Instant soft can of squid and preparation method thereof

Abstract

The application discloses a kind of instant squid soft cans and preparation method thereof, belong to aquatic product processing field.The application is tenderized by biological enzyme, is vacuum tumbling pickled by ultrasonic wave-pulse electric field cooperation, is locked flavor and is shaped by negative pressure low-temperature steam flash evaporation, is pre-fragrant by low-temperature plasma, and finally is carried out electron beam irradiation cold sterilization by special composite seasoning liquid.The application is processed at low temperature / normal temperature all the way, realizes commercial sterility by electron beam irradiation, induces protein cross-linking to lock elastic brittle taste by relying on the colloid component of seasoning liquid, and antioxidant components inside and outside cooperate to protect color;Low-temperature plasma produces fat fragrance, irradiation drives non-thermal Maillard reaction to generate baking meat flavor, and eliminates irradiation peculiar smell.The application process is suitable for various squid products, and the product is elastic and crisp, natural in color and luster, normal-temperature shelf life is not less than 12 months, and is suitable for industrialization.

Description

Technical Field

[0001] This invention relates to the field of aquatic product processing, specifically to a ready-to-eat soft canned squid and its preparation method. Background Technology

[0002] Squid is a large-scale marine cephalopod product with tender flesh, high protein content, and rich in nutrients such as taurine and amino acids, making it suitable for developing room-temperature ready-to-eat soft-canned products, meeting current consumer demands for convenient and nutritious diets. However, the industrial production of ready-to-eat soft-canned squid faces many technical bottlenecks, one of the major challenges being the sterilization process.

[0003] Low-acid soft canned goods stored at room temperature typically rely on high-temperature, high-pressure sterilization at 121°C. This sterilization method is technically mature, widely available, and thorough, consistently achieving commercial sterility. Furthermore, the high-temperature process generates a rich, roasted meat aroma through Maillard and caramelization reactions, compensating for the lack of natural flavor in seafood. However, due to the poor thermal stability of squid myofibrillar proteins, high temperature and pressure cause severe denaturation of muscle proteins and hydrolysis of muscle fibers. The resulting product is soft, mushy, and loses a significant amount of elasticity, losing its characteristic crisp and chewy texture. High temperatures also accelerate lipid oxidation and induce severe browning, causing the squid's natural pinkish-white color to turn yellow and dark, deteriorating the product's appearance. It also leads to the significant degradation and loss of heat-sensitive nutrients (such as taurine, various amino acids, and vitamins). In addition, although the heat of high temperature and pressure can generate flavor, the severe denaturation of muscle proteins causes the flavor substances infused during the initial marinating process to be lost with the cooking liquid, ultimately resulting in uneven flavor throughout the product.

[0004] Electron beam irradiation cold sterilization, being a physical cold sterilization process performed entirely at room temperature and pressure, avoids high-temperature heat damage and maximizes the preservation of the raw material's original crisp texture, natural color, and heat-sensitive nutrients. The irradiated product can have a shelf life of over 12 months at room temperature, making it a superior choice for ensuring the squid's taste and appearance. However, electron beam irradiation kills microorganisms solely through ionization, without the heat-driven Maillard reaction. The finished product lacks the rich meaty aroma and roasted fragrance produced by traditional heat processing, resulting in a thin flavor. Furthermore, irradiation ionization can trigger the oxidative decomposition of fats and sulfur-containing amino acids in aquatic products, producing a typical "irradiation off-flavor" that destroys the squid's natural freshness. In addition, this invention also found that the free radicals generated by irradiation continuously attack muscle proteins and lipids. Without a complementary color-protecting and texture-protecting formula, electron beam irradiation can easily lead to problems such as tough meat and darkened color.

[0005] While the existing processing patent CN108991106A applies electron beam irradiation cold sterilization to the production of canned fresh walnuts, effectively preserving the crispness of the nuts by leveraging the high oil content and natural antioxidant polyphenols of walnuts, its entire process cannot be directly adapted to squid processing. Directly applying the electron beam irradiation treatment method of this patent would have a significant negative impact on squid products. Walnuts have a dense protein structure and their oils can form a natural protective layer, making them more resistant to irradiation. In contrast, squid is mainly composed of water-soluble muscle protein and lacks endogenous antioxidants. Directly using the same irradiation process would cause muscle protein degradation and loosening, resulting in a prominent irradiation odor, along with a series of quality defects such as decreased whiteness and continuous loss of elasticity. Furthermore, this patent does not include a matching system for color protection and textural stabilization of aquatic proteins, making it difficult to solve the various negative problems caused by irradiation in squid processing.

[0006] Aside from the inherent contradictions in the sterilization process itself, the current complete processing chain for canned squid still suffers from multiple shortcomings in supporting procedures. Squid muscle fibers are dense and firm, and traditional still water soaking and marinating can only achieve surface flavoring, resulting in low flavor penetration efficiency and a bland taste inside the finished product. Conventional hot water blanching and shaping processes dissolve a large amount of flavor precursors that have penetrated in the early stages, causing the loss of base flavor. Traditional aroma-enhancing methods such as hot air baking can lead to side effects such as browning and softening of the meat. Most existing processing solutions only improve a single process individually and lack a comprehensive low-temperature collaborative processing system.

[0007] In summary, the industry urgently needs an integrated processing solution that combines multiple technologies. This solution should not only rely on electron beam irradiation for cold sterilization to avoid the loss of texture, color, and nutrients caused by high-temperature sterilization, but also incorporate physical processing methods such as bio-enzyme tenderization, ultrasonic combined with pulsed electric field synergistic vacuum tumbling marinating, negative pressure low-temperature steam flash evaporation for flavor locking and shaping, and low-temperature plasma pre-enhancing. At the same time, it should be combined with a special compound seasoning liquid containing colloids, antioxidants, and flavor precursors. Through the synergistic effect of multiple processes and ingredients, this solution can compensate for the deficiencies of electron beam irradiation, such as insufficient flavor, easy generation of irradiation off-flavors, and damage to color and texture. It should also simultaneously solve the whole-chain production problems such as uneven flavoring, flavor loss, and deterioration of processing quality. Summary of the Invention

[0008] Technical issues Traditional high-temperature and high-pressure sterilization results in soft-cooked squid that is mushy, brown in color, loses nutrients, and has uneven flavor. Simple electron beam irradiation, on the other hand, produces a thin flavor, generates irradiation odor, and easily damages the squid's texture and color. Meanwhile, traditional marinating, shaping, and flavoring processes present multiple technical challenges, such as poor flavor penetration, flavor loss, and quality deterioration.

[0009] Technical solution To address the aforementioned technical problems, this invention provides a method for preparing ready-to-eat soft-canned squid. This method utilizes bio-enzymatic tenderization technology combined with multi-dimensional physical field forced penetration marinating to accelerate mass transfer and penetration of the marinating liquid. It employs negative pressure low-temperature steam flash evaporation to lock in flavor substances, and low-temperature plasma-assisted aroma enhancement. Finally, it uses electron beam irradiation for gentle cold sterilization, effectively solving problems such as textural deterioration, browning, and insufficient flavor. This preparation method, with its entire low-temperature or room-temperature processing technology chain, systematically overcomes the shortcomings of existing technologies.

[0010] Furthermore, the electron beam irradiation technology used in this invention can synergize with specific components in the marinade to form a stable gel network structure while ensuring commercial sterility. This locks in the elastic and brittle texture, maintains the color of the squid in the can, and also creates a multi-layered, complex flavor. The method is simple to operate, highly efficient, and safe. It is applicable not only to soft-canned foods but also to traditional hard-canned foods.

[0011] This invention aims to develop a method for preparing ready-to-eat squid soft canned food. Under the premise of ensuring commercial sterility, it can greatly improve the textural deterioration and browning caused by traditional high-temperature and high-pressure sterilization, while solving the problem of insufficient flavor after cold sterilization. Overall, it improves the texture, color and flavor of the product, which is of great significance for improving the quality of such canned products and supporting the sustainable development of the canned food industry.

[0012] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing ready-to-eat soft canned squid includes the following steps: (1) Raw material pretreatment: Clean, peel, trim, and drain the squid; (2) Bio-enzyme tenderization: The squid pretreated in step (1) is placed in a solution containing complex protease and enzymatically hydrolyzed at 20~40℃ to relax the muscle fibers without causing excessive hydrolysis. After enzymatic hydrolysis, the squid is washed and drained. (3) Ultrasonic combined with pulsed electric field synergistic vacuum tumbling marinating: The squid tenderized in step (2) is immersed in the compound seasoning liquid, and under vacuum conditions, ultrasonic and pulsed electric field treatment is applied to marinate and flavor the squid. (4) Negative pressure low temperature steam flash setting: The squid marinated in step (3) is placed in a negative pressure environment and saturated water steam is introduced to gently denature and set the surface protein, forming a sealed layer to lock in the flavor substances, while simultaneously inactivating enzymes and reducing surface bacteria. (5) Low-temperature plasma-assisted flavor enhancement: The squid after shaping in step (4) is subjected to low-temperature plasma treatment. The high-energy active particles in the plasma undergo specific molecular transformation with flavor precursors and macromolecules to generate flavor compounds. (6) Packing and vacuum sealing: Pack the squid processed in step (5) and the compound seasoning liquid together into a high-barrier, high-temperature resistant, light-proof flexible packaging bag and vacuum seal it to obtain a soft canned semi-finished product. (7) Electron beam irradiation and mild cold sterilization: The soft canned semi-finished product described in step (6) is subjected to electron beam irradiation treatment.

[0013] Furthermore, in step (1), the squid can be fresh squid or thawed squid; the squid includes squid ears, squid tentacles, and squid carcass pieces.

[0014] Furthermore, in step (2), the complex protease is a mixture of papain and bromelain, with the amount of papain added being 100~200 U / g squid and the amount of bromelain added being 100~200 U / g squid.

[0015] Furthermore, the enzymatic hydrolysis time in step (2) is 10 to 50 minutes.

[0016] Furthermore, the components of the compound flavoring liquid include trehalose, konjac glucomannan, collagen peptides, sodium isoascorbate, cysteine, and ribose.

[0017] Furthermore, the compound flavoring liquid contains 4-10 parts of trehalose, 0.5-1.5 parts of konjac glucomannan, 1-3 parts of collagen peptides, 0.1-0.5 parts of sodium isoascorbate, 0.1-0.5 parts of cysteine, and 0.2-1.0 parts of ribose per 100 parts by weight.

[0018] Furthermore, the compound seasoning liquid is composed of the following components in parts by weight: 4-10 parts trehalose, 0.5-1.5 parts konjac glucomannan, 1-3 parts collagen peptide, 0.1-0.5 parts sodium isoascorbate, 0.1-0.5 parts cysteine, 0.2-1.0 parts ribose, 1-2 parts yeast extract, 1-3 parts salt, and 80-95 parts water.

[0019] Furthermore, the process parameters for ultrasonic combined with pulsed electric field synergistic vacuum tumbling and marinating in step (3) are as follows: vacuum degree -0.8 BAR, tumbling speed 4~10 r / min; ultrasonic frequency 20~60 kHz, power 200~400 W; pulsed electric field strength 0.5~3 kV / cm, pulse frequency 1~100 Hz, pulse width 0.01~0.1 ms; using an alternating mode of ultrasonic and pulsed electric field, the total processing time is 30~60 minutes.

[0020] Furthermore, the alternating mode is as follows: ultrasonic treatment for 4-6 minutes is alternated with pulsed electric field treatment for 2-3 minutes, and vacuum tumbling is performed continuously throughout the entire treatment process.

[0021] Furthermore, the parameters for negative pressure low-temperature steam flash evaporation and shaping in step (4) are: vacuum degree -0.04~-0.08 MPa, saturated steam temperature 60~75 ℃, processing time 1~3 minutes, and the squid center temperature not exceeding 50 ℃ during the processing.

[0022] Furthermore, the parameters of the low-temperature plasma-assisted flavor enhancement process in step (5) are as follows: dielectric barrier discharge is used, the discharge gas is a nitrogen-oxygen mixture, the input power is 100~500 W, the processing distance is 1~5 cm, and the processing time is 10~60 seconds; the surface temperature of the squid does not exceed 40 ℃ during the processing, and the color does not change significantly.

[0023] Furthermore, the compound seasoning liquid injected in step (6) can be diluted or used directly; the mass ratio of squid to compound seasoning liquid is 1:0.3~1:0.8.

[0024] Furthermore, in step (6), the high-barrier, high-temperature resistant, and light-proof flexible packaging bag is a composite bag containing an aluminum foil layer.

[0025] Furthermore, in step (7), the electron beam irradiation adopts a double-sided irradiation process, the electron beam energy is 5~15 MeV, the irradiation dose rate is 0.5~2 kGy / s, and the irradiation dose is 4~10 kGy; the electron beam irradiation is carried out at room temperature and pressure, and the product temperature rise during the process does not exceed 5℃.

[0026] At room temperature, the electron beam irradiation used in this invention achieves the following functions: a. Kill microorganisms to achieve commercial sterility, avoiding softening and browning caused by high temperatures; b. Induces squid ear protein to undergo cross-linking reaction with trehalose, konjac glucomannan and collagen peptides in the compound seasoning liquid to form a stable gel network structure and lock in the elastic and brittle texture; c. It stimulates endogenous taurine to reach an excited state and exogenous sodium isoascorbate to generate a strong reducing free radical dynamic quenching effect, producing a "endogenous-exogenous" synergistic antioxidant effect, protecting the natural color of squid ears; d. Targeted driving of non-thermal Maillard reaction between sulfur-containing amino acids and reducing sugars, blocking off-flavor generation pathways, while generating cooked meat aroma and roasted aroma compounds, which synergistically form multi-layered complex flavors with the lipid aroma compounds generated in step (5).

[0027] The present invention also provides a ready-to-eat squid soft canned product obtained according to the above preparation method.

[0028] Furthermore, the textural characteristics of the ready-to-eat squid soft canned food are as follows: hardness 1500~4000g, elasticity 0.80~0.95, color L* value ≥60, W value ≥60, and shelf life at room temperature not less than 12 months.

[0029] Beneficial effects (1) The bio-enzyme tenderizing technology provided by this invention, combined with multi-dimensional physical field forced penetration marinating, can effectively accelerate the mass transfer and penetration of the marinating liquid. Then, the negative pressure low temperature steam flash evaporation is used to fix and lock the flavor substances. It is not only suitable for the flavoring treatment of squid products, but also for the flavoring process of other aquatic products such as fish and shellfish. It is easy to operate, highly efficient, and suitable for industrial production.

[0030] (2) This invention completely abandons high-temperature thermal sterilization and adopts electron beam cold sterilization combined with irradiation-induced protein-colloid cross-linking to actively construct a stable gel network structure, lock the elastic and brittle texture, and effectively solve the problem of texture deterioration caused by traditional high-temperature and high-pressure sterilization.

[0031] (3) The preparation method of the present invention does not cause thermal browning. It uses electron beam energy to excite endogenous taurine to reach an excited state, and exogenous sodium isoascorbate generates a strong reducing free radical dynamic quenching effect, which produces a synergistic antioxidant effect, protects the natural color of squid, and is stable for long-term storage.

[0032] (4) This invention utilizes electron beam targeting to drive non-thermal Maillard reactions between sulfur-containing amino acids and reducing sugars, blocking off-flavor generation pathways, while generating cooked meat aroma and roasted aroma compounds, which synergistically form multi-layered complex flavors with lipid aroma compounds generated by low-temperature plasma, completely solving the problems of insufficient flavor and irradiation taste in electron beam cold sterilization products. Detailed Implementation

[0033] The following detailed description of specific embodiments of the present invention is provided in conjunction with examples. Many specific details are set forth in the following description to provide a thorough understanding of the invention; however, the invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0034] The following compound seasoning liquid is composed of: 6 parts trehalose, 1 part konjac glucomannan, 2 parts collagen peptides, 0.3 parts sodium isoascorbate, 0.3 parts cysteine, 0.5 parts ribose, 1.5 parts yeast extract, 2 parts salt, and 86.4 parts water.

[0035] Example 1 S1. Raw material pretreatment: Wash, peel, trim, and drain the squid that has been thawed to 4°C.

[0036] S2. Bio-enzymatic tenderization: The pretreated squid from step S1 is placed in an aqueous solution containing papain (100,000 U / g) and bromelain (50,000 U / g). The mass ratio of the complex proteases in the aqueous solution is 1:3, the enzyme concentration is 300 U / g water, the amount of papain added is 120 U / g squid, and the amount of bromelain added is 180 U / g squid. The squid is gently enzymatically hydrolyzed at 37 °C for 30 minutes to relax the muscle fibers without causing over-hydrolysis. After enzymatic hydrolysis, the squid is washed and drained.

[0037] S3. Ultrasonic and pulsed electric field combined with vacuum tumbling and marinating: The tenderized squid from step S2 is immersed in the compound seasoning liquid. Under a vacuum of -0.8 BAR, ultrasonic waves with a frequency of 40 kHz and a power of 300 W and a pulsed electric field with an intensity of 2 kV / cm, a pulse frequency of 50 Hz, and a pulse width of 0.05 ms are applied simultaneously. The ultrasonic treatment is repeated for 5 minutes and the pulsed electric field treatment for 2 minutes. Vacuum tumbling at a speed of 7 r / min is carried out continuously throughout the entire process. The marinating process lasts for 42 minutes.

[0038] S4. Low-temperature steam flash setting under negative pressure: The squid marinated in step S3 is placed in a negative pressure environment with a vacuum degree of -0.08 MPa and subjected to gentle denaturation and setting of surface proteins by low-temperature saturated water steam at 60 ℃ for 2 minutes. During the process, the core temperature of the squid does not exceed 50 ℃, so as to form a sealed layer to lock in the flavor substances, while simultaneously inactivating enzymes and reducing surface bacteria.

[0039] S5. Low-Temperature Plasma-Assisted Flavor Enhancement: The squid, after being shaped in step S4, is subjected to low-temperature plasma treatment using dielectric barrier discharge. The discharge gas is a nitrogen-oxygen mixture, with an input power of 300 W, a treatment distance of 3 cm, and a treatment time of 30 seconds. During the treatment, the surface temperature of the squid does not exceed 40 °C. High-energy active particles in the plasma undergo specific molecular transformations with flavor precursors and macromolecules to generate flavor compounds.

[0040] S6. Packaging and Vacuum Sealing: The squid processed in step S5 and the compound seasoning liquid are packed together in an aluminum-containing high-barrier, high-temperature resistant, and light-proof flexible packaging bag at a material-to-liquid ratio of 1:0.3, and then vacuum sealed to obtain a soft canned semi-finished product.

[0041] S7. Electron beam irradiation for mild cold sterilization: The semi-finished soft canned food described in step S6 is subjected to electron beam irradiation treatment. The electron beam energy is 10 MeV, the irradiation dose rate is 1 kGy / s, and the irradiation dose is controlled at 10 kGy.

[0042] Example 2 The method is the same as in Example 1, except that: in step S2, the mass ratio of papain to bromelain is 1:1, the enzyme concentration is 500 U / g, and the treatment time is 20 minutes; in step S7, the electron beam irradiation dose is 8 kGy.

[0043] Example 3 The method is the same as in Example 1, except that: in step S2, the mass ratio of papain to bromelain is 1:5, the enzyme concentration is 100 U / g, the treatment temperature is 20 ℃, and the treatment time is 50 minutes; in step S4, the saturated water vapor temperature is 75 ℃.

[0044] Example 4 Referring to the method of Example 1, the difference is that: in step S3, the ultrasonic frequency is 60 kHz, the power is 400 W, the pulse electric field strength is 3 kV / cm, and the total processing time is 56 minutes; in step S5, the plasma processing time is 60 seconds; and in step S7, the electron beam irradiation dose is 8 kGy.

[0045] Example 5 Referring to the method in Example 1, the difference is that: in step S3, the ultrasonic frequency is 20 kHz, the power is 200 W, and the pulse electric field strength is 0.5 kV / cm; in step S5, the low-temperature plasma input power is 100 W and the processing time is 10 seconds; in step S7, the electron beam irradiation dose is 8 kGy.

[0046] Example 6 Referring to the method in Example 1, the difference is that in step S3, the ultrasonic frequency is 60 kHz, the power is 400 W, the pulse electric field strength is 3 kV / cm, the pulse frequency is 100 Hz, and the pulse width is 0.01 ms; in step S4, the saturated water vapor temperature is 75 ℃ and the processing time is 1 minute; in step S5, the low-temperature plasma input power is 500 W, the processing distance is 1 cm, and the processing time is 60 seconds.

[0047] Comparative Example 1 (High Temperature and High Pressure Sterilization) The method is the same as in Example 1, except that the traditional high temperature and high pressure sterilization process is used, that is, step S7 is replaced by high temperature and high pressure sterilization at 121°C for 20 minutes.

[0048] Comparative Example 2 (without tenderization) The method is the same as in Example 1, except that step S2, bio-enzyme tenderization, is omitted, that is, after pretreatment, ultrasonic combined with pulsed electric field synergistic vacuum tumbling and marinating treatment is directly performed.

[0049] Comparative Example 3 (Traditional Still Water Marinating) Referring to the method of Example 1, the difference is that in step S3, only traditional soaking and marinating is used, that is, the squid is soaked in the compound seasoning liquid and marinated in still water at 4 ℃ for 42 minutes, instead of using ultrasonic combined with pulse electric field and vacuum tumbling.

[0050] Comparative Example 4 (Traditional blanching for shaping) Referring to the method of Example 1, the difference is that in step S4, only the traditional blanching and shaping treatment is used, that is, the marinated squid is kept in hot water at 85 ℃ for 3 minutes, instead of using negative pressure low temperature steam flash steaming for shaping.

[0051] Comparative Example 5 (without added flavor) The method is the same as in Example 1, except that step S5, low-temperature plasma-assisted aroma enhancement, is omitted, i.e., after shaping, the product is directly bagged and vacuum-sealed.

[0052] Comparative Example 6 (Traditional Hot Air Baking for Flavor Enhancement) Referring to the method of Example 1, the difference is that step S5, low-temperature plasma-assisted aroma enhancement, is replaced by traditional hot air baking aroma enhancement, that is, the shaped squid is placed in an oven and treated with high-speed hot air at 40 ℃ for 30 minutes, and turned over once every 15 minutes during this process.

[0053] Comparative Example 7 (Compound flavoring liquid with no specific ingredients) The method is the same as in Example 1, except that trehalose, konjac glucomannan, collagen peptides, sodium isoascorbate, cysteine ​​and ribose are not added to the compound flavoring liquid in step S3.

[0054] Comparative Example 8 (without pulsed electric field) Referring to the method of Example 1, the difference is that in step S3, only ultrasonic combined with vacuum tumbling and marinating is used, without alternating pulsed electric fields.

[0055] Comparative Example 9 (Electron beam irradiation only) Referring to the method of Example 1, the difference is that: step S2, biological enzyme tenderization, step S3, ultrasonic combined with pulsed electric field synergistic vacuum tumbling and marinating, step S4, negative pressure low temperature steam flash evaporation and shaping, and step S5, low temperature plasma assisted aroma enhancement are omitted. That is, after the raw materials are pretreated, they are directly immersed in a compound seasoning liquid without specific ingredients and marinated in still water for 42 minutes. After marinating, they are kept in hot water at 85 ℃ for 3 minutes, and then bagged, sealed and directly subjected to electron beam irradiation.

[0056] Indicator Measurement (1) Determination of commercial sterility: Meets the commercial sterility requirements for canned food. According to national standard GB 4789.26-2023, one sample from each group was stored at 4℃ as a control, and the remaining samples were incubated at 36℃ for 10 days. During the incubation period, the bags were checked daily for bulging. After the incubation period, the commercial sterility was determined by pH value, smear staining microscopy, and sensory evaluation.

[0057] (2) Determination of texture: The prepared squid was cut into 1*1*1cm pieces. 3 The size was determined using a texture analyzer equipped with a flat-bottomed cylindrical probe (P / 50) in TPA mode. The experimental parameters were as follows: pre-test velocity 2 mm / s, test velocity 1 mm / s, post-test velocity 2 mm / s, trigger force 5 g, compression set 50%, interval between two probe tests 5 s, and data acquisition rate 200 Hz. Hardness and elasticity were selected as the textural properties indicators, with six replicates per group.

[0058] (3) Color determination: The color of the squid was quantitatively analyzed using a colorimeter under a D65 light source in reflectance mode. Three samples were used in each group, and the color of each sample was measured at three different locations on its surface. The results were expressed as L*, a*, and b* values, and the average value was taken. The whiteness calculation formula is as follows:

[0059] In the formula: L* is the brightness of the squid, a* is the redness of the squid, b* is the yellowness of the squid, and W is the whiteness of the squid.

[0060] (4) Sensory evaluation: Six key attributes were selected, including color (yellowish-brown to pinkish-white), odor (degree of squid characteristic aroma), off-odor (sterilized smell / irradiated smell), texture (soft to crisp), taste, and overall acceptability. A 9-point scale was used for rating (1-3 = weak / unpleasant, 4-6 = moderate, 7-9 = strong / pleasant).

[0061] Table 1 Different treatment methods

[0062] Table 2. Effects of different treatment methods on the commercial asepticity, texture, and color of canned squid.

[0063] Table 3. Effects of different treatment methods on the sensory evaluation of canned squid.

[0064] Hardness and elasticity reflect the textural characteristics of squid, while L* and W reflect its color. Commercial sterility is a safety indicator, and flavor is determined by a combination of sensory evaluations. Table 2 shows that all squid soft canned products prepared using different processing methods meet commercial sterility standards. Hardness and elasticity are key indicators for evaluating the textural characteristics of aquatic products. Table 2 shows that the squid in Comparative Example 1 (high-temperature and high-pressure sterilization) had the lowest hardness and elasticity, at 1521.83g and 0.80 respectively, demonstrating that traditional high-temperature and high-pressure sterilization severely damages the texture. Example 1 showed moderate hardness and the highest elasticity of 0.95. The color of the examples was significantly better than the comparative examples, with Example 1 (the optimal example) achieving an L* value of 79.58 and a W value of 78.82. Example 1 had the highest total sensory evaluation score, exhibiting the best sensory quality.

[0065] Specifically, as can be seen from Comparative Example 1 and Example 1, traditional high-temperature and high-pressure sterilization at 121℃ severely damages the texture of squid. The squid's hardness and elasticity are the lowest among all groups. High temperature causes severe denaturation of muscle proteins and fiber shrinkage, resulting in a loss of the squid's crisp and elastic texture. The color also deteriorates significantly, with a substantial decrease in L* brightness value and whiteness W, indicating that high temperature induces severe browning, causing the product to turn yellow and dark. This proves that traditional high-temperature sterilization is the core cause of the deterioration in the taste and appearance of canned squid, while electron beam cold sterilization at room temperature can completely avoid the defects caused by heat damage.

[0066] Specifically, as can be seen from Comparative Example 2 and Example 1, omitting the bio-enzyme tenderizing process will result in overly tough meat and reduced elasticity. This confirms that bio-enzyme tenderizing can relax fibers, creating channels for the penetration of seasoning liquid and subsequent protein cross-linking, which is a crucial preliminary step for improving taste and flavor.

[0067] Specifically, combining Comparative Example 3 and Example 1, it can be seen that static pickling results in poor flavor penetration, with only the surface layer adsorbing the seasoning liquid, resulting in a bland internal flavor and a significantly reduced sensory score. This demonstrates that alternating ultrasonic waves and pulsed electric fields combined with vacuum tumbling can enhance mass transfer and penetration, making it a core pickling process for achieving uniform flavor penetration, improved texture, and color preservation.

[0068] Specifically, as can be seen from Comparative Example 4 and Example 1, traditional blanching in 85°C hot water causes a large loss of specific precursor substances that have penetrated during the previous marinating process. In contrast, the negative pressure low-temperature steam flash evaporation and shaping process forms a sealed layer by gently denaturing the surface of saturated steam under negative pressure. Without contact with liquid water, it can effectively lock in specific components, preserve the marinating effect, and lay the foundation for subsequent electron beam energy activation. This is a key step in locking in flavor.

[0069] Specifically, as can be seen from Comparative Example 5 and Example 1, omitting the low-temperature plasma-assisted aroma-enhancing process results in a weak overall aroma, a lack of lipid-based flavor compounds, a low sensory score for odor, and a prominent irradiation odor that masks the natural freshness of the squid. This indicates that low-temperature plasma can generate lipid-based flavor compounds at low temperatures, neutralizing the irradiation odor from the electron beam, while also helping to protect the color. It is a key process to compensate for the flavor defects caused by cold sterilization.

[0070] Specifically, comparing Comparative Example 6 and Example 1, it can be seen that hot air baking at 40℃ easily induces browning, significantly reducing L* and whiteness W, causing the product to turn yellow. Simultaneously, the increased hot air temperature also leads to meat hardening and reduced elasticity. The off-flavors produced during baking can also overlap with irradiation odors, resulting in poor sensory appeal and overall acceptability. The comparison demonstrates that low-temperature plasma operates at a consistently low temperature without thermal damage, enhancing flavor without compromising color and texture, making it far superior to traditional hot air flavoring.

[0071] Specifically, as can be seen from Comparative Example 7 and Example 1, after removing the functional components of trehalose, konjac glucomannan, collagen peptides, sodium isoascorbate, cysteine, and ribose from the compound flavoring liquid, the color-protecting system failed, resulting in a significant decrease in brightness and whiteness. It also became prone to oxidation and darkening during storage. This indicates a lack of colloid and peptide cross-linking substrates, preventing the formation of a stable gel network under electron beam irradiation. Furthermore, the absence of reducing sugars and cysteine, flavor precursors, prevents the generation of roasted aromas under irradiation, resulting in a prominent irradiation off-flavor and a low taste score. This demonstrates that the synergistic effect of the multi-components in the specialized compound flavoring liquid is the core formula basis for achieving color protection, stable texture, elimination of irradiation odor, and the generation of complex flavors.

[0072] Specifically, as can be seen from Comparative Example 8 and Example 1, if only ultrasonic vacuum tumbling is retained during marinating, removing the alternating pulsed electric field treatment will result in insufficient flavor penetration depth, a decrease in sensory evaluation score, inadequate muscle fiber filling, significantly reduced product elasticity, a thin aroma profile, and more pronounced irradiation off-flavors. This indicates that the pulsed electric field can further open the fiber gaps and promote the penetration of macromolecular colloids and flavor precursors into the meat, exhibiting a synergistic effect with ultrasound; both are indispensable.

[0073] Specifically, as can be seen from Comparative Example 9 and Example 1, if all core pre-processing steps are removed, the resulting product exhibits an unbalanced texture: the meat is tough and lacks elasticity; the color-protecting system is completely absent, resulting in a dull color; there is insufficient flavor precursor, and the irradiation off-flavor is severe, with the lowest aroma and taste scores across all groups. This demonstrates that the entire process of the present invention—including bio-enzyme tenderization, multi-dimensional physical field marinating, negative pressure flash steaming, plasma aroma enhancement, special seasoning liquid, and electron beam cold sterilization—is an organic whole. The functions of each step are complementary, and the effects are non-linearly superimposed. The absence of any number of steps will simultaneously damage the texture, color, and flavor, and electron beam irradiation alone cannot solve all processing defects.

[0074] In summary, this invention, through nine comparative examples, respectively replacing / omitting steps such as sterilization, tenderization, marinating, shaping, aroma enhancement, and seasoning formulas, verifies that each step of the entire process and the dedicated seasoning liquid are indispensable and have a synergistic effect. Traditional high-temperature sterilization severely damages the texture and color of squid. Although electron beam cold sterilization avoids heat damage, its use alone results in poor flavor and irradiation odor, requiring a complete set of supporting processes. The four pretreatment steps—biological enzyme tenderization, ultrasonic + pulsed electric field composite marinating, negative pressure low-temperature flash steam shaping, and low-temperature plasma aroma enhancement—are used in a step-by-step manner. Arbitrarily omitting or replacing them with traditional processes will result in defects such as poor meat quality, insufficient flavor penetration, flavor loss, dark color, and weak aroma. The colloidal, antioxidant, and flavor precursor components in the compound seasoning liquid are key to color protection, quality stabilization, and removal of irradiation odor. Removing these components will lead to a comprehensive deterioration in product quality. This demonstrates that the entire process is an organic whole, not a simple superposition of steps. Without multiple core steps, using only electron beam sterilization will result in multiple problems with taste, color, and flavor. It can be seen that the fully low-temperature coupling process of this invention can take into account commercial sterility, a crisp and chewy texture, natural color, and complex aroma, and its overall quality is significantly better than that of traditional processing methods.

[0075] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing ready-to-eat soft-serve squid, characterized in that, Includes the following steps: (1) Raw material pretreatment: Clean, peel, trim, and drain the squid; (2) Bio-enzyme tenderization: The squid pretreated in step (1) is placed in a solution containing complex protease and enzymatically hydrolyzed at 20~40℃; (3) Ultrasonic combined with pulsed electric field synergistic vacuum tumbling marinating: The squid tenderized in step (2) is immersed in the compound seasoning liquid, and under vacuum conditions, ultrasonic and pulsed electric field treatment is applied to marinate and flavor the squid. (4) Negative pressure low temperature steam flash setting: Place the squid marinated in step (3) in an environment with a vacuum degree of -0.04~-0.08 MPa, and introduce saturated water steam at 60~75 ℃ for 1~3 minutes to perform gentle denaturation and setting of surface proteins; (5) Low-temperature plasma-assisted flavor enhancement: The squid after shaping in step (4) is subjected to low-temperature plasma treatment; the low-temperature plasma treatment is: dielectric barrier discharge is used, the discharge gas is a nitrogen-oxygen mixture, the input power is 100~500 W, the treatment distance is 1~5 cm, and the treatment time is 10~60 seconds. (6) Packaging and vacuum sealing: Pack the squid processed in step (5) and the compound seasoning liquid into a packaging bag and vacuum seal it to obtain a soft canned semi-finished product; (7) Electron beam irradiation and cold sterilization: The soft canned semi-finished product described in step (6) is subjected to electron beam irradiation treatment. The electron beam irradiation adopts double-sided irradiation, the electron beam energy is 5~15 MeV, the irradiation dose rate is 0.5~2 kGy / s, and the irradiation dose is 4~10 kGy. The components of the compound flavoring liquid include trehalose, konjac glucomannan, collagen peptides, sodium isoascorbate, cysteine, and ribose.

2. The preparation method according to claim 1, characterized in that, In step (1), the squid is fresh squid or thawed squid; the squid includes squid ears, squid tentacles, and squid carcass pieces.

3. The preparation method according to claim 1, characterized in that, In step (2), the complex protease is a mixture of papain and bromelain. The amount of papain added is 100~200 U / g squid, and the amount of bromelain added is 100~200 U / g squid.

4. The preparation method according to claim 1, characterized in that, The compound flavoring liquid contains 4-10 parts of trehalose, 0.5-1.5 parts of konjac glucomannan, 1-3 parts of collagen peptides, 0.1-0.5 parts of sodium isoascorbate, 0.1-0.5 parts of cysteine, and 0.2-1.0 parts of ribose per 100 parts by weight.

5. The preparation method according to claim 1, characterized in that, The compound seasoning liquid is composed of the following components in parts by weight: 4-10 parts trehalose, 0.5-1.5 parts konjac glucomannan, 1-3 parts collagen peptides, 0.1-0.5 parts sodium isoascorbate, 0.1-0.5 parts cysteine, 0.2-1.0 parts ribose, 1-2 parts yeast extract, 1-3 parts salt, and 80-95 parts water.

6. The preparation method according to claim 1, characterized in that, The process parameters for ultrasonic combined with pulsed electric field synergistic vacuum tumbling and marinating in step (3) are: vacuum degree -0.8 BAR, tumbling speed 4~10 r / min; ultrasonic frequency 20~60kHz, power 200~400 W; The pulsed electric field strength is 0.5~3 kV / cm, the pulse frequency is 1~100 Hz, and the pulse width is 0.01~0.1ms. The alternating mode of ultrasonic and pulsed electric field is adopted, and the total processing time is 30~60 minutes. The alternating mode is: ultrasonic treatment for 4~6 minutes and pulsed electric field treatment for 2~3 minutes are alternated. Vacuum tumbling is carried out continuously throughout the entire processing.

7. The preparation method according to claim 1, characterized in that, In step (6), the mass ratio of squid to compound seasoning liquid is 1:0.3 to 1:0.

8.

8. A ready-to-eat soft canned squid, characterized in that, The ready-to-eat squid soft canned food is prepared by the method according to any one of claims 1 to 7.

Images