Unfreezing method of quick-frozen ginger

Abstract

The invention relates to the technical field of food, in particular to an unfreezing method of quick-frozen ginger. According to the application, four excellent unfreezing modes are selected:-20 DEG C microwave combined magnetic nano unfreezing (-20 DEG C MMAT),-20 DEG C ultrasonic combined vacuum packaging unfreezing (-20 DEG C UVPT),-10 DEG C microwave combined magnetic nano unfreezing (-10 DEG C MMAT) and-10 DEG C ultrasonic combined vacuum packaging unfreezing (-10 DEG C UVPT). Wherein the modes of-10 DEG C ultrasonic wave combined vacuum packaging unfreezing (-10 DEG C UVPT) and-20 DEG C microwave combined magnetic nanometer unfreezing (-20 DEG C MMAT) are better, and the unfreezing effect of the later unfreezing mode is more complete and wider. Therefore, a-20 DEG C microwave combined magnetic nano thawing (-20 DEG C MMAT) thawing mode has better effects in the aspects of maintaining the eating quality, the content of characteristic functional components and the volatile components of the frozen ginger in thawing. And a more suitable thawing method can be selected according to different actual conditions.

Description

Technical Field

[0001] The invention relates to the technical field of food, in particular to a thawing method of quick-frozen ginger. Background Art

[0002] Ginger has a unique aroma and spicy taste. my country is rich in ginger resources. As one of the world's largest ginger producers and consumers, the annual output is as high as 12 to 13 million tons. Since the ginger harvest period is highly seasonal and concentrated, and the fresh ginger has a high water content (85% to 95%), it is easy to degrade, brown and lose juice during storage, resulting in a short shelf life. Therefore, a large amount of fresh ginger needs to be further processed and stored, such as drying, soaking, etc. However, the dried products made by drying, air drying or freeze drying will greatly reduce the unique aroma and strong spicy taste of ginger, and the ginger tissue fibrosis is more serious, and the edibility is low. It is generally used for medicinal purposes, oral or external use, or for extracting raw materials. In addition, the preservation and storage technology of ginger is still mainly based on traditional earth pits, which are prone to produce ginger maggots, and the secondary pollution problem is serious. The problem of ginger quality deterioration has become a technical problem that plagues planting and processing companies.

[0003] Freezing is the most common food preservation technology, which can maximize the preservation of food flavor and quality. Although frozen storage can delay the aging of fruit and vegetable tissues, inhibit microbial contamination, and extend the storage period, freezing will cause the starch and protein in fruits and vegetables to lose their water-holding capacity, and the repeated formation of ice crystals during the freezing and thawing process will also destroy the cell structure of fruit and vegetable tissues. During the thawing process, the activity of enzymes and microorganisms will increase, the juice loss rate will also increase, and the vitamins, proteins, salts, etc. dissolved in the juice will also be lost, reducing the flavor and nutritional value of fruits and vegetables.

[0004] The ginger thawing technologies currently studied cannot meet the needs of the rapid development of the modern food industry due to their respective limitations. For example, the development of traditional thawing technology is limited by its low thawing efficiency and microbial contamination, while the expensive equipment cost, uneven heating and poor penetration are some of the problems that need to be solved urgently by some new thawing technologies. Therefore, it is of great practical significance to study a thawing technology that is efficient, energy-saving and can maximize the original quality of ginger. Summary of the invention

[0005] In order to solve the above technical problems existing in the prior art, the present invention provides a method for thawing quick-frozen ginger, comprising the following steps:

[0006] The invention discloses a method for thawing quick-frozen ginger, which adopts ultrasonic combined with vacuum packaging for thawing.

[0007] Furthermore, the ultrasonic combined vacuum packaging thawing is to thaw the vacuum-packed and sealed quick-frozen ginger under ultrasonic conditions of a temperature of 20 to 30° C. and a power of 300 to 400 W. The specific ultrasonic conditions are a temperature of 25° C. and a power of 350 W.

[0008] A method for thawing quick-frozen ginger adopts microwave combined with magnetic nano thawing.

[0009] Furthermore, the microwave combined with magnetic nano thawing is to place the vacuum-sealed quick-frozen ginger in a 0.05-0.2 mg / mL ferroferric oxide solution and thaw it with a 300-350W microwave, and the thawing is considered complete when the center temperature reaches 4°C. Preferably, the concentration of the ferroferric oxide solution is 0.1 mg / mL; the microwave power is 320W.

[0010] Furthermore, the thawing is completed when the central temperature reaches 4°C.

[0011] Furthermore, the quick-frozen ginger is quick-frozen ginger that is stored at -5 to -25° C. after quick freezing. Preferably, the quick freezing is to quickly reduce the temperature of the ginger to -18° C., that is, quick freezing is completed.

[0012] A method for thawing quick-frozen ginger adopts ultrasonic combined with vacuum packaging to thaw the ginger when the ginger is stored at -5 to -15°C; and adopts microwave combined with magnetic nano to thaw the ginger when the ginger is stored below -15°C.

[0013] This application selects four excellent thawing methods: microwave combined with magnetic nano thawing at -20℃ (-20℃

[0014] MMAT), -20℃ ultrasonic combined with vacuum packaging thawing (-20℃UVPT), ​​-10℃ microwave combined with magnetic nano thawing (-10℃MMAT), -10℃ ultrasonic combined with vacuum packaging thawing (-10℃UVPT). Among them, -10℃ ultrasonic combined with vacuum packaging thawing (-10℃UVPT) and -20℃ microwave combined with magnetic nano thawing (-20℃MMAT) are better, and the latter thawing method has a more comprehensive and wider thawing effect. Therefore, the -20℃ microwave combined with magnetic nano thawing (-20℃MMAT) thawing method is better in maintaining the edible quality, characteristic functional ingredient content, and volatile components of quick-frozen ginger. A more suitable thawing method can be selected according to different actual situations.

[0015] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0016] 1. After standardizing and cumulatively ranking the four indicators of 18 different thawing methods, this application found that the optimal thawing method is microwave combined with magnetic nano thawing at -20°C (-20°C MMAT), with a score of -4.33; the other three better thawing methods are ultrasonic combined with vacuum packaging thawing at -20°C (-20°C UVPT) (-3.24), microwave combined with magnetic nano thawing at -10°C (-10°C MMAT) (-3.02), and ultrasonic combined with vacuum packaging thawing at -10°C (-10°C UVPT) (-2.43).

[0017] 2. The present application found that the soluble solids content was higher after microwave combined with magnetic nano thawing (2.5% at -20°C, 2.43% at -10°C), the moisture content was the highest after microwave combined with magnetic nano thawing at -10°C (92.05%), the malondialdehyde content was the lowest after microwave combined with magnetic nano thawing at -20°C (0.41%), and the peroxidase activity was the highest (9.42%). Through OPLS-DA and cluster analysis, it was found that the quality characteristics of small yellow ginger after microwave combined with magnetic nano thawing at -20°C were closest to those of fresh small yellow ginger, followed by ultrasonic combined with vacuum packaging thawing at -10°C and microwave combined with magnetic nano thawing at -10°C.

[0018] 3. The characteristic components of five small yellow gingers were measured by high performance liquid chromatography: 6-gingerol, 8-gingerol, 6-shogaol, 10-I gingerol, and 10-shogaol, and the specific content was determined by the external standard method. The difference and connection between the characteristic components of small yellow ginger after different thawing methods and fresh small yellow ginger were compared. The content of different characteristic components varies greatly. The content of 6-gingerol and 6-shogaol can differ by 200 times. Among the five characteristic components, 6-gingerol has the highest content and is also the one with the most obvious difference in characteristic components between different thawing methods. In the characteristic component clustering heat map, the content of characteristic components after thawing by ultrasonic combined with vacuum packaging at -10℃ and thawing by ultrasonic combined with vacuum packaging at -20℃ is closer to that of fresh small yellow ginger. In the characteristic component evaluation, these two thawing methods are superior to others.

[0019] 4. This application uses an electronic nose combined with GC-MS for analysis. In the OPLS-DA analysis and cluster heat map analysis of 54 volatile compounds in small yellow ginger, it was found that the volatile components of the -20℃MMAT and -10℃UVPT sample treatment methods were not much different from those of fresh small yellow ginger. In the OAV cluster heat map and PCA analysis, it was found that the volatile flavor components of small yellow ginger after thawing at -20℃MMAT and -10℃UVPT were closer to those of fresh small yellow ginger. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the thawing time curve (part) of small yellow ginger under different thawing methods.

[0021] Figure 2 It is the thawing rate of small yellow ginger under different thawing methods.

[0022] Figure 3 It is the color difference of turmeric under different thawing methods.

[0023] Figure 4 It is the juice loss rate of turmeric under different thawing methods.

[0024] Figure 5 It is the hardness of turmeric under different thawing methods.

[0025] Figure 6 It is the soluble solid content of turmeric under different thawing methods.

[0026] Figure 7 It is the moisture content of turmeric under different thawing methods.

[0027] Figure 8 It is the content of malondialdehyde in small yellow ginger under different thawing methods.

[0028] Fig. 9 It is the peroxidase activity of turmeric under different thawing methods.

[0029] Fig.10 Note: Figures A, B, C, D, E, F, and G are fresh turmeric, -20℃ TN, -20℃ TW, -10℃ UVPT, -20℃ UVPT, -10℃ MMAT, and -20℃ MMAT, respectively.

[0030] Fig.11 It is the microstructure of turmeric under different thawing methods.

[0031] Fig.12 This is the OPLS-DA of turmeric under different thawing methods.

[0032] Fig.13 is the model cross-validation result.

[0033] Fig.14 This is the clustering heat map of different thawing methods of small yellow ginger.

[0034] Fig.15 This is the HPLC chart of the standard substance of characteristic components in turmeric.

[0035] Fig.16 This is the HPLC graph of characteristic functional components of small yellow ginger under different thawing methods.

[0036] Fig.17 It is the content of characteristic functional ingredients of small yellow ginger under different thawing methods.

[0037] Fig.18 This is the cluster heat map of the characteristic functional components of small yellow ginger in different thawing methods. Note: The response values ​​of W5S and W1W are reduced by 100 times; different lowercase letters indicate significant differences, P<0.05.

[0038] Fig.19 It is a radial stacked bar graph of the response of the electronic nose to turmeric under different thawing methods.

[0039] Fig. 20 This is the principal component loading diagram of the electronic nose of small yellow ginger under different thawing methods.

[0040] Fig.21 This is the PCA diagram of the electronic nose of small yellow ginger under different thawing methods.

[0041] Fig. 22 It is the content of volatile substances in turmeric under different thawing methods.

[0042] Fig.23 is the model cross-validation result.

[0043] Fig.24 OPLS-DA of volatile compounds in turmeric under different thawing methods.

[0044] Fig.25 This is the clustering heat map of volatile substances in different thawing methods of small yellow ginger.

[0045] Fig.26 This is the cluster heat map (OAV) of volatile substances in ginger with different thawing methods. Note: 1. (R)-(+)-α-pinene; 2. a-pinene; 3. camphene; 4. sabinene; 5. β-pinene; 6. β-myrcene; 7. a-phellandrene; 8. limonene; 9. β-phellandrene; 10. α-terpinene; 11. δ-elemene; 12. (Z)-β-farnesene; 13. (E)-β-farnesene; 14. α-farnesene; 15. isoborneol; 16. α-terpineol; 17. geraniol; 18 nerolidol; 19. (R)-(+)-citronellal; 20. bornyl acetate; 21. 2-undecanone; 22. methylheptenone.

[0046] Fig. 27 The PCA(OAV) of volatile substances in different thawing methods of turmeric. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further defined below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0048] Example 1: Preliminary screening of different thawing methods for quick-frozen small yellow ginger based on thawing efficiency

[0049] Materials and instruments

[0050] Materials: Small yellow ginger: from the small yellow ginger planting base in Zhenning County, Anshun City, Guizhou Province; harvested in May, select fresh small yellow ginger without mechanical damage, mildew, good color and overall integrity. Fe3O4, 20nm, Shanghai Zhongzhi New Materials Co., Ltd., Shanghai.

[0051] Instruments and equipment:

[0052] Table 1 Main instruments

[0053]

[0054] Experimental method: Quick freezing of small yellow ginger: Select fresh small yellow ginger without mechanical damage, mildew, good color and overall integrity and clean it. Based on the previous experiments, peel the small yellow ginger and cut it into cubes of about 2 cm. Insert the thermocouple thermometer probe into the center of the ginger block to sense the center temperature of the ginger block in real time. Spray it with liquid nitrogen at -80℃ for quick freezing. When the center temperature drops to -18℃, the quick freezing is completed. At this time, the ginger blocks are divided into two batches, one batch is stored in a -20℃ refrigerator, and the other batch is stored in a -10℃ refrigerator. Both batches of ginger blocks are thawed using 9 different thawing methods. After thawing, measure the thawing time, color difference, juice loss rate, and hardness difference.

[0055] Thawing method of quick-frozen small yellow ginger:

[0056] Thaw Naturally (TN): Place the quick-frozen ginger pieces at room temperature (25°C) and wait until the core temperature reaches 4°C, which means the thawing is complete.

[0057] Thaw in still Water (TW): Soak the quick-frozen ginger pieces in 25°C pure water until the center temperature reaches 4°C, which means the thawing is complete.

[0058] Thaw at low temperatures (TLT): Place the quick-frozen ginger pieces in a 4°C refrigerator until the core temperature reaches 4°C, which is considered complete.

[0059] Thaw at low Temperature and high Humidity (TTH): Place the quick-frozen ginger in a fresh-keeping thawing device, turn on the fan and atomizer switches to thaw, and the thawing is completed when the center temperature reaches 4°C.

[0060] Ultrasonic Thawing (UT): Put the quick-frozen small yellow ginger into an ultrasonic container, use water as the medium, set the conditions to 25°C and 350W of power, and when the center temperature reaches 4°C, the thawing is considered complete.

[0061] Ultrasonic combined with Vacuum Packaging Thawing (UVPT): Place the vacuum-packed quick-frozen small yellow ginger into an ultrasonic container and set the temperature to 25°C and the power to 350W for thawing. Thawing is complete when the center temperature reaches 4°C.

[0062] Microwave Thawing (MT): Use a microwave device to thaw the quick-frozen small yellow ginger, adjust the power to 320W, and wait until the center temperature reaches 4°C, the thawing is considered complete.

[0063] Microwave combined vacuum packaging thawing (MVPT): Place the vacuum-sealed quick-frozen small yellow ginger together with the packaging bag into the microwave device, adjust the power to 320W, and wait until the center temperature reaches 4°C, the thawing is considered complete.

[0064] Microwave combined Magnetic Nano Thawing (MMAT): Place the vacuum-sealed quick-frozen small yellow ginger in a 0.1 mg / mL ferroferric oxide solution and thaw it with a 320W microwave. When the center temperature reaches 4°C, the thawing is considered complete.

[0065] Determination of the thawing time of quick-frozen small yellow ginger: Insert the thermometer probe into the center of a 2 cm cube of small yellow ginger. Set the instrument to measure the temperature once every second, record the temperature changes of the ginger block over time, and determine the thawing time required for different thawing methods.

[0066] Determination of color difference of quick-frozen small yellow ginger after thawing: Peel the fresh small yellow ginger and cut it into cubes of about 2 cm. After calibrating the colorimeter, select one side of the surface of the fresh small yellow ginger for L*, a* and b* testing. Then the sample is quick-frozen and thawed in different ways. After thawing, the L*, a* and b* values ​​are tested on the same side of the small yellow ginger. Each thawing method is repeated 5 times. L*, a* and b* represent the brightness value, redness value and yellowness value of the sample respectively. The average value of each site is used to represent the color of the small yellow ginger to be tested. The total color difference value (ΔE) is calculated by the formula

[0067]

[0068] Where ΔL* is the difference in brightness between the fresh sample and the thawed sample, Δa* is the difference in redness between the fresh sample and the thawed sample, and Δb* is the difference in yellowness between the fresh sample and the thawed sample.

[0069] Determination of juice loss rate of quick-frozen small yellow ginger after thawing: take out the quick-frozen small yellow ginger, thaw it using different thawing methods, and weigh it with an analytical balance after thawing. Measure each group 5 times and take the average value.

[0070]

[0071] Wherein m1 is the mass of small yellow ginger before thawing (g); m2 is the mass of small yellow ginger after thawing (g).

[0072] Determination of hardness of quick-frozen turmeric after thawing: A texture analyzer was used to conduct a full texture test (TPA) on the thawed turmeric, which can also be called a double chewing test. The probe of the texture analyzer is used to simulate the chewing movement of the human mouth and compress the turmeric twice. This article uses a P36 / R flat-bottomed cylindrical probe with a trigger force of 5g. The speed before, during and after the test is 1mm / s, and the compression deformation of the sample is 30%. Five samples are taken for each thawing method to measure their hardness, and the final result is the average value.

[0073] Data processing: Excel 2206 software was used for data statistics and analysis, Origin 2021 software was used for drawing, and IBSSPSS Statistics 26 was used for data standardization and analysis of significant differences (P < 0.05).

[0074] Results and Analysis

[0075] Effects of different thawing methods on the thawing time of quick-frozen small yellow ginger: Figure 1 It can be seen that within the range of -4℃ to 4℃, all temperature curves are not smooth and have burrs, which means that the shorter the time of repeated freezing and thawing during thawing, the better. The shorter the thawing time, the faster the time to pass through the ice crystal zone, and the less damage to the cells caused by repeated freezing and thawing. Figure 2 The time consumed by TLT is more than ten times that of other thawing methods, while the thawing time of MT, MVPT, and MMAT is significantly shorter than other thawing methods, and the fastest MT only takes 30 seconds at -10°C. Therefore, in terms of the thawing rate of quick-frozen small yellow ginger, TN and TLT conditions are the worst, while MT, MVPT, and MMAT conditions are the best.

[0076] The effect of different thawing methods on the color difference of quick-frozen small yellow ginger: During the thawing process, the ice crystals of small yellow ginger are repeatedly frozen and thawed, the cells are destroyed, and the juice and pigment in the cells leak out, causing the color of ginger to change. During the TW thawing process, small yellow ginger is in direct contact with water for a long time, which accelerates the extravasation of cell fluid and the outflow of intracellular substances, so the color changes significantly.

[0077] Although the TLT thawing conditions are mild, the thawing time is too long, the recrystallization seriously damages the cell structure, the enzyme and substrate are in more complete contact, enzymatic browning is more likely to occur, and the color difference is aggravated.

[0078] MT has a fast thawing time and a more intense heating method. Such rapid heating will cause greater damage to the structure of the cell wall of turmeric. It is also easy to cause uneven heating, resulting in overheating of some areas of turmeric and causing burning, which further aggravates the color change.

[0079] Compared with UT, UVPT avoids the contact of small yellow ginger with external air and moisture by vacuum packaging small yellow ginger, which limits the outflow of cell fluid to a certain extent and reduces the color difference.

[0080] MMAT is a newer thawing technology. Compared with traditional MT, it has a better effect in maintaining food quality. Magnetic nanoparticles can accelerate the transfer of microwave heat in food by inducing local magnetic fields and adjusting their position and aggregation degree, avoiding local overheating. It can heat and thaw food more evenly and reduce the damage of microwaves to food.

[0081] Therefore, from Figure 3 It can be concluded that in the process of thawing quick-frozen small yellow ginger, the color difference of TW, TLT, and MT thawing conditions changes significantly, and UVPT and MMAT conditions are more conducive to reducing the color difference of small yellow ginger after thawing.

[0082] The impact of different thawing methods on the juice loss rate of quick-frozen small yellow ginger: When frozen food is thawed, the water produced by the melting of ice crystals is not completely absorbed by the tissue and returns to the pre-freezing state. Part of the water mixed with some nutrients is separated from the inside of the food and becomes lost fluid. Therefore, the smaller the juice loss rate, the better the thawing effect.

[0083] The thawing conditions of TLT are relatively mild, and the evaporation rate of water is slow, but the moisture in the air will condense on the wall or surface inside the refrigerator to form frost, resulting in a relatively dry environment. In addition, the ventilation effect inside the refrigerator will also cause the relative humidity to decrease. Therefore, although the TLT juice loss rate is slower, the amount of lost liquid will not decrease, but will increase, because the thawing time is long.

[0084] During the MT thawing process, microwaves can quickly heat the water in the turmeric, which will cause the ice crystals to melt quickly and release a large amount of water. In addition, since water is absorbed faster than ice, this will cause uneven MT thawing. Therefore, during the thawing process, the outer layer of the turmeric can be easily heated to high temperature, resulting in local dehydration and more serious juice loss.

[0085] Under TTH conditions, the temperature gradient generated during the thawing process can be moderated, reducing the degree of damage to cells caused by thawing. In addition, water molecules in the air in a low-temperature and high-humidity environment will adhere to the surface of the frozen turmeric to form tiny water droplets. These water droplets can provide local moisture, maintain the humidity of the turmeric, and slow down the loss of turmeric juice.

[0086] Compared with UVPT, during the UT thawing process, the turmeric comes into direct contact with water. Although this will promote the outflow of intracellular substances, it can also replenish the juice loss during the thawing of the turmeric to some extent.

[0087] Therefore, from Figure 4 It can be concluded that in the process of thawing quick-frozen turmeric, the turmeric juice loss is serious under TLT and MT conditions, while TTH and UT conditions are more conducive to the thawing of turmeric.

[0088] The impact of different thawing methods on the hardness of quick-frozen turmeric: During the thawing process, turmeric is often frozen and thawed repeatedly. The ice crystals continue to grow, penetrate the cell walls, and destroy the cell tissue, making it unable to play its original supporting role. It loses its original rigidity and becomes soft. Therefore, the greater the hardness after thawing, the closer it is to the hardness of fresh turmeric, which means the better the thawing effect.

[0089] Therefore, from Figure 5 It can be concluded that during the TN, TW and TLT thawing process of quick-frozen turmeric, the ice crystals are repeatedly frozen and thawed, causing the cell membrane and cell wall to be destroyed, and the mutual support and tension between cell tissues will be reduced. Therefore, compared with fresh turmeric, quick-frozen turmeric will lose some of the integrity and stability of its cell tissue after thawing, making it more likely to become soft and lose its original hardness.

[0090] Compared with UVPT, UT will be forced to reabsorb some water to replenish its juice loss under the pressure of the external water environment during the thawing process, but its internal cell structure has become loose, so its hardness is not as good as UVPT.

[0091] MT thawing is an efficient thawing method, but it will lead to uneven thawing and cell damage, causing the turmeric to become soft and lose its original hardness. In comparison, MVPT and MMAT thawing are more gentle. Vacuum packaging can reduce moisture loss on the food surface and maintain the moisture and quality of the food; while magnetic nanoparticles can alleviate local overheating during microwave thawing and better maintain the hardness of fresh turmeric.

[0092] Correlation analysis and standardized comparison of time, color difference, juice loss rate and hardness difference in different thawing methods of quick-frozen small yellow ginger:

[0093] Table 2 shows that the thawing time of small yellow ginger was significantly positively correlated with color difference and juice loss rate in different thawing methods (r=0.547, 0.515, P<0.05, respectively). The color difference index was significantly positively correlated with the juice loss rate in different thawing methods of small yellow ginger (r=0.515, P<0.05), and was extremely significantly positively correlated with the hardness difference (the hardness of fresh small yellow ginger minus the hardness of thawed small yellow ginger, taking the average value) (r=0.605, P<0.01). Pigments usually exist in cell sap. When small yellow ginger is thawed, the cell sap will be lost due to cell damage, resulting in an increase in the juice loss rate. At the same time, the pigments in these cell sap will also be lost, resulting in the change of color of small yellow ginger.

[0094] Table 2 Correlation analysis of thawing time, color difference, juice loss rate and hardness difference of small yellow ginger

[0095]

[0096] Note: * indicates significant difference (P<0.05); ** indicates extremely significant difference (P<0.01)

[0097] In Table 3, the data of thawing time, color difference, juice loss rate and hardness difference were standardized by Z-score (i.e., the original data was subtracted from the mean value and divided by the standard deviation to obtain a normal distribution big data with a mean of 0 and a standard deviation of 1). The lower the value, the better the thawing effect of a single factor. The cumulative addition of different index values ​​and the arrangement from low to high can preliminarily judge the advantages and disadvantages of the 18 thawing methods. The first four thawing methods (i.e., microwave combined with magnetic nano thawing at -20°C, ultrasonic combined with vacuum packaging thawing at -20°C, microwave combined with magnetic nano thawing at -10°C, and ultrasonic combined with vacuum packaging thawing at -10°C) were selected for further analysis later.

[0098] Table 3 Ranking of various indicators of small yellow ginger under different thawing methods

[0099]

[0100] Conclusion: The results showed that the thawing rate index was significantly positively correlated with color difference and juice loss rate (r=0.547 and 0.515, respectively, P<0.05), the color difference index was significantly positively correlated with juice loss rate (r=0.515, P<0.05), and was extremely significantly positively correlated with the hardness difference (the hardness of fresh small yellow ginger minus the hardness of thawed ginger, taking the average value) (r=0.605, P<0.01).

[0101] Among the thawing rate indicators, microwave thawing (MT) has the fastest rate, with an average thawing rate of about 30s; low temperature thawing (TLT) has the worst effect, with a thawing rate of 3-4h. Among the color difference indicators, ultrasonic combined with vacuum packaging thawing (UVPT) and microwave combined with magnetic nano thawing (MMAT) have better effects; static water thawing (TW), low temperature thawing (TLT), and microwave thawing (MT) have poorer effects. Among the juice loss rate indicators, low temperature and high humidity thawing (TTH) and ultrasonic thawing (UT) have the best thawing effects, with a juice loss rate of about 5%; -20℃ low temperature thawing / microwave thawing (-20℃TLT / MT) has the worst effect, with a juice loss rate of 15%, which is three times that of the former. Among the hardness indicators, the thawing effects of different methods are not as different as the first three indicators. Among them, -20℃ ultrasonic combined with vacuum packaging thawing (-20℃UVPT), ​​microwave combined with vacuum packaging thawing (MVPT), ​​and microwave combined with magnetic nano thawing (MMAT) have better effects, and the other thawing methods have poorer effects.

[0102] After standardizing and accumulating the four indicators of 18 different thawing methods, it can be found that the optimal thawing method is -20℃ microwave combined with magnetic nano thawing (-20℃MMAT), with a score of -4.33; the other three better thawing methods are -20℃ ultrasonic combined with vacuum packaging thawing (-20℃UVPT) (-3.24), -10℃ microwave combined with magnetic nano thawing (-10℃MMAT) (-3.02), -10℃ ultrasonic combined with vacuum packaging thawing (-10℃UVPT) (-2.43). The effects of these four thawing methods on the edible quality, functional component content, and flavor changes of quick-frozen small yellow ginger after thawing will be further studied in the future.

[0103] Example 2: Effects of different thawing methods on the edible quality of small yellow turmeric

[0104] Materials and instruments

[0105] Materials and reagents: Small yellow ginger: from the small yellow ginger planting base in Zhenning County, Anshun City, Guizhou Province; harvested in May, select fresh small yellow ginger without mechanical damage, mildew, good color and overall integrity. Trichloroacetic acid (TCA), thiobarbituric acid (TBA), NaOH, glacial acetic acid, sodium acetate trihydrate, polyethylene glycol 6000 (PEG 6000), polyvinyl pyrrolidone (PVPP), Triton X-100, guaiacol, hydrogen peroxide were purchased from Chengdu Mansite Biotechnology Co., Ltd. Instruments and equipment:

[0106] Table 4 Main instruments

[0107]

[0108]

[0109] Experimental methods

[0110] Sample pretreatment: Select fresh small yellow ginger that is complete, free of mold, mechanical damage, and good in color, and wash it clean. Based on the previous experiments, peel the small yellow ginger and cut it into cubes of about 2 cm. Insert the thermocouple thermometer probe into the center of the ginger block and spray it with liquid nitrogen at -80℃ for quick freezing. When the center temperature drops to -20℃, the quick freezing is complete. At this time, the ginger blocks are divided into two batches, one batch is stored in a -20℃ refrigerator, and the other batch is stored in a -10℃ refrigerator. Take out the ginger blocks and thaw them at the corresponding storage temperature under natural conditions at -20℃, static water conditions at -20℃, ultrasonic combined vacuum packaging conditions at -10℃, ultrasonic combined vacuum packaging conditions at -20℃, microwave combined magnetic nano conditions at -10℃, and microwave combined magnetic nano conditions at -20℃.

[0111] Determination of soluble solid content of turmeric: refer to NY / T 2637-2014 Determination of soluble solid content of fruits and vegetables - refractometer method with slight modifications for determination, take appropriate amount of turmeric and put it into high-speed tissue crusher for crushing, filter it twice with 4 layers of gauze and then filter it once with filter paper, collect the final filtrate as the test solution, use digital sugar meter (with automatic temperature compensation function) for determination, and conduct 5 parallel determinations.

[0112] Determination of moisture content of small yellow ginger: After the small yellow ginger was thawed by different methods, it was placed in a moisture meter to determine its moisture content. The measurements were performed 5 times in parallel and the results were averaged.

[0113] Determination of malondialdehyde content in turmeric: For the determination of malondialdehyde content, refer to the "Guide to Post-harvest Physiological and Biochemical Experiments of Fruits and Vegetables".

[0114] Determination of peroxidase activity of ginger: The determination of peroxidase activity was based on the "Guide to Postharvest Physiological and Biochemical Experiments of Fruits and Vegetables" with slight modifications.

[0115] Determination of cell membrane permeability of ginger: The cell membrane permeability is indirectly determined by measuring the concentration of electrolytes in the intracellular and extracellular fluids. The principle is that changes in cell membrane permeability will affect the concentration of electrolytes in the intracellular and extracellular fluids and the ion exchange capacity, thereby changing the conductivity. The ginger was thawed by different methods, and its tissue was punched with an 8mm diameter puncher, and then cut into 4mm thick slices, and cut into small discs. 2g was put into a small beaker, and 20mL of deionized water was added to soak and rinse 3 times. The water on the disc was absorbed with filter paper, and then 50mL of deionized water was added to soak for 1h. After soaking for 1h, its conductivity was measured to be P1, and then boiled for 15min. After cooling to room temperature, water was added to replenish it to the original scale, and its conductivity was measured to be P2. The conductivity of deionized water is P0:

[0116]

[0117] Observation of the microstructure of small yellow ginger after thawing: After the ginger pieces are thawed, soak them in glutaraldehyde fixative at 4°C for 12 hours, take them out and rinse them with 0.2mol / L phosphate buffer for 30 minutes, rinse three times, then dehydrate them with 40%, 60%, and 80% ethanol for 30 minutes, then dehydrate them with 95% and 100% ethanol for 1 hour, finally put them in an ultra-low temperature refrigerator for 12 hours and freeze-dry them in a freeze dryer. Take out the freeze-dried samples and fix them on the short column of the scanning electron microscope (SEM), and then electroplate the samples. Use a scanning electron microscope to scan and photograph the microstructure of the samples at an accelerating voltage of 15KV.

[0118] Data processing: Excel 2206 software was used for data statistics and analysis, Origin 2021 and SIMCA 14.1 software were used for drawing, and IBS SPSS Statistics 26 was used for data standardization and analysis of significant differences (P < 0.05).

[0119] Results and Analysis

[0120] Effects of different thawing methods on the soluble solids content of ginger: the results are shown in Figure 6 .

[0121] During the thawing process, the cells of the ginger were destroyed, and the solution and soluble solids in the cells dissolved in the water, resulting in a decrease in the concentration of soluble solids. During the thawing process at -20℃TW, the ginger was submerged in water, and the contents flowed out and dispersed in the water. The measured soluble solids content was lower than that of fresh ginger.

[0122] However, during the freezing and thawing process, the cells are destroyed, and the soluble solids and other nutrients in the cells are released into the water, making the soluble solids content easier to detect. This is why the soluble solids content detected by -20℃TN and -10℃ / -20℃MMAT is higher than that of fresh small yellow ginger.

[0123] Thawing will lead to water loss and changes in tissue structure, thus affecting the flavor and texture of turmeric. Therefore, the soluble solids content of thawed turmeric is relatively low, and its flavor and texture will also be affected. UVPT is milder than TN and MMAT because the ultrasonic thawing process promotes the breakage of ice crystals and the movement of water molecules through ultrasonic vibration, so that the frozen material gradually heats up to achieve the thawing effect. In comparison, microwave thawing has a faster heating rate, which may cause local overheating and thermal damage to turmeric, while natural thawing may cause the outer layer of turmeric to thaw first, while the inside is still frozen, resulting in uneven texture. Overall, the UVPT thawing method is better, and there is no significant difference in thawing at different temperatures for the same thawing method (UVPT or MMAT).

[0124] Effects of different thawing methods on the moisture content of small yellow ginger: the results are shown in Figure 7 .

[0125] -20℃TN / TW is a more direct thawing method. Compared with UVPT and MMAT, it causes more severe damage to turmeric cells and takes longer to pass through the ice crystal zone, so the loss of moisture content is greater.

[0126] At low temperatures, the water in turmeric exists in the form of ice crystals. When ice crystals are formed, the cells are easily destroyed, resulting in a decrease in the water holding capacity after thawing. As the temperature rises, the ice crystals begin to melt and turn from solid to liquid, and liquid water can relatively easily penetrate into the food surface. The thawing rate of -20℃UVPT / MMAT is slower than that of -10℃UVPT / MMAT, so the water loss is relatively large and the water content is less than that of -10℃UVPT / MMAT.

[0127] Ultrasonic thawing is a process that applies high-frequency sound waves to food samples, which produces local vibrations and tiny bubble bursts, intensifying the thermal motion of water molecules and increasing the temperature of the sample. The heat generated by this action can increase the temperature of the sample in a short period of time, thereby accelerating the melting of ice. During the thawing process, the frequency of ultrasound is generally between 20kHz and 100kHz, and the temperature generated by the bubble burst is not high. Therefore, ultrasonic thawing is gentler than microwave thawing and will not cause overheating and local damage. Therefore, the difference in moisture content of UVPT at different temperatures (no significant difference) is smaller than that of MMAT at different temperatures (significant difference). The moisture content of -10℃ MMAT is slightly higher than that of fresh turmeric, which is speculated to be due to the slight difference in moisture content between different turmerics.

[0128] In general, the moisture content loss under -20℃TN / TW thawing was significantly greater than that under UVPT and MMAT thawing, while the moisture content after -10℃UVPT / MMAT thawing was not significantly different from that of fresh turmeric.

[0129] Effects of different thawing methods on the content of malondialdehyde in ginger:

[0130] During the thawing process of small yellow ginger, the soluble solid content and the malondialdehyde content were negatively correlated. Figure 8 It can be seen that the MDA content of -20℃TN / TW is higher than that of UVPT, the MDA content of UVPT is higher than that of MMAT, and the MDA content of -10℃UVPT / MMAT is higher than that of -20℃UVPT / MMAT, which corresponds to the soluble solid content in 3.4.1. From another perspective, microwave thawing converts internal molecular friction into heat energy, so that the water in the small yellow ginger can be thawed quickly, and the thawing rate is higher than that of ultrasonic thawing, which reduces the oxidation reaction time of lipids in the cell membrane. Therefore, the MDA content of MMAT is lower than that of UVPT. Other small yellow gingers in the same batch of small yellow gingers are quick-frozen and stored for subsequent different thawing treatments, while fresh small yellow gingers are left naturally. During the aging process, the activity of endogenous enzymes will increase, resulting in the gradual oxidation and decomposition of fatty acids and phospholipids in the small yellow ginger, and then the production of MDA, which makes the MDA content of fresh small yellow ginger higher than that of thawed small yellow ginger.

[0131] Effects of different thawing methods on the activity of peroxidase (POD enzyme) in ginger: the results are shown in Fig. 9 .

[0132] When quick-frozen turmeric is thawed at -10℃, compared with thawing at -20℃, ice crystals are more likely to thaw and penetrate into the turmeric cells at a relatively high temperature, making enzymes and other substances inside the turmeric cells thaw faster and restore their activity better. Therefore, after thawing, the peroxidase activity of -10℃ UVPT is better than that of -20℃ UVPT.

[0133] Compared with UVPT thawing, MMAT has a faster heating rate, which can make the temperature of small yellow ginger close to the optimal reaction temperature of the enzyme more quickly during thawing, thereby increasing the activity of peroxidase.

[0134] The molecular structure of peroxidase is not easy to change when small yellow ginger is stored at low temperature. When small yellow ginger is stored at -20℃, the preservation effect of peroxidase is better than that at -10℃, and the thawing rate of -10℃ / -20℃MMAT is almost the same, so the peroxidase activity of -20℃MMAT after thawing is better than that of -10℃MMAT.

[0135] Effects of different thawing methods on cell membrane permeability of ginger: Results are shown in Fig.10 .

[0136] The thawing time of -20℃ TN / TW is relatively long. During this process, ice crystals are repeatedly generated and broken, which causes the swelling and rupture of the cell membrane, greatly increasing the permeability of the cell membrane.

[0137] The vibration of ultrasound will produce mechanical pressure on the cell membrane, and the electromagnetic waves of microwaves will cause the polar molecules in the food to continuously change their arrangement direction in the high-frequency changing electromagnetic field, causing constant collision and friction between the molecules. Both of these will lead to damage to the cell membrane over a long period of time. Therefore, the cell membrane permeability after thawing at -20℃UVPT / MMAT is greater than that at -10℃UVPT / MMAT. From a numerical point of view, there is no significant difference between the cell membrane permeability thawed at -10℃UVPT / MMAT and that of fresh turmeric.

[0138] Effects of different thawing methods on the microstructure of small yellow ginger:

[0139] Fig.11 The effect of different thawing methods on the microstructure of small yellow ginger is shown. After magnification 100 times, the cell structure of fresh small yellow ginger is tight, the connection between cells is smooth, there are fewer holes, and no large holes appear. Under the scanning electron microscope, the cell structure of -20℃TN small yellow ginger is not as three-dimensional as that of fresh small yellow ginger. Some cells are continuously destroyed, and large holes appear. The cell pore structure of -20℃TW small yellow ginger is severely deformed, wide outside and narrow inside, and is bowl-shaped. It is speculated that it was submerged in water during the thawing process, and the cells were ruptured under the invasion of water pressure and osmosis. The cell structure of -10℃UVPT small yellow ginger is slightly flat, which is not much different from fresh small yellow ginger. -20℃UVPT small yellow ginger is severely damaged, and the cells are stacked and flat. The cells of -10℃MMAT small yellow ginger are slightly wrinkled, but the connection between cells is smooth, and there are no obvious holes. The cells of -20℃MMAT small yellow ginger are arranged in uneven layers, and the depression and swelling are obvious. Therefore, in the microstructure of turmeric, the structure of fresh turmeric is the best, which is the first grade; -10℃UVPT / MMAT is second, which is the second grade; -20℃TN / TW and -20℃UVPT / MMAT are worse, which are the third grade.

[0140] In summary, compared with -20℃TN / TW and -20℃UVPT / MMAT, the cell microstructure of quick-frozen turmeric after thawing under -10℃UVPT / MMAT conditions was closer to that of fresh turmeric under scanning electron microscopy.

[0141] OPLS-DA analysis:

[0142] In this analysis, the independent variable fit index (R2X) is 1, the dependent variable fit index (R2Y) is 0.778, and the model prediction index (Q2) is 0.649. R2 and Q2 exceeding 0.5 indicate that the model fitting results are acceptable. Fig.12 , Fig.13As shown in the figure, after 200 permutation tests, the intersection point of the Q2 regression line and the vertical axis is less than 0, indicating that the model does not overfit, the model verification is effective, and the different groups are relatively scattered in the figure. It is believed that the results can be used for the identification and analysis of the quality of small yellow ginger under different thawing methods.

[0143] Cluster heat map analysis:

[0144] In order to analyze the quality difference and relationship between fresh small yellow ginger after thawing by different thawing methods, a cluster heat map analysis was conducted based on the five indicators of soluble solid content, moisture content, malondialdehyde content, peroxidase activity, and microstructure in this chapter, plus the thawing rate, color difference, juice loss rate, and hardness difference in the previous chapter, and fresh small yellow ginger, natural thawing at -20℃ (-20℃TN), static water thawing at -20℃ (-20℃TW), ultrasonic combined vacuum packaging thawing at -10℃ (-10℃UVPT), ​​ultrasonic combined vacuum packaging thawing at -20℃ (-20℃UVPT), ​​microwave combined magnetic nano thawing at -10℃ (-10℃MMAT), and microwave combined magnetic nano thawing at -20℃ (-20℃MMAT). In the microstructure observation, the first, second, and third grades are taken as 1, 2, and 3 respectively. In the four indicators of thawing rate, color difference, juice loss rate, and hardness difference in Chapter 2, the default value for fresh turmeric is 0.

[0145] like Fig.14 The upper tree shows the clustering of fresh small yellow ginger and small yellow ginger samples after different thawing methods. The left tree shows the clustering of conventional quality indicators. The different color blocks in the middle reflect the content of conventional quality indicators in small yellow ginger. The color blocks are composed of red, white and blue. The darker the red, the lower the content, the darker the blue, the higher the content, and white is in between.

[0146] From the conventional quality indicators on the left, the small yellow ginger samples are divided into two categories, one of which is peroxidase activity, water content, soluble solids content, and the other is thawing rate, color difference, juice loss rate, hardness difference, malondialdehyde content, and microstructure. From the upper clustering, fresh small yellow ginger and microwave combined with magnetic nano thawing at -20℃ (-20℃MMAT) are classified into a small category, indicating that the results of the 10 conventional quality indicators of the cluster analysis of these two samples are closest to each other. Ultrasonic combined with vacuum packaging thawing at -10℃ (-10℃UVPT) and microwave combined with magnetic nano thawing at -10℃ (-10℃MMAT) are classified into another small category. Similarly, these four belong to the same category, which is distinguished from another large category of static water thawing at -20℃ (-20℃TW) and ultrasonic combined with vacuum packaging thawing at -20℃ (-20℃UVPT).

[0147] It can be concluded that among the different thawing methods of small yellow ginger, microwave combined with magnetic nano thawing at -20℃ (-20℃MMAT) is the best, followed by ultrasonic combined with vacuum packaging thawing at -10℃ (-10℃UVPT) and microwave combined with magnetic nano thawing at -10℃ (-10℃MMAT).

[0148] Conclusion: The experiment mainly studies the relationship and difference between the five indicators of soluble solids content, moisture content, malondialdehyde content, peroxidase activity and microstructure of quick-frozen small yellow ginger after thawing by six different thawing methods, including natural thawing at -20℃ TN, static water thawing at -20℃ (-20℃ TW), ultrasonic combined with vacuum packaging thawing at -10℃ (-10℃ UVPT), ​​ultrasonic combined with vacuum packaging thawing at -20℃ (-20℃ UVPT), ​​microwave combined with magnetic nano thawing at -10℃ (-10℃ MMAT) and microwave combined with magnetic nano thawing at -20℃ (-20℃ MMAT). Taking fresh small yellow ginger as the benchmark, the advantages and disadvantages of these thawing methods are evaluated.

[0149] In the determination of soluble solid content, the three thawing methods of -20℃TN, -20℃UVPT, and -10℃MMAT had no significant difference in content results from fresh small yellow ginger. In the determination of moisture content, the two thawing methods of -10℃UVPT and -10℃MMAT had no significant difference in content results from fresh small yellow ginger, with the moisture content reaching 90%. The moisture content of -20℃TN was the lowest, only 75.27%, followed by -20℃TW, with a moisture content of 79.625%. In the determination of malondialdehyde content, the malondialdehyde content of -20℃MMAT was the lowest, only 0.4137 (nmol / g mF). In the peroxidase activity assay, the fresh turmeric had the highest enzyme activity, reaching 12.13 (ΔOD470 / min·g); the -20℃ TN enzyme activity was the lowest, at 6.4 (ΔOD470 / min·g), only half the level of fresh turmeric; compared with other thawing methods, the -10℃ / -20℃ MMAT enzyme activity was higher, reaching 8.17 and 9.42 (ΔOD470 / min·g) respectively. In the cell membrane permeability test, the results of each thawing method were quite different. The -20℃ UVPT value was the highest at 0.89, while the fresh turmeric was only 0.24, which was 3.7 times that of the fresh turmeric. The -10℃ UVPT / MMAT results were better, at 0.26 and 0.33, respectively, with no significant difference from the fresh turmeric. In the observation of the microstructure of turmeric, the -10℃ UVPT / MMAT cell tissue structure was better, which was consistent with the fresh turmeric.

[0150] In the OPLS-DA diagram, there is no obvious overlap between the groups of small yellow ginger with different thawing methods. It is believed that this result can be used for the identification and analysis of the quality of small yellow ginger under different thawing methods. The cluster heat map results integrate some indicators in Chapter 2 to make the data more complete.

[0151] On the whole, after measuring 10 indicators including thawing rate, color difference, juice loss rate, hardness, soluble solids, moisture content, malondialdehyde content, peroxidase activity, cell membrane permeability and microstructure, it was found that the quality characteristics of quick-frozen yellow ginger after microwave combined with magnetic nano thawing at -20℃ (-20℃MMAT) were closest to those of fresh yellow ginger, followed by ultrasonic combined with vacuum packaging thawing at -10℃ (-10℃UVPT) and microwave combined with magnetic nano thawing at -10℃ (-10℃MMAT). The quality of yellow ginger after thawing by the other three thawing methods, ultrasonic combined with vacuum packaging thawing at -20℃ (-20℃UVPT), ​​natural thawing at -20℃ (-20℃TN) and static water thawing at -20℃ (-20℃TW), was quite different from that of fresh yellow ginger.

[0152] Example 3: Effects of different thawing methods on the content of characteristic functional components of small yellow turmeric

[0153] Materials and instruments

[0154] Material:

[0155] Table 5 Main reagents

[0156]

[0157] instrument:

[0158] Table 6 Main instruments

[0159]

[0160] Experimental methods

[0161] Preparation of test solution: Referring to Example 2, thawed small yellow ginger in different ways, chopped with a knife, 3.0 g of sample was ground in a mortar, poured into a conical flask, 45 mL of methanol was added, ultrasonic extraction was performed at 50 ° C for 1 h, and the sample solution was filtered (a disposable sterile syringe was connected to a 0.22 μm organic microporous filter membrane, 1.00 mL of the upper solution was aspirated and transferred into the syringe tube, the injection rod was slowly pushed, and the sample solution was injected into the liquid injection bottle, and analyzed on the machine).

[0162] Preparation of reference solution: Accurately weigh 20 mg of 6-gingerol, 8-gingerol, 6-shogaol, 10-gingerol, and 10-shogaol standard substances, then dissolve them in methanol and make up to 10 mL as the mother solution of the small yellow ginger standard substance, and refrigerate for later use.

[0163] HPLC conditions: Chromatographic conditions: 228-34937-92-SC Shim-pack VP-ODS column (4.6 mm×25 cm, 5 μm); detection wavelength 224 nm, injection volume 20 μL, column temperature 30°C, mobile phase gradient setting (A: distilled water; B: acetonitrile).

[0164] Table 7 HPLC conditions

[0165]

[0166] Data processing: Excel 2206 software was used for data statistics and analysis, Origin 2021 software was used for drawing, and IBSSPSS Statistics 26 was used for data standardization and analysis of significant differences (P < 0.05).

[0167] Results and Analysis

[0168] Preparation of standard curve: Take appropriate amount of mother solution of various reference substances, add methanol for stepwise dilution, make a series of solutions with different gradients, use them as linear test solutions, measure under the above HPLC conditions, and record their peak time and peak area. Take appropriate amount of various test solution for detection, observe their peak and compare with the reference substance to determine the concentration range of the reference substance. Linear regression is performed with the concentration of the test substance (X axis) and the peak area (Y). The results are shown in Table 8. The five test substances have a relatively good linear relationship in the range of 0-250μg / mL, and the correlation coefficients are all greater than 0.999.

[0169] Table 8 Linear relationship of each standard

[0170]

[0171] High performance liquid chromatography of reference substance and test substance: Take the standard reference substance stock solution and measure it according to the above HPLC conditions. Fig.15 The results showed that the detection method had a stable baseline, the five characteristic components did not overlap, and the separation effect was good. It can effectively detect the characteristic components of fresh small yellow ginger and small yellow ginger samples with different thawing methods within 30 minutes. Take the test solution and measure it according to the conditions of 4.3.3. The experimental results are shown in Fig.16 Table 9 shows the retention time positioning results of characteristic components.

[0172] Table 9 Retention time positioning results of each characteristic component

[0173]

[0174] Effects of different thawing methods on the content of characteristic functional components of turmeric: Fig.17Among them, 6-gingerol is the one with the highest content among the five characteristic components of small yellow ginger, and it is also the one with the most obvious difference among the five characteristic components between different thawing methods. The contents of 6-gingerol, 8-gingerol, 6-shogaol, and 10-gingerol in fresh small yellow ginger and samples treated under -10℃ / -20℃ UVPT conditions are very close, indicating that small yellow ginger is closer to its fresh state after being thawed by these two thawing methods.

[0175] Depend on Fig.18 It can be seen that the upper tree is the clustering between fresh small yellow ginger and small yellow ginger samples after different thawing methods. From the upper clustering, different thawing methods can be simply divided into two categories according to the content differences of the five characteristic components, one close to fresh small yellow ginger and the other far away from fresh small yellow ginger. From the figure, it can be seen that ultrasonic combined vacuum packaging thawing at -10℃ (-10℃ UVPT) and ultrasonic combined vacuum packaging thawing at -20℃ (-20℃ UVPT) are closer to fresh small yellow ginger, indicating that these two thawed small yellow ginger samples are closest to fresh small yellow ginger in the cluster analysis of 6-gingerol, 8-gingerol, 6-shogaol, 10-gingerol, 10-shogaol 5 characteristic component content results.

[0176] Conclusion: The experiment in this chapter mainly studies the influence of six different thawing methods on the characteristic components of quick-frozen small yellow ginger after thawing, including natural thawing at -20℃ TN, static water thawing at -20℃ TW, ultrasonic combined with vacuum packaging thawing at -10℃ UVPT, ultrasonic combined with vacuum packaging thawing at -20℃ UVPT, microwave combined with magnetic nano thawing at -10℃ MMAT, and microwave combined with magnetic nano thawing at -20℃ MMAT. The five characteristic components of small yellow ginger, 6-gingerol, 8-gingerol, 6-shogaol, 10-gingerol, and 10-shogaol, were measured by high performance liquid chromatography, and the specific content was determined by external standard method. Among these five characteristic components, 6-gingerol has the highest content, which can reach 4000μg / g, and 6-shogaol has the lowest content, which is less than 20μg / g, and the difference between the two is 200 times. The contents of the three characteristic components, 8-gingerol, 10-gingerol and 10-shogaol, were similar, at about 500 μg / g. In the characteristic component clustering heat map, the content of characteristic components after thawing at -10℃ combined with ultrasonic vacuum packaging (-10℃ UVPT) and thawing at -20℃ combined with ultrasonic vacuum packaging (-20℃ UVPT) was closer to that of fresh small yellow ginger. In the characteristic component evaluation, these two thawing methods were superior to others.

[0177] Example 4 Effects of different thawing methods on volatile flavor substances in small yellow ginger

[0178] Materials and instruments

[0179] Ingredients: Small yellow turmeric: from the small yellow turmeric planting base in Zhenning County, Anshun City, Guizhou Province; harvested in May, select fresh small yellow turmeric with no mechanical damage, no mold, good color and overall integrity.

[0180] Main instruments:

[0181] Table 10 Main instruments

[0182]

[0183]

[0184] Test methods

[0185] Sample pretreatment: refer to Example 2.

[0186] Electronic nose determination: After quick-frozen small yellow ginger was thawed in different ways, 3 g of each sample was weighed and placed in a sampling bottle, which was sealed and allowed to stand for 30 min. The gas at the top of the sampling bottle was sucked with an electronic nose probe and its volatile flavor substances were analyzed and determined. The parameters set for the electronic nose were interval time 1 s, automatic cleaning time 300 s, zeroing time 5 s, insertion time 5 s, measurement time 120 s, suction flow rate 300 mL / min, and injection flow rate 300 mL / min. Four parallel experiments were performed in each group.

[0187] Table 11 Electronic nose sensor performance

[0188]

[0189] GC-MS determination

[0190] SPME conditions: The samples were thawed in different ways and then cut into pieces. About 2 g of the sample was weighed, and 15 μL of the internal standard solution (decanedioic acid, 1.7784 mg / mL) was accurately added. The sample was placed in the sampling bottle of the solid phase microextraction instrument, and a manual injector equipped with a 2 cm-50 / 30 μm DVB / CAR / PDMSStableFlex fiber head was inserted. After headspace extraction for 60 min under flat-plate heating conditions at 70 °C, the extraction head was removed and immediately inserted into the gas chromatograph injection port (temperature 250 °C) for thermal decomposition injection.

[0191] GC-MS detection conditions: the chromatographic column is an Agilent HP-5MS (60m×0.25mm×0.25μm) elastic quartz capillary column, the initial temperature is 50℃ (retained for 2min), the temperature is increased to 80℃ at 8℃ / min, then to 145℃ at 3℃ / min, and to 310℃ at 8℃ / min, maintained for 5min, and the running time is 53.04min; the vaporization chamber temperature is 250℃; the carrier gas is high-purity He (99.999%); the column head pressure is 16.69psi, the carrier gas flow rate is 1.0mL / min, the split ratio is 50:1, and the solvent delay time is 3min. The ion source is an EI source; the ion source temperature is 230℃; the quadrupole temperature is 150℃; the electron energy is 70eV; the emission current is 34.6μA; the multiplier voltage is 1729V; the interface temperature is 280℃; the mass range is 29~500amu.

[0192] Data processing

[0193] Qualitative and quantitative methods: The peaks in the total ion flow chart were retrieved by the mass spectrometry computer data system and checked against the Nist20 and Wiley275 standard mass spectra to determine the volatile chemical components. N-decane was selected as the internal standard to quantify the small yellow ginger samples. Each group was repeated three times. The mass concentration C1 (μg / g) was calculated as follows:

[0194]

[0195] Where: A1 is the peak area of ​​volatile flavor substances, A0 is the peak area of ​​internal standard, C0 is the mass concentration of internal standard solution (mg / mL), V0 is the volume of internal standard solution (μL), and m is the sample mass (g).

[0196] OAV method analysis: The OAV calculation formula is as follows:

[0197]

[0198] Where: C1 is the mass concentration of volatile compounds, OT i is the threshold value for volatile compounds.

[0199] Analysis and processing software: Excel 2206 software was used for data statistics and analysis, Origin 2021 software was used to draw radial stacked bar charts, PCA diagrams, fingerprint maps, and cluster heat maps, IBS SPSS Statistics 26 was used to standardize the data and analyze significant differences (P < 0.05), and SIMCA 14.1 software was used for orthogonal partial least squares-discriminant analysis (OPLS-DA).

[0200] Results and analysis: Analysis of the quality differences of small yellow ginger under different thawing methods based on electronic nose technology: In order to more intuitively compare the characteristics of volatile flavor substances of small yellow ginger under different thawing methods, the peak response intensity of the samples under 10 different sensors was plotted into a radial stacked bar graph, as shown in Figure 2. Fig.19 There are obvious differences in the response strength of different samples to the sensor. The sensitivity of W5S and W1W to the volatile flavor substances of the samples is much greater than that of other sensors. Among them, the W5S sensor is very sensitive to nitrogen oxides, and the sensitivity is very large. The W1W sensor is sensitive to inorganic sulfides and many olefin compounds.

[0201] from Fig.19 It can be seen that the 10 electronic nose sensors all have significant differences in their response values ​​to the odor of the small yellow ginger samples. In the W1C, W3C, and W5C sensors, the odor response values ​​of the small yellow ginger under UVPT thawing are significantly greater than those of other thawed samples. In the W5S and W2W sensors, the difference in the odor response values ​​of various types of small yellow ginger is slightly smaller. In the W6S and W2S sensors, the odor response values ​​of the samples after -20℃TW thawing are significantly greater than those of other thawed samples. In the W1S and W3S sensors, the odor response values ​​of the small yellow ginger at -20℃TW / TN are significantly greater than those of other thawed samples. In the W1W sensor, the odor response values ​​of the samples after -20℃TN thawing are significantly greater than those of other thawed samples.

[0202] After quick-frozen turmeric was treated by different thawing methods, the response values ​​of -10℃ UVPT turmeric samples in W5C, W1W, and W2W sensors were not significantly different from those of fresh turmeric, the response values ​​of -10℃ MMAT turmeric samples in W1C, W1W, and W2W were not significantly different from those of fresh turmeric, and the response values ​​of -20℃ MMAT turmeric samples in W5S, W1S, and W2W were not significantly different from those of fresh turmeric. However, the response values ​​of the electronic nose sensors under other thawing methods were significantly different from those of fresh turmeric. Therefore, the difference in volatile compounds between samples under different thawing conditions can be preliminarily judged by the size of the sensor signal response value.

[0203] exist Fig. 20 In the loading diagram, the closer the spatial distance between the arrows, the higher the correlation between the sensor response value indicators of the volatile flavor of small yellow ginger in the electronic nose measurement. Principal component 1 is negatively correlated with three sensor response value indicators (W1C, W3C, W5C), and the other seven are positively correlated. Principal component 2 is negatively correlated with the response value indicators of W1W, W5S, and W2W, and the other seven are positively correlated. In the figure, PC1 is 61.9%, PC2 is 18.7%, and the cumulative contribution rate of the two principal components is 80.6%. All 10 sensors of the electronic nose can be well explained by these two principal components.

[0204] PCA was used to further analyze the results of the electronic nose measurement. Fig.21 As shown, PC1 is 61.9%, PC2 is 18.7%, and the cumulative contribution rate of the two principal components is 80.6%, indicating that the overall information of the original data can be effectively reflected. In the PCA diagram, except for the -20℃TN condition, the distances between the other thawing conditions and the same group of fresh small yellow ginger samples are relatively close, indicating that the thawing effect of quick-frozen small yellow ginger is not very stable when the -20℃TN thawing condition is adopted. There is an overlapping part between fresh small yellow ginger and -10℃UVPT in the PCA diagram, indicating that after the small yellow ginger is thawed under the -10℃UVPT condition, its volatile flavor substances are very different from those of fresh small yellow ginger under the electronic nose measurement. Similarly, after the small yellow ginger is treated under -10℃MMAT and -20℃MMAT conditions, there is no significant difference in the volatile compounds between the two under the electronic nose measurement.

[0205] Analysis of volatile components of ginger with different thawing methods:

[0206] The volatile compound components and contents of fresh turmeric, -20℃TN / TW, -10℃ / -20℃UVPT, and -10℃ / -20℃MMAT thawed turmeric samples were analyzed and identified by the HS-SPME combined with GC-MS. The Chinese name, substance type, CAS number, retention coefficient, and average mass concentration of the detected volatile substances are shown in Table 10.

[0207] Table 12 shows the changes in the volatile components of small yellow ginger after different thawing methods. GC-MS detected a total of 54 volatile compounds (a total of 39 volatile compounds), including 27 olefin compounds (a total of 25), 8 alcohol compounds (a total of 4), 5 aldehyde compounds (a total of 5), 2 ketone compounds (a total of 1), 2 ester compounds (a total of 2), and 10 other compounds (a total of 2). Among them, there are 46 volatile components in fresh small yellow ginger, and the volatile substances of small yellow ginger after thawing at -20℃TN / TW, -10℃ / -20℃UVPT, and -10℃ / -20℃MMAT are 44, 47, 45, 47, 46, and 46 respectively.

[0208] The number of volatile substances detected in small yellow ginger after thawing at -20℃TW and -20℃UVPT was the largest. Among these volatile components, β-phellandrene, α-curcumene, gingerol, α-farnesene, β-bisabolene, β-sesquiphellandrene, Z-citral, (E)-3,7-dimethyl-2,6-octadienal and other substances had high mass concentrations after thawing by different methods. Among them, bicyclohexene (41.53μg / g), trans-nerolidol (24.35μg / g), eucalyptus alcohol (45.27μg / g), borneol (202.24μg / g), and borneol (202.24μg / g) only existed in the samples of -20℃TW; (+)-convolvulol (25.21μg / g) only existed in the samples of -10℃UVPT; β-cuberene contained in fresh turmeric was not detected after thawing at -20℃TN / TW, (R)-3,7-dimethyl-6-octenol, geraniol, and methylheptenone were not detected after thawing at -20℃TW, and 4-isopropyltoluene and 3-methyl-2-(3-methyl-2-butenyl)furan were not detected after thawing at -20℃TN / TW and -10℃UVPT.

[0209] Table 12 Volatile components of ginger under different thawing methods

[0210]

[0211]

[0212]

[0213] Note: “-” indicates that the substance was not detected; different lowercase letters in the same row indicate significant differences, P<0.05

[0214] Table 13 Types of volatile substances in small yellow ginger under different thawing methods

[0215]

[0216] From Table 13, Fig. 22 It can be seen that the types and overall changes in mass concentrations of 7 types of volatile substances in small yellow ginger after thawing in different ways, including olefins, alcohols, esters, aldehydes, ketones, acids, and other types. The main volatile flavor components of fresh small yellow ginger and samples thawed in different ways are olefins, aldehydes, and alcohols, among which olefins have the highest mass concentration, accounting for about 76.9% of the total mass concentration of volatile substances.

[0217] In the thawing methods of small yellow ginger, the total mass concentration of different volatile components has obvious differences in different thawing methods. In fresh small yellow ginger and different thawing methods, the mass concentrations of olefins and alcohols are higher after thawing at -20℃TN / TW and -10℃MMAT, the mass concentrations of aldehydes and ketones are higher after thawing at -10℃UVPT and -10℃ / -20℃MMAT, and the mass concentrations of esters and other substances are higher after thawing at -20℃TN / TW and -10℃UVPT. Overall, the mass concentration of volatile substances in fresh small yellow ginger is less than that after thawing in different methods. The reason is that the cells of fresh small yellow ginger are compact and the structure is intact, while the SPME conditions are relatively mild, which cannot fully release the volatile components in fresh small yellow ginger. After thawing, the cell structure of small yellow ginger is not as strong as before, it becomes soft, and the aroma components are easy to volatilize.

[0218] There are 39 volatile substances in fresh yellow ginger and different thawing methods. Among them, the mass concentrations of 8 substances, β-phellandrene, α-curcumene, gingerol, α-farnesene, β-bisabolene, β-sesquiphellandrene, Z-citral, and (E)-3,7-dimethyl-2,6-octadienal, are all above 100μg / g, whether in fresh yellow ginger or in yellow ginger thawed in different ways. After yellow ginger is thawed by -20℃TN / UVPT and -10℃MMAT, the above 8 substances will increase to varying degrees, and the maximum can reach 4078.82μg / g (gingerol), with a large change. The mass concentrations of the 8 volatile substances in yellow ginger decreased overall after thawing under -10℃UVPT conditions, and increased overall after thawing under -20℃MMAT conditions, but compared with other thawing methods, the rise and fall arc changes are smaller.

[0219] The 46 volatile components in fresh yellow ginger can be detected after thawing in different ways. After thawing at -10℃ / -20℃MMAT conditions, the detected volatile components are all 46, and the types and quantities of volatile components of fresh yellow ginger are consistent, with only a difference in mass concentration; after thawing at -20℃UVPT conditions, there is only one more volatile substance than fresh yellow ginger, and its mass concentration is 28.15μg / g. Some volatile substances are only detected in fresh yellow ginger and some stages after thawing in different ways. The mass concentration of β-cuberene in fresh turmeric was 19.03±2.01μg / g, and the mass concentrations in -10℃ / -20℃UVPT and -10℃ / -20℃MMAT were 7.5±0.93, 16.18±10.98, 36.06±8.61, and 19.68±1.73μg / g, respectively. It was not detected in -20℃TN / TW. Bicycloselene was only detected in -20℃TW with a mass concentration of 41.53μg / g. (R)-3,7-dimethyl-6-octenol and geraniol were only not detected in -20℃TW, but were present in the other methods with little difference in mass concentration, averaging 27.70μg / g and 36.80μg / g, respectively. Trans-nerolidol and eucalyptol were only detected at -20℃TW, with mass concentrations of 24.35 and 45.27±20.7μg / g, respectively. Methylheptenone was not detected at -20℃TW, and its mass concentration in fresh turmeric was 0.64±0.11μg / g, which was not significantly different from the mass concentrations measured at -20℃TN, -10℃UVPT, and -20℃MMAT, while the mass concentrations measured at -20℃UVPT and -10℃MMAT were twice that of fresh turmeric. 4-Isopropyltoluene and 3-methyl-2-(3-methyl-2-butenyl)furan were detected in fresh turmeric, -20℃UVPT, and -10℃ / -20℃MMAT, but not detected at -20℃TN / TW and -10℃UVPT. L-borneol was not detected in fresh turmeric, but was only detected in -20℃TW condition, with a mass concentration of 202.24μg / g. (+)-Paraquinone was not detected in fresh turmeric, but was only detected in -10℃UVPT condition, with a mass concentration of 25.21μg / g.

[0220] Olefin compounds are the main volatile components in fresh turmeric and turmeric thawed in different ways. The olefin compounds in fresh turmeric and turmeric thawed in different ways are 26, 25, 26, 26, 26, 24 and 26 respectively. The main olefin compounds are camphene, β-phellandrene, α-curcumene, zingiberene, α-farnesene, β-bisabolene and β-sesquiphellandrene. Among them, zingiberene is the olefin compound with the highest mass concentration. The mass concentrations of fresh turmeric and turmeric after thawing in different ways are 2406.41±263.81μg / g, 4375.04±1493.51μg / g, 4078.82±1583.18μg / g, 418.75±46.04μg / g, 3158.5±449.45μg / g, 4274.73±1231.06μg / g and 2830.11±489.73μg / g, respectively.

[0221] There are 7 kinds of alcohol compounds in fresh turmeric samples, and the alcohol compounds after thawing in different ways are 7, 7, 6, 7, 7, and 7 respectively. The content of alcohol compounds in turmeric is relatively small. Among all thawing treatment conditions, the mass concentration of nerolidol after -20℃TW treatment is the highest, which is 71.53±18.26μg / g; followed by -10℃UVPTgeraniol (52.51μg / g), α-terpineol (54.14μg / g), -10℃MMATgeraniol (57.6μg / g), α-terpineol (50.36μg / g), -20℃TNnerolidol (52.37μg / g); the mass concentrations of the remaining alcohol compounds are all below 50μg / g.

[0222] Five aldehyde compounds were detected in fresh turmeric, and there was no increase or decrease after different thawing methods. The mass concentration of (E)-3,7-dimethyl-2,6-octadienal was high in fresh turmeric and after different thawing methods, and the overall change was not obvious. The highest mass concentration reached 1158.68±65.07μg / g after treatment under -20℃ UVPT conditions. The mass concentration of Z-citral was second only to (E)-3,7-dimethyl-2,6-octadienal among aldehyde compounds, with an average mass concentration of 421.11μg / g. The mass concentration of other aldehyde compounds did not exceed 50μg / g, which was significantly lower than these two categories.

[0223] Ketones and esters account for a very low proportion of the volatile flavor components of turmeric, accounting for 0.12% and 0.16% of the total volatile compounds, respectively. Among them, there are two ketones in fresh turmeric and thawed turmeric, namely methyl heptenone and 2-undecanone, and only the -20℃ TW condition treatment lacks methyl heptenone. There are two esters in fresh turmeric and thawed turmeric, namely borneol acetate and citronellyl acetate, with an average content of 7.04μg / g and 6.17μg / g. A total of 10 volatile components were detected in other substances, 5 of which were 4-isopropyltoluene, 3-methyl-2-(3-methyl-2-butenyl) furan, isoborneol, borneol, and (+)-convolvulol. Among other substances, isoborneol accounts for a high proportion, reaching 49.6%.

[0224] Effects of different thawing methods on the volatile components of quick-frozen small yellow ginger:

[0225] OPLS-DA separates the data set and extracts the main relevant variables by building a multivariate linear regression model. Compared with unsupervised methods such as PCA, OPLS-DA can better identify the differences between samples and determine which variables can best distinguish different categories of samples. Therefore, it has important application value in classifying and identifying different categories of samples.

[0226] The independent variable fit index (R2X) in this analysis is 0.993, the dependent variable fit index (R2Y) is 0.98, and the model prediction index (Q2) is 0.763. R2 and Q2 exceeding 0.5 indicate that the model fitting results are acceptable. After 200 permutation tests, Fig.23 As shown, the intersection point of the Q2 regression line and the vertical axis is less than 0, indicating that the model is not overfitting and the model verification is valid.

[0227] Compared with PCA analysis, OPLS-DA analysis has stronger classification ability. Under the premise that the model does not have overfitting and the model verification is effective, Fig.24 There is still some overlap in the OPLS-DA diagram between fresh turmeric and -20℃ microwave combined with magnetic nano thawing (-20℃MMAT), which means that the volatile components of turmeric after thawing under -20℃MMAT conditions cannot be well distinguished from the volatile components of fresh turmeric, and the volatile components of the two are very similar.

[0228] In order to further analyze the differences and connections between the volatile flavor substances of fresh small yellow ginger and small yellow ginger after thawing in different ways, cluster analysis of the volatile flavor substances among various small yellow ginger samples was performed. The results are shown in Fig.25The upper tree is the clustering of fresh small yellow ginger and small yellow ginger samples after different thawing methods, and the left tree is the clustering of volatile substance mass concentration. The depth of the middle color block reflects the high and low mass concentration of volatile substances in small yellow ginger. From the upper clustering, small yellow ginger samples can be divided into two categories. Fresh small yellow ginger, microwave combined with magnetic nano thawing at -20℃ (-20℃MMAT), and ultrasonic combined with vacuum packaging thawing at -10℃ (-10℃UVPT) are classified as the first category, and natural thawing at -20℃ (-20℃TN), static water thawing at -20℃ (-20℃TW), ultrasonic combined with vacuum packaging thawing at -20℃ (-20℃UVPT), ​​and microwave combined with magnetic nano thawing at -10℃ (-10℃MMAT) are classified as the second category. The mass concentration of volatile flavor substances in the second category is significantly higher than that in the first category, and the two parts are clearly classified.

[0229] In the first category, fresh turmeric and -20℃ microwave combined with magnetic nano thawing (-20℃MMAT) belong to the same subcategory, and the color blocks in the cluster diagrams of the two are basically the same, indicating that after thawing under -20℃MMAT conditions, the types and contents of volatile flavor components of turmeric are basically the same as those of fresh turmeric, which is consistent with the OPLS-DA results.

[0230] These two belong to the same category as -10℃ UVPT. In the cluster heat map, it can be seen that -10℃ UVPT is higher than fresh turmeric and -20℃ MMAT only in the contents of citronellyl acetate, geraniol, γ-cadinene, (+)-tetramer, geraniol D, α-bergamotene, and (+)-7-epi-sesquiterpene. The colors of other color blocks tend to be consistent, which indicates that after thawing under -10℃ MMAT conditions, the volatile flavor components of turmeric can be basically consistent with those of fresh turmeric.

[0231] In the cluster heat map, the color blocks of the areas of natural thawing at -20℃ (-20℃TN) and static water thawing at -20℃ (-20℃TW) show completely opposite change trends from the color blocks of the areas of fresh small yellow ginger, which indicates that small yellow ginger cannot maintain its original volatile aroma characteristics well after being thawed by these two types of thawing methods.

[0232] Changes in aroma activity value (OAV) of key flavor substances in small yellow ginger during different thawing methods:

[0233] The OAV value indicates the relative aroma intensity of the ingredient in the food. When 0.1≤ROAV<1, the volatile substance plays an auxiliary role in the overall flavor of turmeric; when ROAV≥1, the volatile substance is the key volatile substance of turmeric. The higher the OAV value, the greater the contribution of the ingredient to the overall aroma of the food.

[0234] Since the contribution of volatile compounds to the flavor of small yellow ginger depends on the specific content and threshold of each aroma substance, the GC-MS test results of small yellow ginger samples combined with OAV can more comprehensively compare the differences and connections between the volatile aroma of small yellow ginger after thawing in different ways and fresh small yellow ginger, and identify the volatile compounds with major flavor contributions in small yellow ginger. By consulting the data, the odor thresholds of 22 aroma compounds were obtained, and OAV was calculated by combining the thresholds of each compound, as shown in Table 14. When OAV<1, the volatile substance has a modifying effect on the flavor of the small yellow ginger sample, and OAV≥1 indicates that the volatile substance contributes more to the overall aroma of small yellow ginger and is an important aroma compound.

[0235] It can be seen from Table 13 that in the range of 1≤OAV<10, each type of turmeric sample contains two volatile aroma components; in the range of 10≤OAV<100, -20℃MMAT samples contain 8 volatile aroma components, fresh turmeric and -10℃UVPT samples contain 7, -20℃UVPT samples contain 6, -20℃TW and -10℃MMAT samples contain 5, and -20℃TN samples contain 3; in the range of 100≤OAV<1000, -20℃TN / TW samples each contain 9 volatile aroma components, -10℃MMAT samples contain 8, -20℃UVPT samples contain 6, fresh turmeric and -10℃UVPT samples contain 5, and -20℃MMAT samples contain 4; in the range of OAV>1000, -20℃TW samples contain 6 volatile aroma components, and the other treatment methods and fresh turmeric each contain 8.

[0236] In general, except for the methyl heptenone not detected after -20℃ TW treatment, the OAV values ​​of fresh turmeric and turmeric thawed in 6 different ways were all ≥1; in the turmeric samples, the only volatile aromas with 1≤OAV<10 were nerolidol and methyl heptenone, among which nerolidol had the characteristic odors of wood, rose and apple.

[0237] The aroma activity values ​​of camphene, sabinene, β-pinene and δ-elemene in the seven types of samples of small yellow turmeric are all in the range of 10≤OAV<100; the aroma activity values ​​of (R)-(+)-α-pinene, a-phellandrene, limonene and (E)-β-farnesene are all in the range of 100≤OAV<1000; the aroma activity values ​​of β-phellandrene, α-terpinene and α-farnesene are all in the range of 1000≤OAV<10000; the aroma activity value OAV of (Z)-β-farnesene is all>10000.

[0238] Table 14 OAV values ​​of volatile components of small yellow ginger under different thawing methods

[0239]

[0240]

[0241] In order to clarify the contribution of volatile flavor compounds with OAV greater than 1 to the flavor of fresh turmeric and turmeric with different thawing methods, cluster analysis and principal component analysis of fresh turmeric and turmeric with different thawing methods were performed based on the 22 volatile flavor compounds obtained by OAV analysis. Fig.26 Cluster heat map results, Fig. 27 The results of principal component analysis.

[0242] exist Fig.26 In the figure, from the upper clustering, the small yellow ginger samples can be divided into two categories and three subcategories. Fresh small yellow ginger, -20℃ microwave combined with magnetic nano thawing (-20℃MMAT), -10℃ ultrasonic combined with vacuum packaging thawing (-10℃UVPT) are classified as the first subcategory, -20℃ natural thawing (-20℃TN) and -20℃ static water thawing (-20℃TW) are classified as the second subcategory, -20℃ ultrasonic combined with vacuum packaging thawing (-20℃UVPT) and -10℃ microwave combined with magnetic nano thawing (-10℃MMAT) are classified as the third subcategory. The color of the first subcategory tends to be red and the tone is uniform, indicating that its overall OAV value is small and the values ​​are similar, which means that the volatile flavor contribution of fresh small yellow ginger, -20℃MMAT, and -10℃UVPT samples is the same, which is consistent with the clustering heat map from the overall analysis. Fig.26 The results were consistent, and the classification results of flavor compounds of fresh turmeric and turmeric with different thawing methods were very stable.

[0243] exist Fig. 27 The cumulative variance contribution of PC1 and PC2 is 89.6%, which can reflect most of the information of the data. The balls of different colors represent fresh small yellow ginger and small yellow ginger samples after 6 different thawing methods, the numbers represent the volatile flavor compounds, and the length and direction of the arrows represent the influence of volatile substances on the overall flavor of fresh small yellow ginger and small yellow ginger samples after 6 different thawing methods. Fig. 27 It can be seen that volatile compounds such as sabinene, (R)-(+)-citronellal, and bornyl acetate contribute greatly to the overall flavor of -20℃UVPT samples; volatile compounds such as β-myrcene, α-farnesene, and nerolidol contribute greatly to the overall flavor of -10℃MMAT samples; (R)-(+)-α-pinene, camphene, geraniol, and methylheptenone contribute greatly to the overall flavor of -20℃TN samples; geraniol and 2-undecanone contribute greatly to the overall flavor of -20℃TW samples.

[0244] In addition, fresh turmeric, -20℃MMAT, -10℃UVPT Fig. 27The intervals between the -20℃UVPT, -10℃MMAT, and -20℃TN / TW samples are relatively close, and there is a large gap between them and they do not overlap. This indicates that except for the similarities in the aroma characteristics of fresh turmeric, -20℃MMAT, and -10℃UVPT samples, there are obvious differences in aroma between the other samples.

[0245] in conclusion:

[0246] In the electronic nose detection, sensors W5S and W1W are very sensitive to the volatile flavor components of small yellow ginger, which indirectly reflects that olefins account for a large proportion of the flavor components of small yellow ginger. Each type of small yellow ginger sample has different significant differences in the 10 sensors of the electronic nose, indicating that the volatile components of small yellow ginger after different thawing methods have certain differences. In the electronic nose PCA analysis, multiple types of thawed small yellow ginger samples can be clearly separated, but there is some overlap between fresh small yellow ginger and -10℃ UVPT samples, which means that after thawing under -10℃ UVPT conditions, its volatile flavor category is highly similar to that of fresh small yellow ginger.

[0247] In the GC-MS test, a total of 54 volatile compounds were separated and detected, including 27 olefins, 9 alcohols, 5 aldehydes, 2 ketones, 2 esters, and 10 other substances. Olefins are the main flavor substances in small yellow ginger, accounting for about 76.9% of the total volatile substance mass concentration. The 46 volatile components in fresh small yellow ginger can be detected after thawing in different ways. After thawing small yellow ginger at -10℃ / -20℃MMAT conditions, the volatile components detected are all 46, and the types and quantities of volatile components are consistent with those of fresh small yellow ginger, with only a difference in mass concentration.

[0248] In the analysis of volatile components, OPLS-DA analysis was performed on 54 volatile compounds in small yellow ginger. The results showed that the model was not overfitted and the verification was effective. Multiple types of thawed small yellow ginger samples could be clearly separated, but fresh small yellow ginger and -20℃MMAT samples had some overlap, which means that after thawing under -20℃MMAT conditions, its volatile flavor types and mass concentrations were highly similar to those of fresh small yellow ginger. In the cluster heat map, -20℃MMAT samples and fresh small yellow ginger belonged to the same subcategory, and the two belonged to another subcategory with -10℃UVPT, which was clearly distinguished from other thawing methods. The three had a high degree of similarity in color blocks, which showed that the volatile components of -20℃MMAT and -10℃UVPT sample treatment methods were not much different from those of fresh small yellow ginger.

[0249] In the changes of aroma activity value (OAV) of key flavor substances, the aroma activity values ​​of 22 volatile compounds are all greater than one, indicating that these 22 volatile substances contribute greatly to the overall aroma of small yellow ginger and are important aroma compounds. In its OAV cluster heat map, fresh small yellow ginger, -20℃ MMAT, and -10℃ UVPT are classified into the same category, indicating that the volatile flavor contributions of these three are basically the same. From the overall analysis, it is consistent with the cluster heat map. Fig.25 The results were consistent. In the OAV principal component analysis, -10℃UVPT, -20℃MMAT and fresh turmeric were close, indicating that the volatile flavor contribution of the three was similar.

[0250] In summary, the volatile flavor components of turmeric thawed by -20℃MMAT and -10℃UVPT are closer to those of fresh turmeric, and the results of various analysis methods are the same. The classification results of flavor compounds of fresh turmeric and turmeric thawed by different methods are relatively stable.

[0251] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A method for thawing quick-frozen ginger, characterized in that: Thawing is done by ultrasonic combined with vacuum packaging.

2. The method for thawing quick-frozen ginger according to claim 1, characterized in that: The ultrasonic combined vacuum packaging thawing is to thaw the vacuum-packed sealed quick-frozen ginger under ultrasonic conditions of a temperature of 20-30° C. and a power of 300-400W.

3. The method for thawing quick-frozen ginger according to claim 2, characterized in that: The specific ultrasonic conditions were temperature 25°C and power 350W.

4. A method for thawing quick-frozen ginger, characterized in that: Microwave combined with magnetic nano thawing is used.

5. The method for thawing quick-frozen ginger according to claim 6, characterized in that: The microwave combined with magnetic nano thawing is to place the vacuum-sealed quick-frozen ginger in a 0.05-0.2 mg / mL ferroferric oxide solution and thaw it with a 300-350W microwave. When the center temperature reaches 4°C, the thawing is considered complete.

6. The method for thawing quick-frozen ginger according to claim 7, characterized in that: The concentration of the ferrosoferric oxide solution is 0.1 mg / mL; the microwave power is 320W.

7. The method for thawing quick-frozen ginger according to any one of claims 1 to 6, characterized in that: The thawing is completed when the central temperature reaches 4°C.

8. The method for thawing quick-frozen ginger according to any one of claims 1 to 6, characterized in that: The quick-frozen ginger is quick-frozen ginger that is stored at -5 to -25°C after quick freezing.

9. The method for thawing quick-frozen ginger according to claim 8, characterized in that: The quick freezing is to quickly reduce the temperature of the ginger to -18°C, that is, the quick freezing is completed.

10. A method for thawing quick-frozen ginger, characterized in that: When ginger is stored at -5 to -15°C, it is thawed by ultrasonic combined with vacuum packaging; when it is stored below -15°C, it is thawed by microwave combined with magnetic nano.

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