Cooling method for freezing without unfreezing shrinkage before dead meat after slaughtering

Abstract

The invention discloses a cooling method for freezing meat after slaughtering before dead meat without causing unfreezing shrinkage, and belongs to the field of meat freezing treatment. The cooling method comprises the following steps: quickly cooling the slaughtered and dead meat to a central temperature of-3 to-10 DEG C, and then quickly transferring the meat to a storage environment of-2 to 2 DEG C for storage. According to the method, the meat product is subjected to instant point freezing treatment before being stiffened, and the temperature is rapidly reduced, so that microbial pollution can be reduced, the shelf life of the meat can be prolonged, and the cooling and drying loss can be remarkably reduced. After point freezing reaches the target temperature, the beef is quickly transferred to an environment of-2 to 2 DEG C for low-temperature storage, and the treatment mode avoids the risks of freezing shrinkage and unfreezing shrinkage, meanwhile, the meat can keep good tenderness, the production efficiency is improved, the shelf life of the beef is prolonged, and meanwhile, the economic benefits of the beef cattle industry are improved.

Description

Technical Field

[0001] The invention relates to the field of meat freezing treatment, in particular to a cooling method for "spot freezing" of meat before rigor mortis after slaughter without inducing thawing and shrinkage. Background Art

[0002] According to the theory of the transformation of animal muscle into edible meat after slaughter, the carcass / meat needs to be slowly cooled to 0-4℃ to produce tender meat, but this process often takes 24-48 hours or even longer to complete. Long-term cooling not only consumes a lot of energy, but also causes 1-2% or even higher quality loss due to the evaporation of water on the surface of the carcass / meat. A slaughterhouse that slaughters 100 cows a day will lose 1-2 cows a day, causing an economic loss of about 20,000 to 30,000 yuan. Therefore, how to reduce cooling dry loss and improve production efficiency has always been a key issue that the meat industry needs to solve.

[0003] Many people try to cool down the meat quickly after slaughter, but too fast a cooling rate, such as when the pH is greater than 6.0 and the temperature is lower than 12°C, will cause the muscle to contract violently, which is often called "cold contraction" because there is still energy available for contraction in the muscle. If beef is frozen when the pH is greater than 6.0, the muscle will contract more violently than "cold contraction" during the thawing process due to the destruction of muscle cells by the freeze-thaw process, which leads to the release of a large amount of sarcoplasmic reticulum calcium ions, i.e. "thaw contraction". In recent years, some scholars have developed a very fast chilling (VFC) method, which is to quickly reduce the core temperature of the muscle to 0°C or -1°C within 5 hours after slaughter (before rigor mortis). This cooling method meets the definition of cold contraction, but no contraction occurs. Many scholars have explained that this is because a faster cooling rate can form a frozen layer on the surface of the muscle, which in turn produces an ice shell binding effect on the internal meat, limiting the contraction of the internal meat. However, there is still a risk of thawing contraction in the subsequent thawing process of meat after ultra-fast cooling. This disadvantage also limits its industrial application to a certain extent. Summary of the invention

[0004] The purpose of the present invention is to provide a cooling method for meat products that can be "spot-frozen" before rigor mortis after slaughter without causing thawing shrinkage, so as to solve the problems existing in the above-mentioned prior art. The cooling method of the present invention avoids the risks of freezing shrinkage and thawing shrinkage, and can keep the meat products tender, improve production efficiency, extend the shelf life of beef, and improve the economic benefits of the beef cattle industry while ensuring the quality of meat products.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a cooling method for "spot freezing" of meat before rigor mortis after slaughter without inducing thawing shrinkage, comprising the steps of rapidly cooling the meat before rigor mortis after slaughter to a central temperature of -3°C to -10°C, and then rapidly transferring the meat to a storage environment at -2-2°C for storage.

[0007] Furthermore, the pH of the meat before rigor mortis is greater than 6.0, and the temperature is greater than 28°C.

[0008] Furthermore, the rapid cooling time is within 0 to 4 hours.

[0009] Furthermore, the central temperature is -7°C to -10°C.

[0010] Furthermore, the storage is vacuum storage.

[0011] Furthermore, the meat product includes beef.

[0012] The present invention discloses the following technical effects:

[0013] The invention adopts a "spot freezing" method to freeze the beef to -3 to -10°C before rigor mortis (pH greater than 6.0) on the basis of ultra-fast cooling, and then quickly transfers the beef to a -2-2°C environment for low-temperature storage. During the subsequent thawing (-2-2°C) and subsequent low-temperature storage (-2-2°C), no obvious muscle contraction is caused, and the tenderness of the muscle is greatly improved.

[0014] The present invention performs a "spot freezing" treatment on meat products before rigor mortis. By rapidly lowering the temperature, it can not only reduce microbial contamination and extend the shelf life of meat, but also significantly reduce cooling dry consumption. After the "spot freezing" reaches the target temperature, it is quickly transferred to a -2-2°C environment for low-temperature storage. This treatment method avoids the risks of freezing shrinkage and thawing shrinkage, while enabling the meat to maintain good tenderness, which is a challenge to the classic "thawing shrinkage" theory. Utilizing the cooling method of the present invention, there is no need to perform conventional cooling and acid removal treatment on the slaughtered cattle carcasses, which can save energy and dry consumption in the process of acid removal and cooling (24-48 hours), improve production efficiency, and at the same time does not affect the edible qualities of beef such as tenderness, extend the shelf life of beef, and improve the economic benefits of the beef cattle industry while ensuring the quality of meat. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 The temperature changes of beef in each group from 0.5h to 48h after slaughter, where ao means the difference reached a significant level (P<0.05);

[0017] Figure 2 The pH value changes of beef in each group from 0.5h to 48h after slaughter, where ai means the difference reached a significant level (P<0.05);

[0018] Figure 3 is the myometre length of beef in each treatment group 48 hours after slaughter, where ac means the difference reaches a significant level (P<0.05);

[0019] Figure 4 The shear force values ​​of beef in each treatment group at different storage times after slaughter, where ah means the difference reached a significant level (P<0.05);

[0020] Figure 1 to Figure 4 In the data, VFC-Ⅰ~Ⅳ represent the treatment groups in which the core temperature of beef was reduced to 12℃, -3℃, -7℃ and -10℃ after "spot freezing" before rigor mortis after slaughter, respectively; Control represents the control group with conventional cooling after hot slaughter. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0023] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0024] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0025] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0026] Example

[0027] 1. Grouping and processing

[0028] The longissimus dorsi muscle of hybrid cattle (Luxi Yellow Cattle × Simmental Cattle, 20-24 months old) slaughtered in a commercial slaughterhouse was taken, and each longissimus dorsi muscle was cut into 5 cm thick steaks. Randomly divided into 5 groups, VFC-Ⅰ~Ⅳ were pre-rigidity "spot freezing" treatment groups, and Control was a control group with conventional cooling after hot culling. Ensure that the pH of each group of meat is >6.0 and the temperature is >28℃ before freezing, that is, each group of meat is pre-rigidity meat.

[0029] The steaks in the pre-rigor "spot-frozen" treatment group were packaged and immersed in a cooling liquid (55% (v / v) propylene glycol) in a -30°C cold storage, so that they reached different core temperatures (12, -3, -7 and -10°C) within 3 hours, achieving the effect of rapid cooling before rigor mortis. When each treatment group reached the target core temperature, it was quickly transferred to a storage environment of -2-2°C and stored in a vacuum package. The control group used conventional cooling methods to slowly cool the beef to -2-2°C.

[0030] 2. Verify the core temperature and pH drop rate of beef in the early period after slaughter (24h)

[0031] Starting from 0.5 h after slaughter, the core temperature of the longissimus dorsi muscle was measured with a Testo 105 insertion thermometer every 10 min until 5 h after slaughter, and then the core temperature of the muscle was measured at 10 h, 24 h, and 48 h after slaughter. The probe was inserted to a depth of about 2.5 cm, and the temperature was measured three times in succession to take the average value.

[0032] The pH values ​​of samples at 0.5 h after slaughter and during storage (10-48 h after slaughter) were measured using a SenvenGo portable pH meter. Three points were measured for each beef sample and the average value was taken. The pH value of samples in the early period after slaughter (3, 10 and 24 h) was measured as follows: liquid nitrogen frozen samples (2.0 g) were taken, 20 mL of pre-cooled homogenization buffer (5 mmol / L sodium iodoacetate, 150 mmol / L potassium chloride, pH = 7.0) were added, and homogenized at 1000 rpm for 30 s. Subsequently, the homogenate was measured three times continuously using a SevenCompact desktop pH meter and the average value was taken. Before each measurement, the probe of the above pH meter was calibrated with buffer (pH = 7.00 and pH = 4.00).

[0033] The core temperature and pH value of beef within 48 hours after slaughter are as follows: Figure 1-Figure 2 As shown. Figure 1 It can be seen that the core temperature of beef in the "spot freezing" treatment group before rigor mortis after slaughter dropped faster than that in the control group, and the core temperature of beef in the "spot freezing" treatment group was able to drop to different target temperatures within 4 hours after slaughter.

[0034] The pH difference between the treatment groups was not significant at the beginning of post-slaughter (0.5h), but the difference gradually became significant as the time after slaughter increased. It can also be seen in the figure that "spot freezing" cooling slowed down the rate of pH decline in post-slaughter muscles, and at 48h after slaughter, the pH value difference of muscles basically disappeared.

[0035] 3. Verify the sarcomere length of the sample that has been "spot-frozen" and cooled to the target temperature and then thawed and stored at 0-4°C until 48 hours after slaughter. The method for determining the sarcomere length is as follows:

[0036] Weigh 2.0 g of beef samples from each group 48 hours after slaughter, cut them into pieces and place them in a beaker containing 18 mL of sucrose solution (0-4 ° C, 0.25 mol / L), and homogenize them at a low speed (6000 r / min, 1 min). The suspension was aspirated to make a slide, and the slide was observed using an Olympus BX41 biological microscope. The clear myometrium images in the field of view after magnification 1000 times were selected for photography. Five parallel samples (slides) were taken for each sample, and 30 photos were selected for each slide for subsequent analysis. The myometrium length was measured using Image-Pro Plus version 6.0 software, and the average value of the measurement results was the myometrium length of the sample.

[0037] The results are as follows Figure 3 As shown by Figure 3 It can be seen that the length of the myometrium in each treatment group before post-mortem rigor mortis was longer than 1.5 μm, and no cold shrinkage or thawing shrinkage occurred. It is generally believed that when the myometrium length is shorter than 1.5 μm, it is cold shrinkage, and the tenderness of the meat will be significantly reduced.

[0038] 4. Verify the shear force value of the sample that was "spot-frozen" and cooled to the target temperature and then thawed and stored at -2-2℃ for 14 days

[0039] The shear force value is determined as follows:

[0040] The steak was placed in a vacuum packaging bag and heated in a water bath (80°C) until the core temperature reached 70°C before being taken out. After being refrigerated (0-4°C) overnight, the steak was taken out and the cooking loss was first measured. Then, a hollow sampler (1.27 cm in diameter) was used to sample along the muscle fiber direction (pay attention to avoid tendons and fat; n=6). The shear force value of the selected beef meat column was measured using the HDP / BSW probe of the texture analyzer (TA-XT2i, Stable Micro System). The measurement conditions were controlled by Texture ExpertⅤ1.0 software, and the average value of 6 meat columns was taken as the shear force value of the steak.

[0041] The results are as follows Figure 4 As shown by Figure 4 It can be seen that after the "point freezing" treatment with different cooling center temperatures, there are certain differences in the initial shear force value of beef. Among them, the initial tenderness of the "point freezing" treatment group with the center temperature dropped to -7°C is the best. With the extension of storage time, the tenderness of each treatment is improved. The muscle tenderness of the "point freezing" treatment group with the center temperature dropped to -7 and -10°C at 14 days after slaughter is the best. This result shows that thawing and storing samples cooled to the target temperature at -2-2°C until cooling can not only effectively improve the tenderness of the initial beef, but also has good tenderization potential during the maturation period.

[0042] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A cooling method for "spot freezing" of meat before rigor mortis after slaughter without causing thawing and shrinkage, characterized in that: The method comprises the steps of rapidly cooling the meat after slaughter and before rigor mortis to a core temperature of -3°C to -10°C, and then rapidly transferring the meat to a storage environment at -2-2°C for storage.

2. The cooling method according to claim 1, characterized in that: The pH of the meat before rigor mortis is >6.0 and the temperature is >28°C.

3. The cooling method according to claim 1, characterized in that: The rapid cooling time is within 0 to 4 hours.

4. The cooling method according to claim 1, characterized in that: The core temperature is -7°C to -10°C.

5. The cooling method according to claim 1, characterized in that: The storage is vacuum storage.

6. The cooling method according to claim 1, characterized in that: The meat product includes beef.

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