and 34 compared to Comparative Example 16, further reducing power consumption. Furthermore, the high thermal conductivity of the refrigerant described in Example 25 can weaken the heat-blocking effect of the 0.05 mm thick PE film, resulting in no significant difference in the total freezing time, freezing phase transition time, or power consumption between Examples 33 and 34. This means that the refrigerant described in the present invention, when used for immersion freezing, can significantly reduce the freezing time and freezing energy consumption of meat products, greatly improving product production efficiency.

[0081] In order to verify the effect of the coolant provided by the present invention on improving food quality and its water retention performance, the present invention conducted texture measurement, water retention capacity (WHC) measurement, freeze-thaw loss measurement, protein loss rate measurement, and moisture retention rate measurement on the longissimus dorsi muscle of the pig in Examples 33, 34, and Comparative Example 16, and measured the sodium chloride content and amino acid content in the samples. The measurement methods and results are described in detail below.

[0082] (1) Texture Measurement Method: The longissimus dorsi muscles of the pigs from Example 33, Example 34, and Comparative Example 16 were thawed and cut into 1.5 cm × 1.5 cm × 1.5 cm pieces. The pieces were measured using the TPA mode of the TA-XT plus physical property analyzer. The test parameters were as follows: the probe was a P / 36R stainless steel cylindrical probe, the pre-measurement speed was 2 mm / s, the mid-measurement speed was 1 mm / s, the post-measurement speed was 5 mm / s, the compression ratio was 40%, the trigger type was auto, the time interval between two compression measurements was 5.0 s, and the data collection rate was 400 pps.

[0083] (2) Water-Holding Capacity (WHC) Determination Method: After thawing, weigh 2-3 g of each of the longissimus dorsi muscles from Example 33, Example 34, and Comparative Example 16 and place them in a centrifuge tube (with filter paper at the bottom). Record the weights of the empty centrifuge tube (m0) and the centrifuge tube containing the sample (m1). Centrifuge the tubes in a centrifuge (10,000 g, 4°C, 10 min). Remove the sample from the centrifuge tube and weigh it (m2). WHC is expressed as the ratio of the weight of the remaining sample after centrifugation to the weight of the sample before centrifugation. The calculation formula is as follows:

[0084] WHC (%) = m2 / (m1-m0) × 100

[0085] (3) Freeze-thaw loss determination method: The weight of the longissimus dorsi muscle of the pig before freezing in Example 33, Example 34, and Comparative Example 16 was recorded respectively (m0), and the longissimus dorsi muscle of the pig after freezing was thawed (24 h, 4°C). The exudate on the surface of the thawed sample was wiped dry and weighed (m1). The freeze-thaw loss calculation formula is as follows:

[0086] Freeze-thaw loss (%) = (m0-m1) / m0×100

[0087] (4) Method for determining protein loss rate: The weight of the longissimus dorsi muscle of pigs before freezing in Example 33, Example 34 and Comparative Example 16 was recorded respectively (m0), the longissimus dorsi muscle of pigs after freezing treatment was thawed (24 h, 4°C), the exudate during the thawing process was collected and the volume (v1) was recorded, the volume of the cooling agent after freezing treatment in Example 34 was recorded (v2), and the protein concentration (c1) of the exudate during the thawing process of the longissimus dorsi muscle of pigs in Example 33, Example 34 and Comparative Example 16 and the protein concentration (c2) of the cooling agent after freezing treatment in Example 34 were respectively determined using a BCA protein concentration kit.

[0088] The protein loss rate calculation method of Example 33 and Comparative Example 16 is as follows:

[0089] Protein loss rate (%) = (v1×c1) / m o ×100

[0090] The protein loss rate calculation method of Example 34 is as follows:

[0091] Protein loss rate (%) = (v1×c1+v2×c2) / m 0σ ×100

[0092] (5) Water retention rate determination method: The weight of the longissimus dorsi muscle of the pig in Example 33, Example 34 and Comparative Example 16 before freezing (m0) was recorded respectively, and the longissimus dorsi muscle of the pig after freezing treatment was thawed (24 h, 4°C), and the exudate on the surface of the thawed sample was wiped dry and weighed (m1). The water content (w0) of the longissimus dorsi muscle of the pig in Example 33, Example 34 and Comparative Example 16 after thawing was determined according to the method in the national standard GB 5009.3-2016. The calculation formula of the water retention rate is as follows:

[0093] Moisture retention rate (%) = (m1×w0) / m0×100

[0094] (6) Sodium chloride content determination method: The sodium chloride content of the longissimus dorsi muscle of the pig in Example 33, Example 34 and Comparative Example 16 was determined according to the method in the national standard GB 5009.44-2016.

[0095] (7) L-Proline Assay: After thawing the longissimus dorsi muscle of the pigs in Example 33, Example 34, and Comparative Example 16, 0.5 g of each sample was accurately weighed and placed in a centrifuge tube. 10 ml of a 4% (w / w) 5-sulfosalicylic acid solution was added, and the mixture was ultrasonically treated for 30 min in a dark place and then allowed to stand for 30 min. The centrifuge tube was then placed in a centrifuge and centrifuged for 30 min (10,000 g, 4°C). After centrifugation, 1 ml of the supernatant was filtered through a PES membrane (0.22 μm) and injected into a brown sample bottle for later use. The amino acid content was determined using an automatic amino acid analyzer.

[0096] The texture and WHC test results of the longissimus dorsi muscle of pigs in Example 33, Example 34 and Comparative Example 16 are shown in Table 2 below.

[0097] Table 2 Texture and WHC of pig longissimus dorsi muscle after immersion freezing and air freezing and thawing

[0098]

[0099] Note: Different letters in ab indicate significant differences among different treatment groups for the same index (P<0.05).

[0100] As shown in Table 2, compared with Example 34 and Comparative Example 16, the hardness of the longissimus dorsi muscle of the pig in Example 33 increased significantly, which is beneficial to improving its texture quality. Compared with Example 33 and Comparative Example 16, the WHC of the longissimus dorsi muscle of the pig in Example 34 increased significantly. The L-proline and sodium chloride infused into the longissimus dorsi muscle of the pig in Example 34 can reduce the proportion of free water in the meat product and increase the proportion of bound water and non-mobile water, thereby improving the water retention of the meat product and contributing to the processing characteristics of the meat product. In other words, the application of the coolant of the present invention to immersion freezing can significantly improve the texture quality or water retention of meat products.

[0101] The test results of freeze-thaw loss, protein loss rate, water retention rate, sodium chloride content and L-proline content of the longissimus dorsi muscle of the pig in Example 33, Example 34 and Comparative Example 16 are shown in Table 3.

[0102] Table 3 Freeze-thaw loss, protein loss rate, water retention rate, sodium chloride content and L-proline content of pig longissimus dorsi muscle after immersion freezing and air freezing

[0103]

[0104] Note: Different letters in ac indicate significant differences among different treatment groups for the same index (P<0.05).

[0105] As can be seen from Table 3, the freeze-thaw loss of Example 33 and Example 34 is significantly lower than that of Comparative Example 16, and the freeze-thaw loss reduction effect of Example 34 is the best. The reduction of freeze-thaw loss can increase the yield of product, which is beneficial to the industrial production of food. Due to the high thermal conductivity of the cooling agent described in Example 25, the freezing speed of Example 33 and Example 34 is greatly improved, so that the ice crystal volume formed in the longissimus dorsi muscle of pig during freezing is smaller and evenly distributed, reducing the degree of damage to the longissimus dorsi muscle cell tissue and the degree of denaturation of protein, thereby significantly improving the water retention rate of Example 33 and Example 34, and significantly reducing the protein loss rate, which ultimately shows a significant reduction in freeze-thaw loss. That is, the cooling agent and food freezing method provided by the present invention are applied to immersion freezing and can significantly reduce the freeze-thaw loss and protein loss of meat products, which is beneficial to improving the yield and nutritional quality of products.

[0106] In addition, compared with Example 33, the L-proline and sodium chloride contents in Example 34 were significantly increased. The infiltration of L-proline and sodium chloride not only enables the meat product to achieve integrated freeze-curing, reducing the number of processing steps, but also improves the water retention of the meat product and inhibits the loss of protein in the meat product. As a result, the moisture retention rate of Example 34 is further improved, the protein loss rate is further reduced, and the freeze-thaw loss is further reduced. In other words, the coolant provided by the present invention can directly contact the food, thereby increasing the permeability of amino acids and sodium chloride, achieving integrated freeze-curing of meat products, reducing the number of processing steps, and further improving the yield and nutritional quality of the product, which is conducive to consumers' nutritional needs for high-quality food.

[0107] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and are not intended to limit the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0108] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

Claims

1. A coolant, characterized in that: Calculated by mass percentage, the coolant comprises 16% to 37% of amino acid, 10.5% to 15% of sodium chloride, and the remainder comprises water; Wherein, the amino acids include one or more of glycine, L-lysine and L-proline.

2. The coolant according to claim 1, characterized in that: When the refrigerant is suitable for temperatures above -20°C, its components include 16% to 25% amino acids, 10.5% to 15% sodium chloride, and the rest include water; when the refrigerant is suitable for temperatures between -20°C and -30°C, its components include 24% to 30% amino acids, 11.5% to 15% sodium chloride, and the rest include water; when the refrigerant is suitable for temperatures between -30°C and -40°C, its components include 30% to 37% amino acids, 11.5% to 15% sodium chloride, and the rest include water.

3. The brine according to claim 2, characterized in that: The coolant is suitable for temperatures above -20°C, and its components include 16% to 20% glycine, 10.5% to 14.5% sodium chloride, and the balance is water; alternatively, the coolant includes 17% to 24% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; alternatively, the coolant includes 21% to 25% L-proline, 11.5% to 15% sodium chloride, and the balance is water.

4. The brine according to claim 2, characterized in that: The coolant is suitable for temperatures between -20°C and -30°C, and its components include 24% to 30% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; alternatively, the coolant includes 25% to 30% L-proline, 11.5% to 15% sodium chloride, and the balance is water.

5. The brine according to claim 2, characterized in that: The coolant is suitable for temperatures between -30°C and -40°C, and its components include 30% to 37% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; alternatively, the coolant includes 30% to 35% L-proline, 11.5% to 15% sodium chloride, and the balance is water.

6. Use of the coolant according to any one of claims 1 to 5 in freezing food.

7. A food freezing method, characterized in that: include: Prepare the coolant according to any one of claims 1 to 5; The pre-packaged or unpackaged food to be frozen is immersed in the coolant for freezing, and the solid-liquid mass ratio of the food to be frozen to the coolant is 1:6 to 1:

20.

8. The food freezing method according to claim 7, characterized in that: When the operating temperature is above -20°C, the coolant comprises 16% to 25% amino acid, 10.5% to 15% sodium chloride, and the balance is water; When the operating temperature is -20°C to -30°C, the coolant comprises 24% to 30% amino acid, 11.5% to 15% sodium chloride, and the balance is water; When the operating temperature is -30°C to -40°C, the coolant includes 30% to 37% amino acid, 11.5% to 15% sodium chloride, and the balance is water.

9. A food freezing method according to claim 7, characterized in that: When the operating temperature is above -20°C, the brine comprises 16% to 20% glycine, 10.5% to 14.5% sodium chloride, and the balance is water; alternatively, the brine comprises 17% to 24% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; alternatively, the brine comprises 21% to 25% L-proline, 11.5% to 15% sodium chloride, and the balance is water; When the operating temperature is -20°C to -30°C, the coolant comprises 24% to 30% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; or the coolant comprises 25% to 30% L-proline, 11.5% to 15% sodium chloride, and the balance is water; When the operating temperature is -30°C to -40°C, the coolant includes 30% to 37% L-lysine, 11.5% to 15% sodium chloride, and the balance is water; or, the coolant includes 30% to 35% L-proline, 11.5% to 15% sodium chloride, and the balance is water.

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