A method for removing fishy smell and improving gel properties of surimi based on the electric field effect and its application

Abstract

The present invention discloses a method for removing fishy smell and improving gel properties of surimi based on the electric field effect and its application, which relates to the technical field of surimi product production. The method comprises the following steps: treating surimi rinsing wastewater with a low-voltage direct current electric field to obtain a rinsing recovery solution; using the rinsing recovery solution to rinse fresh surimi, and introducing nitrogen microbubbles during the rinsing process to fully contact with the surimi; then rinsing with clear water and dehydrating to complete the treatment. By selecting the rinsing recovery solution treated by the electric field and cooperating with the introduction of nitrogen microbubbles, the method of the present invention makes the content of myofibrillar protein and moisture content of the rinsed surimi relatively high, and the fat content and fishy smell substances significantly reduced; the gel strength of the final gel product reaches 493.03 g·cm, meeting the 3A grade surimi standard (gel strength ≥ 400 g·cm), effectively improving the quality, color and flavor of surimi gel; the operation is simple, the efficiency is high, and it is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of surimi product production, and particularly relates to a method for removing fishy smell and improving gel properties of surimi based on electric field effect and its application. Background Art

[0002] Surimi products are deeply loved by consumers due to their characteristics such as high protein, low fat, tender taste, convenience and speed. However, with problems such as overfishing of marine fish resources and the intensification of marine pollution, the raw materials of surimi products have gradually shifted from seawater fish to freshwater fish. Although freshwater fish have a wide source, problems such as low myofibrillar protein content, high fat content, strong endogenous protease and cathepsin activities have led to poor gel properties (color, gel strength, water holding capacity, etc.) of surimi, greatly limiting its application in surimi processing. The common fishy smell problem in freshwater surimi not only affects the product flavor but also reduces the acceptance of consumers.

[0003] Currently, at home and abroad, the fishy smell is mainly removed by improving the rinsing process, physical methods, chemical methods and biological methods. Although the traditional clean water rinsing process is simple to operate, it will produce a large amount of surimi rinsing wastewater containing water-soluble proteins, increasing the subsequent wastewater treatment cost and difficulty. The clean water rinsing process also has problems such as low surimi yield and incomplete fishy smell removal. Physical methods (such as sensory masking method), although convenient, effective, low-cost and highly flexible, only mask the fishy smell substances rather than remove them, and may also damage the original flavor of surimi. Chemical methods (such as acid-base salts, antioxidants and ozone treatment) can effectively reduce the fishy smell of surimi, but there are risks such as chemical residue, high cost and introduction of foreign odors. Biological methods (such as enzyme preparations or microbial fermentation) can degrade fishy smell substances, but they are mainly applicable to liquid or fermented fish products, and the application range is limited. Therefore, developing an efficient and environmentally friendly fishy smell removal technology is of great significance for improving the color and quality of freshwater surimi products. Summary of the Invention

[0004] In view of the above deficiencies of the prior art, the present invention provides a method for removing fishy smell and improving gel properties of surimi based on electric field effect and its application. The present invention uses the supernatant of surimi rinsing wastewater treated by low-voltage direct current electric field to rinse the fresh surimi to be treated, and nitrogen microbubbles are also introduced during the rinsing process, which not only effectively reduces the fat content and fishy smell in surimi, but also significantly improves the gel strength, water holding capacity and puncture performance of surimi products, improves the color of surimi products, and meets the 3A grade surimi standard with gel strength ≥ 400 g·cm. Specifically, it is achieved through the following technologies.

[0005] A method for removing fishy smell and improving gel properties of surimi based on electric field effect includes the following steps:

[0006] Take the surimi washing wastewater, treat it with a low-voltage direct current electric field, and centrifuge to obtain the supernatant to get the washing recovery liquid.

[0007] Use the washing recovery liquid to perform the first washing on the fresh surimi to be treated; use clean water for the second washing, and let it stand to complete the treatment of the fresh surimi to be treated; during the first washing and the second washing, nitrogen is also introduced throughout the process and nitrogen microbubbles are generated to contact the fresh surimi to be treated.

[0008] The surimi washing wastewater selected in the present invention refers to the supernatant after the initially collected surimi washing wastewater is simply decolorized by activated carbon and then subjected to centrifugal precipitation treatment.

[0009] In order to improve the gel properties of surimi products, the present invention selects the washing recovery liquid treated by a low-voltage direct current electric field to perform the first washing on the fresh surimi to be treated, and uses clean water for the second washing; and nitrogen is introduced and microbubbles are generated during the two washings. Finally, it is found that the synergistic cooperation of the two process steps can significantly improve the gel properties of surimi.

[0010] The present invention applies a low-voltage direct current electric field to the surimi washing wastewater, which can also promote the rapid aggregation and precipitation of negatively charged protein molecules in the surimi washing wastewater, realizing efficient solid-liquid separation and protein recovery. The electrolysis of the wastewater can produce reactive oxygen species (such as ·OH, H2O2), and when the source of the surimi washing wastewater is tap water, hypochlorous acid (HClO) / hypochlorite (ClO - ), chlorine and other substances can be electrolyzed, which can effectively degrade the organic substances that produce fishy smell (such as trimethylamine, aldehydes, ketones, etc.), and reduce the fishy smell when subsequently washing the fresh surimi to be treated. The introduced nitrogen can also inhibit the lipid peroxidation reaction and reduce the generation of fishy smell substances such as aldehydes (such as hexanal, nonanal) and sulfides.

[0011] The present invention uses a low-voltage direct current electric field to treat surimi washing wastewater, and uses the treated washing recovery liquid for the washing of fresh surimi, which can also realize the recycling of water resources, providing an efficient and environmentally friendly technical means for surimi processing enterprises.

[0012] Further, the mass ratio of the fresh surimi to be treated to the washing recovery liquid is 1:(2 - 6).

[0013] Furthermore, the mass ratio of the fresh surimi to be treated to the washing recovery liquid is 1:4.

[0014] Further, the method of treating with a low-voltage direct current electric field is to treat at 10 - 30 °C and a voltage of 30 - 50 V for 20 - 40 min.

[0015] Furthermore, the method of treating with a low-voltage direct current electric field is to treat at 25 °C and a voltage of 50 V for 30 min.

[0016] Further, the method of centrifuging to obtain the supernatant is to centrifuge at 8000 - 10000 r / min for 10 - 20 min.

[0017] More specifically, the method of centrifuging to obtain the supernatant is to centrifuge at 10000 r / min for 15 min.

[0018] Further, the conditions for the first rinsing are rinsing at 4℃ ± 1℃ for 1 - 9 min, and the standing time after rinsing is 10 - 30 min.

[0019] More specifically, the conditions for the first rinsing are rinsing at 4℃ for 9 min, and the standing time after rinsing is 20 min.

[0020] Further, in the rinsing recovery liquid per unit volume, the nitrogen gas introduction amount is 1.0 - 3.0 mg / (min·L).

[0021] More specifically, in the rinsing recovery liquid per unit volume, the nitrogen gas introduction amount is 3 mg / (min·L).

[0022] More specifically, on the basis of any one of the above methods for fish mince deodorization and improving gel properties based on the electric field effect, after the second rinsing and standing, dehydration, chopping, forming, heating, and cooling treatments are sequentially carried out;

[0023] The method of chopping is as follows: at 4℃ ± 1℃, after adding salt and ice water, chop at 2000 - 3000 r / min for 3 min.

[0024] Further, the addition amount of the salt is 1.5 - 2% of the mass of the fish mince after dehydration treatment, and the addition amount of the ice water is 70 - 80% of the mass of the fish mince after dehydration treatment.

[0025] Further, the method of heating is water bath heating at 30 - 40℃ for 20 - 40 min, and then water bath heating at 80 - 90℃ for 10 - 30 min; the method of cooling is cooling in ice water at 0 - 4℃ for 10 - 30 min.

[0026] More specifically, the method of heating is water bath heating at 40℃ for 30 min, and then water bath heating at 90℃ for 10 min; the method of cooling is cooling in ice water at 0℃ for 20 min.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] 1. The present invention selects a rinsing recovery liquid treated by a low-voltage direct-current electric field, which synergistically acts with nitrogen microbubbles. It can not only effectively reduce the fishy smell in surimi gel products, but also promote the cross-linking between protein molecules, significantly improving the gel properties of surimi. The gel strength reaches 493.03 g·cm, meeting the 3A-grade surimi standard (gel strength ≥ 400 g·cm).

[0029] 2. The method provided by the present invention has a simple process and is easy to operate. It does not require the addition of any chemical reagents. The rinsing recovery liquid used is obtained by treating surimi rinsing wastewater with a low-voltage direct-current electric field. Its only oxidation by-product is water, and there are very few substances such as organic matter and heavy metals. It can be directly used to rinse fresh surimi or clean raw fish, realizing the recycling of wastewater and significantly improving the economic benefits of surimi and its processing enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a diagram showing the influence results of the water-holding capacity of surimi gel under different rinsing methods. DETAILED DESCRIPTION OF THE INVENTION

[0031] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0032] In some embodiments of the present invention, the method for surimi deodorization and improving gel properties includes the following steps:

[0033] Take surimi rinsing wastewater, treat it with a low-voltage direct-current electric field, and centrifuge to obtain the supernatant as the rinsing recovery liquid;

[0034] Use the rinsing recovery liquid to perform the first rinse on the fresh surimi to be treated; perform the second rinse with clean water and let it stand to complete the treatment of the fresh surimi to be treated. During the first rinse and the second rinse, nitrogen is also introduced to generate nitrogen microbubbles to contact the fresh surimi to be treated.

[0035] Optionally, the fresh surimi processed by the present invention can be fish meat paste from any source. In the following specific embodiments, in order to facilitate comparison, silver carp surimi without heads, fish skins, internal organs, and fish bones purchased from the farmers' market of Huazhong Agricultural University is used.

[0036] Optionally, surimi rinsing wastewater refers to the supernatant obtained by simply decolorizing the initially collected surimi rinsing wastewater with activated carbon and then performing centrifugal precipitation treatment.

[0037] Optionally, the mass ratio of the fresh surimi to be processed to the rinsing recovery liquid is 1:(2 - 6); specifically, 1:4 can be selected.

[0038] Optionally, the method of treating with a low-voltage direct current electric field is to treat at 10 - 30 °C and 30 - 50 V voltage for 20 - 40 min; specifically, it can be selected to treat at 25 °C and 50 V voltage for 30 min.

[0039] Optionally, the method of centrifuging to obtain the supernatant is to centrifuge at 8000 - 10000 r / min for 10 - 20 min; specifically, it can be selected to centrifuge at 10000 r / min for 15 min.

[0040] Optionally, the conditions for the first rinsing are rinsing at 4 °C ± 1 °C for 1 - 9 min, and the standing time after rinsing is 10 - 30 min; specifically, it can be selected to rinse at 4 °C for 9 min, and the standing time after rinsing is 20 min.

[0041] Optionally, in the rinsing recovery liquid per unit volume, the nitrogen gas introduction amount is 1.0 - 3.0 mg / (min·L); specifically, the nitrogen gas introduction amount can be selected as 3 mg / (min·L).

[0042] After the above-mentioned treatments for surimi deodorization and improvement of gel properties, dehydration, chopping, shaping, heating, and cooling treatments are sequentially carried out after the second rinsing and standing;

[0043] The method of chopping is: at 4 °C ± 1 °C, after adding salt and ice water, chop at 2000 - 3000 r / min for 3 min.

[0044] Optionally, when chopping, the addition amount of the salt is 1.5 - 2% of the mass of the surimi after dehydration treatment, and the addition amount of the ice water is 70 - 80% of the mass of the surimi after dehydration treatment.

[0045] Optionally, the method of heating is water bath heating at 30 - 40 °C for 20 - 40 min, and then water bath heating at 80 - 90 °C for 10 - 30 min; the method of cooling is cooling in ice water at 0 - 4 °C for 10 - 30 min.

[0046] Specifically, the method of heating can be selected as water bath heating at 40 °C for 30 min, and then water bath heating at 90 °C for 10 min; the method of cooling can be selected as cooling in ice water at 0 °C for 20 min.

[0047] The following examples and comparative examples are designed according to the actual test scheme in Table 1 below.

[0048] Table 1

[0049]

[0050] Example 1

[0051] The method for removing fishy smell and improving gel properties of surimi provided in this example is as follows:

[0052] (1) Treat the surimi washing wastewater with a low-voltage DC electric field (50 V) at 25 °C for 30 min, dehydrate and centrifuge at 10,000 r / min for 15 min, and take the supernatant to obtain the washing recovery liquid.

[0053] (2) First washing: Use the washing recovery liquid to wash the fresh surimi. The mass ratio of the washing recovery liquid to the fresh surimi is 1:4, and the washing time is 9 min; after the washing is completed, let it stand for 20 min, dehydrate and centrifuge at 10,000 r / min for 15 min to obtain the surimi after the first washing.

[0054] During the first washing process, use a microbubble generator to generate and introduce nitrogen, and the introduction amount is 3 mg / (min·L) to generate nitrogen microbubbles, so that the nitrogen microbubbles are in full contact with the raw material surimi.

[0055] (3) Second washing: Select clean water to replace the washing recovery liquid and wash the surimi after the first washing. The mass ratio of the clean water to the surimi after the first washing is 1:4, and the washing method is the same as that in step (2) to obtain the surimi after the second washing.

[0056] During the second washing process, use a microbubble generator to generate and introduce nitrogen, and the introduction amount is 3 mg / (min·L) to generate nitrogen microbubbles, so that the nitrogen microbubbles are in full contact with the raw material surimi.

[0057] (4) Based on the mass of the surimi after the second washing, add 2% of table salt and 80% of ice water to the surimi after the second washing, and chop and stir at 2,000 r / min for 3 min.

[0058] (5) Use a sausage stuffing machine to stuff it into a casing with a diameter of 20 mm and then seal and form it.

[0059] (6) Heat the sealed and formed surimi gel in two stages. The first heating temperature is 40 °C and the heating duration is 30 min; the second heating temperature is 90 °C and the heating duration is 10 min to obtain the thermoformed surimi gel.

[0060] (7) Cool it in ice water at 0 °C for 20 min to obtain the final surimi product.

[0061] Comparative Example 1

[0062] This comparative example provides a method for removing fishy smell from surimi and improving its gel properties. The difference compared with Example 1 is that the rinsing recovery liquid is replaced with fresh water during the first rinsing. The specific steps are as follows:

[0063] (1) First rinsing: Fresh surimi is rinsed with fresh water. The mass ratio of fresh water to fresh surimi is 1:4, and the rinsing time is 9 min; after rinsing, it is left standing for 20 min and then dehydrated and centrifuged at 10000 r / min for 15 min to obtain surimi.

[0064] During the first rinsing process, nitrogen is generated and introduced by a microbubble generator at a flow rate of 3 mg / (min·L) to produce nitrogen microbubbles, so that the nitrogen microbubbles are in full contact with the raw surimi.

[0065] (2) Second rinsing: The same as step (3) of Example 1 to obtain the surimi after the second rinsing.

[0066] During the first rinsing process, nitrogen is generated and introduced by a microbubble generator at a flow rate of 3 mg / (min·L) to produce nitrogen microbubbles, so that the nitrogen microbubbles are in full contact with the raw surimi.

[0067] No external electric field treatment is applied during the above first rinsing and second rinsing processes. The subsequent steps are the same as steps (4)-(7) of the example to obtain the final surimi product.

[0068] Comparative Example 2

[0069] This comparative example provides a method for removing fishy smell from surimi and improving its gel properties. The difference compared with Example 1 is that the rinsing recovery liquid is replaced with fresh water during the first rinsing, and an external electric field (50 V) treatment is applied during the first rinsing process; nitrogen microbubbles are not introduced during the second rinsing. The specific steps are as follows:

[0070] (1) First rinsing: Fresh surimi is rinsed with fresh water. The mass ratio of fresh water to fresh surimi is 1:3, and the rinsing time is 3 min; after rinsing, it is left standing for 20 min and then dehydrated and centrifuged at 10000 r / min for 15 min to obtain the surimi after the first rinsing. An external electric field of 50 V is applied during the first rinsing process.

[0071] (2) Second rinsing: Fresh water is used again to perform a secondary rinsing on the surimi after the first rinsing. The mass ratio of fresh water to fresh surimi is 1:3, and the rinsing time is 3 min; after rinsing, it is left standing for 20 min and then dehydrated and centrifuged at 10000 r / min for 15 min to obtain the surimi after the second rinsing.

[0072] The subsequent steps are the same as steps (4)-(7) of Example 1 to obtain the final surimi product.

[0073] Comparative Example 3

[0074] This comparative example provides a method for fish mince deodorization and improving gel properties. The difference compared with Example 1 is that during the first rinsing, the rinsing recovery liquid is replaced with clear water, and during the second rinsing, the clear water is replaced with the rinsing recovery liquid. The specific steps are as follows:

[0075] (1) Treat the fish mince rinsing wastewater with a low-voltage direct current electric field (50 V) at 25°C for 30 min, centrifuge at 10,000 r / min for 15 min, and take the supernatant to obtain the rinsing recovery liquid.

[0076] (2) First rinsing: Use clear water to rinse the fresh fish mince. The mass ratio of clear water to fresh fish mince is 1:4, and the rinsing time is 9 min; after rinsing, let it stand for 20 min, centrifuge at 10,000 r / min for 15 min, and separate the fish mince after the first rinsing.

[0077] During the first rinsing process, use a microbubble generator to generate and introduce nitrogen, with an introduction amount of 3 mg / (min·L), generate nitrogen microbubbles, and make the nitrogen microbubbles fully contact with the raw fish mince.

[0078] (3) Second rinsing: Use the rinsing recovery liquid to rinse the fish mince after the first rinsing. The mass ratio of the rinsing recovery liquid to the fish mince after the first rinsing is 1:4, and the rinsing time is 9 min; after rinsing, let it stand for 20 min, centrifuge at 10,000 r / min for 15 min, and obtain the fish mince after the second rinsing.

[0079] During the second rinsing process, use a microbubble generator to generate and introduce nitrogen, with an introduction amount of 3 mg / (min·L), generate nitrogen microbubbles, and make the nitrogen microbubbles fully contact with the raw fish mince.

[0080] The subsequent steps are the same as steps (4)-(7) of Example 1 to obtain the final fish mince product.

[0081] Comparative Example 4

[0082] This comparative example provides a method for fish mince deodorization and improving gel properties. The difference compared with Example 1 is that during the first rinsing, the rinsing recovery liquid is replaced with clear water and an external direct current electric field is introduced. The specific steps are as follows:

[0083] (1) First rinsing: Use clear water to rinse the fresh fish mince. The mass ratio of clear water to fresh fish mince is 1:4, and the rinsing time is 9 min; after rinsing, let it stand for 20 min, centrifuge at 10,000 r / min for 15 min, and separate the fish mince after the first rinsing.

[0084] During the first rinsing process, nitrogen gas is generated by a microbubble generator and introduced at a flow rate of 3 mg / (min·L) to produce nitrogen microbubbles, enabling the nitrogen microbubbles to come into full contact with the raw fish mince. Additionally, a DC electric field of 50 V is applied.

[0085] (2) Second rinsing: The fish mince that has undergone the first rinsing is rinsed with clear water. The mass ratio of the clear water to the fish mince after the first rinsing is 1:4, and the rinsing time is 9 min. After the rinsing is completed, it is left to stand for 20 min and then centrifuged at 10,000 r / min for 15 min to obtain the fish mince after the second rinsing.

[0086] During the second rinsing process, nitrogen gas is generated by a microbubble generator and introduced at a flow rate of 3 mg / (min·L) to produce nitrogen microbubbles, enabling the nitrogen microbubbles to come into full contact with the raw fish mince.

[0087] The subsequent steps are the same as steps (4)-(7) of Example 1 to obtain the final fish mince product.

[0088] Comparative Example 5

[0089] This comparative example provides a method for fish mince deodorization and improving gel properties. The difference compared with Example 1 is that the clear water is replaced with the rinsing recovery liquid during the second rinsing. It specifically includes the following steps:

[0090] (1) At 25°C, the fish mince rinsing wastewater is treated with a low-voltage DC electric field (50 V) for 30 min and then centrifuged at 10,000 r / min for 15 min. The supernatant is taken to obtain the rinsing recovery liquid.

[0091] (2) First rinsing: The fresh fish mince is rinsed with the rinsing recovery liquid. The mass ratio of the rinsing recovery liquid to the fresh fish mince is 1:4, and the rinsing time is 9 min. After the rinsing is completed, it is left to stand for 20 min and then centrifuged at 10,000 r / min for 15 min to separate the fish mince after the first rinsing.

[0092] During the first rinsing process, nitrogen gas is generated by a microbubble generator and introduced at a flow rate of 3 mg / (min·L) to produce nitrogen microbubbles, enabling the nitrogen microbubbles to come into full contact with the raw fish mince.

[0093] (3) Second rinsing: The fish mince after the first rinsing is rinsed with the rinsing recovery liquid. The mass ratio of the rinsing recovery liquid to the fish mince after the first rinsing is 1:4, and the rinsing time is 9 min. After the rinsing is completed, it is left to stand for 20 min and then centrifuged at 10,000 r / min for 15 min to obtain the fish mince after the second rinsing.

[0094] During the second rinsing process, nitrogen gas is generated by a microbubble generator and introduced at a rate of 3 mg / (min·L) to produce nitrogen microbubbles, which are brought into full contact with the raw fish mince.

[0095] The subsequent steps are the same as steps (4)-(7) of Example 1 to obtain the final fish mince product.

[0096] Comparative Example 6

[0097] This comparative example provides a method for fish mince deodorization and improving gel properties. The difference compared with Example 1 is that during the first rinsing, the rinsing recovery liquid is replaced with ordinary fish mince rinsing wastewater.

[0098] Ordinary fish mince rinsing wastewater is the wastewater obtained after removing fish mince from fresh fish mince rinsed with clear water. The mass ratio of clear water to fresh fish mince is 1:4, and the rinsing time is 9 min; after rinsing, it is left standing for 20 min and then centrifuged at 10,000 r / min for 15 min for dehydration.

[0099] Specifically, it includes the following steps:

[0100] (1) First rinsing: Use ordinary fish mince rinsing wastewater to rinse fresh fish mince. The mass ratio of ordinary fish mince rinsing wastewater to fresh fish mince is 1:4, and the rinsing time is 9 min; after rinsing, it is left standing for 20 min and then centrifuged at 10,000 r / min for 15 min to separate the fish mince after the first rinsing.

[0101] During the first rinsing process, nitrogen gas is generated by a microbubble generator and introduced at a rate of 3 mg / (min·L) to produce nitrogen microbubbles, which are brought into full contact with the raw fish mince.

[0102] (3) Second rinsing: Use clear water to rinse the fish mince after the first rinsing. The mass ratio of clear water to the fish mince after the first rinsing is 1:4, and the rinsing time is 9 min; after rinsing, it is left standing for 20 min and then centrifuged at 10,000 r / min for 15 min to obtain the fish mince after the second rinsing.

[0103] During the second rinsing process, nitrogen gas is generated by a microbubble generator and introduced at a rate of 3 mg / (min·L) to produce nitrogen microbubbles, which are brought into full contact with the raw fish mince.

[0104] The subsequent steps are the same as steps (4)-(7) of Example 1 to obtain the final fish mince product.

[0105] Comparative Example 7

[0106] This comparative example provides a method for removing fishy smell from surimi and improving gel properties. The difference compared with Example 1 is that during the first rinsing, the rinsing recovery liquid is replaced with ordinary surimi rinsing wastewater, and an external direct current electric field is applied. The specific steps are as follows:

[0107] (1) First rinsing: Use ordinary surimi rinsing wastewater to rinse fresh surimi. The mass ratio of ordinary surimi rinsing wastewater to fresh surimi is 1:4, and the rinsing time is 9 min; after rinsing, let it stand for 20 min, and centrifuge at 10000 r / min for 15 min to separate the surimi obtained from the first rinsing.

[0108] During the first rinsing process, nitrogen gas is generated and introduced using a microbubble generator, with an introduction amount of 3 mg / (min·L) to generate nitrogen microbubbles, so that the nitrogen microbubbles are in full contact with the raw surimi; and a direct current electric field of 50 V is also applied.

[0109] (2) Second rinsing: Use clear water to rinse the surimi obtained from the first rinsing. The mass ratio of clear water to the surimi after the first rinsing is 1:4, and the rinsing time is 9 min; after rinsing, let it stand for 20 min, and centrifuge at 10000 r / min for 15 min to obtain the surimi after the second rinsing.

[0110] During the second rinsing process, nitrogen gas is generated and introduced using a microbubble generator, with an introduction amount of 3 mg / (min·L) to generate nitrogen microbubbles, so that the nitrogen microbubbles are in full contact with the raw surimi.

[0111] The subsequent steps are the same as steps (4)-(7) of Example 1 to obtain the final surimi product.

[0112] Comparative Example 8

[0113] This comparative example provides a method for removing fishy smell from surimi and improving gel properties. The difference compared with Example 1 is that during the first rinsing, the rinsing recovery liquid is replaced with ordinary surimi rinsing wastewater, and an external direct current electric field is applied, and nitrogen microbubbles are not introduced during the first rinsing and the second rinsing. The specific steps are as follows:

[0114] (1) First rinsing: Use ordinary surimi rinsing wastewater to rinse fresh surimi. The mass ratio of ordinary surimi rinsing wastewater to fresh surimi is 1:4, and the rinsing time is 9 min; after rinsing, let it stand for 20 min, and centrifuge at 10000 r / min for 15 min to separate the surimi obtained from the first rinsing. A direct current electric field of 50 V is also applied during the first rinsing.

[0115] (2)Second rinsing: Fresh fish mince was rinsed with clear water. The mass ratio of clear water to the fish mince after the first rinsing was 1:4, and the rinsing time was 9 min; after the rinsing was completed, it was left standing for 20 min, and then dehydrated and centrifuged at 10,000 r / min for 15 min to obtain the fish mince after the second rinsing.

[0116] The subsequent steps were the same as steps (4)-(7) of Example 1 to obtain the final fish mince product.

[0117] Test Example 1: Color analysis was performed on the fish mince products prepared in the above examples and comparative examples.

[0118] Color analysis was performed on the fish mince gels of Example 1 and Comparative Examples 1-8. The specific method was as follows: The color of the fish mince gel samples was measured using a high-precision spectrocolorimeter. The samples were cut into uniform thin slices with a height of 20 mm and a thickness of 5 mm, and their L* (brightness), a* (redness), and b* (blueness) values were measured. Four parallels were measured for each group of samples. The calculation formula for the whiteness value W was as follows:

[0119] .

[0120] Table 2 Effects of different rinsing methods on the color of fish mince gel

[0121]

[0122] Note: Different letters indicate significant differences between samples (P < 0.05).

[0123] The color results of the fish mince gels treated with different rinsing methods are shown in Table 2 above. It can be seen that whether 1 part or 2 parts of the rinsing recovery liquid was added, there was a slight increase in the whiteness value compared to Comparative Example 1. Therefore, adding the rinsing recovery liquid during the fish mince rinsing process will not have an adverse effect on the color of the fish mince gel samples, and can improve the whiteness of the fish mince gel to a certain extent and improve the color of the fish mince gel.

[0124] Test Example 2: Texture analysis was performed on the fish mince products prepared in the above examples and comparative examples.

[0125] Texture analysis was performed on the fish mince gels of Example 1 and Comparative Examples 1-8. The specific analysis method was as follows: The fish mince gel samples were cut into cylinders with dimensions of 10×10×20 mm, and a texture analyzer was used to measure the strength of the fish mince gel. Measurement parameters: The probe model was P / 2.5S, the penetration distance was 15 mm, the pre-test speed was 2 mm / s, the test speed was 1 mm / s, and the post-test speed was 2 mm / s. Four parallels were set for each group, and the test results were averaged.

[0126] Table 3 Effects of different rinsing methods on the performance of fish mince gel

[0127]

[0128] Note: Different letters indicate significant differences among samples (P < 0.05).

[0129] The gel properties of surimi corresponding to different rinsing methods are shown in Table 3. The gel strength of surimi of Example 1 reaches a maximum of 493.03 g cm, which is 15.83% higher than that of Comparative Example 1, 19.73% higher than that of Comparative Example 2, 3.51% higher than that of Comparative Example 3, 9.78% higher than that of Comparative Example 4, 6.58% higher than that of Comparative Example 5, 18.61% higher than that of Comparative Example 6, 12.78% higher than that of Comparative Example 7, and 22.41% higher than that of Comparative Example 8.

[0130] By comparing Example 1 with Comparative Example 1, or comparing Example 1 with Comparative Example 6, it can be seen that when only nitrogen is introduced during rinsing and no electric field is applied, the effect of improving the gel strength of the surimi is not as good as that of Example 1, regardless of whether clean water or ordinary surimi rinsing wastewater is used for the first rinsing.

[0131] By comparing Example 1 with Comparative Example 4, or Example 1 with Comparative Example 7, it can be seen that when nitrogen is introduced during rinsing and an electric field is applied during the first rinsing, the effect of improving the gel strength of the surimi is not as good as that of Example 1, and Comparative Example 4 is stronger than Comparative Example 1, and Comparative Example 7 is stronger than Comparative Example 6. This shows that even if an electric field is applied during the first rinsing, the improvement of the gel strength of the surimi is relatively limited. This may be because the application of an electric field during the first rinsing process causes thermal denaturation of local proteins, destroys the protein structure, and reduces its gel strength.

[0132] By comparing Comparative Examples 1, 2 and 4, or Comparative Examples 6-8, it can be seen that no matter whether clean water or ordinary fish paste rinsing wastewater is used, the lack of any of the two processes of "applying an electric field during rinsing" and "introducing nitrogen" will affect the final fish paste gel performance.

[0133] By comparing Example 1 and Comparative Example 3, it can be seen that when the order of rinsing recovery liquid and clean water is changed, when clean water is used first and then rinsing recovery liquid is used, the gel strength of the surimi cannot be improved to the maximum extent. This may be because the rinsing recovery liquid is used for the first rinsing, and some of the protein contained in it can form a protective layer, reducing the initial loss of protein in the fresh surimi, and then the second clean water rinsing further removes impurities, thereby improving the gel strength of the surimi; while the first rinsing uses clean water, which will dissolve and wash away a large amount of soluble protein, resulting in a large initial loss of protein, resulting in a weaker final gel network structure.

[0134] By comparing Example 1 and Comparative Example 5, it can be seen that replacing the fresh water during the second rinsing with the rinsing recovery liquid will result in worse surimi gel properties than those in Example 1. This may be because when the rinsing recovery liquid is reused during the second rinsing, it will cause excessive oxidation of myofibrillar proteins, which will instead affect the surimi gel properties.

[0135] Upon analysis, it may be because:

[0136] As an inert gas, nitrogen (N2) can protect the free sulfhydryl groups (-SH) in the active center of transglutaminase (TGase) from inactivation, and can also inhibit the rupture of lysosomal membranes, reduce the content of cathepsins, and delay their degradation of myofibrillar proteins; thereby enhancing the degree of protein crosslinking and ultimately increasing the gel strength of surimi.

[0137] The rinsing recovery liquid treated by low-voltage direct current electric field can promote the appropriate unfolding of the myofibrillar structure of surimi gel, expose more hydrophobic groups, thereby enhancing the degree of protein crosslinking and further increasing the gel strength of surimi. The residual salts (such as CaCl2) in the rinsing recovery liquid may activate endogenous enzymes (such as transglutaminase, TGase) and promote protein crosslinking. In addition, a part of small molecular peptides or denatured proteins in the rinsing recovery liquid may also adsorb onto the surface of fresh surimi during the rinsing process, filling the voids in the gel network and improving the texture of surimi gel.

[0138] Thus, it can be seen that the synergistic cooperation of the two process steps can promote the crosslinking between protein molecules in surimi, thereby significantly improving the gel properties of surimi.

[0139] Test Example 3: Water-holding capacity analysis of the surimi products prepared in the above examples and comparative examples

[0140] The water-holding capacity of the surimi gels in Example 1 and Comparative Examples 1-8 was analyzed. The specific method was as follows: The surimi gel was cut into thin slices with a thickness of about 5 mm, and the mass m0 was accurately weighed. The sample was wrapped with 3 layers of filter paper and placed at the bottom of a centrifuge tube, and centrifuged at 5000 r / min for 15 min. After centrifugation, the sample was taken out and weighed again as m1. The water-holding capacity WHC of the surimi gel was calculated according to the following formula:

[0141] ;

[0142] In the formula: m0 is the mass of the surimi gel, in g; m1 is the mass of the sample surimi gel after centrifugation, in g.

[0143] The water-holding capacity results of surimi gels treated by different rinsing methods are as Figure 1 shown. It can be seen that compared with Comparative Examples 1-8, using the rinsing recovery liquid first and then rinsing can significantly improve the water-holding capacity of surimi gel (P < 0.05).

[0144] This may be because of the combined effect of the rinsing recovery liquid and the nitrogen gas introduction process, which promotes the cross-linking between protein molecules, enhances the stability of the protein network, and confines more water in the gel network. Using clear water for the second rinsing can remove the excessive ions and small molecule impurities accumulated in the recovery liquid and avoid their interference with protein cross-linking.

[0145] Test Example 4: Sensory evaluation of the surimi products prepared in the above examples and comparative examples

[0146] Perform sensory evaluation on the surimi gels of Example 1 and Comparative Examples 1-8. The specific method is as follows:

[0147] Select 10 food major students, with a male-to-female ratio of 1:1 and aged between 20 and 30. According to GB / T 16291.1-2012, train their odor recognition ability and observation ability, and then conduct sensory evaluation on the surimi gel samples. Then, according to the settings of GB / T 10221-2012 Sensory Analysis Terms and GB / T 37062-2018 Guidelines for Sensory Evaluation of Aquatic Products, evaluate the surimi gel from the aspects of earthy smell, inherent fish smell, fishy smell, and sour smell. Use a 0-10 point system to evaluate the odor intensity, where 1 point indicates that the odor is very light and 10 points indicates that the odor is very strong. The final odor score is the average value.

[0148] The results of the surimi gel strength under different rinsing methods are shown in Table 4 below.

[0149] Table 4 Descriptive sensory evaluation of the odor of surimi gels treated with different rinsing methods

[0150]

[0151] Note: Different letters represent significant differences between samples (P < 0.05).

[0152] As can be seen from Table 4 above, earthy smell is one of the main factors affecting the flavor of freshwater fish, mainly caused by geosmin and trimethylamine (TMA). It can be seen from Table 4 that rinsing the surimi with the surimi rinsing recovery liquid (Example 1, Comparative Example 3, Comparative Example 5) can significantly reduce the earthy smell of the surimi gel, and the effect of Example 1 is the most significant. The fishy smell is caused by aldehyde compounds (such as hexanal and nonanal) produced by the oxidation of unsaturated fatty acids in freshwater fish, which is the characteristic flavor of oxidized fish oil. Example 1 significantly reduces the fishy smell of the surimi gel, indicating that this treatment method has the best deodorization effect. Compared with other comparative examples, using the surimi rinsing recovery liquid to rinse the surimi in Example 1 significantly increases the fish fragrance of the surimi gel.

[0153] It can also be seen from Table 4 that using the recovered surimi washing solution to wash surimi (Example 1, Comparative Example 3, Comparative Example 5) can significantly reduce the rancid smell of surimi gel. Among them, only the surimi gel in Example 1 has the lowest rancid smell. This may be because the active ingredients in the recovered washing solution (such as low-concentration chloride ions, residual protease, etc.) can effectively inhibit the formation of the fishy substance trimethylamine, and using clean water for the second washing can remove the volatile fishy substances (such as TMA, piperidine compounds) that have formed in the surimi.

[0154] Test Example 5: Test the volatile components of the surimi products prepared in the above examples and comparative examples

[0155] Perform volatile component tests on the surimi gels of Example 1 and Comparative Examples 1-8. The specific test method is as follows:

[0156] (1) Solid-phase microextraction: Put 3.0 g of the sample into a 20 mL headspace vial, add 6 mL of saturated NaCl and 10 μL of the internal standard TMP (100 mg / kg), put in a magnetic rotor, and quickly cover the cap. Then place it in a magnetic stirring water bath at 60 °C to equilibrate for 30 min. Then insert the aged extraction head into the headspace of the sample vial.

[0157] (2) Adsorb at 60 °C for 30 min, insert into the GC injection port for desorption for 5 min, and perform GC-MS analysis. All samples are measured in parallel three times.

[0158] Chromatography (GC) conditions: The temperature programming is an initial temperature of 40 °C, held for 3 min, then heated at a rate of 5 °C / min to 90 °C, held for 5 min, and then heated at a rate of 10 °C / min to 250 °C, held for 6 min. The injection port temperature is maintained at 250 °C;

[0159] Mass spectrometry (MS) conditions: Use an EI ion source, electron energy 70 eV; ion source temperature 250 °C, ion scan range 35 - 500 m / z, detector voltage 1000 V.

[0160] (3) The volatile compounds are compared and analyzed according to the NIST Chemistry WebBook mass spectrometry library and the Willey standard library built into the triple quadrupole gas chromatography mass spectrometer (Agilent Instruments Co., Ltd., Singapore, model: 7000D). The substance with the highest matching degree is the target volatile flavor substance. The concentration of each volatile compound in the sample is quantified by the ratio of the peak area of each compound to the peak area of the internal standard compound, with the unit of μg / kg.

[0161] The fishy smell of freshwater fish mainly comes from volatile compounds such as aldehydes, alcohols, and ketones produced by unsaturated fatty acids. Among them, hexanal, nonanal, decanal, 1-octen-3-ol, and 1-octen-3-one are the most important flavor-active volatile substances. The results of the volatile components of surimi treated by different rinsing methods are shown in Table 5 below.

[0162] Table 5 Effects of Different Rinsing Methods on Volatile Components of Surimi Gel

[0163]

[0164] Note: Different letters indicate significant differences between samples (P < 0.05).

[0165] As can be seen from Table 5 above, in Comparative Example 1, the concentration of hexanal was 263.78 μg / kg, the concentration of nonanal was 556.34 μg / kg, the concentration of decanal was 439.23 μg / kg, the concentration of 1-octen-3-ol was 793.32 μg / kg, and the concentration of 1-octen-3-one was 31.56 μg / kg. Compared with Comparative Example 1, after being treated by different rinsing methods, the contents of hexanal, nonanal, decanal, 1-octen-3-ol, and 1-octen-3-one can be significantly reduced, and the degree of decrease in Example 1 is the largest. This may be because the dual effects of the rinsing recovery liquid and the introduction of nitrogen further degraded the residual odor substances, while inhibiting fat oxidation and microbial activities. The nitrogen microbubbles hindered the binding of odor molecules to proteins through surface adsorption.

[0166] The above specific embodiments have described the implementation of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solutions of the present invention, and these simple variations all belong to the protection scope of the present invention.

Claims

1. A method for removing fishy smell from surimi and improving gel properties based on electric field effect, characterized in that: The following steps are involved: Take the fish surimi rinsing wastewater, treat it with a low-voltage direct current electric field, and centrifuge to obtain the supernatant to obtain the rinsing recovery liquid; The fresh fish paste to be processed is rinsed for the first time using the rinsing recovery liquid; the fresh fish paste to be processed is rinsed for the second time using clean water and left to stand to complete the processing of the fresh fish paste to be processed; during the first rinsing and the second rinsing, nitrogen is introduced throughout the process to generate nitrogen microbubbles to contact the fresh fish paste to be processed.

2. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to claim 1, characterized in that: The mass ratio of the fresh fish paste to be processed to the rinsing recovery liquid is 1:(2-6).

3. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to claim 1, characterized in that: The method of using low voltage direct current electric field treatment is to treat at 10-30°C and 30-50 V for 20-40 min.

4. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to claim 1, characterized in that: The method of taking the supernatant by centrifugation is 8000-10000 r / min for 10-20 min.

5. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to claim 1, characterized in that: The first rinsing condition is 4°C±1°C for 1-9 min, and the standing time after rinsing is 10-30 min.

6. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to claim 1, characterized in that: The nitrogen flow rate per unit volume of the rinsing recovery liquid is 1.0-3.0 mg / (min·L).

7. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to any one of claims 1 to 6, characterized in that: After the second rinsing and standing, dehydration, chopping, shaping, heating and cooling are performed in sequence; The chopping method is: adding salt and ice water at 4°C±1°C, and chopping at 2000-3000 r / min for 3 min.

8. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to claim 7, characterized in that: The amount of salt added is 1.5-2% of the mass of the dehydrated surimi, and the amount of ice water added is 70-80% of the mass of the dehydrated surimi.

9. The method for removing fishy smell from surimi and improving gel properties based on electric field effect according to claim 7, characterized in that: The heating method is heating in a 30-40° C. water bath for 20-40 min, and then heating in a 80-90° C. water bath for 10-30 min; the cooling method is cooling in 0-4° C. ice water for 10-30 min.

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