Research method for controlling deterioration of conditioned frozen storage quality of chicken wings by steady-state EGCG (epigallocatechin gallate)

Abstract

The invention relates to the technical field of conditioning meat products, and provides a method for controlling and researching frozen storage quality deterioration of conditioned chicken wings by steady-state EGCG (epigallocatechin gallate), which comprises the following steps: step 1, sample treatment: conditioning unfrozen chicken wings; step 2, measuring the color, the unfreezing loss, the ferrimyoglobin, the sulfydryl, the Shore band, the thiobarbituric acid value TBARS and the volatile basic nitrogen TVB-N of the conditioned chicken wings; 3, analyzing a result; changes of color, unfreezing loss, ferrimyoglobin content, sulfydryl, Shore band, thiobarbituric acid value TBARS and volatile basic nitrogen TVB-N in the chicken wing freezing and thawing process are analyzed and conditioned; and 4, performing sensory evaluation according to the sensory evaluation table. According to the method, the control of the steady-state EGCG on the frozen storage quality deterioration of the conditioned chicken wings can be better studied.

Description

Technical Field

[0001] The present invention relates to the technical field of prepared meat products, and in particular, to a research method for controlling the deterioration of the frozen storage quality of prepared chicken wings by steady-state EGCG. Background Art

[0002] The frozen storage method can reduce the life activities of microorganisms and the chemical reactions that occur in the meat products themselves to a relatively low level, making the frozen meat products have the outstanding advantage of a longer shelf life compared to chilled fresh meat products. This has also attracted more and more attention in the meat products industry. However, after the meat products are made into finished products by quick-freezing and then frozen and stored, and finally thawed to the edible state, the quality of the frozen meat products will be reduced to varying degrees during this process.

[0003] The water in meat products generally begins to condense at -2 to -0.5 °C, and the water in it will completely condense when the temperature drops to -65 to -62 °C. During the freezing process, if the water in the meat products is not frozen thoroughly or the freezing treatment time is too long, the quality of the meat products during frozen storage will be significantly reduced, thus affecting the purchasing intention of consumers and reducing the economic benefits of food enterprises. Therefore, to ensure its quality, the freezing temperature is generally controlled at about -23 °C, and after the quick-freezing is completed, it is stored at -18 °C. The main reasons for the quality changes during the frozen storage of meat products are mainly the following categories:

[0004] (1) Freeze-thaw cycle: Thawing the frozen meat is a freeze-thaw cycle. Generally, multiple freeze-thaw cycles will occur during the sales process of meat products. It is mainly the change in temperature that causes the phenomenon of repeated freezing and thawing. The quality of frozen prepared meat products will gradually deteriorate with the increase in the number of freeze-thaw cycles. The temperature will rise during the thawing process, enabling the rapid reproduction of microorganisms and thus reducing the edible quality of the prepared meat products. At the same time, the prepared meat products will show the phenomenon of juice loss. In addition, the soluble substances in the prepared meat products, such as proteins, salts, amino acids, etc., will also decrease with the juice loss. During the freezing process, the water in the prepared meat products forms new ice crystals again, destroying the structure of the myofibrillar protein in the prepared meat products and thus leading to a decrease in the edible quality.

[0005] (2) Freezing temperature and time: The oxidation of fat and protein is indirectly affected by the freezing temperature and time. One of the main factors affecting the taste, flavor, and texture deterioration of meat products is fat oxidation. Therefore, fat oxidation will reduce the consumption rate. This is because the products of fat oxidation will produce unpleasant odors and endanger human health at the same time. Meanwhile, during the protein oxidation process, due to the chemical bond action of protein molecules, protein aggregates will be formed, resulting in a significant decrease in the eating quality and nutritional quality of meat, such as tenderness, flavor, and taste. Since the oxidation reaction has a strong dependence on temperature, the higher the temperature, the more intense the oxidation reaction. Therefore, the lower the freezing temperature, the better the quality of the prepared meat products and the longer the shelf life.

[0006] (3) Freezing rate: The faster the freezing rate, the smaller and more uniform the ice crystals formed, and the less damage to the myofibrillar protein structure of the prepared meat products; the slower the freezing rate, the larger and more irregular the ice crystals formed, and the greater the damage to the myofibrillar protein structure of the prepared meat products. However, it is not that the faster the freezing rate, the better. An excessively fast freezing rate is prone to problems such as too large a temperature difference and uneven freezing, resulting in a decrease in the quality of the prepared meat products.

[0007] In recent years, with the increasing pursuit of a better life by people, the consumption demand for prepared meat products has been increasing. However, during the freezing storage of meat products, due to reasons such as temperature fluctuations, the eating quality of meat products decreases, spoilage occurs, and it endangers human health. Therefore, ensuring the quality and safety of meat products during freezing storage has become a major challenge for meat product processing enterprises and meat product sales enterprises.

[0008] Prepared chicken wings are a typical type of prepared meat product and have become the mainstream of consumption in recent years. The reason why consumers have a very high willingness to consume chicken wings is that the price of chicken wings is moderate, and it has a high protein content, low fat and cholesterol content. However, during the freezing storage process, chicken wings will experience phenomena such as juice loss, a large number of microorganisms will multiply, the protein in the meat will be decomposed, and at the same time, the fat and protein in the meat will also oxidize, seriously affecting the sensory quality, nutritional value, food safety, and shelf life of meat products. There are quality deterioration problems such as discoloration during the freezing storage of this product, which has become a key factor restricting the healthy and rapid development of the industry. Therefore, it is extremely urgent to break through the technical bottleneck of the quality deterioration of prepared chicken wings during freezing storage. Summary of the Invention

[0009] The content of the present invention is to provide a research method for controlling the quality deterioration of prepared chicken wings during freezing storage by using stable EGCG, which can preferably study the control of the quality deterioration of prepared chicken wings during freezing storage by using stable EGCG.

[0010] A research method for controlling the quality deterioration of prepared chicken wings during freezing storage by using stable EGCG according to the present invention includes the following steps:

[0011] Step 1, sample treatment, conditioning the thawed chicken wings.

[0012] Step 2, measuring the color, thawing loss, metmyoglobin, sulfhydryl group, Shore bands, thiobarbituric acid value (TBARS), and volatile basic nitrogen (TVB-N) of the conditioned chicken wings.

[0013] Step 3, result analysis.

[0014] Analyze the changes in color, thawing loss, metmyoglobin content, sulfhydryl group, Shore bands, thiobarbituric acid value (TBARS), and volatile basic nitrogen (TVB-N) during the freeze-thaw process of the conditioned chicken wings.

[0015] Step 4, conduct sensory evaluation according to the sensory evaluation form.

[0016] Preferably, in Step 1, after thawing the chicken wings, wash them and divide them into two groups: a blank treatment group and an EGCG treatment group. The blank treatment group is marinated according to the following formula:

[0017] 100 g of fresh chicken wings, 20 g of ice water, 2 g of salt;

[0018] The EGCG treatment group is marinated according to the following formula:

[0019] 100 g of fresh chicken wings, 20 g of ice water, 2 g of salt, 0.5 g of EGCG and aqueous solution of acerola cherry;

[0020] Let the salt, EGCG and aqueous solution of acerola cherry evenly coat the chicken wings, and let them stand for 12 h; after marinating, put the chicken wings into a plastic bag and seal it, freeze at -18 °C for 56 h, and thaw at 4 °C for 16 h as one freeze-thaw cycle. Samples are taken for index detection after 0, 1, 2, 3, and 4 freeze-thaw cycles respectively.

[0021] Preferably, the specific method for measuring the color is as follows:

[0022] Use a spectrophotometric colorimeter to measure the color of the conditioned chicken wings;

[0023] Before measurement, dry the surface moisture of the conditioned chicken wing sample with filter paper; align the measurement port of the spectrophotometric colorimeter with the blackboard and whiteboard for calibration; during measurement, place the lens of the spectrophotometric colorimeter vertically on the meat surface, and the lens port needs to be closely attached to the chicken wing surface without light leakage. Press the measurement button to measure and record the brightness value L * , redness value a * , yellowness value b * , measure at least 3 points for each sample, and take the average of the 3 points as its L * , a * , b * .

[0024] Preferably, the thawing loss is determined as follows:

[0025] The surface moisture of the marinated chicken wings after the 0th freeze-thaw cycle is blotted dry with filter paper and weighed, denoted as m0. After the marinated chicken wing samples are thawed in a 4°C refrigerator for 16 h, the surface moisture is blotted dry with filter paper. The thawed samples are weighed, denoted as m, and measured in parallel 3 times. The calculation is performed according to the following formula:

[0026] Thawing loss (%) = (m0 - m) / m0 × 100%.

[0027] Preferably, the metmyoglobin is determined as follows:

[0028] After the marinated chicken wing samples are thawed in a 4°C refrigerator for 16 h, 5.0 g of the meat sample is weighed, 25 mL of phosphate buffer is added, and homogenized at 1000 r / min for 1 min. Then, it is left standing in a 4°C refrigerator for 40 - 60 min and centrifuged. The supernatant is taken and filtered with filter paper. Subsequently, 200 μl of the filtrate is added to a 96-well plate, and the absorbance of the filtrate at wavelengths of 503, 525, 582, and 557 nm is measured with an enzyme-linked immunosorbent assay reader. The relative content of metmyoglobin MetMb is calculated according to the following formula:

[0029] That is: MetMb (%) = (-2.514R1 + 0.777R2 + 0.800R3 + 1.098) * 100

[0030] In the formula: R1, R2, and R3 are the ratios of the absorbance values at 572, 565, and 545 nm to the absorbance value at 525 nm, respectively.

[0031] Preferably, the sulfhydryl groups are determined as follows:

[0032] The total sulfhydryl group content in the protein is determined using a total sulfhydryl group assay kit. The detection principle is that sulfhydryl groups react with 5,5'-dithiobis-(2-nitrobenzoic acid) to form a yellow compound with a maximum absorption peak at 412 nm.

[0033] Preferably, the Shore band is determined as follows:

[0034] The extracted myoglobin is scanned with a UV-visible spectrophotometer in the wavelength range of 380 - 450 nm at a speed of 1000 nm / min, with the blank being phosphate buffer solution.

[0035] Preferably, the thiobarbituric acid value TBARS is determined by spectrophotometry, and the volatile basic nitrogen TVB-N is determined by an automatic Kjeldahl nitrogen analyzer.

[0036] Preferably, in step 3, the blank treatment group and the EGCG treatment group are compared to analyze the effect of EGCG on the quality deterioration of the marinated chicken wings.

[0037] The beneficial effects of the present invention are as follows:

[0038] The present invention uses chicken wings as raw materials, adds salt and ice water as auxiliary materials, and divides them into two groups. One group is added with EGCG and acerola cherry aqueous solution as the EGCG treatment group, and the other group without other substances is the blank treatment group, to explore the research on the control of quality deterioration of marinated chicken wings during frozen storage by stable EGCG. By measuring indicators such as its color, thawing loss, metmyoglobin, sulfhydryl group, Shore band, thiobarbituric acid, volatile basic nitrogen, and sensory evaluation, etc., the influence of EGCG on the quality deterioration of marinated chicken wings during frozen storage can be better analyzed. Brief Description of the Drawings

[0039] Figure 1 It is a flowchart of a research method for controlling the quality deterioration of marinated chicken wings during frozen storage by stable EGCG;

[0040] Figure 2 It is a schematic diagram of the change in thawing loss during the freeze-thaw process of marinated chicken wings;

[0041] Figure 3 It is a schematic diagram of the change in the relative content of metmyoglobin during the freeze-thaw process of marinated chicken wings;

[0042] Figure 4 It is a schematic diagram of the change in sulfhydryl group content during the freeze-thaw process of marinated chicken wings;

[0043] Figure 5 It is a schematic diagram of the change in Shore band during the freeze-thaw process of marinated chicken wings in the blank treatment group;

[0044] Figure 6 It is a schematic diagram of the change in Shore band during the freeze-thaw process of marinated chicken wings in the EGCG treatment group;

[0045] Figure 7 It is a schematic diagram of the change in TBARS value during the freeze-thaw process of marinated chicken wings;

[0046] Figure 8 It is a schematic diagram of the change in TVB-N value during the freeze-thaw process of marinated chicken wings;

[0047] Figure 9 It is a schematic diagram of the sensory evaluation during the freeze-thaw process of marinated chicken wings in the blank treatment group;

[0048] Figure 10 It is a schematic diagram of the sensory evaluation during the freeze-thaw process of marinated chicken wings in the EGCG treatment group. Detailed Embodiments

[0049] To further understand the content of the present invention, the present invention will be described in detail with reference to the drawings and embodiments. It should be understood that the embodiments are only for explaining the present invention rather than limiting it.

[0050] Example

[0051] As Figure 1 shown, this example provides a research method for controlling the deterioration of the frozen storage quality of marinated chicken wings by steady-state EGCG, which includes the following steps:

[0052] Step 1, sample treatment, marinate the thawed chicken wings.

[0053] Step 2, measure the color, thawing loss, metmyoglobin, sulfhydryl group, Shore band, thiobarbituric acid value TBARS, and volatile basic nitrogen TVB-N of the marinated chicken wings.

[0054] Step 3, result analysis;

[0055] Analyze the changes in color, thawing loss, metmyoglobin content, sulfhydryl group, Shore band, thiobarbituric acid value TBARS, and volatile basic nitrogen TVB-N during the freeze-thaw process of the marinated chicken wings; compare the blank treatment group and the EGCG treatment group to analyze the effect of EGCG on the deterioration of the quality of the marinated chicken wings.

[0056] Step 4, conduct a sensory evaluation according to the sensory evaluation form.

[0057] Sample treatment

[0058] After thawing the chicken wings, wash them and divide them into two groups: the blank treatment group and the EGCG treatment group. The blank treatment group is marinated according to the following formula:

[0059] 100 g of fresh chicken wings, 20 g of ice water, 2 g of salt;

[0060] The EGCG treatment group is marinated according to the following formula:

[0061] 100 g of fresh chicken wings, 20 g of ice water, 2 g of salt, 0.5 g of EGCG and acerola cherry aqueous solution;

[0062] Let the salt, EGCG, and acerola cherry aqueous solution evenly coat the chicken wings, and let them stand for 12 h; after marinating, put the chicken wings into a plastic bag and seal them, freeze them at -18 °C for 56 h, and thaw them at 4 °C for 16 h as one freeze-thaw cycle. Samples are taken and tested for index detection after 0, 1, 2, 3, and 4 freeze-thaw cycles respectively.

[0063] Measurement of color

[0064] Use a spectrophotometric colorimeter to measure the color of the marinated chicken wings; before measurement, dry the surface moisture of the marinated chicken wing samples with filter paper; align the measurement port of the spectrophotometric colorimeter with the blackboard and whiteboard for calibration; during measurement, place the lens of the spectrophotometric colorimeter vertically on the meat surface, and the lens opening needs to be closely attached to the chicken wing surface without light leakage, then press the measurement button to measure and record the brightness value L of the meat sample respectively *, Redness value a * , Yellowness value b * , For each sample, at least 3 points are measured, and the average value of the 3 points is taken as its L * , a * , b * .

[0065] Determination of thawing loss

[0066] Blot the surface moisture of the marinated chicken wings after the 0th freeze-thaw cycle with filter paper and weigh it, denoted as m0; after thawing the marinated chicken wing samples in a 4°C refrigerator for 16 h, blot the surface moisture with filter paper; weigh the thawed samples, denoted as m, and measure in parallel 3 times; calculate according to the following formula:

[0067] Thawing loss (%) = (m0 - m) / m0 × 100%.

[0068] Determination of metmyoglobin

[0069] After thawing the marinated chicken wing samples in a 4°C refrigerator for 16 h, weigh 5.0 g of meat sample, add 25 mL of phosphate buffer (40 mmol / L, pH 6.8, 4°C), homogenize at 1000 r / min for 1 min, then let it stand in a 4°C refrigerator for 40 - 60 min and centrifuge (8000 r / min, 10 min, 4°C), take the supernatant and filter it with filter paper; then add 200 μl of the filtrate to a 96-well plate, and measure the absorbance of the filtrate at wavelengths of 503, 525, 582, and 557 nm with an enzyme-labeled instrument; calculate the relative content of metmyoglobin MetMb according to the following formula:

[0070] That is: MetMb (%) = (-2.514R1 + 0.777R2 + 0.800R3 + 1.098) * 100

[0071] Where: R1, R2, and R3 are the ratios of the absorbance values at 572, 565, and 545 nm to that at 525 nm, respectively.

[0072] Determination of sulfhydryl groups

[0073] Use a total sulfhydryl determination kit to determine the total sulfhydryl content in the protein; the detection principle is that sulfhydryl groups react with 5,5'-dithiobis-(nitrobenzoic acid) (DTNB) to form a yellow compound, which has a maximum absorption peak at 412 nm.

[0074] Determination of Shore band

[0075] Scan the extracted myoglobin in the wavelength range of 380 - 450 nm with a UV-visible spectrophotometer at a speed of 1000 nm / min, and use a phosphate buffer solution (pH = 6.8, 0.04 M) as the blank.

[0076] Determination of thiobarbituric acid value (TBARS)

[0077] Refer to the spectrophotometry method in GB / T 5009.181-2016 "National Food Safety Standard - Determination of Malondialdehyde in Foods".

[0078] Determination of total volatile basic nitrogen (TVB-N)

[0079] Refer to the automatic Kjeldahl nitrogen analyzer in CB / T 5009.228-2016 "National Food Safety Standard - Determination of Total Volatile Basic Nitrogen in Foods".

[0080] Color changes during freeze-thaw cycles of marinated chicken wings

[0081] The color of meat products is an important indicator for evaluating meat quality, which is related to whether the product can be accepted by consumers. As shown in Table 1, the color difference values L*, a*, and b*.

[0082] Table 1 Color change table of marinated chicken wings during freeze-thaw cycles

[0083]

[0084] As can be seen from Table 1, with the increase in the number of freeze-thaw cycles, the L* value and a* value of the samples gradually decreased, but the b* value of both groups gradually increased, indicating that the color of marinated chicken wings became worse with the increase in the number of repeated freeze-thaw cycles. L* reflects the brightness value of meat. The decrease in the L* value may be due to the loss of juice during the repeated freeze-thaw process of marinated chicken wings, and the light scattering also weakened accordingly, resulting in the surface color becoming darker. The L* value of the blank treatment group decreased from the initial 75.75 to 71.84, while that of the EGCG treatment group decreased from the initial 75.54 to 72.43. The decrease in the brightness value of the EGCG treatment group was significantly less than that of the blank treatment group. The experimental results show that EGCG can delay the darkening of the color of marinated chicken wings. a* reflects the redness value of meat. The decrease in the a* value may be due to the degradation of pigments during the repeated freeze-thaw process of marinated chicken wings, and at the same time, the unstable oxymyoglobin will be oxidized to brown metmyoglobin. The results show that the redness value of the EGCG treatment group decreased from -0.83 to -1.86, and that of the blank treatment group decreased from -0.73 to -2.19, indicating that the EGCG treatment group is better than the blank treatment group in maintaining the redness value of meat color. The b* value represents the yellowness value of meat. The increase in the b* value may be due to the oxidation reaction of the fat in marinated chicken wings, and the reaction between its oxidation product free radicals and amine substances in proteins produces yellow pigments. The yellowness value of the EGCG treatment group increased from 2.152 to 5.43, and that of the blank treatment group increased from 3.35 to 6.98. The increase in the b* value of the EGCG treatment group was significantly lower than that of the blank treatment group, indicating that the EGCG treatment group has a better effect on maintaining the yellowness value of meat compared to the blank treatment group.

[0085] The results showed that during the repeated freeze - thaw process, compared with the blank control group, the reduction values of L* value and a* value in the EGCG treatment group were less, and the increase value of b* value was also less. This was because EGCG had antioxidant and color - protecting effects, reflecting that EGCG had a better effect on maintaining the quality of marinated chicken wings.

[0086] Changes in thawing loss during the freeze - thaw process of marinated chicken wings

[0087] Water - holding capacity is an important quality index for evaluating the quality of meat products, which directly affects the changes of meat products during processing and storage. Water loss will lead to a decrease in the hardness, flavor and nutritional components of the meat after thawing, reducing consumer acceptance. Therefore, thawing loss is one of the important indexes for evaluating the quality of marinated chicken wings.

[0088] As Figure 2 shown, the thawing loss of marinated chicken wings increased with the increase in the number of freeze - thaw cycles. The main reason might be that the ice crystals formed during repeated freeze - thawing damaged the muscle fibers of marinated chicken wings, resulting in the deformation of the tissue of the sample, causing water to diffuse out of the cells, and increasing the water mobility of the meat. With the increase in the number of freeze - thaw cycles, the thawing loss of the samples in the blank control group increased significantly from 3.66% to 7.33%, while the thawing loss of the marinated chicken wings treated with EGCG was less than that of the blank control group during 4 freeze - thaw cycles, and its thawing loss increased from the initial 3.13% to 6.79%. The experimental results showed that EGCG could improve the water - holding performance of marinated chicken wings. This might be because EGCG, as an antioxidant, could indirectly affect the water - holding capacity of muscles, and the level of water - holding capacity depended on the pH value of the meat and the degree of lipid oxidation. Fat oxidation could lead to protein oxidation, and protein oxidation would cause muscle fiber contraction and reduce the water - holding capacity of muscles.

[0089] Changes in metmyoglobin content during the freeze - thaw process of marinated chicken wings

[0090] The content of myoglobin is one of the main factors affecting the color of meat products. As the muscle continuously contacts with air, the reduced myoglobin (divalent iron) will react with oxygen in the air in two different ways - oxidation reaction and oxygenation reaction, and generate two different - colored substances respectively. When myoglobin undergoes an oxygenation reaction, bright - red oxymyoglobin ((divalent iron)) will be generated, which will not significantly affect the color of the meat. However, when myoglobin undergoes an oxidation reaction, brown metmyoglobin (trivalent iron) will be generated, and its accumulation to a certain extent will lead to the browning of the meat color, significantly affecting the color of the meat.

[0091] As Figure 3As shown, with the increase in the number of freeze-thaw cycles, the relative content of metmyoglobin in both groups showed an upward trend. This is because metmyoglobin underwent a continuous oxidation reaction with oxygen. Among them, the relative content of metmyoglobin in the blank treatment group increased from the initial 30.56% to 38.64%, while that in the EGCG treatment group increased from the initial 30.39% to 36.27%. The experimental results showed that the growth rate of the relative content of metmyoglobin in the EGCG treatment group was smaller than that in the blank treatment group. The results indicated that EGCG could significantly reduce the formation rate of metmyoglobin, thereby inhibiting the browning of meat.

[0092] Changes in the sulfhydryl group content during the freeze-thaw process of marinated chicken wings

[0093] The oxidation process of proteins is very complex, and sulfhydryl groups are reactive functional groups in proteins. The sulfhydryl groups of cysteine are easily attacked by free radicals and oxidized to disulfide bonds. Subsequently, the degree of protein oxidation can be measured by determining the decrease in sulfhydryl groups.

[0094] The changes in the sulfhydryl group content of marinated chicken wings during the freeze-thaw process are shown by Figure 4 As shown. It can be seen from the figure that with the increase in the number of freeze-thaw cycles, the sulfhydryl group content in both groups of marinated chicken wings showed a downward trend, but the decrease rate in the EGCG treatment group was lower than that in the blank treatment group. There was little difference in the sulfhydryl group content between the two groups at the 0th freeze-thaw cycle. The sulfhydryl group content in the blank treatment group was 2.5267 μmol / g, and that in the EGCG treatment group was 2.5291 μmol / g. However, during the subsequent four freeze-thaw cycles, the sulfhydryl group content in the EGCG treatment group was significantly higher than that in the blank treatment group. After the 4th freeze-thaw cycle, the sulfhydryl group content of the marinated chicken wings treated with EGCG was 0.9500 μmol / g, while that of the marinated chicken wings treated with the blank was 0.7533 μmol / g. The experimental results can show that EGCG can effectively inhibit the degree of protein oxidation of marinated chicken wings.

[0095] Changes in the Shore bands during the freeze-thaw process of marinated chicken wings

[0096] The changes in the Shore bands of the marinated chicken wings in the blank treatment group during the freeze-thaw process and the changes in the Shore bands of the marinated chicken wings in the EGCG treatment group during the freeze-thaw process are shown in Figure 5 and Figure 6 as shown.

[0097] From Figure 5 and Figure 6It can be seen that with the increase in the number of freeze-thaw cycles, the Shore bands of both groups showed blue shifts to varying degrees. The Shore band of the blank treatment group showed a blue shift from 408 nm at the 0th freeze-thaw cycle to 404 nm at the 4th freeze-thaw cycle. At the same time, the Shore band of the EGCG treatment group also showed a blue shift from 406 nm at the 0th freeze-thaw cycle to 404 nm at the 4th freeze-thaw cycle. Previous related studies have shown that a similar blue shift in the Shore band can be observed when oxymyoglobin turns into metmyoglobin. Therefore, the blue shift of the Shore peak in the experimental results indicates that the myoglobin in the marinated chicken wings undergoes an oxidation reaction during repeated freeze-thaw cycles.

[0098] Changes in TBARS value during the freeze-thaw process of marinated chicken wings

[0099] The TBARS value is one of the important indicators reflecting the degree of lipid oxidation in food. When food is stored at freezing and refrigeration temperatures, the lipids in the food are oxidized, and unsaturated fatty acids form hydroperoxides, which then decompose into secondary products, including malondialdehyde and other carbonyl compounds that cause off-flavors.

[0100] Changes in TBARS value during the freeze-thaw process of marinated chicken wings are as Figure 7 shown. It can be seen from the figure that with the increase in the number of freeze-thaw cycles, the TBARS values of both groups showed an upward trend, but the rising rate of the EGCG treatment group was smaller than that of the blank treatment group. At the 0th freeze-thaw cycle, the TBARS value of the blank treatment group was 0.1933 mg / kg, while the TBARS value of the EGCG treatment group was 0.0400 mg / kg. This result may be because EGCG began to inhibit lipid oxidation during static marination. After 4 freeze-thaw cycles, the TBARS values of the blank treatment group and the EGCG treatment group were 0.3800 mg / kg and 0.1500 mg / kg, respectively. Compared with the TBARS values at the 0th freeze-thaw cycle, both showed a significant increase. The results indicate that EGCG can significantly inhibit the degree of lipid oxidation in marinated chicken wings.

[0101] Changes in TVB-N value during the freeze-thaw process of marinated chicken wings

[0102] TVB-N is an important indicator for judging the freshness of meat products. The proteins in livestock and poultry meat are decomposed under the action of enzymes and bacteria to produce alkaline nitrogen-containing substances such as ammonia and amines. These ammonia or amine substances can combine with acidic substances in the meat tissue to form basic nitrogen. Basic nitrogen is volatile and is also called total volatile nitrogen (TVB-N).

[0103] As Figure 8As shown in the figure, with the increase in the number of freeze-thaw cycles, the content of volatile basic nitrogen in both groups increased significantly. However, the increase in the EGCG treatment group was smaller than that in the blank treatment group. The TVB-N value of the blank treatment group increased from the initial 9.85 mg / 100 g to 14.70 mg / 100 g. According to the national food safety standard GB2707-2016 in China, the TVB-N value of fresh and frozen meat should be ≤ 15.00 mg / 100 g. After 4 freeze-thaw cycles, the blank treatment group was close to the standard of spoiled meat. The TVB-N of the EGCG treatment group increased from the initial 7.26 mg / 100 g to 11.08 mg / 100 g. The results indicate that EGCG can effectively inhibit the spoilage of marinated chicken wings, significantly inhibit the decomposition of proteins caused by enzymes or bacteria, and is beneficial to improving the freshness of marinated chicken wings.

[0104] Sensory evaluation of marinated chicken wings during the freeze-thaw process

[0105] Take the marinated chicken wings out of the refrigerator at -18 °C, and reheat them by microwave. The reheating conditions are a microwave power of 650 w and a microwave time of 4 min. After reheating, take them out and cool for 15 min before conducting a sensory evaluation. The weight of each index is shown in the appendix, and the sensory evaluation form is shown in Table 2:

[0106] Table 2 Sensory evaluation form

[0107]

[0108] The radar charts of the sensory evaluation of marinated chicken wings in the blank treatment group during the freeze-thaw process and the sensory evaluation of marinated chicken wings in the EGCG treatment group during the freeze-thaw process are as Figure 9 and Figure 10 shown.

[0109] With the increase in the number of freeze-thaw cycles, the overall sensory scores of marinated chicken wings decreased. However, the overall sensory score of the EGCG treatment group was significantly higher than that of the blank treatment group. Compared with the blank treatment group, the appearance, taste, flavor, and acceptability of the EGCG treatment group were significantly better than those of the blank treatment group. In terms of odor, there was no significant change in the EGCG treatment group and the blank treatment group at the 0th and 1st freeze-thaw cycles. However, after the 4th freeze-thaw cycle, the odor scores of both the EGCG treatment group and the blank treatment group decreased significantly, and an off-odor occurred. The results indicate that EGCG can significantly improve the edible quality of marinated chicken wings.

[0110] In this example, by measuring indicators such as its color, thawing loss, metmyoglobin, sulfhydryl group, Shore spectrum, thiobarbituric acid, volatile basic nitrogen, and sensory evaluation, etc., it is possible to better analyze the effect of EGCG on the quality deterioration of marinated chicken wings during frozen storage. The results show that EGCG can significantly improve the quality deterioration of marinated chicken wings during frozen storage.

[0111] The above is a schematic description of the present invention and its embodiments. This description is not restrictive. What is shown in the drawings is only one of the embodiments 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, without departing from the gist of the present invention, design similar structural forms and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. Research method for controlling the deterioration of the quality of marinated chicken wings during frozen storage by steady-state EGCG, characterized in that: It includes the following steps: Step 1: Sample treatment, conditioning the thawed chicken wings. Step 2: Measuring the color, thawing loss, metmyoglobin, sulfhydryl group, Shaw bands, thiobarbituric acid value (TBARS), and volatile basic nitrogen (TVB-N) of the conditioned chicken wings. Step 3: Result analysis. Analyzing the changes in color, thawing loss, metmyoglobin content, sulfhydryl group, Shaw bands, thiobarbituric acid value (TBARS), and volatile basic nitrogen (TVB-N) during the freeze-thaw process of the conditioned chicken wings. Step 4: Conducting sensory evaluation according to the sensory evaluation form.

2. The research method for controlling the deterioration of the quality of frozen marinated chicken wings by steady-state EGCG according to claim 1, wherein: In Step 1, after thawing the chicken wings, wash them and divide them into two groups: a blank treatment group and an EGCG treatment group. The blank treatment group is marinated according to the following formula: 100 g of fresh chicken wings, 20 g of ice water, 2 g of salt. The EGCG treatment group is marinated according to the following formula: 100 g of fresh chicken wings, 20 g of ice water, 2 g of salt, 0.5 g of EGCG and acerola cherry aqueous solution. Let the salt, EGCG, and acerola cherry aqueous solution evenly coat the chicken wings, and let them stand for 12 h. After marinating, put the chicken wings into a plastic bag and seal it. Freeze at -18°C for 56 h and thaw at 4°C for 16 h for one freeze-thaw cycle. Samples are taken for index detection after 0, 1, 2, 3, and 4 freeze-thaw cycles respectively.

3. The research method for controlling the deterioration of the quality of chilled marinated chicken wings by steady-state EGCG according to claim 2, wherein: Specifically, the measurement of color is as follows: Use a spectrophotometer to measure the color of the conditioned chicken wings. Before measurement, dry the surface moisture of the marinated chicken wing samples with filter paper; align the measuring port of the spectrophotometer with the blackboard and whiteboard for calibration; during measurement, place the lens of the spectrophotometer vertically on the meat surface, and the lens opening needs to fit tightly against the chicken wing surface without light leakage. Press the measurement button to measure and record the brightness value L of the meat sample respectively * , redness value a * , yellowness value b * . Measure at least 3 points for each sample, and take the average of the 3 points as its L * , a * , b * .

4. The research method for controlling the deterioration of the quality of chilled marinated chicken wings by steady-state EGCG according to claim 3, wherein: Specifically, the measurement of thawing loss is as follows: Blot the surface moisture of the conditioned chicken wings after the 0th freeze-thaw cycle with filter paper and weigh it, denoted as m0. After thawing the conditioned chicken wing samples in a 4°C refrigerator for 16 h, blot the surface moisture with filter paper. Weigh the thawed samples respectively, denoted as m, and measure them in parallel 3 times. Calculate according to the following formula: Thawing loss (%) = (m0 - m) / m0 × 100%.

5. The research method for controlling the deterioration of the quality of marinated chicken wings during frozen storage by using stable EGCG according to claim 4, characterized in that: Specifically, the measurement of metmyoglobin is as follows: After thawing the conditioned chicken wing samples in a 4°C refrigerator for 16 h, weigh 5.0 g of the meat sample, add 25 mL of phosphate buffer, homogenize at 1000 r / min for 1 min, then let it stand in a 4°C refrigerator for 40 - 60 min and centrifuge. Take the supernatant and filter it with filter paper. Subsequently, add 200 μl of the filtrate to a 96-well plate, and use an enzyme-linked immunosorbent assay (ELISA) reader to measure the absorbance of the filtrate at wavelengths of 503, 525, 582, and 557 nm respectively. Calculate the relative content of metmyoglobin (MetMb) according to the following formula: That is: MetMb (%) = (-2.514R1 + 0.777R2 + 0.800R3 + 1.098) * 100 In the formula: R1, R2, and R3 are the ratios of the absorbance values at 572, 565, and 545 nm to the absorbance value at 525 nm respectively.

6. The research method for controlling the deterioration of the quality of chilled marinated chicken wings by steady-state EGCG according to claim 5, characterized in that: Specifically, the measurement of sulfhydryl group is as follows: Use a total sulfhydryl group assay kit to measure the total sulfhydryl group content in the protein. The detection principle is that the sulfhydryl group reacts with 5,5'-dithiobis-(2-nitrobenzoic acid) to form a yellow compound, which has a maximum absorption peak at 412 nm.

7. The research method for controlling the deterioration of the quality of chilled marinated chicken wings by steady-state EGCG according to claim 6, characterized in that: Specifically, the measurement of Shaw bands is as follows: Scan the extracted myoglobin in the wavelength range of 380 - 450 nm with a UV-visible spectrophotometer at a speed of 1000 nm / min, and use phosphate buffer solution as the blank.

8. The research method for controlling the deterioration of the quality of chilled marinated chicken wings by steady-state EGCG according to claim 7, characterized in that: The thiobarbituric acid value (TBARS) was determined by spectrophotometry, and the total volatile basic nitrogen (TVB-N) was determined by an automatic Kjeldahl nitrogen analyzer.

9. The research method for controlling the deterioration of the quality of chilled marinated chicken wings by steady-state EGCG according to claim 8, characterized in that: In step 3, the blank treatment group and the EGCG treatment group were compared to analyze the effect of EGCG on the quality deterioration of marinated chicken wings.

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