Application of daidzein in fresh keeping of raw fish food materials

Abstract

The invention discloses an application of daidzein in preservation of aquatic product food materials, and discovers that daidzein can be converted into tiny water drops in an atomization form, the tiny water drops are coated on the surfaces of raw fish food materials, and the raw fish food materials are stored in preservation modes such as low-temperature cold storage or ultralow-temperature freezing. According to the present invention, the increase of the volatile basic nitrogen (TVB-N) content and the thiobarbituric acid (TBARs) value during the storage period of the fish food material can be significantly relieved, the oxidative decomposition of proteins and fats during the whole storage process can be effectively delayed, and especially the freshness and the sensory quality of the raw fish food material can be well maintained under the ultra-low temperature freezing condition. Daidzein and low-temperature or ultralow-temperature preservation jointly act, so that the raw fish keeps the freshness quality similar to that of fresh food materials, the traditional eating mode that the raw fish is eaten after being killed is changed, the commercial value of the raw fish is greatly improved, and industrial development of the raw fish is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of aquatic product preservation, and in particular relates to the application of daidzein in the preservation of raw fish food. Background Art

[0002] The traditional way of processing sashimi is to kill the fish immediately before eating, which greatly enhances the freshness of the ingredients. With people's pursuit of high-quality and special food, the sashimi market continues to grow. The industrialization of sashimi is an inevitable trend of future development, and timely and effective preservation methods are the key to the industrialization of sashimi ingredients.

[0003] The growth and reproduction of microorganisms and the activity of inherent enzymes in meat are often the main causes of meat spoilage. Low temperature can inhibit the activity of enzymes and the life activities of most microorganisms, thereby delaying the deterioration and corruption of food and achieving the purpose of storage and preservation. It is currently the most widely used preservation method for aquatic products. However, chemical reactions such as non-enzymatic browning and fatty acid oxidation at low temperatures have a great impact on the changes in color, texture, smell, flavor and nutritional quality of aquatic products, especially for sashimi, which requires high freshness quality. Single low-temperature storage and preservation cannot meet the requirements of sashimi lovers for food quality. It is necessary to combine other preservation technologies to meet the requirements of sashimi ingredients for freshness quality.

[0004] In addition, considering that many fish in sashimi may carry parasites, such as Anisakis, etc. Therefore, the prior art usually recommends the use of ultra-low temperature freezing (-60℃~-80℃) to preserve raw fish ingredients, because ultra-low temperature freezing can effectively kill these parasites and protect the health of the eater. At the same time, ultra-low temperature freezing can better alleviate chemical reactions such as non-enzymatic browning and fatty acid oxidation of food compared to conventional low-temperature refrigeration. However, under ultra-low temperature freezing preservation conditions, the water in the food during the preservation process will form ice crystals, destroy the cell structure, cause the destruction of the fish tissue structure and the deterioration of the taste, freeze denaturation of protein, loss of juice, loss of nutrients, etc. These problems have caused the freshness quality of ultra-low temperature frozen ingredients to be unable to be similar to that of fresh ingredients.

[0005] Daidzein, CAS number: 486-66-8, chemical name 4,7-dihydroxyisoflavone, molecular formula C15H10O4, molecular mass 254.24, is a yellow crystalline solid, soluble in some organic solvents. It has strong antioxidant activity and can neutralize free radicals to combat cellular oxidative damage. It also has multiple biological activities such as anti-inflammatory, antibacterial, anti-tumor and anti-platelet aggregation. There are no reports on the role of daidzein in the low-temperature or ultra-low-temperature freezing and preservation of raw fish ingredients. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects and shortcomings in the prior art and provide an application of daidzein in the preparation of aquatic product food preservative.

[0007] The second object of the present invention is to provide a method for preserving aquatic products.

[0008] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0009] The present invention uses daidzein in the preservation of raw fish ingredients. It is found that under low-temperature refrigeration conditions (4°C), the pH of fish fillets treated with daidzein within 72 hours is significantly higher than that of the control group, while the content of volatile basic nitrogen (TVB-N) and thiobarbituric acid (TBARs) is significantly lower than that of the control group, and there is no difference with 0h, and the taste of the fish fillets is not affected; under ultra-low temperature freezing conditions (-80°C), the pH of fish fillets treated with daidzein within 14 days is significantly higher than that of the control group, while the content of TVB-N and TBRAS is significantly lower than that of the control group, and the taste of the fish fillets is not affected. In addition, the present invention finds that the thawing loss rate of raw fish ingredients stored in ultra-low temperature freezing increases with the extension of storage time during storage, and the water holding capacity is significantly reduced, while the freeze-thaw loss rate of fish tissue treated with daidzein during storage increases less, and the water holding capacity maintains a small change from the initial state, which can delay the quality damage of the ingredients caused by freezing to a certain extent, so that the frozen raw fish ingredients maintain a good glossiness and a sweet and crisp taste. The results showed that daidzein treatment of sashimi ingredients could effectively delay the oxidative decomposition of protein and fat during the entire preservation process of refrigeration or freezing, and thus well maintain the freshness and sensory quality of sashimi ingredients.

[0010] Therefore, the present invention provides the use of daidzein in preparing aquatic product food preservative.

[0011] Furthermore, the preservative is a low-temperature refrigeration preservative or an ultra-low-temperature freezing preservative, that is, a preservative used together with low-temperature refrigeration preservation or ultra-low-temperature freezing preservation.

[0012] Furthermore, the ultra-low temperature freezing preservative preserves aquatic food ingredients by any of the following ways: (1) delaying the pH drop rate during the storage of aquatic food ingredients; (2) reducing the content of thiobarbituric acid reactants in aquatic food ingredients; (3) inhibiting the number of bacterial colonies during the storage of aquatic food ingredients; (4) reducing the content of volatile basic nitrogen in aquatic food ingredients; (5) maintaining the water holding capacity and thawing loss rate of aquatic food ingredients during storage.

[0013] Furthermore, the preservative is obtained by dissolving and diluting daidzein.

[0014] Furthermore, the preservative is a coating preservative.

[0015] Furthermore, the concentration of daidzein in the preservative is 0.2-0.6 mg / mL, preferably 0.5 mg / mL.

[0016] The present invention also provides a method for preserving aquatic products, which comprises coating or soaking fresh aquatic product ingredients with daidzein, vacuum-packing the ingredients and storing them at low or ultra-low temperatures; the soaking time is 2 to 5 minutes.

[0017] Furthermore, the concentration of daidzein is 0.2-0.6 mg / mL.

[0018] Preferably, the concentration of daidzein is 0.5 mg / mL.

[0019] Furthermore, the coating method is to pass the fresh-keeping liquid through an atomizer to atomize it into small particles attached to the surface of the food, or to spray the fresh-keeping liquid directly onto the surface of the food with a spray bottle.

[0020] Furthermore, the soaking time is 2 to 4 minutes.

[0021] Furthermore, the low temperature is 0-4°C.

[0022] Furthermore, the ultra-low temperature is -60 to -80°C.

[0023] Furthermore, the aquatic product is fish.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides the application of daidzein in the preservation of aquatic food materials. The present invention finds that daidzein can be converted into tiny water droplets in the form of atomization and coated on the surface of raw fish food materials. It can work synergistically with preservation methods such as low-temperature refrigeration and ultra-low-temperature freezing, and can significantly alleviate the increase of volatile basic nitrogen (TVB-N) content and thiobarbituric acid (TBARs) value of fish food materials during storage, effectively delay the oxidative decomposition of protein and fat during the entire storage process, especially under ultra-low-temperature freezing conditions, the increase of freeze-thaw loss rate of fish meat tissue treated with daidzein is small, the water holding capacity is maintained and the change of the initial state is small, and the quality damage caused by freezing to food materials can be delayed to a certain extent, so that the frozen raw fish food materials maintain good gloss, sweet and crisp taste, and well maintain the freshness quality and sensory quality of raw fish food materials. The daidzein and low-temperature or ultra-low-temperature preservation work together to keep the freshness quality of raw fish similar to that of fresh food materials, which not only changes the traditional eating method of raw fish, which is to kill and eat it immediately, but also greatly improves the commodity value of raw fish and promotes the industrialization development of raw fish. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1This is a picture of raw fish stored at 4℃ for 24 hours. Note: ck 阴 It's fresh fish, ck 阳 It refers to sashimi that has not been coated and refrigerated at 4°C for 24 hours, and TM refers to sashimi that has been coated with daidzein preservative solution and then refrigerated at 4°C for 24 hours.

[0027] Figure 2 This is a picture of raw fish frozen at -80℃ for 24 hours. 阴 It's fresh fish, ck 阳 It is sashimi that has been frozen at -80℃ for 24 hours without coating, and TM is sashimi that has been coated with daidzein preservative solution and then frozen at -80℃ for 24 hours.

[0028] Figure 3 This is the change of fish moisture during -80℃ ultra-low temperature freezing and preservation. Figure 3 A is the freeze-thaw loss rate during storage; B is the water holding capacity during storage. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0030] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0031] Experimental Materials:

[0032] Daidzein, CAS No.: 486-66-8, chemical name: 4,7-dihydroxyisoflavone, molecular formula: C 15 H 10 O4, molecular mass is 254.24, chemical structure is as follows:

[0033]

[0034] Preparation of daidzein (0.5 mg / mL) preservative solution: Weigh 0.05 g daidzein, add it to 2 mL of anhydrous ethanol to fully dissolve it, and then add deionized water to make up to 100 mL.

[0035] Grass carp fillets: purchased from Hema Fresh Supermarket, slaughtered according to the method of raw fish, bled, removed the main spines in the middle, peeled and took out the fish fillets.

[0036] Control group (CK): fresh grass carp fillets without any treatment.

[0037] Treatment group (TM): fresh grass carp fillets coated with daidzein preservative solution.

[0038] Example 1 Determination of Physicochemical Indexes Related to Freshness of Grass Carp Fillets Stored at 4°C

[0039] 1. Experimental Methods

[0040] 1. Vacuum-pack the control group and the treatment group and store them in a 4°C refrigerator for 72 hours.

[0041] 2. Determination of physical and chemical indicators related to fish freshness

[0042] (1) Referring to the microdiffusion method in GB 5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food", the total volatile basic nitrogen (TVB-N) of the control group and the treatment group was measured at 0h, 24h, 48h and 72h. Volatile basic nitrogen (TVB-N) refers to the alkaline nitrogen-containing substances such as ammonia and amines produced by the decomposition of proteins in animal foods due to the action of enzymes and bacteria during the spoilage process. It is one of the important indicators reflecting the freshness changes of aquatic products.

[0043] (2) Referring to the spectrophotometric method in GB 5009.181-2016 "National Food Safety Standard Determination of Malondialdehyde in Food", the thiobarbituric acid reactive substances (TBARs) values ​​of total fat samples in the control group and the treatment group were measured at 0h, 24h, 48h and 72h. Thiobarbituric acid reactive substances (TBARS) are the main indicators of the degree of fat oxidation in meat.

[0044] (3) pH determination method: 5.00 g of sample was placed in a beaker, 50 mL of distilled water was added, homogenized and centrifuged for 10 min at 7 000 r / min, and the supernatant was taken and the pH value of the fish meat was measured using a pH meter (Mettler-Toledo Instruments (Shanghai) Co., Ltd.). Each sample was measured three times in parallel.

[0045] 2. Experimental Results

[0046] from Figure 1 The results showed that after the grass carp fillets treated with daidzein preservative solution were stored at 4°C for 24 hours, the transparency of the fillets was higher than that of the grass carp fillets not treated with daidzein preservative solution, and was close to the transparency of fresh fillets, indicating that the daidzein preservative solution has a certain preservation effect on fish fillets.

[0047] 1. The pH values ​​of grass carp samples in the CK and TM groups were measured at 0, 24, 48 and 72 hours of refrigeration time, and the results are shown in Table 1. As can be seen from the table, in the CK and TM groups, the pH values ​​of grass carp samples showed a trend of first increasing and then decreasing, but the increase in the TM group was larger than that in the CK group. Through one-way analysis of variance and then pairwise comparison by the least significant difference method (LSD test), at 24h, the pH values ​​of the CK and TM groups were significantly higher than those at 0h (p<0.05), which were 6.52±0.02 and 6.75±0.01, respectively. At the same time, after two independent sample t-test comparisons, at 24h and 48h, the pH values ​​of the TM group were significantly higher than those of the CK group (p<0.05). This shows that the refrigeration time has an effect on the pH of grass carp samples, and the pH value of the TM group increased significantly, indicating that adding preservative solution can avoid meat acidification, thereby better maintaining the stability of grass carp samples.

[0048] 2. The total volatile base nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARs) values ​​of grass carp samples in the CK group and TM group at 0, 24, 48 and 72 hours of refrigeration time were measured. The results are shown in Table 1. As can be seen from the table, for sashimi ingredients that have not been treated with daidzein preservative solution and stored at 4°C, the contents of TVB-N and TBRAS increased significantly with the extension of storage time. After 72 hours of storage, the contents of TVB-N and TBRAS increased by 9.61 mg / 100 g and 0.32 mg MDA / kg respectively compared with fresh ingredients, which are almost twice that of fresh ingredients. When sashimi ingredients were pretreated with daidzein preservative solution by coating or soaking, the TBARS content of fish meat did not increase significantly after 72 hours, and the TVB-N content remained at a value similar to that of fresh ingredients within 48 hours. Therefore, pretreatment with daidzein preservative solution combined with storage and preservation at 4°C can effectively delay the oxidative decomposition of protein and fat during single low-temperature storage and preservation, so that sashimi ingredients can still maintain a freshness similar to that of fresh ingredients after being stored at low temperature for two days, and the freshness quality of ingredients can be maintained within the acceptable range for sashimi lovers, thereby changing the traditional eating method of sashimi that kills and eats immediately, which is more in line with the needs of market development.

[0049] Table 1 Changes in pH, total volatile base nitrogen (TVBN) and thiobarbituric acid reactive substances (TBARS) of grass carp fillets stored at 4°C

[0050]

[0051] Note: Significant difference between TM group and CK group at the same time point (p<0.05), different letters represent significant differences between different cold storage time points in the same treatment group.

[0052] Example 2 Determination of Physicochemical Indexes Related to Freshness of Grass Carp Fillets Stored at -80°C

[0053] 1. Experimental Methods

[0054] 1. The control group and the treatment group were vacuum packed and stored in -80℃ ultra-low temperature refrigerator for 14 days.

[0055] 2. The method for determining the physical and chemical indicators related to fish freshness is the same as in Example 1.

[0056] 3. Determination of moisture content in the freezing process of raw fish ingredients:

[0057] (1) Thawing loss rate

[0058] Weigh the grass carp meat before thawing on a scale and record the mass as M1. After thawing, pour out the juice lost after thawing, use absorbent paper to absorb the juice on the surface of the grass carp meat, weigh it again, weigh and record the mass as M2. The juice loss rate is calculated according to the following formula.

[0059]

[0060] (2) Water holding capacity

[0061] Weigh about 2g of thawed fish meat, record the mass as M1, wrap it with filter paper, centrifuge it at 4℃, 5000r / min, remove the filter paper, weigh it with weighing paper and record the mass as M2, centrifuge it at 4℃, repeat the test 3 times and take the average value. Calculate according to the following formula.

[0062]

[0063] 2. Experimental Results

[0064] from Figure 2 The results showed that after the grass carp fillets treated with daidzein preservative solution were stored at -80℃ ultra-low temperature for 24 hours, the transparency of the fillets was higher than that of the grass carp fillets not treated with daidzein preservative solution, and was close to the transparency of fresh fillets, indicating that the daidzein preservative solution has a certain preservation effect on fish fillets.

[0065] 1. The pH values ​​of grass carp samples in the CK and TM groups were measured at 0, 24h, 3D, 7D and 14D freezing time. The results are shown in Table 2. It can be seen from the table that in the CK and TM groups, the pH values ​​of grass carp samples showed a trend of first increasing and then decreasing, but the increase in the TM group was larger than that in the CK group. In the measurement of 24h and later, the pH value of the TM group was significantly higher than that of the CK group (p<0.05). This shows that the freezing time has an effect on the pH of the grass carp samples, and the pH value of the TM group increased significantly, indicating that adding preservative solution can avoid meat acidification, thereby better maintaining the stability of grass carp samples.

[0066] 2. The TVB-N content of grass carp samples in CK group and TM group at freezing times of 0, 24h, 3D, 7D and 14D was determined, and the results are shown in Table 2. It can be seen from the table that after -80℃ ultra-low temperature freezing preservation, the TVB-N content of sashimi increased by 4.25mg / 100g in 72h and 7.12mg / 100g in 14 days; however, after sashimi treated with daidzein preservative solution and stored at -80℃, the TVB-N content of sashimi only increased by 2.9mg / 100g in 72h and 3.24mg / 100g in 14 days, and the growth of TVB-N was 1.19 times lower than that of single ultra-low temperature freezing preservation. The increase in TVB-N of sashimi ingredients stored for 14 days is only equivalent to the increase in TVB-N of fish meat refrigerated at 4°C for 24 hours. Therefore, pretreatment with daidzein preservative solution can further delay the protein denaturation of fish meat and significantly improve the freshness of sashimi. The freshness of sashimi frozen for 14 days maintains the same freshness as that stored at 4°C for 24 hours.

[0067] 3. The TBRAS values ​​of grass carp samples in the CK group and the TM group at freezing times of 0, 24h, 3D, 7D and 14D were measured, and the results are shown in Table 2. It can be seen from the table that the TBRAS content of sashimi ingredients stored at -80℃ ultra-low temperature increased by 0.5mg MDA / kg after 14 days. The TBRAS content of sashimi ingredients pretreated with daidzein preservative solution was basically unchanged after being frozen at -80℃ for 72h, and the TBRAS value only increased by 0.19mg MDA / kg after 14 days of storage. The addition of daidzein preservative solution and -80℃ freezing can effectively delay fat oxidation during storage and preserve the freshness quality of sashimi ingredients to the greatest extent.

[0068] 4. Changes in fish moisture during -80℃ ultra-low temperature freezing and preservation Figure 3As shown in the figure, the ice crystals formed during the preservation process caused the destruction of the fish tissue structure, freeze denaturation of protein, loss of juice and loss of nutrients. For the fish stored in ultra-low temperature storage alone, the thawing loss rate increased with the extension of storage time and the water holding capacity decreased significantly. However, in the synergistic group treated with daidzein preservative solution, the freeze-thaw loss rate increased less during storage, and the water holding capacity remained slightly different from the initial state.

[0069] Therefore, daidzein plays an important role in maintaining the pH, volatile basic nitrogen content, thiobarbituric acid reactant content, water holding capacity, thawing loss rate, taste, freshness and nutrition of fish in ultra-low temperature freezing preservation. Therefore, daidzein can be used as a fish ultra-low temperature freezing preservation solution.

[0070] Table 2 - Changes in pH, total volatile base nitrogen (TVBN), and thiobarbituric acid reactive substances (TBARS) of grass carp fillets stored at 80°C

[0071]

[0072] Example 3 Sensory evaluation experiment of raw fish ingredients

[0073] 1. Experimental Methods

[0074] The grass carp fillets stored in Example 1 and Example 2 were subjected to sensory evaluation, and 8 tasters (a professional panel for sashimi sensory evaluation) were selected. The sensory evaluation criteria are shown in Table 3.

[0075] Table 3 Sensory evaluation standards

[0076]

[0077]

[0078] 2. Experimental Results

[0079] 1. The sensory evaluation results are shown in Table 4. Under 4°C low-temperature refrigeration conditions, the sensory quality of sashimi raw materials decreased significantly with the extension of time. However, the sashimi raw materials treated with daidzein preservative solution showed significant differences in color, flavor and texture compared with the untreated group. Therefore, pretreatment of sashimi raw materials with daidzein preservative solution can delay the decline in sensory quality to a certain extent.

[0080] Table 4 Sensory evaluation results of raw fish ingredients stored at 4℃ for different periods of time

[0081]

[0082] 2. The sensory evaluation results are shown in Table 5. For sashimi ingredients frozen at -80°C, as time goes by, the sensory quality of color, texture, and taste of sashimi ingredients that have not been pretreated with preservative liquid coating decreases significantly, and the transparency of the sashimi is significantly reduced, losing its characteristics. For sashimi ingredients treated with daidzein preservative liquid, pretreatment of sashimi ingredients with daidzein preservative liquid can delay the quality damage caused by freezing to the ingredients to a certain extent, so that the frozen sashimi ingredients maintain a good gloss and a sweet and crisp taste.

[0083] Table 5 Sensory evaluation results of raw fish ingredients stored at -80℃ for different days

[0084]

Claims

1. Application of daidzein in the preparation of preservatives for aquatic food ingredients.

2. The use according to claim 1, characterized in that: The preservative is a low-temperature refrigeration preservative or an ultra-low-temperature freezing preservative.

3. The use according to claim 1 or 2, characterized in that: The preservative is a coating preservative.

4. A method for preserving aquatic products, characterized in that: The method comprises the steps of coating or soaking fresh aquatic product ingredients with daidzein, vacuum packaging the ingredients and storing the ingredients at low or ultra-low temperatures; the soaking time is 2 to 5 minutes.

5. The method according to claim 4, characterized in that: The concentration of daidzein is 0.2-0.6 mg / mL.

6. The method according to claim 5, characterized in that: The concentration of daidzein is 0.5 mg / mL.

7. The method according to claim 4, characterized in that: The soaking time is 2 to 4 minutes.

8. The method according to claim 4, characterized in that: The low temperature is 0-4°C.

9. The method according to claim 4, characterized in that: The ultra-low temperature is -60 to -80°C.

10. The use according to claim 1 or the method according to claim 4, characterized in that: The aquatic product is fish.

Images