Method for targeted reduction and control of N-dimethyl nitrosamine pollutants in squid processing

Abstract

The invention discloses a method for targeted reduction and control of N-dimethyl nitrosamine pollutants in squid processing, and the method is characterized in that edible squid tissues are subjected to specific solution dipping and specific ultraviolet light irradiation treatment, and targeted efficient reduction of N-dimethyl nitrosamine is realized by using the synergistic effect of the two. According to the method, the inhibition rate of the N-dimethyl nitrosamine in the squid material can reach 61.0%-91.0%, and the content of the N-dimethyl nitrosamine in the squid material is reduced to be below a limit value from being obviously higher than the limit value 4.0 microgram / kg; the specific solution dipping alleviates the increase of the nitrite residual quantity of the edible squid tissue and the increase of the oxidation degree caused by the ultraviolet light irradiation; after the treated squid material is treated in typical processing modes such as high-temperature baking or deep-frying, the capability of re-increasing the content of N-dimethyl nitrosamine is obviously reduced. In addition, the edible squid tissue treated by the method has the advantages that the content of N-dimethyl nitrosamine is low, and the shelf life of a final product can be effectively prolonged.

Description

Technical Field

[0001] This invention relates to food processing and safety technology, specifically to a method for targeted reduction and control of N-dimethylnitrosamine contaminants during squid processing. Background Technology

[0002] N-Nitrosodimethylamine (NDMA) is a nitrosamine compound, primarily derived from amine compounds (R1NHR2) and nitrosyl ions (NO3) provided by a nitrosating agent (Y-NO3). + The reaction involves electrophilic substitution between N-dimethylnitrosamine and other substances. N-nitrosamine is classified as a Group 2A carcinogen by the International Agency for Research on Cancer (IARC), meaning it has potential carcinogenic effects on humans. According to the national standard GB 2762, "National Food Safety Standard - Limits of Contaminants in Food," the limit for N-nitrosamine in aquatic products (excluding canned aquatic products) and dried aquatic products is 4.0 μg / kg. Whether this standard is met directly affects whether the relevant products can be legally sold on the market and has a significant impact on the healthy and sustainable development of the entire aquatic product processing industry.

[0003] Generally, squid needs to be rapidly frozen to below -18°C after being caught and transported via cold chain to delay spoilage. The edible portion of squid is high in protein (approximately 16%–20%). As the freshness of the squid decreases or spoilage occurs, the protein components can decompose into various amine compounds (such as dimethylamine, trimethylamine, proline, putrescine, aliphatic polyamines, spermine, pyrrolidine, and glycine). Furthermore, squid naturally contains trimethylamine oxide (TMAO), which readily decomposes into dimethylamine (DMA) under the action of microorganisms or catalysis by endogenous enzymes, providing an important precursor for the formation of N-dimethylnitrosamine. The sources of nitrosyl compounds during squid processing mainly include: ① naturally occurring nitrates in seawater and nitrates and nitrites that may be added during processing (nitrates can be reduced to nitrites under the action of microorganisms); ② nitrogen oxides produced by smoking, grilling, and other processes; ③ nitrites generated from the conversion of other nitrogen-containing compounds under specific conditions. The formation and accumulation of the aforementioned amine precursors and nitrosyl compounds make N-nitrosodimethylamine (NDI) readily generated during squid processing. According to incomplete statistics from food sampling inspection announcements issued by the National and some provincial market supervision administrations from 2019 to 2024, there have been 75 cases of NDI exceeding the standard in squid products, reflecting the prevalence of this contaminant in squid foods and the urgency of risk control. Therefore, establishing a targeted reduction and control method for NDI during squid processing is of great significance.

[0004] Currently, the reduction of N-nitrosodimethylamine (N-dimethylnitrosamine) mainly relies on the addition of exogenous inhibitors. There are few reports on processes that achieve targeted reduction and control of N-nitrosodimethylamine by altering processing steps, nor are there studies on their effectiveness. In squid product processing, trimming and cleaning are essential steps. Therefore, developing a highly efficient targeted reduction and control technology for N-nitrosodimethylamine within these essential processing steps would address the problem of excessive levels at its source. This technology is not only applicable to large-scale food production but can also serve the catering industry, demonstrating significant application value. Summary of the Invention

[0005] Objective of the Invention: This invention provides a method for targeted reduction and control of N-nitrosodimethylamine (NDM) contaminants in squid feed through a combination of "specific solution immersion + ultraviolet irradiation". The method provided by this invention can effectively reduce the NDM content in raw squid and ensure that the final product meets national standards.

[0006] Technical solution: The method for targeted reduction and control of N-dimethylnitrosamine pollutants in squid processing according to the present invention includes the following steps: (1) Raw material pretreatment: Thaw frozen squid or take fresh squid directly, and after heat treatment or without heat treatment, trim and clean to remove inedible parts to obtain edible squid tissue; (2) Solution immersion treatment: Add a specific solution with a pH value of 3~5 and a temperature of 20~30℃ to a container of a specific treatment equipment, and then place the edible squid tissue obtained in step (1) into the container of the specific treatment equipment, control the material accumulation thickness to be 6~9 cm, and make the liquid surface submerge the material by 0.2~2.0 cm; control the circulation of the treatment solution by a variable frequency centrifugal pump, and maintain the flow rate at 0.5~0.8 m / s, so that the solution and the material are in dynamic contact. (3) Ultraviolet irradiation treatment: The material immersed in the specific solution in step (2) is subjected to ultraviolet irradiation; the wavelength of the ultraviolet light is 250~260 nm, the irradiation intensity is 1200~1800 μW / cm², the distance between the ultraviolet light source and the liquid surface of the material is 5~50 cm, and the irradiation time is 20~35 min. (4) Impurity removal and purification treatment: The squid material after step (3) is washed with running water or ultrasonically to obtain clean squid material.

[0007] The targeted treatment equipment for reducing and controlling N-dimethylnitrosamine according to the method includes: a material transfer control module, an impregnation treatment container module, an ultraviolet irradiation module, a solution circulation module, a safety protection module, and a control module. The material transfer control module is used to transport squid material; the impregnation treatment container module is used to hold a specific solution and impregnate the material; the ultraviolet irradiation module is located above or to the side of the impregnation treatment container to irradiate the material inside the container; the solution circulation module includes circulation pipelines and a variable frequency centrifugal pump to circulate the treatment solution within the impregnation treatment container; the safety protection module includes components to shield ultraviolet light and ensure safe material handling; and the control module mainly enables human-machine interaction for equipment operation, primarily including a touch screen, buttons, indicator lights, and a digital display.

[0008] The specific processing equipment includes an ultraviolet irradiation device comprising a lifting and adjusting mechanism and an ultraviolet lamp assembly mounted thereon; in the material transfer control module, ultraviolet irradiation module, and solution circulation module, the material in contact with the impregnation solution is selected as acid-resistant food-grade stainless steel or plastic; the control module integrates material transfer control, ultraviolet light intensity sensing, solution flow sensing control, solution temperature and pH sensing control, and programmable logic control functions.

[0009] The method described in step (1) involves heat treatment at 80-90°C.

[0010] The method described in step (1) includes cartilage and viscera as inedible parts; and the edible squid tissues include the carcass, arms, fins and endothelial membrane of the carcass.

[0011] The method described herein uses either squid or Pacific squid.

[0012] In the method described above, when the N-nitrosodimethylamine content in the edible squid tissue significantly exceeds 4.0 μg / kg in step (1), the solute components of the specific solution described in step (2) include ferulic acid, L-ascorbic acid, vitamin E, tea polyphenols, and sodium D-isoascorbate, and the concentrations of each solute in the solution are as follows: ferulic acid 180~220 mg / L, L-ascorbic acid 380~420 mg / L, vitamin E 280~320 mg / L, tea polyphenols 250~320 mg / L, and sodium D-isoascorbate 480~550 mg / L. Preferably, the vitamin E is selected from food-grade vitamin E powder.

[0013] In the method described in step (1), if the N-nitrosodimethylamine content in the edible squid tissue slightly exceeds or does not exceed 4.0 μg / kg, the solute component of the specific solution described in step (2) includes a combination of vitamin E 280~320 mg / L and sodium D-isoascorbate 480~550 mg / L, or a combination of tea polyphenols 250~320 mg / L and sodium D-isoascorbate 480~550 mg / L.

[0014] The pH of the treatment solution is adjusted using food-grade citric acid or sodium hydroxide in the method described above.

[0015] The ultrasonic cleaning method described in step (4) has a material-to-water ratio of 1:3 to 1:5, an ultrasonic power of 150 to 250W, and a cleaning time of 180 to 300 seconds.

[0016] More preferably, the specific processing device: (1) The assembly line operation method is adopted. The core is a rectangular processing tank container, which contains a specific solution. The material enters from the feed end on the left, moves to the right under the drive of the internal material conveyor belt, passes through the solution treatment area, and is discharged from the discharge end on the right after being irradiated by ultraviolet light.

[0017] (2) The design features of the specific processing equipment include: a material transfer control module for conveying squid material; an immersion treatment container module for holding a specific solution and immersing the material; an ultraviolet irradiation module located above or to the side of the immersion treatment container for irradiating the material inside the container; a solution circulation module, which includes circulation pipelines and a variable frequency centrifugal pump for circulating the treatment solution inside the immersion treatment container; a safety protection module, including components for shielding ultraviolet light and ensuring safe material processing; and a control module, which mainly realizes the human-machine interaction of equipment operation, mainly including touch screen, buttons, indicator lights, and digital display components. The design features of the specific processing equipment also include that the materials in contact with the immersion solution in the material transfer control module, ultraviolet irradiation module, and solution circulation module are acid-resistant food-grade stainless steel or plastic; and that the control module integrates material transfer control, ultraviolet light intensity sensing, solution flow sensing control, solution temperature and pH sensing control, and programmable logic control functions.

[0018] (3) The ultraviolet irradiation device includes a lifting and adjusting mechanism and an ultraviolet lamp assembly mounted thereon; the total length of the irradiation equipment is 3000 mm, the total height is 1300 mm, the height of the treatment tank is 560 mm, and the width is 900 mm. In actual design, the equipment size can be scaled up proportionally to adapt to the requirements of different raw material processing volumes. The total height refers to the distance from the ground to the ultraviolet lamp assembly platform, and the height of the treatment tank refers to the distance from the ground to the bottom of the tank.

[0019] (4) Ultraviolet lamp assembly: Located directly above the treatment tank, it is installed on a liftable platform. This is the core unit of the equipment, which irradiates the materials below by emitting ultraviolet light.

[0020] (5) Lifting platform: The supporting structure that connects the ultraviolet lamp group, allowing the lamp group to be adjusted up and down, and the ultraviolet irradiation distance to be adjusted according to process requirements.

[0021] (6) Light-blocking protective curtain: Located above the discharge end of the equipment, it is used to prevent ultraviolet light from leaking out, protect the safety of operators, and also play a role in dust prevention.

[0022] (7) Variable frequency centrifugal pump: installed at the bottom of the equipment and connected to the liquid discharge pipeline. Its function is to maintain the circulation of liquid in the tank, and to ensure that all parts of the liquid can be uniformly irradiated by ultraviolet light by controlling the solution flow rate. It can also be used for the discharge and return of the treated solution and the circulation of washing liquid during equipment cleaning.

[0023] (8) Material conveyor belt: Located inside the liquid, used to transport materials to or from the irradiation treatment area, and to carry materials in the irradiation treatment area.

[0024] Beneficial effects: Compared with the prior art, the advantages of the present invention are: (1) The method provided by the present invention can efficiently target and reduce N-nitrosodimethylamine in squid materials, and can also effectively alleviate the increase in nitrite residue and oxidation degree of edible squid tissue caused by ultraviolet radiation. (2) The technology provided by the present invention is not only suitable for treating squid tissue with protein denaturation after heating, but also suitable for treating squid tissue with undenatured protein. (3) After squid materials are treated by the method provided by the present invention, the N-nitrosodimethylamine content can be reduced from significantly higher than 4.0 μg / kg to significantly lower than 4.0 μg / kg, and the treated squid materials are more suitable for use as raw materials for deep-processed products (such as ready-to-eat squid food), so that deep-processed products have a longer shelf life. (4) After squid materials are treated by the method provided by the present invention, they are more resistant to high-temperature baking or frying, that is, they have a lower N-nitrosodimethylamine content after high-temperature baking or frying. (5) After the squid material is processed by the method provided by the present invention, it is more resistant to freezing and cold storage, and has a lower N-dimethylnitrosamine content during freezing and cold storage. Attached Figure Description

[0025] Figure 1 The standard curve for the determination of N-dimethylnitrosamine content;

[0026] Figure 2 The effect of different solution pH treatments on the N-nitrosodimethylamine content in squid tissues;

[0027] Figure 3 The effect of different ferulic acid addition amounts on the inhibition rate of N-dimethylnitrosamine and the change in nitrite content; Figure 3 Left and middle figures: Effect of ferulic acid addition on the inhibition rate of N-dimethylnitrosamine; Figure 3 The right-middle figure shows the effect of ferulic acid addition on nitrite content; different letters on the index results indicate significant differences between the results. P <0.05);

[0028] Figure 4 The effect of different L-ascorbic acid addition amounts on the inhibition rate of N-dimethylnitrosamine and changes in nitrite content; Figure 4 Left and middle figures: Effect of L-ascorbic acid dosage on the inhibition rate of N-dimethylnitrosamine; Figure 4 The right-middle figure shows the effect of L-ascorbic acid addition on nitrite content; different letters on the index results indicate significant differences between the results. P <0.05);

[0029] Figure 5 The difference lies in the effect of vitamin E addition on the inhibition rate of N-dimethylnitrosamine and the change in nitrite content; Figure 5 Left and middle figures: Effect of vitamin E addition on the inhibition rate of N-dimethylnitrosamine; Figure 5 The right-middle figure shows the effect of vitamin E supplementation on changes in nitrite content. Different letters on the indicator results indicate significant differences between the results. P <0.05);

[0030] Figure 6 The effects of different amounts of tea polyphenols added on the inhibition rate of N-dimethylnitrosamine and the changes in nitrite content were investigated. Figure 6 Left figure: Effect of tea polyphenol addition on the inhibition rate of N-dimethylnitrosamine; Figure 6 The right-middle figure shows the effect of tea polyphenol addition on nitrite content; different letters on the index results indicate significant differences between the results. P <0.05);

[0031] Figure 7 The effect of different amounts of sodium D-isoascorbate on the inhibition rate of N-dimethylnitrosamine and the change in nitrite content; Figure 7 Left and middle figures: Effect of D-isoascorbic acid sodium dosage on the inhibition rate of N-dimethylnitrosamine; Figure 7 The right-middle figure shows the effect of sodium D-isoascorbate addition on changes in nitrite content; different letters on the index results indicate significant differences between the results. P <0.05);

[0032] Figure 8 This is a roadmap of a method for targeted reduction and control of N-dimethylnitrosamine contaminants in squid processing according to the present invention;

[0033] Figure 9 These are three views of a specific treatment device used in a method for targeted reduction and control of N-dimethylnitrosamine contaminants in squid processing according to the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Specifically, the determination of N-nitrosodimethylamine (NDMA) content follows Method II of GB 5009.26-2023 "National Food Safety Standard - Determination of N-nitrosamine Compounds in Food"; the determination of nitrite content follows Method II of GB 5009.33-2016 "National Food Safety Standard - Determination of Nitrite and Nitrate in Food"; and the determination of thiobarbituric acid value follows the direct method of GB / T 35252-2017 "Determination of 2-Thiobarbituric Acid Value in Animal and Vegetable Oils". The NDMA inhibition rate is defined as the percentage of the difference between the NDMA content in the material without intervention and the NDMA content in the material after intervention, relative to the NDMA content in the material without intervention.

[0036] Step (1): Raw material pretreatment: Take frozen squid to thaw or take fresh squid directly, perform appropriate heat treatment, and combine with trimming and cleaning processes to remove inedible parts and obtain edible squid tissue; Step (2): Feeding and solution immersion: Add a specific solution with a pH of 3-5 and a temperature of 20-30℃ to the container of the specific processing equipment, and then place the edible squid tissue obtained in step (1) into the container of the specific processing equipment, control the material accumulation thickness to be 6-9 cm, and make the liquid surface submerge the material by 0.2-2.0 cm; control the circulation of the processing solution by a variable frequency centrifugal pump, and maintain the flow rate at 0.5-0.8 m / s, so that the solution and the material are in dynamic contact. Step (3): Ultraviolet irradiation treatment: Use ultraviolet light to irradiate the material in step (2); the wavelength of the ultraviolet lamp is 250~260nm, the distance between the ultraviolet lamp and the liquid surface of the material is 5~50cm, the ultraviolet light intensity is 1200~1800 μW / cm², and the irradiation time is controlled at 20~35 min. Step (4): Impurity removal and purification treatment: The squid material obtained in step (3) is treated by running water or ultrasonic cleaning to remove impurities and clean the squid material to obtain clean squid material.

[0037] Method roadmap as follows Figure 8 As shown.

[0038] According to the determination method, the standard curve for the determination of N-dimethylnitrosamine content is as follows: Figure 1 As shown.

[0039] The present invention will now be described in detail with reference to the embodiments.

[0040] Example 1 (1) Raw material pretreatment: Take frozen squid, thaw it and place it in hot water at 80~90℃ for 10 min. After trimming and cleaning, edible squid tissue is obtained.

[0041] (2) Selection of ultraviolet light wavelength Different wavelengths of ultraviolet light can affect the reduction of N-nitrosodimethylamine in edible squid tissue. This study investigated the effect of different ultraviolet light wavelengths on the reduction of N-nitrosodimethylamine in squid samples to select a suitable ultraviolet light wavelength. The relevant experiments are as follows.

[0042] Experimental method: The edible squid tissue (ketone body) obtained in (1) was placed in a container of a specific processing device, and the material accumulation thickness was controlled to be 8 cm. Without adding a specific solution, ultraviolet lamps with different ultraviolet wavelengths (185, 230, 240, 254 nm) were used to directly irradiate the material at a distance of 40 cm for 30 min under the condition of ultraviolet light intensity of 1800 μW / cm². Then, ultrasonic cleaning was used to remove impurities and clean the sample to obtain a clean sample. A blank control experiment was set up to analyze the N-dimethylnitrosamine content, nitrite content and thiobarbituric acid value of the sample. The experimental results are shown in Table 1.

[0043]

[0044] Experimental Results and Analysis: Table 1 shows that the 254nm ultraviolet light wavelength was the most effective in reducing the NMDA content of the squid samples, decreasing it from 14.80 μg / kg to 3.12 μg / kg, with an inhibition rate of 78.1%, significantly higher than other wavelengths of ultraviolet light. Therefore, the 254nm wavelength ultraviolet light is preferred. Direct irradiation of the samples with ultraviolet light leads to an increase in nitrite residue and severe oxidation. Experimental results show that after irradiation of the squid samples with 254nm ultraviolet light, the nitrite content increased from 6.4 mg / kg to 10.7 mg / kg, and the thiobarbituric acid value increased from 0.82 mg / kg to 2.48 mg / kg. The increase in nitrite content is related to the degradation of NMDA, and the resulting increase in nitrite content is detrimental to the quality of the squid. In addition, the increase in thiobarbituric acid value indicates an increased degree of oxidation in the treated material. Therefore, direct irradiation of squid samples with ultraviolet light has its drawbacks.

[0045] (3) Selection of solution pH Different solution pH values ​​affect the reduction of N-nitrosodimethylamine in edible squid tissue. This study investigated the effect of different solution pH values ​​on the reduction of N-nitrosodimethylamine in squid samples to select a suitable solution pH. The relevant experiments are as follows.

[0046] Experimental method: Solutions with different pH values ​​(pH 3, 4, 5, 6, 7, 8, 9) were prepared using citric acid and sodium hydroxide and added to the container of a specific processing equipment. Then, the edible squid tissue (ketone body) obtained in (1) was placed in the container of the specific processing equipment, and the material accumulation thickness was controlled to be 7 cm, so that the liquid surface submerged the material by 0.4 cm and the solution flow rate was 0.60 m / s. Then, the material immersed in the solution was irradiated for 20 min under the conditions of ultraviolet light wavelength of 254 nm, irradiation intensity of 1800 μW / cm², and ultraviolet lamp distance of 40 cm from the liquid surface. Then, ultrasonic cleaning was used to remove impurities and clean the sample to obtain a clean sample. A blank control experiment was set up to analyze the N-dimethylnitrosamine content of the sample. The experimental results are shown in Figure 2 .

[0047] Experimental Results and Analysis: From Figure 2 It can be seen that the N-dimethylnitrosamine content of the samples was significantly lower at pH values ​​of 3, 4, and 5 than at other pH values. P <0.05), but there was no significant difference in N-dimethylnitrosamine content caused by these three pH values ​​( P＞0.05). When the pH values ​​were 3, 4, and 5, the N-nitrosodimethylamine content of the samples decreased from 12.4 μg / kg in the blank control to 2.56, 2.47, and 2.31 μg / kg, respectively, and the N-nitrosodimethylamine inhibition rates were 79.4%, 80.1%, and 81.4%, respectively, all higher than the inhibition rate of 78.1% in (2). Therefore, soaking edible squid tissue in a solution with a specific pH can effectively improve the reduction of N-nitrosodimethylamine. Food-grade citric acid was used to adjust the pH value of the solution, preferably to 3-5.

[0048] (4) Selection of single solute components and concentrations in the solution The composition and concentration of solutes in a solution affect the reduction of N-nitrosodimethylamine in edible squid tissue. This study investigated the effects of different solute compositions and concentrations on the reduction of N-nitrosodimethylamine in squid samples, and selected the appropriate solute composition and concentration. The relevant experiments are as follows.

[0049] Experimental methods: Ferulic acid solution (100, 200, 300, 400, 500 mg / L), L-ascorbic acid solution (100, 200, 300, 400, 500 mg / L), vitamin E solution (100, 200, 300, 400, 500 mg / L), tea polyphenol solution (100, 200, 300, 400, 500 mg / L), and D-isoascorbic acid sodium solution (100, 200, 300, 400, 500 mg / L) were prepared at different concentrations. The pH of each solution was adjusted to 3 with food-grade citric acid. The effects of different solute components and concentrations on the reduction of N-dimethylnitrosamine in squid samples were investigated, and the differences in nitrite content in the treated samples were analyzed. The edible squid tissue (ketone body) obtained in (1) was placed in a container in a specific processing device, with the material accumulation thickness controlled at 7 cm, the liquid surface submerging the material by 0.4 cm, and the solution flow rate at 0.60 m / s. Then, the material immersed in the solution was irradiated for 15 min under the conditions of ultraviolet light wavelength of 254 nm, irradiation intensity of 1800 μW / cm², and ultraviolet lamp distance of 40 cm from the liquid surface. Then, ultrasonic cleaning was used to remove impurities and clean the sample to obtain a clean sample. A blank control experiment was set up to analyze the nitrite and N-dimethylnitrosamine content of the sample and calculate the N-dimethylnitrosamine inhibition rate. The experimental results are shown in the figure below. Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 .

[0050] Experimental Results and Analysis: From Figure 3 It can be seen that when ferulic acid is added at a concentration of 200 mg / L, the inhibition rate of N-dimethylnitrosamine is significantly higher than that at other concentrations. P<0.05); the lowest nitrite content was observed in the treated sample when ferulic acid was added at a concentration of 400 mg / L. Figure 4 It can be seen that when the L-ascorbic acid concentration is 400 mg / L, the inhibition rate of N-dimethylnitrosamine is significantly higher than that at other concentrations. P <0.05); the lowest nitrite content was observed in the treated sample when the L-ascorbic acid concentration was 400 mg / L. Figure 5 It can be seen that when the vitamin E concentration is 300 mg / L, the inhibition rate of N-dimethylnitrosamine is significantly higher than that at other concentrations. P <0.05); the lowest nitrite content was observed in the treated sample when the vitamin E concentration was 300 mg / L. Figure 6 It can be seen that when the amount of tea polyphenols added is 300 mg / L, the inhibition rate of N-dimethylnitrosamine is significantly higher than that of other added amounts. P <0.05); the nitrite content of the treated sample was lowest when the amount of tea polyphenols added was 300 mg / L. Figure 7 It can be seen that when the sodium D-isoascorbate concentration is 500 mg / L, the inhibition rate of N-dimethylnitrosamine is significantly higher than that at other concentrations. P <0.05); the lowest nitrite content was observed in the treated sample when the sodium D-isoascorbate concentration was 100 mg / L. Overall, the preferred concentrations were: ferulic acid 200 mg / L, L-ascorbic acid 400 mg / L, vitamin E 300 mg / L, tea polyphenols 300 mg / L, and sodium D-isoascorbate 500 mg / L.

[0051] (5) Selection of ultraviolet irradiation intensity and irradiation time under the synergistic effect of five solution solutes Ultraviolet (UV) irradiation intensity and duration affect the reduction of N-nitrosodimethylamine (N-dimethylnitrosamine) in edible squid tissue. This study investigated the effects of different UV irradiation intensities and durations on the reduction of N-nitrosodimethylamine in squid samples, and selected the appropriate UV irradiation intensity and duration. The relevant experiments are as follows.

[0052] Experimental method: Prepare a solution of various solute components with a concentration of ferulic acid 200 mg / L, L-ascorbic acid 400 mg / L, vitamin E 300 mg / L, tea polyphenols 300 mg / L, and D-isoascorbic acid sodium 500 mg / L. Then adjust the pH of the solution to 3 with citric acid before use. Add the prepared solution to the container of a specific processing device, and then place the edible squid tissue (ketone body) obtained in (1) into the container, control the material accumulation thickness to be 7 cm, so that the liquid surface submerges the material by 0.6 cm and the solution flow rate is 0.60 m / s. Then, under the condition of ultraviolet light wavelength of 254 nm, the irradiation intensity and irradiation time in Table 2 are used to conduct the sample irradiation test at a distance of 40 cm from the liquid surface of the ultraviolet lamp. Then, use ultrasonic cleaning to remove impurities and clean the sample to obtain a clean sample. Detect the N-dimethylnitrosamine (NDMA) content, nitrite content and thiobarbituric acid value of the sample. The control experiment differed from the experimental group experiment in that: Control experiment 1 involved directly irradiating the sample with 254nm ultraviolet light without immersing the sample in a solution; Control experiment 2 involved irradiating the sample with 254nm ultraviolet light and immersing the sample in a citric acid solution at pH 3, without adding ferulic acid, tea polyphenols, L-ascorbic acid, vitamin E, or sodium D-isoascorbate. The experimental results are shown in Table 2.

[0053]

[0054] Experimental Results and Analysis: Table 2 shows that for the experimental group, to maintain relatively consistent NDMA, nitrite, and thiobarbituric acid content in the treated samples by increasing irradiation intensity, the irradiation time can be reduced accordingly. With irradiation intensities of 1200 μW / cm², 1500 μW / cm², and 1800 μW / cm², the irradiation times are 35 min, 25 min, and 20 min, respectively. Therefore, an irradiation intensity of 1200-1800 μW / cm² and an irradiation time of 20-35 min are preferred. For the experimental group, both nitrite and thiobarbituric acid content decreased with increasing irradiation intensity and decreasing irradiation time. The lowest levels of both nitrite and thiobarbituric acid were achieved at an irradiation intensity of 1800 μW / cm² and an irradiation time of 20 min. Compared with control group 1, the NDMA content, nitrite content, and thiobarbituric acid value in experimental group 5 decreased from 3.10 μg / kg, 11.7 mg / kg, and 3.14 mg / kg to 2.55 μg / kg, 0.8 mg / kg, and 0.53 mg / kg, respectively; compared with control group 2, the NDMA content, nitrite content, and thiobarbituric acid value in experimental group 5 decreased from 2.96 μg / kg, 8.1 mg / kg, and 2.44 mg / kg to 2.55 μg / kg, 0.8 mg / kg, and 0.53 mg / kg, respectively. Therefore, the technical effect of reducing NDMA in the sample through the synergistic effect of the five solutes is significantly better, not only reducing NDMA contaminants in the sample more effectively, but also resulting in lower nitrite content and thiobarbituric acid value in the treated sample.

[0055] (6) Technical effect of this method on edible squid tissues with different N-nitrosodimethylamine contents In the method of this invention, the initial N-nitrosodimethylamine content of the edible squid tissue obtained in step (1) affects the technical effect of the method. Relevant experiments were conducted as follows.

[0056] Experimental method: The experimental raw material was edible squid tissue (ketone body) with N-dimethylnitrosamine content of 26.25ug / kg and 8.20ug / kg, respectively. A solution with ferulic acid added at 200mg / L, L-ascorbic acid added at 400mg / L, vitamin E added at 300mg / L, tea polyphenols added at 300mg / L, and D-isoascorbic acid sodium added at 500mg / L was prepared, and then the pH of the solution was adjusted to 3 with citric acid before use. The prepared solution was added to the container of a specific processing device, and then the edible squid tissue (ketone body) obtained in (1) was placed in the container, and the material accumulation thickness was controlled at 7 cm, so that the liquid surface submerged the material by 1.0 cm and the solution flow rate was 0.60m / s. Then, under the conditions of ultraviolet light wavelength of 254nm and irradiation power of 1800μW / cm², an irradiation test was carried out at a distance of 35cm from the liquid surface of the ultraviolet lamp for 20min. Then, ultrasonic cleaning was used to remove impurities and clean the sample to obtain a clean sample. The N-dimethylnitrosamine (NDMA) content and nitrite content of the sample were tested.

[0057] Experimental Results and Analysis: After treatment, the N-nitrosodimethylamine (N-dimethylnitrosamine) content of edible squid tissue (ketone bodies) with contents of 26.25 ug / kg and 8.20 ug / kg decreased to 6.12 ug / kg and 1.61 ug / kg, respectively. Therefore, the method of this invention can significantly reduce the N-nitrosodimethylamine content in squid, with an inhibition rate of 61.0%~83.4%. Furthermore, the nitrite content of edible squid tissue (ketone bodies) before treatment was 13.0 mg / kg and 7.8 mg / kg, respectively. After treatment, the nitrite content of the samples decreased to 1.8 mg / kg and 1.1 mg / kg, respectively, with a nitrite reduction rate of 83.7~85.8% (nitrite reduction rate is defined as the percentage of the difference between the nitrite content in the material before and after the intervention, relative to the nitrite content in the material before intervention; the same applies below). Furthermore, the ultraviolet irradiation in the method of the present invention has a sterilization effect, and the impurity removal and purification treatment has a cleaning effect. Therefore, the edible squid tissue treated by the method of the present invention is clean and safe, and is more resistant to freezing and refrigeration storage. It also has a lower N-dimethylnitrosamine content during freezing and refrigeration storage.

[0058] Example 2 In the method of this invention, changing the method conditions can affect the reduction effect of N-nitrosodimethylamine in edible squid tissue; unsuitable method conditions can lead to a decrease in the reduction effect of N-nitrosodimethylamine. Relevant experiments were conducted as follows.

[0059] Experimental Method: Frozen squid was thawed and then placed in 90℃ hot water for 10 min. After trimming and cleaning, edible squid tissue was obtained. A solution was prepared with 250 mg / L ferulic acid, 350 mg / L L-ascorbic acid, 150 mg / L vitamin E, 250 mg / L tea polyphenols, and 250 mg / L sodium D-isoascorbate. The pH of the solution was then adjusted to 3 with citric acid. The prepared solution was added to a container in a specific processing device, and the edible squid tissue (ketone body) was placed in the container, with the material accumulation thickness controlled at 9 cm, the liquid surface submerging the material by 2.5 cm, and the solution flow rate at 0.60 m / s. Then, an irradiation test was conducted for 20 min under ultraviolet light conditions of 254 nm wavelength and 1200 μW / cm², with the ultraviolet lamp 40 cm away from the liquid surface. Finally, ultrasonic cleaning was used to remove impurities and obtain a clean sample. The N-dimethylnitrosamine (NDMA) content of the sample was tested.

[0060] Experimental results and analysis: The results showed that the N-nitrosodimethylamine content in edible squid tissue (ketone body) decreased from 12.73 ug / kg to 6.96 ug / kg, indicating that the N-nitrosodimethylamine reduction effect was not ideal.

[0061] Example 3 In the method of this invention, changing the method conditions affects the reduction effect of N-nitrosodimethylamine in edible squid tissue. The effect of changing the method conditions on the reduction effect of N-nitrosodimethylamine was investigated. The relevant experiments are as follows.

[0062] Experimental Method: Frozen squid was thawed and then placed in 90℃ hot water for 10 min. After trimming and cleaning, edible squid tissue was obtained. A solution was prepared with 150 mg / L ferulic acid, 300 mg / L L-ascorbic acid, 250 mg / L vitamin E, 200 mg / L tea polyphenols, and 530 mg / L sodium D-isoascorbate. The pH of the solution was then adjusted to 3 with citric acid. The prepared solution was added to a container in a specific processing device, and the edible squid tissue (ketone body) was placed in the container, with the material accumulation thickness controlled at 9 cm, the liquid surface submerging the material by 2 cm, and the solution flow rate at 0.60 m / s. Then, an irradiation test was conducted for 20 min under ultraviolet light conditions at a wavelength of 254 nm and an irradiation power of 1800 μW / cm², with the ultraviolet lamp 40 cm away from the liquid surface. Finally, ultrasonic cleaning was used to remove impurities and obtain a clean sample. The N-dimethylnitrosamine (NDMA) content of the sample was tested.

[0063] Experimental results and analysis: The results showed that the N-dimethylnitrosamine content in edible squid tissue (ketone body) decreased from 14.73 ug / kg to 6.25 ug / kg.

[0064] Example 4 In the method of this invention, when the N-dimethylnitrosamine content in the edible squid tissue in step (1) slightly exceeds or does not exceed 4.0 μg / kg, the method still has significant effects after appropriately reducing the types of specific solutes in the solution in step (2) and using appropriate solute concentrations. Related experiments were conducted as follows.

[0065] Experimental Method: Frozen squid was thawed and placed in 90℃ hot water for 10 min. After trimming and cleaning, edible squid tissue was obtained. Two solutions were prepared: Experimental Group 1 (containing 280 mg / L vitamin E and 520 mg / L sodium D-isoascorbate) and Experimental Group 2 (containing 250 mg / L tea polyphenols and 550 mg / L sodium D-isoascorbate). The pH of each solution was adjusted to 3 with citric acid before use. The prepared solutions were added to a container in a specific processing device, and the edible squid tissue (ketone bodies) was placed in the container, with the material accumulation thickness controlled at 9 cm, the liquid surface submerging the material by 0.8 cm, and the solution flow rate at 0.60 m / s. Then, an irradiation test was conducted for 20 min at a UV light wavelength of 254 nm and an irradiation power of 1800 μW / cm², with the UV lamp 40 cm away from the liquid surface. Finally, ultrasonic cleaning was used to remove impurities and obtain clean samples. The N-nitrosodimethylamine (NDMA) content of the samples was tested. The test results are shown in Table 3.

[0066]

[0067] Experimental Results and Analysis: As shown in Table 3, using the solution in Experimental Group 1 (containing Vitamin E 280 mg / L and D-isoascorbic acid sodium 520 mg / L) can reduce the N-nitrosodimethylamine content of edible squid tissues ranging from 6.54 ug / kg to 10.44 ug / kg to below 4.0 ug / kg after treatment. Furthermore, samples with higher N-nitrosodimethylamine content before treatment exhibited relatively higher N-nitrosodimethylamine content after treatment, with NDMA inhibition rates ranging from 68.5% to 74.4%. Table 3 shows that using the solution in experimental group 2 (containing 250 mg / L tea polyphenols and 550 mg / L sodium D-isoascorbate) reduced the N-nitrosodimethylamine (NDMA) content in edible squid tissue ranging from 4.78 μg / kg to 9.65 μg / kg to below 4.0 μg / kg after treatment, with NDMA inhibition rates ranging from 63.0% to 68.3%. Therefore, even when the NDMA content in edible squid tissue slightly exceeds 4.0 μg / kg, the method of this invention still has significant effects by appropriately reducing the types of solutes in the specific solution and using suitable solute concentrations.

[0068] Example 5 In the method of this invention, after obtaining edible squid tissue through step (1), the order of soaking in a specific solution followed by ultraviolet irradiation cannot be changed. If ultraviolet irradiation is used followed by soaking in the specific solution, the effect of reducing N-dimethylnitrosamine will be significantly weakened. Related experiments were conducted as follows.

[0069] Experimental Method 1: Frozen squid was thawed and then placed in 90℃ hot water for 10 min. After trimming and cleaning, edible squid tissue was obtained. A solution was prepared with 200 mg / L ferulic acid, 400 mg / L L-ascorbic acid, 300 mg / L vitamin E, 300 mg / L tea polyphenols, and 500 mg / L sodium D-isoascorbate. The pH of the solution was then adjusted to 3 with citric acid. The prepared solution was added to a container in a specific processing device, and the edible squid tissue (ketone body) was placed in the container, with the material accumulation thickness controlled at 9 cm, the liquid surface submerging the material by 2 cm, and the solution flow rate at 0.60 m / s. Then, an irradiation test was conducted for 20 min under ultraviolet light conditions of 254 nm wavelength and 1800 μW / cm², with the ultraviolet lamp 40 cm away from the liquid surface. Finally, ultrasonic cleaning was used to remove impurities and obtain a clean sample. The N-nitrosodimethylamine (NDMA), nitrite, and thiobarbituric acid values ​​of the samples were tested. During the test, the solution flow rate was controlled at 0.60 m / s.

[0070] Experimental Method 2: The edible squid tissue (ketone bodies) obtained in Experimental Method 1 was placed in a container, with the material accumulation thickness controlled at 9 cm. An irradiation test was conducted for 20 minutes at a UV lamp distance of 42 cm from the liquid surface under UV light conditions of 254 nm wavelength and 1800 μW / cm². The sample was then immersed in the solution prepared in Experimental Method 1 for 20 minutes at a flow rate of 0.60 m / s before being removed. Ultrasonic cleaning was then used to remove impurities and obtain a clean sample. The N-nitrosodimethylamine (NDMA) content, nitrite content, and thiobarbituric acid value of the sample were then measured.

[0071] Experimental Results and Analysis: For sample method 1, the N-nitrosodimethylamine inhibition rate reached 76.3%, the nitrite content decreased from 5.5 mg / kg to 1.2 mg / kg, and the thiobarbituric acid value decreased from 1.27 mg / kg to 0.43 mg / kg. For test method 2, the N-nitrosodimethylamine inhibition rate reached 69.9%, however, the nitrite content increased from 5.5 mg / kg to 9.8 mg / kg, and the thiobarbituric acid value increased from 1.27 mg / kg to 2.56 mg / kg. Therefore, the technique of impregnation with a specific solution followed by ultraviolet irradiation is significantly more effective than the technique of ultraviolet irradiation followed by impregnation with a specific solution. The former has a higher N-nitrosodimethylamine inhibition rate and results in lower nitrite content and thiobarbituric acid value in the treated sample.

[0072] Example 6 The method of this invention is suitable not only for processing edible squid tissue with denatured proteins after heating, but also for processing edible squid tissue with proteins that have not been denatured by heat, although the effects differ. Relevant experiments were conducted as follows.

[0073] Experimental Methods: Frozen squid was thawed at 4ºC, trimmed, and cleaned to obtain edible squid tissue with undenatured proteins. Simultaneously, frozen squid was thawed and placed in 90℃ hot water for 10 min, trimmed, and cleaned to obtain edible squid tissue with denatured proteins after heat treatment. Solutions were prepared with 200 mg / L ferulic acid, 400 mg / L L-ascorbic acid, 300 mg / L vitamin E, 300 mg / L tea polyphenols, and 500 mg / L sodium D-isoascorbate. The pH of the solutions was adjusted to 3 with citric acid before use. The prepared solutions were added to containers in a specific processing device. Edible squid tissue with undenatured proteins (ketone bodies) and edible squid tissue with denatured proteins (ketone bodies) were then placed in the containers, with a material accumulation thickness of 9 cm, a liquid surface submerging the material by 2 cm, and a solution flow rate of 0.60 m / s. Then, an irradiation test was conducted for 20 minutes at a UV light wavelength of 254 nm and an irradiation power of 1800 μW / cm², with the UV lamp 40 cm above the liquid surface. Following this, ultrasonic cleaning was used to remove impurities and obtain clean samples. Two batches of samples from different frozen squid raw materials were tested to detect the N-nitrosodimethylamine (NDMA) content and calculate the NDMA inhibition rate.

[0074] Experimental Results and Analysis: For the first batch of frozen squid raw materials, the NDMA inhibition rate of edible squid tissue (ketone bodies) with undenatured proteins after treatment was 87.3%, while that of edible squid tissue (ketone bodies) with denatured proteins after heat treatment was 76.4%. For the second batch of frozen squid raw materials, the NDMA inhibition rate of edible squid tissue (ketone bodies) with undenatured proteins after treatment was 91.0%, while that of edible squid tissue (ketone bodies) with denatured proteins after heat treatment was 83.4%. Therefore, heat denaturation of squid proteins negatively impacts the technical effectiveness of this method. However, the method of this invention is still suitable for treating edible squid tissue with denatured proteins after heat treatment.

[0075] Example 7 The edible squid tissue treated by the method of this invention is more resistant to high-temperature baking or frying, meaning it has a lower N-nitrosodimethylamine content after high-temperature baking or frying. Related experiments were conducted as follows.

[0076] Experimental Method: Frozen squid was thawed and placed in 90℃ hot water for 10 min. After trimming and cleaning, edible squid tissue was obtained. A solution was prepared with 200 mg / L ferulic acid, 400 mg / L L-ascorbic acid, 300 mg / L vitamin E, 300 mg / L tea polyphenols, and 500 mg / L sodium D-isoascorbate. The pH of the solution was then adjusted to 3 with citric acid. The prepared solution was added to a container in a specific processing device, and the edible squid tissue (ketone body) was placed in the container, with the material accumulation thickness controlled at 9 cm, the liquid surface submerging the material by 1.2 cm, and the solution flow rate at 0.60 m / s. Then, an irradiation test was conducted for 20 min under ultraviolet light conditions of 254 nm wavelength and 1800 μW / cm², with the ultraviolet lamp 40 cm away from the liquid surface. Finally, ultrasonic cleaning was used to remove impurities and obtain a clean sample. Then, the cleaned samples were baked at 95ºC for 45 min and fried at 145ºC for 2 min, respectively. The initial N-nitrosodimethylamine (NDMA) content of the samples before baking or frying, and the N-nitrosodimethylamine (NDMA) content of the samples after baking or frying, were measured. At the same time, a batch of fresh squid was selected, trimmed and cleaned to obtain edible squid tissue, and baked and fried under the same conditions as control experiments. The experimental results are shown in Table 4.

[0077]

[0078] Experimental Results and Analysis: Table 4 shows that the initial NDMA content of the control group samples was lower than that of the experimental group. However, after baking or frying under the same conditions, the NDMA content of the control group samples was higher. Therefore, the edible squid tissue treated by the method of this invention is more resistant to high-temperature baking or frying, that is, it has a lower N-nitrosodimethylamine content after high-temperature baking or frying.

[0079] Example 8 In this invention, the solution is controlled to circulate at a certain flow rate, ensuring dynamic contact between the solution and the edible squid tissue material. Otherwise, the technical effect would be weakened. Relevant experiments were conducted as follows.

[0080] Experimental Method: Frozen squid was thawed and then placed in 90℃ hot water for 10 min. After trimming and cleaning, edible squid tissue was obtained. A solution containing multiple solutes was prepared, including ferulic acid (200 mg / L), L-ascorbic acid (400 mg / L), vitamin E (300 mg / L), tea polyphenols (300 mg / L), and sodium D-isoascorbate (500 mg / L). The pH of the solution was then adjusted to 3 with citric acid. The prepared solution was added to a container in a specific processing device, and the edible squid tissue (ketone body) was placed in the container. The material accumulation thickness was controlled at 7 cm, with the liquid surface submerging the material by 0.7 cm and the solution flow rate at 0.60 m / s. Then, an irradiation experiment was conducted for 20 min under ultraviolet light conditions of 254 nm wavelength and 1800 μW / cm², with the ultraviolet lamp 40 cm away from the liquid surface. The N-nitrosodimethylamine (NDMA), nitrite, and thiobarbituric acid values ​​of the samples were tested. A control experiment was conducted, the difference between which was to turn off the pump and, after the liquid level was submerged in the material by 0.7 cm, set the solution flow rate to 0 m / s.

[0081] Experimental Results and Analysis: The results showed that, compared with the experimental group, the NDMA content, nitrite content, and thiobarbituric acid value of the control group increased from 1.65 μg / kg, 0.7 mg / kg, and 0.49 mg / kg to 2.03 μg / kg, 0.9 mg / kg, and 0.72 mg / kg, respectively. Therefore, the technique of controlling the solution to circulate at a certain flow rate, so that the solution is in dynamic contact with the edible squid tissue material, is more effective.

[0082] Example 9 This embodiment combines Figure 9 The specific treatment equipment used in the method for targeted reduction and control of N-dimethylnitrosamine contaminants in squid processing is described.

[0083] (1) The equipment adopts an assembly line operation mode. The core is a rectangular processing tank container, which contains a specific solution. The material enters from the feed end on the left, moves to the right under the drive of the internal material conveyor belt, passes through the solution processing area, and is discharged from the discharge end on the right after being irradiated by ultraviolet light.

[0084] (2) The design features of the specific processing equipment include: a material transfer control module for conveying squid material; an immersion treatment container module for holding a specific solution and immersing the material; an ultraviolet irradiation module located above or to the side of the immersion treatment container for irradiating the material inside the container; a solution circulation module, which includes circulation pipelines and a variable frequency centrifugal pump for circulating the treatment solution inside the immersion treatment container; a safety protection module, including components for shielding ultraviolet light and ensuring safe material processing; and a control module, which mainly realizes the human-machine interaction of equipment operation, mainly including touch screen, buttons, indicator lights, and digital display components. The design features of the specific processing equipment also include that the materials in contact with the immersion solution in the material transfer control module, ultraviolet irradiation module, and solution circulation module are acid-resistant food-grade stainless steel or plastic; and that the control module integrates material transfer control, ultraviolet light intensity sensing, solution flow sensing control, solution temperature and pH sensing control, and programmable logic control functions.

[0085] (3) The ultraviolet irradiation device includes a lifting and adjusting mechanism and an ultraviolet lamp assembly installed on it; the total length of the irradiation equipment is 3000 mm, the total height is 1300 mm (from the ground to the ultraviolet lamp assembly platform), the height of the treatment tank is 560 mm (from the ground to the bottom of the tank), and the width is 900 mm. In actual design, the equipment size can be scaled up proportionally to meet the requirements of different raw material processing volumes.

[0086] (4) Ultraviolet lamp assembly: Located directly above the treatment tank, it is installed on a liftable platform. This is the core unit of the equipment, which irradiates the materials below by emitting ultraviolet light.

[0087] (5) Lifting platform: The supporting structure that connects the ultraviolet lamp group, allowing the lamp group to be adjusted up and down, and the ultraviolet irradiation distance to be adjusted according to process requirements.

[0088] (6) Light-blocking protective curtain: Located above the discharge end of the equipment, it is used to prevent ultraviolet light from leaking out, protect the safety of operators, and also play a role in dust prevention.

[0089] (7) Variable frequency centrifugal pump: installed at the bottom of the equipment and connected to the liquid discharge pipeline. Its function is to maintain the circulation of liquid in the tank, and to ensure that all parts of the liquid can be uniformly irradiated by ultraviolet light by controlling the solution flow rate. It can also be used for the discharge and return of the treated solution and the circulation of washing liquid during equipment cleaning.

[0090] (8) Material conveyor belt: Located inside the liquid, used to transport materials to or from the irradiation treatment area, and to carry materials in the irradiation treatment area.

[0091] Contents not described in detail in this specification are prior art known to those skilled in the art. The above descriptions are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for targeted reduction and control of N-dimethylnitrosamine pollutants in squid processing, characterized in that, Includes the following steps: (1) Raw material pretreatment: Thaw frozen squid or take fresh squid directly, and after heat treatment or without heat treatment, trim and clean to remove inedible parts to obtain edible squid tissue; (2) Solution immersion treatment: Add a specific solution with a pH value of 3~5 and a temperature of 20~30℃ to a container of a specific treatment equipment, and then place the edible squid tissue obtained in step (1) into the container of the specific treatment equipment, control the material accumulation thickness to be 6~9 cm, and make the liquid surface submerge the material by 0.2~2.0 cm; control the circulation of the treatment solution by a variable frequency centrifugal pump, and maintain the flow rate at 0.5~0.8 m / s, so that the solution and the material are in dynamic contact. (3) Ultraviolet irradiation treatment: The material immersed in the specific solution in step (2) is subjected to ultraviolet irradiation; the wavelength of the ultraviolet light is 250~260 nm, the irradiation intensity is 1200~1800 μW / cm², the distance between the ultraviolet light source and the liquid surface of the material is 5~50 cm, and the irradiation time is 20~35 min. (4) Impurity removal and purification treatment: The squid material after step (3) is washed with running water or ultrasonically to obtain clean squid material.

2. A specific treatment device for targeted reduction and control of N-dimethylnitrosamine according to the method of claim 1, characterized in that, include: The system comprises a material transfer control module, an impregnation container module, an ultraviolet irradiation module, a solution circulation module, a safety protection module, and a control module. The material transfer control module is used to transport squid material. The impregnation container module is used to hold a specific solution and impregnate the material. The ultraviolet irradiation module is located above or to the side of the impregnation container to irradiate the material inside. The solution circulation module includes circulation pipelines and a variable frequency centrifugal pump to circulate the treatment solution within the impregnation container. The safety protection module includes components to shield ultraviolet light and ensure safe material handling. The control module primarily enables human-machine interaction during equipment operation and mainly includes a touchscreen, buttons, indicator lights, and a digital display.

3. The specific processing device according to claim 2, characterized in that, The ultraviolet irradiation device includes a lifting and adjusting mechanism and an ultraviolet lamp assembly mounted thereon; in the material transfer control module, ultraviolet irradiation module, and solution circulation module, the materials in contact with the impregnation solution are selected to be acid-resistant food-grade stainless steel or plastic; the control module integrates material transfer control, ultraviolet light intensity sensing, solution flow sensing control, solution temperature and pH sensing control, and programmable logic control functions.

4. The method according to claim 1, characterized in that, The heat treatment mentioned in step (1) is water treatment at 80~90℃.

5. The method according to claim 1, characterized in that, The inedible parts mentioned in step (1) include cartilage and viscera; the edible squid tissues include the carcass, tentacles, fins and mantle membrane.

6. The method according to claim 1, characterized in that, The squid in question is either the Pacific squid or the Pacific giant squid.

7. The method according to claim 1, characterized in that, In step (1), if the N-nitrosodimethylamine content of the edible squid tissue significantly exceeds 4.0 μg / kg, the solute components of the specific solution described in step (2) include ferulic acid, L-ascorbic acid, vitamin E, tea polyphenols, and sodium D-isoascorbate, and the concentrations of each solute in the solution are as follows: ferulic acid 180~220 mg / L, L-ascorbic acid 380~420 mg / L, vitamin E 280~320 mg / L, tea polyphenols 250~320 mg / L, and sodium D-isoascorbate 480~550 mg / L.

8. The method according to claim 7, characterized in that, If the N-nitrosodimethylamine content in the edible squid tissue in step (1) slightly exceeds or does not exceed 4.0 μg / kg, the solute component of the specific solution described in step (2) includes a combination of vitamin E 280~320 mg / L and sodium D-isoascorbate 480~550 mg / L, or a combination of tea polyphenols 250~320 mg / L and sodium D-isoascorbate 480~550 mg / L.

9. The method according to claim 1 or 7, characterized in that, The pH of the treatment solution is adjusted using food-grade citric acid or sodium hydroxide.

10. The method according to claim 1, characterized in that, The ultrasonic cleaning described in step (4) has a material-to-water ratio of 1:3 to 1:5, an ultrasonic power of 150 to 250W, and a cleaning time of 180 to 300 seconds.

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