A cold storage device and method for the meat cold chain

Abstract

The present invention relates to the technical field of cold chain equipment, and relates to a cold storage device and method for meat cold chain, which includes a box body. A box door is provided on the front side of the box body. Water storage cavities are provided on the top, bottom, left side, right side and rear side of the box body, and the water storage cavities at each place are communicated with each other; A plurality of connecting rods are connected between the top and bottom of the box body. A water storage pipe is arranged inside the connecting rod, and the water storage pipe is communicated with the water storage cavities at the top and bottom of the box body; A notch is provided on the top of the box body, and the notch is communicated with the water storage cavity at the top of the box body. A rubber sheet is hermetically connected to the notch. A convex head is provided on the top of the notch, and a distance sensor is provided on the convex head; The box body is located inside the carriage of a cold chain vehicle, and a refrigeration device is provided on the carriage. The distance sensor is connected and cooperated with the refrigeration device; An appropriate amount of water is stored in the water storage cavity. After the water freezes, the rubber sheet is pushed up, and the distance sensor is used to detect the distance from the rubber sheet to the distance sensor. The present invention can store cold better.

Description

Technical Field

[0001] The present invention relates to the technical field of cold chain equipment, and more specifically, to a cold storage device and method for meat cold chain. Background Art

[0002] The cold chain refers to a special supply chain system in which certain food raw materials, processed foods or semi-finished products, special biological products and medicines, after being purchased, processed and inactivated, are always in the specific low-temperature environment required by the products during the processes of product processing, storage, transportation, distribution, retail and use, reducing losses, preventing pollution and deterioration, so as to ensure food safety, biological safety and drug safety of the products.

[0003] Cold chain trucks are often used in meat transportation. When transferring meat from a cold storage to a cold chain truck, the meat is usually first transferred from the cold storage to a loading platform and then loaded into the cold chain truck bit by bit. If the loading time is relatively long, the meat quality will be affected due to temperature changes. When the meat is loaded into the cold chain truck, the refrigeration equipment of the cold chain truck needs to be frequently used to ensure the low temperature in the carriage. In this way, the frequent use of the refrigeration equipment will reduce its service life. Therefore, a cold storage device and method for meat cold chain are needed to solve the above problems. Summary of the Invention

[0004] The content of the present invention is to provide a cold storage device and method for meat cold chain, which can preferably store cold.

[0005] A cold storage device for meat cold chain according to the present invention includes a box body. A box door is provided on the front side of the box body. Water storage cavities are provided on the top, bottom, left side, right side and rear side of the box body, and the water storage cavities at each place are communicated with each other. A plurality of connecting rods are connected between the top and bottom of the box body. A water storage pipe is arranged inside the connecting rod, and the water storage pipe is communicated with the water storage cavities at the top and bottom of the box body.

[0006] A notch is provided on the top of the box body, and the notch is communicated with the water storage cavity at the top of the box body. A rubber sheet is hermetically connected to the notch. A convex head is provided on the top of the notch, and a distance sensor is provided on the convex head.

[0007] The box body is located inside the carriage of the cold chain truck. A refrigeration device is provided on the carriage, and the distance sensor is connected and cooperated with the refrigeration device.

[0008] An appropriate amount of water is stored in the water storage cavity. After the water freezes, it pushes up the rubber sheet. The distance sensor is used to detect the distance from the rubber sheet to the distance sensor. When the detected distance is greater than a preset threshold, the refrigeration device performs refrigeration until the detected distance is the smallest.

[0009] Preferably, a plurality of rollers are respectively provided on the left side, right side and bottom of the box body, and the rollers can be attached to the corresponding surfaces inside the carriage.

[0010] Preferably, a compartment door is provided at the front side of the compartment, and a first buffer pad is provided on the compartment door; a second buffer pad is provided at the rear side of the compartment door, and the first buffer pad and the second buffer pad sandwich the box body in the middle.

[0011] Preferably, a bottom frame and a top frame are fixedly provided in the notch, a movable frame is provided between the bottom frame and the top frame, and a plurality of fixing devices are provided in the top frame. The fixing device includes a screw rod, the screw rod is internally threaded through the top frame, a support block is provided at the bottom of the screw rod, and the support block can squeeze the movable frame; the edge of the rubber sheet is located between the movable frame and the bottom frame.

[0012] Preferably, a hand wheel is provided at the top of the screw rod.

[0013] Preferably, a cavity is provided at the bottom of the top frame, and the support block can be located in the cavity.

[0014] Preferably, the refrigeration equipment uses a CO2 / NH3 cascade refrigeration system for refrigeration.

[0015] Preferably, water inlet holes and water outlet holes are respectively provided in the water storage cavities at the top and bottom of the box body, and valves are provided on the water inlet holes and the water outlet holes.

[0016] The present invention provides a cold storage method for meat cold chain, which uses the above-mentioned cold storage equipment for meat cold chain and includes the following steps:

[0017] 1. Place the box body in the cold storage for cooling. After the water freezes, the rubber sheet is lifted up to make the detection distance the smallest.

[0018] 2. Load meat into the box body in the cold storage.

[0019] 3. Transfer the box body into the compartment of the cold chain vehicle, connect the distance sensor to the refrigeration equipment, and transport it through the cold chain vehicle.

[0020] 4. During transportation, when the detection distance of the distance sensor is greater than the preset threshold, the refrigeration equipment performs refrigeration until the detection distance is the smallest.

[0021] Preferably, when using the box body for cold storage, the state of the rubber sheet needs to be checked regularly, and if it is abnormal, it needs to be replaced in time.

[0022] The present invention can store cold better and can conveniently transfer meat from a cold storage to a cold chain vehicle. During the transfer, the cold storage device can continuously refrigerate the meat to prevent the meat from spoiling due to temperature changes. When the meat is transferred into the cold chain vehicle, the cold storage device can refrigerate the meat for a certain period of time. When refrigeration is required, the volume change during the transformation between water and ice is used to deform the rubber sheet, so that the distance sensor obtains different distance signals. The refrigeration device refrigerates and stops according to different distance signals. In this way, the refrigeration device does not need to work for a long time and can get sufficient rest, thus ensuring the service life of the refrigeration device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 6 is a schematic structural diagram of a cold storage device for meat cold chain in an embodiment;

[0024] Figure 2 FIG. 10 is a schematic structural diagram of the carriage of a cold chain vehicle in an embodiment;

[0025] Figure 3 FIG. 14 is a schematic structural diagram of a box body in an embodiment;

[0026] Figure 4 FIG. 18 is a schematic structural diagram of a bottom frame, a top frame and a movable frame in an embodiment;

[0027] Figure 5 FIG. 22 is a schematic structural diagram of a fixing device in an embodiment;

[0028] Figure 6 FIG. 26 is a schematic diagram of the degree of fat oxidation of different processed samples in an embodiment;

[0029] Figure 7 FIG. 30 is a schematic diagram of the total sulfhydryl content of different processed samples in an embodiment;

[0030] Figure 8 FIG. 34 is a schematic diagram of the change in pH value of different processed samples in an embodiment;

[0031] FIG. 9(a) is a schematic diagram of the change in L* value of different processed samples in an embodiment;

[0032] FIG. 9(b) is a schematic diagram of the change in a* value of different processed samples in an embodiment;

[0033] FIG. 9(c) is a schematic diagram of the change in b* value of different processed samples in an embodiment;

[0034] Figure 10 FIG. 47 is a schematic diagram of the metmyoglobin content of different processed samples in an embodiment;

[0035] Figure 11 FIG. 51 is a schematic diagram of the change in TVB-N of different processed samples in an embodiment;

[0036] Figure 12 Schematic diagram of the change in the total number of colonies of different processed samples in the examples. Detailed implementation mode

[0037] To further understand the content of the present invention, the present invention will be described in detail in combination with the accompanying drawings and examples. It should be understood that the examples are only for explaining the present invention and not for limiting it.

[0038] Example

[0039] As Figures 1-5 shown, this embodiment provides a cold storage device for meat cold chain, which includes a box body 110. A box door 111 is provided on the front side of the box body 110. Water storage cavities 120 are provided on the top, bottom, left, right and rear sides of the box body 110 and are communicated with each other; A plurality of connecting rods 130 are connected between the top and bottom of the box body 110. A water storage pipe 131 is arranged inside the connecting rod 130, and the water storage pipe 131 is communicated with the water storage cavities 120 at the top and bottom of the box body 110; After the water in the water storage pipe 131 on the connecting rod 130 freezes, it can effectively refrigerate the meat inside the box body 110, thereby improving the refrigeration effect;

[0040] A notch 140 is provided on the top of the box body 110. The notch 140 is communicated with the water storage cavity 120 at the top of the box body 110. A rubber sheet 141 is hermetically connected to the notch 140. A convex head 150 is provided on the top of the notch 140, and a distance sensor 160 is provided on the convex head 150;

[0041] The box body 110 is located inside the carriage 170 of the cold chain vehicle. A refrigeration device 171 is provided on the carriage 170, and the distance sensor 160 is connected and cooperated with the refrigeration device 171;

[0042] An appropriate amount of water is stored in the water storage cavity 120. After the water freezes, the rubber sheet 141 is pushed up. The distance sensor 160 is used to detect the distance from the rubber sheet 141 to the distance sensor 160. When the detected distance is greater than the preset threshold, the refrigeration device 171 performs refrigeration until the detected distance is the smallest.

[0043] After the water in the water storage chambers 120 at the top, bottom, left, right, and rear sides of the box body 110 freezes, it can keep the meat contained in the box body 110 at a low temperature, thus realizing the cold storage of the box body 110; after the water freezes, its volume will increase. In this way, after an appropriate amount of water freezes (a person skilled in the art can obtain the required amount of water according to the actual on-site situation and the size of the notch 140), it can push up the rubber sheet 141 at the notch 140. After the ice melts into water, the rubber sheet 141 gradually returns to its original state; when the rubber sheet 141 is pushed up, the distance between it and the distance sensor 160 gradually decreases. Therefore, when the detection distance detected by the distance sensor 160 is the smallest, it can be considered that the cold storage effect is the best at this time; when the detection distance is greater than the preset threshold, it indicates that refrigeration is required, and the refrigeration device 171 operates. When the detection distance is the smallest, the refrigeration device 171 stops working. In this way, the refrigeration device 171 can get sufficient rest, preventing the refrigeration device 171 from having a short lifespan due to excessive working hours.

[0044] In addition, the meat is first placed into the box body 110, and then the box body 110 is transferred into the carriage 170 of the cold chain vehicle. In this way, the meat can be placed into the box body 110 in the cold storage first (the water in the box body 110 can be cooled in the cold storage to enter the cold storage state). In this way, when the meat is transferred into the carriage 170, the temperature change is small, and the meat is transferred into the carriage 170 at one time, which is very convenient for transportation. It is more time-saving and labor-saving than loading the meat into the carriage 170 bit by bit in the prior art, and the meat is not easily affected by temperature changes and its quality.

[0045] The water storage chamber 120 can also hold brine, so as to make the cold storage temperature lower.

[0046] A plurality of rollers 180 are respectively provided on the left, right, and bottom sides of the box body 110, and the rollers 180 can be attached to the corresponding surfaces inside the carriage 170.

[0047] The setting of the rollers 180 facilitates the stable and convenient entry of the box body 110 into the carriage 170.

[0048] A carriage door 172 is provided on the front side of the carriage 170, and a first buffer pad 173 is provided on the carriage door 172; a second buffer pad 174 is provided on the rear side of the carriage door 172, and the first buffer pad 173 and the second buffer pad 174 sandwich the box body 110 in the middle.

[0049] The setting of the first buffer pad 173 and the second buffer pad 174 can improve the stability of the box body 110 inside the carriage 170.

[0050] A bottom frame 210 and a top frame 220 are fixedly arranged in the notch 140. An activity frame 230 is arranged between the bottom frame 210 and the top frame 220. A plurality of fixing devices are arranged in the top frame 220. The fixing device includes a screw rod 240. The screw rod 240 is internally threaded through the top frame 220. A support block 250 is arranged at the bottom of the screw rod 240. The support block 250 can extrude the activity frame 230. The edge of the rubber sheet 141 is located between the activity frame 230 and the bottom frame 210.

[0051] Since the rubber sheet 141 is often in a deformed state, it is necessary to regularly replace the rubber sheet 141. The edge of the rubber sheet 141 is clamped by the bottom frame 210 and the activity frame 230. The activity frame 130 is fixed by the fixing device in the top frame 220. The rubber sheet 141 can be conveniently installed and removed, and the replacement is very convenient, and the sealing performance is also excellent.

[0052] A hand wheel 260 is arranged at the top of the screw rod 240.

[0053] The hand wheel 260 can rotate the screw rod 240, so as to loosen or tighten the support block 250, which is convenient for the installation and removal of the rubber sheet 141.

[0054] A cavity 221 is arranged at the bottom of the top frame 220. The support block 250 can be located in the cavity 221.

[0055] The cavity 221 can accommodate the support block 250, which can improve the stability of the support block 250 and also protect the support block 250.

[0056] The refrigeration equipment 171 uses a CO2 / NH3 cascade refrigeration system for refrigeration. The CO2 / NH3 cascade refrigeration system is an existing technology, and reference can be made to the patent with the publication number of CN204648736U.

[0057] Water inlet holes 121 and water outlet holes 122 are respectively arranged in the water storage cavities 120 at the top and bottom of the box body 110. Valves are arranged on the water inlet holes 121 and the water outlet holes 122.

[0058] The water inlet holes 121 and the water outlet holes 122 are convenient for replacing and adjusting the water in the water storage cavity 120.

[0059] This embodiment provides a cold storage method for meat cold chain, which uses the above-mentioned cold storage equipment for meat cold chain and includes the following steps:

[0060] 1. Place the box body 110 in the cold storage for cooling. After the water freezes, the rubber sheet 141 is jacked up to make the detection distance the smallest.

[0061] 2. Load meat into the box body 110 in the cold storage.

[0062] III. Transfer the box body 110 into the carriage 170 of the cold chain vehicle (the transfer is carried out on the loading platform, and the surface of the loading platform is flush with the bottom surface of the carriage 170), and connect the distance sensor 160 to the refrigeration equipment 171, and transport it by the cold chain vehicle;

[0063] IV. During the transportation process, when the detection distance of the distance sensor 160 is greater than the preset threshold, the refrigeration equipment 171 performs refrigeration until the detection distance is the smallest.

[0064] When using the box body 110 for cold storage, the state of the rubber sheet 141 needs to be checked regularly. If it is abnormal, it needs to be replaced in time.

[0065] This method can store cold better, and can conveniently transfer meat from the cold storage to the cold chain vehicle. During the transfer, the cold storage equipment can continuously refrigerate the meat to prevent the meat from deteriorating due to temperature changes; when the meat is transferred into the cold chain vehicle, the cold storage equipment can refrigerate the meat for a certain period of time. When refrigeration is required, the volume change during the transformation between water and ice is used to deform the rubber sheet 141, so that the distance sensor 160 obtains different distance signals, and the refrigeration equipment 171 performs refrigeration and stops according to different distance signals. In this way, the refrigeration equipment does not need to work for a long time and can get sufficient rest, thus ensuring the service life of the refrigeration equipment 171.

[0066] The "left", "right", "front", and "back" in this embodiment are relative to Figure 1 to describe.

[0067] In addition, a cold storage agent (used in cooperation with the refrigeration equipment 171) is loaded into the carriage 170. The cold storage agent is an inorganic-organic composite phase change cold storage agent, which is a mixture of water, water-absorbing resin, sodium polyacrylate, sodium hydroxymethylpropylate, sodium sulfate, citric acid, silicon dioxide, and carboxymethyl cellulose.

[0068] Next, experiments are carried out to prove the superiority of adding this cold storage agent.

[0069] 1) Materials and methods

[0070] 1.1) Preparation of samples

[0071] All the longissimus dorsi muscles of pigs used in this experiment were purchased from Yonghui Supermarket, transported back to the laboratory in ice boxes throughout the process, and placed in a refrigerator at 4°C. After removing visible connective tissue and external fat, the pork chops were cut into pieces with dimensions of 80 mm × 60 mm × 20 mm along the muscle fiber direction (each piece weighing approximately 100 ± 0.5 g). The surface was covered with plastic wrap. The samples were divided into two groups, one group was labeled as the "phase change material experimental group", and the other group was the "control group". Both groups were refrigerated at 2°C. At 9:00 am every day, the temperature of both groups was adjusted to 8°C, and a phase change material was added to the phase change material experimental group. At 9:00 pm, the temperature was adjusted back to 2°C and the phase change material was removed. Samples were taken from both groups on the 0th, 2nd, 4th, 6th, and 8th days for the determination of various indicators.

[0072] 1.2) Determination of TBARs

[0073] Weigh 5.00 g of the minced sample and place it into a 100 mL stoppered conical flask. Add 50 mL of 0.75 g / L trichloroacetic acid solution (containing 0.01 g / L of ethylenediaminetetraacetic acid). After shaking well, stopper and seal, place it on a constant temperature water bath oscillator and shake at 50°C for 30 min. After taking it out and cooling to room temperature, filter it with double-layer quantitative slow filter paper, discard the initial filtrate, and collect the remaining filtrate for standby. Mix 5 mL of the filtrate with 5 mL of 0.02 mol / L thiobarbituric acid solution and heat it in a 90°C water bath for 30 min. Use the trichloroacetic acid solution with the same concentration as the blank control, measure the absorbance at 532 nm, and the result is expressed as the content of malondialdehyde (mg / kg sample), and repeat the measurement 3 times.

[0074] 1.3) Redox state of myoglobin

[0075] Take 3 g of minced pork loin sample, add 30 mL of phosphate buffer (0.04 mol / L, pH 6.8), homogenize it at 3000 rpm for 30 s, and then centrifuge it at 3000 g for 30 min under freezing conditions. Subsequently, filter the centrifuged supernatant and measure the absorbance at 503, 525, 582, and 557 nm respectively. Calculate deoxymyoglobin (DeoMb), oxymyoglobin (OxyMb), and metmyoglobin (MetMb) as follows:

[0076] [DeoMb] = C DeoMb / C Mb = -0.534R1 + 1.594R2 + 0.552R3 - 1.329

[0077] [OxyMb] = C OxyMb / C Mb = 0.722R1 - 1.432R2 - 1.659R3 + 2.599

[0078] [MetMb] = C MetMb / C Mb = -0.159R1 - 0.085R2 + 1.262R3 - 0.520

[0079] where R1 = A 582 / A 525 and R2 = A 557 / A 525 and R3 = A 503 / A 525

[0080] 1.4) Determination of total thiol content

[0081] Use a total thiol content detection kit to test the total thiol content by the micro - method. Take 0.1 g of minced pork loin sample, add 1 mL of extraction solution, homogenize in an ice bath, centrifuge at 8000 g for 10 min at room temperature, and take the supernatant for testing. Adjust the wavelength of the microplate reader to 412 nm. Dilute the 25 μmol / mL standard solution with distilled water to standard solutions of 0.5, 0.25, 0.125, 0.0625, 0.03125, 0.015625 μmol / mL, and prepare them freshly before use. Drop them into a 96 - well plate.

[0082] Drawing of the standard curve: Based on the concentration (y, μmol / mL) and absorbance (ΔA standard, x) of the standard tubes, establish a standard curve. According to the standard curve, substitute the measured absorbance (ΔA measurement, x) into the formula to calculate the sample concentration (y, μmol / mL).

[0083] Calculation of total thiol content: Total thiol content (μmol / g mass) = y × V 样总 ÷W

[0084] 1.5) pH measurement

[0085] Prepare a homogenate by homogenizing 10 g of the sample in 90 mL of KCl solution (0.1 mol / L) for 2 minutes using a homogenizer. Read the value with a pH electrode. Calibrate the portable pH meter by the two - point method (buffers with pH values of 4.00 and 7.00) before measurement. The pH meter can be used only when the calibration rate reaches more than 95%. Measure 3 points for each sample and take the average value.

[0086] 1.6) Color measurement

[0087] Use a color difference meter to measure meat color indexes such as L*, a*, b* values of the pork sample. Calibrate the color difference meter with a white standard plate and a black standard plate respectively before use. After opening the vacuum - packed sample, let it develop color at room temperature for 30 min. Select 3 random positions on the cross - section of the sample to measure the surface color, avoiding tendons and fat on the pork surface, and record and take the average value respectively.

[0088] 1.7) Total Volatile Basic Nitrogen (TVB-N)

[0089] After removing fat and fascia from the samples, take 3 g of representative meat samples to be tested from each sample, chop them by hand, accurately weigh 3 g of the meat sample and add it to a beaker. At the same time, add 30 mL of distilled water (the sample and water are added in a ratio of 1:10), stir evenly, and homogenize for 2 - 3 min. The determination is carried out according to the second method in GB 5009.228 - 2016.

[0090] 1.8) Total number of colonies

[0091] The method for determining the total number of colonies is based on the method in GB 4789.2 - 2016 "Food Microbiology Examination: Determination of Total Number of Colonies". Place 10 g of the sample in 990 mL of sterile physiological saline (0.9% NaCl), homogenize with a sterile homogenizer for 2 min, then take out 1 mL of the supernatant for 10 - fold serial dilution. Use the plate pour method with PCA medium, and then place it in an environment of 37 °C for aerobic culture for 36 h. Record the parallel test data three times, and then take the average of the three detections. The result is expressed as the logarithm of the total number of colonies, log CFU / g.

[0092] 1.9) Data analysis

[0093] In all measurements, three samples are taken for each group. All measurements are carried out in triplicate, and the results obtained are the averages of these replicates. Analysis of variance and Duncan's test (significance is defined as P < 0.05) are performed by SPSS 19.0.

[0094] 2) Results and discussion

[0095] 2.1) Degree of fat oxidation

[0096] The degree of fat oxidation of the samples in different treatment groups is reflected by the TBARs value during storage. With the extension of storage time, the TBARs values of the control group and the cold storage agent group both show a gradually increasing trend and are in a low - degree oxidation state. It is worth noting that the samples in the cold storage agent group show more stable changes compared with the control group, indicating that a stable temperature helps to inhibit the fat oxidation of the product during storage. Fat is extremely unstable and prone to oxidation. Oxygen is the main factor affecting the fat oxidation of meat because it reacts with unsaturated fat to form lipid peroxides, and this process involves oxygen absorption and double - bond rearrangement. During storage, lipid oxidation is more intense than protein oxidation, and the TBARS value increases in a storage - time - dependent manner ( Figure 6)。Although no freezing was carried out, the malondialdehyde content in the control group samples reached 0.56 mg / kg on the 8th day, which may be the result of lipid oxidation induced by the formation of oxygen free radical substances in the mitochondria of pork samples. The malondialdehyde content in the phase change material group on the 8th day was significantly lower than that in the control group (0.38 mg / kg). In addition, high levels of lipid oxidation in muscle foods also promote the formation of carbonyl groups, leading to further oxidation of proteins during frozen storage.

[0097] 2.2) Total thiol content

[0098] As the myofibrillar protein with the highest proportion in meat and meat products, it makes significant contributions to the texture, flavor, water-holding capacity and other properties of meat products. However, myofibrillar protein is vulnerable to attack by reactive oxygen species (ROS) during the post-slaughter processing (such as cooling, freezing, irradiation and high-pressure treatment), which accelerates the process of protein oxidation and triggers lipid oxidation and myoglobin oxidation. These chain reactions play an important inducing role in the deterioration process of meat quality (such as tenderness, juiciness and nutritional value). Protein oxidation can be reflected by the loss of thiols. As Figure 7 shown, with the extension of storage time, the total thiol content of both groups of samples showed a gradually decreasing trend. When reaching the 8th day, the total thiol content of the control group samples was 0.18 μmol / g, which was significantly higher than that of the phase change material group samples (0.21 μmol / g). It indicates that under the condition of the phase change material, due to the temperature uniformity during storage, protein oxidation caused by temperature fluctuations was greatly avoided. In addition, thiol oxidation leads to the formation of oxidation derivatives, such as disulfide bonds (RSSR) and sulfite, and these derivatives will lead to a decline in the quality of meat. In addition, the impact of microorganisms on the sample quality during storage cannot be ignored.

[0099] 2.3) pH value

[0100] The pH value is an intuitive manifestation of muscle acidity and directly affects the storability, cooking loss, processing ability, etc. of meat products. It is an important detection index for meat quality. As Figure 8 shown, the pH of freshly slaughtered muscle is mostly 6.0 - 7.0, and then it begins to decline rapidly. After the end of the rigor mortis period, with the extension of the ripening time, the pH begins to rise slowly. In this experiment, the average pH of the two groups of pork samples on the 0th day was about 5.8. After 8 days of variable temperature storage in both groups, the pH increased to a certain extent. It shows that under the refrigeration condition of the muscle within the temperature range of 4°C, the muscle completed the process of resolving rigor and tenderization, and no significant difference was found between the two treatment methods.

[0101] 2.4) Color

[0102] The changes in color difference values of fresh beef under different low-temperature storage methods are shown in Figures 9(a), 9(b), and 9(c). Meat color is the first indicator for consumers to judge the freshness of meat when purchasing meat products, and it is an important indicator for evaluating meat products. The deterioration of meat color is one of the main factors affecting the shelf life of meat products. Color difference values include L* value (brightness value), a* value (redness value), and b* value (yellowness value). As can be seen from the figures, the storage method and storage time have a significant impact on the color difference of the longissimus dorsi muscle of pigs: among them, the brightness value shows a gradually increasing trend with the extension of storage time. The L value of the control group increased significantly from the initial 49.75 to 55.22, while the L value of the sample in the phase change material group increased to 54.3. The brightness value is related to the refraction of light on the surface of the meat product. The increase in the L value may be attributed to the migration of moisture inside the muscle to the surface during refrigeration, resulting in an increase in light refraction; due to the location of the sample, the initial value of the redness value is very low and the change is irregular, which may be related to the myoglobin content in this area; the yellowness value of the sample shows the same trend as the brightness value and increases significantly with the extension of storage time. Some studies have shown that the increase in the yellowness value is positively correlated with the degree of fat oxidation of the sample. Moreover, in the environment of the phase change material, the brightness value and yellowness value of the sample are significantly lower than those of the control group.

[0103] The color of meat products mainly depends on pigment substances in muscle, namely myoglobin and hemoglobin. Some researchers have proposed an enzyme system that can reduce metmyoglobin to myoglobin and named it metmyoglobin reductase activity (MRA). In fresh muscle, this enzyme is very active, and the formed metmyoglobin is quickly reduced to deoxymyoglobin and then oxidized back to oxymyoglobin, thus retaining a bright color. However, as the meat ages or is frozen, the activity of MRA decreases, and metmyoglobin quickly begins to accumulate on the surface of the meat, showing a poor color.

[0104] 2.5) Content of metmyoglobin

[0105] By measuring the content of metmyoglobin, the mechanism of color change of meat products during variable-temperature storage can be better revealed, such as Figure 10As shown in the figure, with the extension of storage time, the metmyoglobin content of the two groups of samples increased significantly. On the 6th day, there was no significant difference in the metmyoglobin content of the samples of the two treatment groups. This shows that myoglobin oxidation occurred during this period. Most studies have proved that all forms of oxidation in meat are interrelated, including protein oxidation, fat oxidation and myoglobin oxidation. This also corresponds appropriately to the evaluation of protein and fat oxidation in the experiment. Therefore, when lipid oxidation occurs in meat, pro-oxidants that react with oxygenated myoglobin can be produced, which in turn leads to the formation of metmyoglobin. The process of protein oxidation also conforms to this logic. The product of lipid oxidation (malondialdehyde) will induce protein oxidation. Oxidation in meat can be regarded as a chain reaction, which is initiated by the lipid part and continued to the myoglobin part. Studies have shown that during the storage of meat, lipid oxidation will intensify, thereby producing a large number of free radicals, leading to an increase in the oxidation rate of myoglobin and an increase in the content of metmyoglobin, causing the color of the meat to change from bright red to brown, showing a poor color.

[0106] 2.6) Volatile basic nitrogen

[0107] During storage, proteins, under the action of microorganisms and enzymes, produce nitrogen-containing alkaline toxic substances such as ammonia (NH3) and amines (R-NH2), which exist in fish meat in the form of volatile basic nitrogen (TVB-N). According to the national standard GB2733-2005 "Sanitary Standards for Fresh and Frozen Animal Aquatic Products", when the volatile basic nitrogen (TVB-N) value is greater than 20mg / 100g, it exceeds the national standard and is not edible. Figure 11 It can be seen that the TVB-N value in the samples gradually increased with the extension of storage time. The TVB-N value of the control group samples exceeded 20mg / 100g on the 4th day of storage, and they had already deteriorated; at this time, the TVB-N value of the samples in the refrigerant group was still within the limit, and exceeded 20mg / 100g on the 8th day. This shows that the refrigerant treatment can effectively extend the shelf life of the product by 2 days.

[0108] 2.7) Total colony count

[0109] Changes in the total number of colonies in the longissimus dorsi muscle of pigs under different low-temperature storage methods Figure 12As shown. Microorganisms are an important cause of the spoilage of chilled fresh pork during storage. The total viable count is one of the important indicators reflecting the freshness of pork and is closely related to the shelf life of fresh pork. As shown in the figure, both the storage time and the storage method have a significant impact on the total viable count of fresh pork. The total viable count of the two groups of samples on the 0th day was 5.37 lgCFU / g, both exceeding 4 lgCFU / g, which was sub-fresh meat. During the subsequent storage process, the growth rate of the total viable count of the samples in the cold storage agent group was significantly lower than that of the control group. On the 2nd day, the total viable count of the control group was 6.30 lgCFU / g, significantly higher than 5.65 lgCFU / g of the samples in the cold storage agent group. In addition, on the 6th day, the total viable count of the samples in the cold storage agent group exceeded 6 lgCFU / g. Referring to the microbial indicators, the shelf life of the samples in the cold storage agent group was about 5 - 6 days, significantly higher than that of the control group, indicating that the treatment with cold storage agent can effectively extend the shelf life of the longissimus dorsi of pigs by 4 days.

[0110] 3) Summary

[0111] This experiment studied the effect of cold storage agent on the quality of the longissimus dorsi of pigs during storage, and focused on investigating the changes in muscle protein, fat oxidation, meat freshness and color during storage, and found that:

[0112] (1) Under the refrigerated environment, the cold storage agent can significantly stabilize the environmental temperature, thereby inhibiting the deterioration of product quality caused by temperature fluctuations, such as stabilizing color and pH, indicating that the cold storage agent is an effective and low-cost preservation method for transporting and storing meat products.

[0113] (2) Cold storage agent refrigeration can effectively inhibit the oxidation of meat protein and fat, and significantly inhibit microorganisms, extending the shelf life of the product.

[0114] The above schematically describes the present invention and its implementation manners. This description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments to this technical solution without creative efforts without departing from the purpose of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A cold storage device for the meat cold chain, characterized in that: It includes a box body (110). A box door (111) is provided on the front side of the box body (110). Water storage cavities (120) are provided on the top, bottom, left side, right side and rear side of the box body (110), and the water storage cavities (120) at each place are communicated with each other; A plurality of connecting rods (130) are connected between the top and bottom of the box body (110). A water storage pipe (131) is provided inside the connecting rod (130), and the water storage pipe (131) is communicated with the water storage cavities (120) at the top and bottom of the box body (110); A notch (140) is provided on the top of the box body (110). The notch (140) is communicated with the water storage cavity (120) on the top of the box body (110). A rubber sheet (141) is hermetically connected to the notch (140). A convex head (150) is provided on the top of the notch (140), and a distance sensor (160) is provided on the convex head (150); A bottom frame (210) and a top frame (220) are fixedly provided in the notch (140). A movable frame (230) is provided between the bottom frame (210) and the top frame (220). A plurality of fixing devices are provided in the top frame (220). The fixing device includes a screw rod (240). The screw rod (240) is threadedly penetrated in the top frame (220). A support block (250) is provided at the bottom of the screw rod (240), and the support block (250) can squeeze the movable frame (230); The edge of the rubber sheet (141) is located between the movable frame (230) and the bottom frame (210); The box body (110) is located in the carriage (170) of a cold chain vehicle. A refrigeration device (171) is provided on the carriage (170), and the distance sensor (160) is connected and cooperated with the refrigeration device (171); An appropriate amount of water is stored in the water storage cavity (120). After the water freezes, the rubber sheet (141) is pushed up. The distance sensor (160) is used to detect the distance from the rubber sheet (141) to the distance sensor (160). When the detected distance is greater than a preset threshold value, the refrigeration device (171) performs refrigeration until the detected distance is the smallest.

2. The cold storage device for meat cold chain according to claim 1, wherein: A plurality of rollers (180) are respectively provided on the left side, right side and bottom of the box body (110), and the rollers (180) can be attached to the corresponding surfaces inside the carriage (170).

3. The cold storage device for meat cold chain according to claim 1, wherein: A carriage door (172) is provided on the front side of the carriage (170). The carriage door (172) is provided with a first buffer pad (173); A second buffer pad (174) is provided on the rear side of the carriage door (172), and the first buffer pad (173) and the second buffer pad (174) clamp the box body (110) in the middle.

4. The cold storage device for meat cold chain according to claim 1, wherein: A hand wheel (260) is provided on the top of the screw rod (240).

5. The cold storage device for meat cold chain according to claim 1, characterized in that: A cavity (221) is provided at the bottom of the top frame (220), and the support block (250) can be located in the cavity (221).

6. The cold storage device for meat cold chain according to claim 1, characterized in that: The refrigeration device (171) uses a CO2 / NH3 cascade refrigeration system for refrigeration.

7. The cold storage device for meat cold chain according to claim 1, characterized in that: Water inlet holes (121) and water outlet holes (122) are respectively provided in the water storage cavities (120) at the top and bottom of the box body (110), and valves are provided on the water inlet holes (121) and the water outlet holes (122).

8. A cold storage method for the meat cold chain, characterized in that: It adopts a cold storage device for meat cold chain as described in any one of claims 1-7, and includes the following steps:

1. Place the box (110) in the cold storage for cooling. After the water freezes, it will push up the rubber sheet (141) to minimize the detection distance.

2. Load the meat into the box (110) in the cold storage.

3. Transfer the box (110) into the carriage (170) of the cold chain vehicle, and connect the distance sensor (160) to the refrigeration equipment (171), and transport it through the cold chain vehicle.

4. During transportation, when the detection distance of the distance sensor (160) is greater than the preset threshold, the refrigeration equipment (171) will refrigerate until the detection distance is minimized.

9. A cold storage method for meat cold chain according to claim 8, characterized in that: When using the box (110) for cold storage, the status of the rubber sheet (141) needs to be checked regularly. If it is abnormal, it needs to be replaced in time.

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