Method for unfreezing sirloin by multi-frequency ultrasound

Abstract

The invention discloses a multi-frequency ultrasonic sirloin thawing method, which adopts a double-frequency sequential ultrasonic treatment thawing mode and comprises the following steps: taking frozen sirloin with the center temperature lower than-20 DEG C, putting a sample into water in an ultrasonic tank by using multi-frequency ultrasonic equipment, controlling the immersion position to be about 0.5-3cm away from the horizontal plane, controlling the water temperature to be 12-20 DEG C, controlling the ultrasonic power to be 900W, and performing ultrasonic treatment for 2-3 hours; when the center of the meat sample is raised to 0 DEG C or above, taking out; the ultrasonic frequency is 22 / 28 kHz, 28 / 40 or 22 / 40 kHz. According to the method, the unfreezing time is short, the unfreezing loss of the sirloin is reduced, the freshness of the sirloin can be reserved to the maximum extent, the tenderness of the sirloin is improved, particularly, the muscle fiber fracture surface of the unfrozen sirloin is smooth, the damage degree of muscle fiber bundles is small, and the unfreezing quality of the quick-frozen sirloin can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of food, and in particular relates to a method for thawing beef brisket with multi-frequency ultrasound. Background Art

[0002] Beef brisket has fine fibers and is rich in protein, minerals and vitamins. However, due to its high nutritional value, it is easy to spoil when stored at room temperature. It needs to be stored frozen to reduce the activity of enzymes in the meat, inhibit the growth of microorganisms, and slow down the rate of spoilage. Freezing is a common method of preserving meat, but the thawing process before processing will have a significant impact on the quality of the meat. Traditional thawing methods such as air or still water have a slow thawing rate, which causes changes in the physical or chemical properties of the meat, causing its texture, color, flavor and other qualities to deteriorate, directly affecting the quality of the thawed meat. For example, a long thawing time will lead to water loss in the meat, fat oxidation, and a decrease in freshness. A suitable thawing method is required for the subsequent processing of meat products.

[0003] Ultrasonic thawing mainly uses the cavitation effect in the liquid medium as the main mechanism. Ultrasonic waves can also cause the liquid medium to vibrate and the thawing materials to vibrate, thereby increasing the heat transfer rate and local temperature, which can accelerate the thawing rate.

[0004] Although there have been reports of ultrasonic-assisted thawing for fish, mutton, etc., due to the different colors, textures, freshness, protein distribution and microstructures of meat from different animals and even different parts of animals, it is difficult to draw on existing technologies. There is currently no method for thawing frozen beef brisket products. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a multi-frequency ultrasonic combined mode beef brisket thawing method that significantly improves the quality of beef brisket after thawing. The purpose of the present invention is achieved by the following means:

[0006] A method for thawing beef brisket by multi-frequency ultrasound adopts a dual-frequency sequential ultrasound treatment thawing mode, takes frozen beef brisket with a center temperature below -20°C, uses a multi-frequency ultrasonic device, places the sample in water in an ultrasonic tank, the immersion point is about 0.5-3 cm from the horizontal plane, controls the water temperature to be 12-20°C, and the ultrasonic power to be 900W. When the center of the meat sample rises to above 0°C, the meat sample is taken out; wherein the frequency is 22 / 28kHz, 28 / 40 or 22 / 40kHz.

[0007] Preferably, the frequency is 22 / 28kHz, 28 / 40kHz dual-frequency sequential ultrasonic treatment. Most preferably, the frequency is 28 / 40kHz dual-frequency sequential ultrasonic treatment.

[0008] Preferably, the immersion point is about 0.5 cm away from the horizontal plane.

[0009] Preferably, the controlled water temperature is 15°C.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention thaws frozen sirloin meat based on a dual-frequency sequential ultrasonic method, and retains a color similar to that of a fresh meat sample after thawing, has a short thawing time, reduces thawing losses of sirloin meat, effectively improves the thawing efficiency of quick-frozen sirloin meat, retains the freshness of the sirloin meat to the greatest extent, and improves the tenderness of the meat, especially after thawing, the cross-section of the sirloin muscle fibers is smoother, and the degree of damage to the muscle fiber bundles is small, which can effectively improve the thawing quality of the quick-frozen sirloin meat.

[0011] The invention provides a method for rapid thawing of quick-frozen beef brisket based on short-time multi-frequency ultrasonic thawing, which can significantly improve the edible quality of the thawed beef brisket. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Effect of multi-frequency ultrasonic thawing on the thawing time of beef brisket

[0013] Figure 2 Effect of multi-frequency ultrasonic thawing on thawing loss rate of beef brisket

[0014] Figure 3 Effect of multi-frequency ultrasonic thawing on cooking loss rate of beef brisket

[0015] Figure 4 Effect of multi-frequency ultrasonic thawing on pH value of beef brisket

[0016] Figure 5 Effect of multi-frequency ultrasonic thawing on volatile basic nitrogen value of beef brisket

[0017] Figure 6 Effect of multi-frequency ultrasonic thawing on malondialdehyde value of beef brisket

[0018] Figure 7 Distribution of myofibrillar proteins in beef brisket under different thawing methods

[0019] Figure 8 Effect of multi-frequency ultrasonic thawing on the microstructure of beef brisket (a&A: fresh meat; b&B: static water thawing; c&C: 40kHz; d&D: 22 / 28kHz; e&E: 28 / 40kHz; f&F: 22 / 40kHz; g&G: 22 / 28 / 40kHz; lowercase and uppercase letters represent magnifications of 300 and 1000 times, respectively) DETAILED DESCRIPTION

[0020] The present invention is further explained below by specific examples:

[0021] Example 1

[0022] Take frozen beef brisket with a center temperature below -20℃, and place it in the water in the ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water level is about 0.5cm. The water temperature is controlled to 15℃ by the circulating water system of the device. The ultrasonic power is 900W. The total volume of water in the ultrasonic tank is 8.0L. When the center of the meat sample rises to 0℃, take it out. The frequency used is 28 / 40kHz dual-frequency sequential ultrasonic treatment.

[0023] Example 2

[0024] Take frozen beef brisket with a center temperature below -20℃, and place it in water in an ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22 / 40kHz dual-frequency sequential ultrasonic treatment.

[0025] Example 3

[0026] Take frozen beef brisket with a center temperature below -20℃, and place it in water in an ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22 / 28kHz dual-frequency sequential ultrasonic treatment.

[0027] Comparative Example 1

[0028] Take frozen beef brisket with a center temperature below -20℃, and place it in the water in the ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22kHz single-frequency ultrasonic mode.

[0029] Comparative Example 2

[0030] Take frozen beef brisket with a center temperature below -20℃, and place it in the water in the ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 28kHz single-frequency ultrasonic mode.

[0031] Comparative Example 3

[0032] Take frozen beef brisket with a center temperature below -20℃, and place it in the water in the ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 40kHz single-frequency ultrasonic mode.

[0033] Comparative Example 4

[0034] Take frozen beef brisket with a center temperature below -20℃, and place it in the water in the ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22+28kHz dual-frequency synchronous ultrasonic treatment.

[0035] Comparative Example 5

[0036] Take frozen beef brisket with a center temperature below -20℃, and place it in the water in the ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 28+40kHz dual-frequency synchronous ultrasonic treatment.

[0037] Comparative Example 6

[0038] Take frozen beef brisket with a center temperature below -20℃, and place it in the water in the ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22+40kHz dual-frequency synchronous ultrasonic treatment.

[0039] Comparative Example 7

[0040] Take frozen beef brisket with a center temperature below -20℃, and use a multi-frequency ultrasonic device to place the frozen beef brisket in the water in the ultrasonic tank, with the immersion point about 0.5cm from the horizontal plane, control the water temperature to 15℃, and the ultrasonic power to 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22 / 40 / 28kHz three-frequency sequential ultrasonic treatment.

[0041] Comparative Example 8

[0042] Take frozen beef brisket with a center temperature below -20℃, and place it in water in an ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22 / 28 / 40kHz three-frequency sequential ultrasonic treatment.

[0043] Comparative Example 9

[0044] Take frozen beef brisket with a center temperature below -20℃, and place it in water in an ultrasonic tank using a multi-frequency ultrasonic device. The immersion distance from the water is about 0.5cm. The water temperature is controlled at 15℃ and the ultrasonic power is 900W. When the center of the meat sample rises to 0℃, take it out. The frequency used is 22+28+40kHz three-frequency synchronous ultrasonic treatment.

[0045] In the above sequential ultrasound working mode, each frequency is excited in turn, and the frequency change time sequence is 5s. The synchronous ultrasound working mode means that the sound fields of all frequencies are excited at the same time.

[0046] Comparative Example 10

[0047] Thawing in static water: Place the quick-frozen beef brisket in an ultrasonic tank and use the equipment's water system to prepare 15°C water for thawing. During this period, the ultrasonic generator is always turned off. When the center of the sample reaches 0°C, take out the sample for testing.

[0048] Test Example 1

[0049] 1.1 Materials and Instruments

[0050] Fresh beef brisket was purchased from RT-Mart Supermarket. The selected beef brisket was quickly packed into a foam box filled with crushed ice and brought back to the laboratory. It was cut into pieces of similar size (2×2×2 cm) for quick freezing and thawing. Sodium dihydrogen phosphate dihydrate, disodium hydrogen phosphate dodecahydrate, sodium chloride, EDTA, sodium hydroxide, hydrochloric acid, Tris base, glycine, SDS, methanol, glacial acetic acid, and protein electrophoresis staining solution were purchased from Sinopharm Chemical Reagent Co., Ltd. Lowry protein concentration determination kit, volatile basic nitrogen (TVB-N) kit, and malondialdehyde (MDA) kit were purchased from Shenggong Biotechnology (Shanghai) Co., Ltd.

[0051] Multi-frequency ultrasonic device, Jiangsu Jiangda Wukesong Biotechnology Co., Ltd.; TMS-PRO food physical property analyzer, FTC, USA; Xinsite HT-9815 thermocouple thermometer, Shenzhen Xinsite Technology Co., Ltd.; L600 medical centrifuge, Hunan Xiangyi Laboratory Instrument Development Co., Ltd.; high-speed refrigerated centrifuge, Aibende International Trade Co., Ltd.; F6 / 10L handheld high-speed homogenizer, Shanghai Jingxin Industrial Development Co., Ltd.; small high-speed centrifuge, Aibende International Trade Co., Ltd.; electrophoresis power supply, Baijing Biological Co., Ltd.; WSC-S colorimeter, Shanghai Jingke Industrial Co., Ltd.; DK-S24 digital display constant temperature water bath, Shanghai Sendi Scientific Instrument Co., Ltd.

[0052] 1.2 Quick freezing and thawing of beef brisket

[0053] Insert the thermometer probe into the center of the fresh meat block and put it into a plastic bag, and then quickly freeze it in an ultra-low temperature refrigerator. When the center temperature of the sample is lower than -20°C, start the thawing experiment. The thawing experiment is carried out according to the methods of Examples 1-3 and Comparative Examples 1-10. When the center temperature of the meat sample rises to 0°C, take it out for testing and analysis.

[0054] 2 Results

[0055] 2.1 Effect of multi-frequency and multi-mode ultrasonic thawing on the thawing time of quick-frozen beef brisket

[0056] Figure 1 The figure shows the effect of ultrasonic thawing on the thawing time of quick-frozen beef brisket at different frequencies. The time required for ultrasonic assisted thawing is shorter than that required for static water thawing (754s). In the single-frequency thawing mode, the time required for 22kHz, 28kHz and 40kHz is 684s, 628s and 613s respectively. In the dual-frequency sequential ultrasonic thawing mode, the thawing time required for 22 / 28kHz, 28 / 40kHz and 22 / 40kHz modes is 547s, 524s and 511s respectively. In the dual-frequency synchronous ultrasonic mode, the thawing time of 22+28kHz, 28+40kHz and 22+40kHz is 617s, 580s and 575s respectively. In the triple-frequency sequential ultrasonic mode, the thawing time of 22 / 40 / 28kHz and 22 / 28 / 40kHz is 583s and 564s respectively. The thawing time of 22+28+40kHz triple-frequency synchronous ultrasonic mode is 530s. Among all modes, the thawing time of 22+28kHz, 28+40kHz, and 22+40kHz dual-frequency sequential ultrasound modes was shorter, which was shortened by 27.4%, 30.5%, and 32.2% respectively compared with static water thawing. In general, the thawing time of dual-frequency and triple-frequency ultrasound was shorter than that of single-frequency ultrasound. The reason may be that the mechanical force generated by cavitation under multi-frequency ultrasound cuts the original ice crystals into small ice crystals, and the cavitation collapse time is shorter than the cavitation collapse time in the single-frequency ultrasound field. The synergistic treatment of ultrasound with different powers significantly reduced the sample thawing time. The microjet action accelerated the heat transfer of the material, causing the ice crystals to be broken into fragments as new crystal nuclei to generate new ice crystals, thereby reducing the size of ice crystal formation and reducing the thawing time to a certain extent.

[0057] 2.2 Effect of multi-frequency and multi-mode ultrasonic thawing on the thawing loss rate of quick-frozen beef brisket

[0058] Figure 2The effect of multi-frequency ultrasonic thawing treatment on the thawing loss rate of beef brisket. The thawing loss rate of beef brisket under static water thawing was 5.25%. In the single-frequency thawing mode, the thawing loss rate of 22kHz was the highest at 5.30%. In the dual-frequency sequential mode, the thawing loss rates of 22 / 28kHz, 28 / 40kHz and 22 / 40kHz were 3.92%, 3.55% and 3.96%, respectively. Among them, the beef brisket thawed by 28 / 40kHz had the smallest thawing loss rate, which was reduced by 32.3% compared with static water thawing. In the dual-frequency synchronous mode, the thawing loss rates of 22+28kHz, 28+40kHz and 22+40kHz were 5.28%, 5.96% and 5.56%, respectively. In the triple-frequency sequential thawing mode, the thawing loss rates of 22 / 40 / 28kHz and 22 / 28 / 40kHz were 6.29% and 5.34%, respectively. The thawing loss in the 22+28+40kHz synchronous mode was 7.90%, which was significantly higher than the thawing loss rate of the samples in the single-frequency and dual-frequency ultrasonic working modes. The high thawing loss in the synchronous mode may be due to the high ultrasonic energy density, which leads to muscle tissue damage and protein destruction, causing the loss of water and soluble substances. Under dual-frequency sequential ultrasonic treatment, the thawing loss decreased significantly, which may be related to the fact that dual-frequency alternating treatment can reduce the thawing time. The cavitation bubbles generated at one frequency can provide cavitation cores for another frequency, which significantly improves the thawing efficiency. The contact time between ultrasound and frozen meat is reduced, reducing its direct physical damage to the sirloin meat tissue. On the other hand, ultrasound improves the myosin structure and improves water retention by modifying the natural structure of the protein or exposing more active groups.

[0059] 2.3 Effect of multi-frequency and multi-mode ultrasonic thawing on the cooking loss rate of quick-frozen beef brisket

[0060] Cooking loss refers to the shrinkage of meat due to the evaporation of water during the cooking process, as well as the volatilization of a small amount of fat and volatile aromatic substances caused in this process. Figure 3The effects of different thawing methods on the cooking loss rate of quick-frozen beef brisket were shown in Figure 2. The cooking loss rate of fresh beef brisket (31.4%) was the lowest, while the cooking loss rates of beef brisket treated with static water thawing and three-frequency simultaneous treatment reached 36.97% and 37.38% respectively. Compared with single-frequency and dual-frequency ultrasonic treatments, triple-frequency ultrasound can produce a stronger cavitation effect. Although its thawing time is shorter than that of single-frequency, the high energy output caused by its frequency superposition will cause serious changes in the internal tissue structure of beef brisket, even exceeding the cooking loss of static water thawing. This is consistent with the thawing loss rate results of triple-frequency ultrasonic thawing meat. For dual-frequency treatment, the cooking loss of thawed meat after 28 / 40, 22 / 40, 22+28, 28+40 and 22+40kHz treatments is lower than that of other ultrasonic modes. Among them, the 28 / 40kHz mode has the lowest cooking loss (33.11%), which is not significantly different from the cooking loss of fresh meat. It can be seen that the alternating sequential mode is more suitable for thawing beef brisket than the simultaneous synchronous mode ultrasonic treatment, which helps to retain the nutrients and moisture in the meat to the greatest extent.

[0061] 2.4 Effect of multi-frequency and multi-mode ultrasonic thawing on the color of quick-frozen beef brisket

[0062] Color is an indicator for consumers to judge the acceptability of beef brisket. The L* value indicates brightness, the a* value indicates redness, and the b* value indicates yellowness. The brighter the color of the beef brisket, the fresher it is, and the larger the L* value. It can be seen from Table 1 that static water thawing affects the L* value and a* value of beef brisket. While the meat is shiny, the red appearance fades, which may be related to the long static water thawing time and the continuous exudation of blood in the tissue. After synchronous ultrasonic treatment, the a* and b* values ​​fluctuated, while the sequential ultrasonic treatment mode had little effect on the a* and b* values ​​of muscle tissue. During the thawing process of frozen meat, factors such as fat oxidation, pigment degradation or protein denaturation will cause color changes. ] . From the perspective of color difference (△E), in single-frequency mode, the ΔE (44.63±1.07) of beef brisket treated with 22kHz is closest to fresh meat (44.02±1.01); in sequential dual-frequency mode, the ΔE value (45.68±0.95) of beef brisket thawed at 22 / 28kHz is closer to fresh meat; in synchronous dual-frequency mode, the ΔE value (45.62±1.50) of beef brisket thawed at 22+40kHz is closest to fresh meat; in triple-frequency mode, the ΔE value (45.55±1.14) of meat treated with 22 / 40 / 28kHz is closest to fresh meat. This shows that the combination of different ultrasonic frequency working modes has a significant effect on the color of beef brisket. The change in color can reflect the impact of the choice of ultrasonic thawing mode on the quality of thawed meat.

[0063] Table 1 Effect of multi-frequency ultrasonic thawing on the color of beef brisket

[0064]

[0065]

[0066] Note: Different lowercase superscripts in the same column indicate significant differences, p<0.05.

[0067] 2.5 Effect of multi-frequency and multi-mode ultrasonic thawing on the texture characteristics of quick-frozen beef brisket

[0068] Texture characteristics are important quality indicators that affect the sensory and functional properties of beef brisket. As can be seen from Table 2, thawing with different ultrasonic frequencies and working modes has a significant effect on the texture index of beef brisket. Under single-frequency 28kHz ultrasonic treatment, the minimum hardness of beef brisket is 362.85±29.63N. After dual-frequency sequential (28 / 40kHz) treatment, the muscle hardness is reduced to 338.68±28.71N; after dual-frequency synchronous (28+40kHz) thawing, the minimum hardness of beef brisket is 314.83±11.31N. In the three-frequency treatment mode, the beef brisket after 22+28+40kHz three-frequency synchronous thawing has the lowest hardness of 282.38±32.46N, which shows that the hardness of beef brisket after three-frequency synchronous ultrasonic treatment is significantly reduced, and the high-frequency density ultrasonic energy has the greatest damage to muscle fibers. This can also be seen from the change index of shear force. The shear force of beef brisket after three-frequency ultrasonic treatment is only 56% of fresh meat. In addition to the significant decrease in hardness after hydrostatic thawing, elasticity, adhesiveness, and chewiness also decreased. Elasticity refers to the ability of beef brisket to deform after being subjected to pressure, but to return to its original shape when the pressure is removed. After ultrasonic thawing, the beef brisket thawed by three-frequency synchronous ultrasound had the lowest elasticity, which was 3.24±0.28mm, and there was no significant difference in elasticity between the other ultrasonic thawing groups. The change trend of the adhesiveness index was consistent with the hardness index, that is, the adhesiveness of the ultrasonic group with decreased hardness also decreased to varying degrees. Chewability is an important food texture indicator. It indicates that the food has the property of continuous resistance to chewing and crushing. For the chewiness and shear force indicators, the 28kHz single-frequency ultrasound treatment significantly showed the lowest chewiness energy consumption of 435.89±23.21mJ, and the corresponding shear force was also the lowest. In dual-frequency sequential ultrasound, the chewiness of 22 / 40kHz is 411.98±23.55mJ, and the corresponding shear force is 88.25±2.26N; the chewiness of beef brisket treated with dual-frequency synchronous ultrasound 22+40kHz is the best (344.65±21.90mJ), and the shear force is 79.81±4.10N. After triple-frequency ultrasound treatment, it is also shown that the chewiness of the thawed meat obtained by synchronous treatment is lower than that of sequential treatment (317.54±33.31mJ), and it has the lowest shear force of 69.57±3.39N. Low chewiness and shear force values ​​indicate that the meat is tender, but combined with the water retention performance index of beef brisket, the meat thawed by triple-frequency synchronous ultrasound may lose water severely and collapse tissue. Although the shear force is low, it is likely to present a soft internal tissue morphology and a deteriorated taste. From this perspective, the combination mode of dual-frequency sequential or synchronous ultrasound is more suitable for thawing beef brisket.

[0069] Table 2 Effect of multi-frequency ultrasonic thawing on the texture characteristics of beef brisket

[0070]

[0071] Note: Different lowercase superscripts in the same column indicate significant differences, p<0.05.

[0072] 2.7 Effect of multi-frequency and multi-mode ultrasonic thawing on TVB-N value of quick-frozen beef brisket

[0073] One of the important indicators for evaluating the degree of meat spoilage is the TVB-N value. Under the action of microorganisms and cell autolysis, the decomposition of compounds such as proteins will lead to an increase in the TVB-N value. Figure 5 The effect of different thawing methods on the TVB-N value of thawed beef brisket is shown. The TVB-N value of beef brisket thawed in static water (7.27 mg / 100 g) is significantly higher than that of fresh meat (3.58 mg / 100 g), while the TVB-N values ​​of beef brisket thawed in different ultrasonic working modes are lower than those of the static water thawing group. Among them, in the dual-frequency ultrasonic thawing group, the TVB-N values ​​of beef brisket treated with 22 / 28kHz and 28 / 40kHz are the lowest, 3.27 mg / 100g and 3.13 mg / 100g, respectively, which are closest to the TVB-N value of fresh meat.

[0074] 2.8 Effect of multi-frequency and multi-mode ultrasonic thawing on the malondialdehyde value of quick-frozen beef brisket

[0075] Depend on Figure 6 It can be seen that after 22 / 40kHz dual-frequency sequential ultrasound treatment, the MDA value of beef brisket is the lowest (0.157 mg / kg), which is closest to the fresh group (0.088 mg / kg), but the value is also nearly 2 times higher than the fresh meat group. This shows that ultrasonic thawing treatment will lead to accelerated oxidation of fat in beef brisket. However, this accelerated oxidation is different in different combination modes. For triple-frequency synchronous ultrasound, the thawed meat has the highest MDA value (0.355 mg / kg), which is 4 times that of fresh meat and 2.2 times that of 22 / 40kHz dual-frequency sequential ultrasound treatment. Triple-frequency synchronous ultrasound significantly accelerates the lipid oxidation process of beef brisket. For other dual-frequency ultrasound treatment groups, the MDA value of thawed meat after 22 / 28kHz and 28 / 40kHz treatment is also low.

[0076] 2.9 Distribution of myofibrillar proteins

[0077] Myofibrillar proteins are proteins that make up myofibrils in muscles, mainly including tropomyosin, myosin, troponin, actomyosin, etc. Based on the working mode with better comprehensive results in the analysis of thawing time, water retention, color, texture, and freshness indicators under the above different ultrasound modes, the distribution of myofibrillar proteins was further analyzed. The results are as follows Figure 7As shown. As can be seen from the figure, there are many total soluble protein bands in the myofibrillar protein of sirloin. The main bands are myosin heavy chain (200kDa) and actin chain (45kDa). Compared with the fresh meat group, no new bands appeared in the static water thawing and ultrasonic thawing groups. The myosin heavy chain of sirloin meat became lighter after static water thawing, indicating that the protein was oxidized or degraded during the thawing process. Under the dual-frequency sequential ultrasonic treatment mode, the density of myosin heavy chain in sirloin treated with 28 / 40kHz decreased, indicating that this frequency improved the distribution of myofibrillar protein to a certain extent, reduced the content of large molecular proteins in muscle tissue, and improved the tenderness of meat, which is consistent with the hardness results.

[0078] 2.10 Microstructure observation

[0079] Figure 8 A&A showed that the sirloin sample without ultrasonic treatment had a smooth cross section, clear cross section, natural texture, and full muscle fibers. Figure 8 b&B), the muscle fiber cross section is curled and bifurcated, the spacing increases, and the inner wall smoothness decreases. The firmness of the meat decreases after static water thawing. After single-frequency 40khHz ultrasonic thawing ( Figure 8 c&C), although the gaps between muscle fibers are smaller than those after static water thawing, some muscle fibers are bent and the gaps between muscle fibers become larger in some parts, and the taste and chewiness of the meat may decrease here. Figure 8 d&D, Figure 8 e&E, Figure 8 f&F show the microscopic characteristics of beef brisket muscle fibers after dual-frequency ultrasound treatment. Compared with the muscle fibers treated with 22 / 28kHz and 22 / 40kHz ultrasound frequencies, which showed different degrees of loose structure and large fractures in cross section, the muscle fibers treated with 28 / 40kHz had a smoother cross section and less damage to the muscle fiber bundles in the cross section. Figure 8 G&G showed that although triple-frequency ultrasound treatment also improved thawing efficiency, for beef brisket, the ultrasonic cavitation effect and the micro-jets generated by triple-frequency sequential ultrasound quickly impacted the muscle fibers, causing them to separate quickly, thus retaining the diaphragms between the muscle fibers. The larger gaps between muscle fibers established drip channels, causing the meat to lose moisture quickly. Therefore, among the ultrasonic thawing treatment methods, 28 / 40kHz sequential dual-frequency ultrasound treatment had little effect on the microscopic characteristics of beef brisket muscle fibers.

[0080] The test method in the above test is as follows:

[0081] 1. Color determination

[0082] The colorimeter was calibrated before the measurement, and each group of parallel meat samples was measured 5 times. Among them, L, a, and b are brightness, red-green, and yellow-blue, respectively. L+ indicates an increase in brightness, and L- indicates a decrease in brightness; a+ and b+ indicate an increase in redness and yellowness, respectively, and vice versa, an increase in greenness and blueness. The calculation of the color difference value ΔE is shown in formula (1):

[0083]

[0084] Where ΔL represents the difference between the sample brightness and the calibration plate value; Δa represents the difference between the sample red and green values ​​and the calibration plate value; Δb represents the difference between the sample yellow and blue values ​​and the calibration plate value.

[0085] 2. Determination of texture characteristics

[0086] The test used a flat-bottomed cylindrical probe and a shear measurement probe for index measurement. The measurement range was set to 2500N, and the starting force was 1N. The probe descent speed was set to 30mm / s, the probe return speed was set to 60mm / s, the compression ratio was 60%, and each group of samples was measured three times.

[0087] 3. Determination of Thawing Loss Rate

[0088] The sample was weighed before thawing and recorded as M0. After the sirloin was thawed, it was blotted dry with absorbent paper towels and weighed immediately and recorded as M1. This was repeated three times. The thawing loss rate was calculated as shown in formula (2).

[0089] Thawing loss rate % = (M0-M1) / M×100(2)

[0090] 4. Determination of cooking loss rate

[0091] After thawing, the surface moisture of the meat sample is blotted with absorbent paper and weighed and recorded as M1. Then, the sample is cooked in a water bath until the core temperature reaches 75°C, then taken out immediately and the surface moisture is blotted. After the meat sample is cooled to room temperature, the mass is weighed and recorded as M2. Repeat 3 times and calculate the cooking loss rate according to formula (3).

[0092] Cooking loss rate % = (M1-M2) / M1×100(3)

[0093] 5. Determination of Volatile Basic Nitrogen (TVB-N) and Malondialdehyde (MDA) Values

[0094] TVB-N was determined using a volatile basic nitrogen kit, and MDA was determined using a malondialdehyde kit. The specific operation process was carried out according to the instructions of each kit, and all indicators were determined within 12 hours.

[0095] 6. pH Determination

[0096] Cut 5.0g of thawed beef brisket into small pieces, add 50mL of deionized water and shake well, homogenize in an ice bath for 1min, homogenize for 10s each time, and stop for 10s. Insert the pH meter electrode directly into the homogenate and read the value after it stabilizes. Repeat the measurement 3 times and take the average value.

[0097] 7. Myofibrillar Protein Extraction

[0098] Weigh 5.0g of thawed meat sample from each group, add 50mL of 20 mmol / L buffer A (pH 7.0, containing 100mmol / L NaCl and 1mmol / L EDTA), mix well, and homogenize at 10000×g for 3min, stop for 10s after every 20s of homogenization to avoid overheating and protein denaturation. Then centrifuge at 5000×g for 10min at 4℃ and take the precipitate. Add 50mL of buffer A again, repeat the above operation twice, and take the precipitate. Add 8× volume of 25mmol / L buffer B (pH 7.0, containing 0.6mol / L NaCl) to the precipitate and homogenize again. Filter with gauze to remove insoluble matter, and the precipitate obtained after centrifugation at 4℃, 5000×g for 15min is myofibrillar protein. The protein content is determined by Lowry method.

[0099] 8. Protein electrophoresis

[0100] The samples were subjected to polyacrylamide gel electrophoresis (SDS-PAGE). The concentration of the myofibrillar protein solution was diluted to 5 mg / mL, mixed with the loading buffer in a 1:1 ratio, and placed in boiling water for 10 minutes to fully dissolve it. The electrophoresis used 12% separation gel and 5% concentration gel, and the sample volume was 10 μL. At the beginning, the electrophoresis voltage was set to 80V. After the bromophenol blue converged into a line, the voltage was adjusted to 120V. After the electrophoresis, the protein staining solution was used for 90 minutes of staining. Use a decolorization shaker for 60 minutes of decolorization, and change the decolorization solution (methanol: glacial acetic acid: deionized water = 3.0:1.0:6.0) every 30 minutes until the gel base color is colorless and transparent.

[0101] 9. Scanning electron microscopy

[0102] First, the thawed beef brisket was fixed by soaking it in 2.5% glutaraldehyde solution overnight. Then, it was dehydrated with ethanol (30% to 90%) gradient, dehydrated with 100% ethanol for 3 times, and washed with isoamyl acetate for 2 times. After being cut into 1mm thick slices by a freezing microtome, it was stuck on the stage and the surface was sprayed with gold. The magnification of the scanning electron microscope observation was set to 300 and 1000.

[0103] 10. Data processing

[0104] All index data were obtained by three repeated experiments and expressed as mean ± standard deviation. SPSS 17.0 software was used for statistical analysis, and Origin 9.0 graphics software was used for image drawing.

Claims

1. A method for thawing beef brisket by multi-frequency ultrasound, characterized in that Adopt dual-frequency sequential ultrasonic thawing mode, take frozen beef brisket with center temperature below -20℃, use multi-frequency ultrasonic equipment, place the sample in water in ultrasonic tank, the immersion distance from horizontal plane is about 0.5-3cm, the water temperature is controlled at 12-20℃, the ultrasonic power is 900W, and the meat sample is taken out when the center temperature rises above 0℃; the ultrasonic frequency is 22 / 28kHz, 28 / 40 or 22 / 40kHz.

2. The method for thawing beef brisket by multi-frequency ultrasound according to claim 1, characterized in that The frequency is 22 / 28kHz and 28 / 40kHz dual-frequency sequential ultrasonic treatment.

3. The method for thawing beef brisket by multi-frequency ultrasound according to claim 1, characterized in that The frequency is 28 / 40kHz dual-frequency sequential ultrasonic treatment.

4. The method for thawing beef brisket by multi-frequency ultrasound according to claim 1, characterized in that The immersion point is about 0.5 cm away from the horizontal plane.

5. The method for thawing beef brisket by multi-frequency ultrasound according to claim 1, characterized in that The controlled water temperature is 15°C.

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