A method of producing a shrimp food

Abstract

The application relates to the technical field of shrimp processing, and discloses a production method of shrimp food, which comprises the following steps: rinsing a shrimp body with 10 DEG C or below clean water, removing shrimp whiskers and shrimp feet, then separating shrimp shells from shrimp meat by using a mechanical shelling machine to obtain shrimp meat, putting the shrimp meat into 0-4 DEG C ice water to soak for 5 min, removing surface mucus and blood dirt, taking out the shrimp meat, and draining surface water by using a centrifuge (rotating speed: 800 r / min, time: 2 min); putting the drained shrimp meat into a composite fresh-keeping solution, a material-to-liquid ratio being 1:2 (mass ratio), 0-4 DEG C low-temperature soaking for 18 min, stirring once every 6 min (rotating speed: 30 r / min) during the soaking; naturally draining the obtained shrimp meat for 8-10 min until no liquid drops on the surface, then uniformly laying the shrimp meat on a silica gel tray, then sending the shrimp meat into a -10 DEG C refrigerator to pre-freeze for 5 min, tunnel type quick freezing at -35 DEG C to -40 DEG C until the center temperature of the shrimp meat is less than or equal to -18 DEG C, vacuum sealing and packaging, and then storing in a -18 DEG C refrigerator; and the application has the effect of realizing resource utilization of shrimp by-products.

Description

Technical Field

[0001] This invention relates to the field of shrimp processing technology, and in particular to a method for preparing shrimp-based food products. Background Technology

[0002] Shrimp, with its tender and nutritious meat, rich in high-quality protein, unsaturated fatty acids, and various minerals, is one of the world's most popular seafood products. Species like the Pacific white shrimp, in particular, are widely used in food processing due to their large-scale farming and high cost-effectiveness. However, shrimp tissues have a high water content, active enzyme systems, and are rich in unsaturated fatty acids, making them highly susceptible to spoilage and discoloration during processing, storage, and transportation. This manifests as protein degradation producing volatile basic nitrogen (TVB-N), enzymatic reactions causing discoloration, and microbial proliferation leading to deterioration in sensory quality, severely impacting shelf life and food safety. This issue has become a key bottleneck restricting the high-quality development of the shrimp food processing industry.

[0003] To extend the shelf life of shrimp products, various preservation methods have been developed, including physical, chemical, and biological preservation. Physical preservation methods, such as low-temperature refrigeration and quick-freezing, can inhibit microbial growth and enzyme activity to some extent, but long-term low-temperature storage still cannot completely prevent nutrient loss and quality decline in shrimp, and they are also energy-intensive. Chemical preservatives, such as phytates and citrates, can delay oxidation and spoilage, but their usage is strictly limited, and excessive addition can easily affect the product flavor. Biological preservation has become a research hotspot in recent years. By adding biological components such as chitosan and natural active peptides to build a preservation barrier, it can inhibit microbial reproduction and reduce nutrient loss, aligning with the consumption trend of health foods.

[0004] Meanwhile, during shrimp processing, byproducts such as shrimp heads and shells can account for 30% to 40% of the total shrimp weight. These byproducts are rich in high-quality components such as astaxanthin, chitin, and active peptides. Currently, most of them are directly discarded or processed at low prices, which not only wastes resources but also easily causes environmental pressure. Therefore, developing a method for producing shrimp food that can realize the resource utilization of shrimp byproducts and maintain stable freshness has significant industrial value and application prospects. Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing shrimp-based food products, which enables the resource utilization of shrimp by-products.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for preparing shrimp food, comprising the following steps:

[0007] (1) Cleaning and grading: Rinse the shrimp with water below 10℃, remove the shrimp whiskers and legs, then use a mechanical sheller to separate the shrimp shell and shrimp meat to obtain shrimp meat. Soak the shrimp meat in ice water at 0~4℃ for 5 minutes to remove surface mucus and blood. After taking it out, use a centrifuge (speed 800r / min, time 2min) to drain the surface water.

[0008] (2) Place the drained shrimp obtained in step (1) into the compound preservation liquid with a material-to-liquid ratio of 1:2 (mass ratio), soak at 0-4℃ for 18 minutes, and stir once every 6 minutes (30r / min).

[0009] (3) Drain the shrimp meat obtained in step (2) naturally for 8-10 minutes until there are no drips on the surface. Then spread it evenly on a silicone tray and put it into a -10℃ cold storage for pre-freezing for 5 minutes. Then tunnel-freeze it at -35~-40℃ until the core temperature of the shrimp meat is ≤-18℃. After vacuum sealing, store it in a -18℃ cold storage.

[0010] By adopting the above technical solutions, the processes of cleaning, soaking, pre-freezing, and quick-freezing are precisely matched with the compound preservation liquid, amplifying the synergistic effect: the low-temperature ice water soaking and centrifugal dehydration in step (1) can remove the mucus and blood on the surface of the shrimp, reduce the initial number of microorganisms, and lay the foundation for subsequent preservation. At the same time, the low temperature condition avoids the activation of the shrimp's own enzyme system, which synergizes with the enzyme inhibition effect of the compound preservation liquid; the low-temperature soaking and intermittent stirring in step (2) can ensure that the film-forming substrate and active ingredients are evenly attached to the surface of the shrimp, and avoid the denaturation of components caused by high temperature, which is compatible with the low-temperature stability of the preservation liquid; the gradient quick-freezing process in step (3) can avoid the formation of large ice crystals inside the shrimp that damage the meat structure. At the same time, the slow freezing process helps the film-forming substrate to fully cross-link and form on the surface of the shrimp, improving the film adhesion, which synergizes with the film-forming characteristics of the compound preservation liquid, and finally achieves a dual improvement in the shrimp preservation effect and sensory quality.

[0011] A further provision of the present invention is as follows: the method for preparing the composite preservative solution is as follows: under a low temperature environment of 0-4℃, gellan gum, pullulan polysaccharide, and propylene glycol alginate are added sequentially to deionized water, and stirred at a low speed of 300-500 r / min for 20-25 min until completely dissolved to obtain a film-forming base solution. Then, shrimp by-product composite extract is added to the film-forming base solution, and stirred at a low speed for 15-20 min until fused. Potassium citrate and sodium phytate are added sequentially, and stirred for 5-8 min. The pH is adjusted to 4.0-4.5. Finally, transglutaminase is added, and stirred at a low speed for 3-5 min to obtain the composite preservative solution.

[0012] A further feature of the present invention is that the composite preservative solution is prepared and used immediately, and stored at 0-4℃ for no more than 12 hours.

[0013] A further provision of the present invention is as follows: The preparation method of the active extract of shrimp by-products is as follows: Shrimp heads and shells collected during the separation of shrimp meat are washed and drained, crushed to a particle size of 5-10 mm using a crusher, and then water is added to the crushed by-products at a material-to-liquid ratio of 1:3 (mass ratio) to adjust the pH to 6.0-6.5. Then, 0.4% neutral protease is added, and the mixture is enzymatically hydrolyzed at a constant temperature of 45-50℃ for 2.5 h, with stirring once every 30 min (speed 50 r / min). The hydrolysate is then transferred to an ultrasonic extraction device, with the ultrasonic power set to 250 W and the temperature set to 40℃, and extracted for 25 min. Finally, the obtained hydrolysate is filtered through a plate and frame filter (100 mesh) to remove residues, and the filtrate is sent to a vacuum concentration device (vacuum degree -0.08 MPa, temperature 50℃) to concentrate to 1 / 5 of the original volume to obtain the active extract of shrimp by-products, which is then refrigerated at 4℃ for later use.

[0014] Through the above technical solution, the enzymatic hydrolysis-ultrasound combined extraction process provides a source guarantee for the preservation and stable efficacy of astaxanthin in shrimp by-product extracts. Neutral protease hydrolysis destroys the chitinous structure of shrimp heads and shells, fully releasing the astaxanthin and other active ingredients encapsulated within. Subsequent ultrasonic extraction further breaks down cell residues, increasing the dissolution rate of astaxanthin. The medium-low temperature process of enzymatic hydrolysis at 45-50℃ and ultrasonic extraction at 40℃ avoids the degradation and isomerization of astaxanthin caused by high temperatures, ensuring stable astaxanthin content and consistent antioxidant activity in the extract. The extract is then vacuum concentrated to 1 / 5 of its original volume, allowing for precise control of the astaxanthin concentration within the appropriate range. This ensures that astaxanthin works synergistically with film-forming substrates, regulators, and other components in proportion, while avoiding abnormal membrane structure due to excessively high astaxanthin concentration or insufficient antioxidant capacity due to excessively low concentration, thus guaranteeing the stability and repeatability of the preservation effect for each batch of products. Meanwhile, the medium-low temperature extraction process is highly compatible with the low-temperature preparation of the compound preservation solution and the low-temperature soaking of shrimp. The entire process of avoiding light and operating at low temperature can maximize the preservation of astaxanthin activity, ensuring that astaxanthin can continue to work synergistically with other components throughout the entire process from extraction to application, laying a core foundation for the stability and effectiveness of the preservation system.

[0015] A further provision of the present invention is that, by total mass, the composite preservative solution comprises: 1.5-2.5% of the shrimp by-product composite extract, 0.015-0.025% of the transglutaminase, 0.06-0.09% of gellan gum, 0.12-0.18% of pullulan, 0.06-0.09% of the propylene glycol alginate, 0.07-0.09% of the potassium citrate, 0.02-0.03% of the sodium phytate, with deionized water as the balance.

[0016] A further feature of the present invention is that the pH of the composite preservative solution is 4.0-4.5, it is prepared at a low temperature of 0-4℃ and stirred at a low speed throughout the process, with a stirring rate of 300-500 r / min.

[0017] The beneficial effects of this invention are:

[0018] 1. This invention achieves a win-win situation of high-value utilization of by-products and stable preservation. Using processing by-products such as shrimp heads and shells as raw materials, it efficiently recovers active ingredients such as astaxanthin and active peptides through precise extraction technology, transforming waste by-products into core preservation components. This not only reduces waste emissions and environmental pressure and increases industrial added value, but also solves the problems of fluctuating effects and short shelf life of traditional preservation technologies by virtue of the strong antioxidant stability of astaxanthin and the synergistic effect of multiple active ingredients. The deep synergy between astaxanthin, film-forming substrates, and regulators constructs a multi-dimensional, stable preservation system encompassing physical barrier, antioxidant, and antibacterial properties. Astaxanthin's broad-spectrum antioxidant activity can maintain shrimp quality for a long time, avoiding the defects of single preservation ingredients being easily deactivated. This ensures that the color, flavor, and texture stability of shrimp are significantly improved during long-term low-temperature storage, achieving a closed-loop industrial chain of "resource recycling - stable preservation," balancing economic benefits, environmental benefits, and product quality stability. Simultaneously, through the synergistic effect of the composite preservation system, it can effectively inhibit the reproduction of microorganisms and oxidation reactions during shrimp storage, significantly reducing TVB-N formation and polyphenol oxidase activity, delaying shrimp blackening, off-odor development, and softening of the meat. This extends the shelf life of shrimp under -18℃ refrigeration conditions by more than 30% compared to existing technologies, while fully preserving the tender texture and nutritional components of the shrimp, significantly improving the sensory quality and food safety of the product.

[0019] 2. This invention utilizes astaxanthin and active peptides from shrimp by-product composite extracts as the core preservative active components for shrimp meat. These components work synergistically with film-forming substrates and food-grade regulators to achieve stable and long-lasting preservation effects. The active extracts from shrimp by-products, such as astaxanthin, active peptides, and chitin derivatives extracted from shrimp shells and heads, form a synergistic system of "carrier locking + active antibacterial" with three film-forming substrates: gellan gum, pullulan, and propylene glycol alginate. This system is the core guarantee for stable preservation. Astaxanthin in the shrimp by-product extract works synergistically with active peptides, chitin derivatives, and polyphenols to exert a core stabilizing effect. Furthermore, astaxanthin, as a strong antioxidant, provides crucial support for the stability of the preservation effect. On one hand, the three-dimensional network film-forming substrate can absorb the astaxanthin in the extract... Multiple active ingredients, including active peptides, are tightly encapsulated to form a "slow-release reservoir," preventing astaxanthin from rapid oxidation and degradation due to light and oxygen exposure. Simultaneously, its slow release during storage ensures that the shrimp surface maintains an effective antioxidant concentration, solving the problems of easy inactivation and short shelf life associated with single antioxidants. Furthermore, the astaxanthin in the extract forms a synergistic barrier network with other active ingredients and film-forming substrates—astaxanthin molecules can fill the microscopic pores of the film, enhancing its ability to block ultraviolet light and oxygen. At the same time, its powerful antioxidant activity scavenges free radicals within and on the surface of the shrimp, blocking the oxidation chain reaction of unsaturated fatty acids. Combined with the antibacterial effect of active peptides and the enzyme-inhibiting effect of chitin derivatives, this forms a multi-dimensional synergy of "antioxidant + antibacterial + enzyme inhibition," covering the main pathways of shrimp spoilage. Crucially, astaxanthin exhibits broad-spectrum and stable antioxidant activity. Its activity is not easily lost in a weakly acidic environment of 4.0-4.5°C and under low-temperature storage conditions. It can effectively delay the blackening of shrimp bodies and the softening of meat due to oxidation, while protecting other active ingredients from oxidation and inactivation. It forms a closed loop of "structural protection-activity enhancement" with the film-forming substrate, significantly improving the sustainability and stability of the preservation effect.

[0020] 3. This invention incorporates three natural polysaccharides—gellan gum, pullulan, and propylene glycol alginate—to form the core of the film-forming substrate. These three components achieve synergistic compatibility in a low-temperature water environment through intermolecular hydrogen bonds and hydrophobic interactions, constructing a dense and resilient three-dimensional network structure. Pullulan, with its excellent water solubility, can quickly spread to form a film substrate, improving the film's uniformity and light transmittance. Gellan gum forms a high-strength gel network at low temperatures, enhancing the film's mechanical support and barrier properties. Propylene glycol alginate improves the film's flexibility and low-temperature stability, preventing cracking due to low-temperature embrittlement during pre-freezing at -10°C and subsequent quick-freezing. Simultaneously, transglutaminase acts as a cross-linking agent, catalyzing the cross-linking reaction between the amino and carboxyl groups on the three polysaccharide molecular chains, further densifying the network structure and improving the film's barrier efficiency against oxygen and microorganisms. It also enhances the adhesion between the film and the shrimp surface, solving the problems of film detachment and preservation failure during low-temperature storage, achieving a synergistic film-forming effect of "substrate formation + cross-linking reinforcement."

[0021] 4. In this invention, potassium citrate and sodium phytate, as food-grade regulators, synergistically enhance the preservation effect with astaxanthin and other active ingredients in the shrimp by-product extract, further strengthening the stability of the preservation effect: First, pH synergistic stabilization: the two regulate the system pH to a weakly acidic range of 4.0-4.5. This environment not only directly inhibits the growth of spoilage bacteria and polyphenol oxidase activity, but also ensures the stable presence of astaxanthin—astaxanthin exhibits the strongest antioxidant activity under weakly acidic conditions. This avoids pH fluctuations leading to its isomerization and inactivation, ensuring that astaxanthin and other active ingredients work synergistically to exert their preservation effect. Second, antioxidant synergistic stabilization: sodium phytate chelates iron, copper, and other metal ions in shrimp meat, blocking the oxidation reaction catalyzed by metal ions, while potassium citrate assists... Enhanced chelation efficiency: These two substances, together with astaxanthin, form a dual antioxidant closed loop of "chelating metal ions + scavenging free radicals." Astaxanthin is responsible for efficiently scavenging existing free radicals, while sodium phytate and potassium citrate block the source of oxidation reactions. The three work synergistically to cover the entire oxidation chain, completely solving the problems of shrimp blackening and flavor deterioration caused by the limited effect of single antioxidant components, and significantly improving the stability of oxidation inhibition effect. Thirdly, the system is compatible and stable. Potassium citrate optimizes the ionic strength of the preservation liquid, improves the compatibility between astaxanthin and the film-forming substrate, avoids astaxanthin precipitation and stratification with polysaccharides under low temperature conditions, ensures that astaxanthin is evenly dispersed in the film, achieves consistent antioxidant and antibacterial effects on the shrimp surface, and eliminates preservation failure caused by insufficient local astaxanthin concentration. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. 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.

[0023] Source of additives:

[0024] 1. Gellan gum, food grade, purity ≥99%, commercially available;

[0025] 2. Pullulan, food grade, viscosity 100~200 mPa·s, commercially available;

[0026] 3. Propylene glycol alginate, food grade, degree of esterification ≥85%, commercially available;

[0027] 4. Neutral protease, food grade, enzyme activity 100,000 U / g, commercially available;

[0028] 5. Potassium citrate, food grade, purity ≥99.5%, commercially available;

[0029] 6. Sodium phytate, food grade, purity ≥98%, commercially available;

[0030] 7. Transglutaminase, food grade, enzyme activity 100U / g, commercially available;

[0031] 8. Citric acid, food grade, purity ≥99.5%, commercially available;

[0032] Example 1

[0033] This embodiment provides a method for preparing shrimp-based food products, with the following specific steps:

[0034] 1. Cleaning and grading: Select 10kg of fresh whiteleg shrimp, rinse the shrimp with 8℃ water to remove impurities from the surface, manually remove the shrimp whiskers and legs, and then send them to a mechanical sheller to separate the shrimp shells from the shrimp meat, collecting 6.2kg of shrimp meat. At the same time, collect 3.8kg of by-products such as shrimp heads and shells for later use. Soak the obtained shrimp meat in 2℃ ice water for 5 minutes, gently stirring twice during this period to remove surface mucus and blood. After taking it out, put it into a centrifuge, set the speed to 800r / min, centrifuge for 2 minutes, drain the surface water, and obtain 6.0kg of drained shrimp meat.

[0035] 2. Preparation of shrimp by-product compound extract: 3.8 kg of shrimp heads and shells collected in step 1 were cleaned, drained of surface moisture, and then crushed into particles with a diameter of 5-8 mm using a crusher. 11.4 kg of water was added to the crushed particles at a material-to-liquid ratio of 1:3 (mass ratio). The pH of the system was adjusted to 6.2 with citric acid. 15.2 g of neutral protease (0.4% of the total particle mass) was added, and the mixture was placed in a 48℃ constant temperature water bath for enzymatic hydrolysis for 2.5 h. During this period, the mixture was stirred once every 30 min at a speed of 50 r / min for 1 min each time. After enzymatic hydrolysis, the hydrolysate was transferred to an ultrasonic extraction device. The ultrasonic power was set to 250W and the extraction temperature to 40℃, and the ultrasonic extraction was performed for 25 minutes. After extraction, the residue was removed by filtration through a 100-mesh filter screen, and 8.6 kg of filtrate was collected. The filtrate was then sent to a vacuum concentration device and concentrated to 1 / 5 of its original volume under a vacuum of -0.08 MPa and a temperature of 50℃, yielding 1.72 kg of shrimp by-product compound extract. The extract was stored at 4℃ for later use. The astaxanthin content in the extract of this embodiment was found to be 0.032 mg / g.

[0036] 3. Preparation of the composite preservative solution: Under a low temperature environment of 2℃, add 0.07 kg of gellan gum, 0.15 kg of pullulan, and 0.07 kg of propylene glycol alginate to 100 kg of deionized water in sequence. Stir at 400 rpm for 22 min until completely dissolved to obtain the film-forming base solution. Add 2.0 kg of the shrimp by-product composite extract prepared in step 2 to the film-forming base solution, and continue stirring at 400 rpm for 18 min until fully combined. Then add 0.08 kg of potassium citrate and 0.025 kg of sodium phytate in sequence, and stir for 6 min. Adjust the pH of the system to 4.2 with citric acid. Finally, add 0.02 kg of transglutaminase and stir at 400 rpm for 4 min to obtain 102.345 kg of the composite preservative solution. Prepare and use immediately. The sources and specifications of all additives are as follows:

[0037] 4. Preservation soaking treatment: Put 6.0 kg of shrimp meat drained in step 1 into the compound preservation solution, control the material-to-liquid ratio to 1:2 (mass ratio), soak in a low temperature environment of 2℃ for 18 minutes, and stir once every 6 minutes at a speed of 30 r / min for 30 seconds each time to ensure that the shrimp meat is evenly contacted with the preservation solution.

[0038] 5. Freezing and storage treatment: Remove the soaked shrimp and let them drain naturally for 9 minutes until there are no drips on the surface. Spread them evenly on a silicone tray (the thickness of each tray should not exceed 2cm). Put them into a -10℃ cold storage for pre-freezing for 5 minutes, and then transfer them to a -38℃ tunnel-type quick-freezing equipment. Quick-freeze until the core temperature of the shrimp reaches -18℃. After taking them out, use a vacuum packaging machine to seal them (250g per bag) and store them in a -18℃ cold storage.

[0039] The astaxanthin content was determined using high-performance liquid chromatography (HPLC). The specific method was as follows: 0.5 g of shrimp by-product compound extract was added to 5 mL of a methanol-dichloromethane mixture (volume ratio 1:1). The mixture was vortexed for 10 min, then ultrasonically extracted for 20 min. After centrifugation at 8000 r / min for 10 min, the supernatant was filtered through a 0.45 μm organic phase filter membrane. The chromatographic conditions were: C18 column (4.6 mm × 250 mm, 5 μm); mobile phase: methanol-acetonitrile-dichloromethane (volume ratio 45:45:10); flow rate: 1.0 mL / min; column temperature: 30 ℃; detection wavelength: 474 nm; injection volume: 20 μL; and astaxanthin content was calculated using the external standard method.

[0040] Example 2

[0041] This embodiment provides a method for preparing shrimp-based food products, with the following specific steps:

[0042] 1. Cleaning and grading: Select 8kg of fresh tiger prawns, rinse the prawns with 5℃ water, remove the prawn whiskers and legs, and then separate them using a mechanical shelling machine to collect 4.9kg of prawn meat and 3.1kg of prawn heads and shells as byproducts; soak the prawn meat in 0℃ ice water for 5min, take it out and centrifuge it at 800r / min for 2min, and drain the water to obtain 4.7kg of prawn meat.

[0043] 2. Preparation of shrimp by-product compound extract: 3.1 kg of shrimp by-products were pulverized to a particle size of 7-10 mm, 9.3 kg of water (material-to-liquid ratio 1:3) was added, the pH was adjusted to 6.0, 12.4 g of neutral protease was added, and the mixture was enzymatically hydrolyzed in a constant temperature water bath at 45 °C for 2.5 h with intermittent stirring (50 r / min, stirring once every 30 min). The hydrolysate was ultrasonically extracted at 250 W and 40 °C for 25 min, filtered through a 100 mesh, and 6.8 kg of filtrate was collected. The filtrate was concentrated under vacuum (-0.08 MPa, 50 °C) to 1.36 kg to obtain the shrimp by-product compound extract. The astaxanthin content was detected by HPLC as described in Example 1 and was 0.029 mg / g. The extract was stored at 4 °C for later use.

[0044] 3. Preparation of compound preservative solution: At 2℃, add 0.06kg gellan gum, 0.12kg pullulan polysaccharide, and 0.06kg propylene glycol alginate to 80kg deionized water and stir at 300r / min for 25min until dissolved; add 1.2kg shrimp by-product compound extract and continue stirring at 300r / min for 20min; then add 0.07kg potassium citrate and 0.02kg sodium phytate in sequence, stir for 8min, adjust the pH to 4.0 with citric acid, add 0.015kg transglutaminase, and stir for 5min to obtain 81.545kg of compound preservative solution, which should be prepared and used immediately.

[0045] 4. Preservation soaking treatment: Put 4.7kg of shrimp meat into the compound preservation solution (material-liquid ratio 1:2), soak at 0℃ for 18 minutes, and stir once every 6 minutes at 30r / min to ensure even soaking.

[0046] 5. Freezing and storage treatment: Drain the shrimp naturally for 8 minutes, spread them flat on a silicone tray, pre-freeze at -10℃ for 5 minutes, tunnel-freeze at -35℃ until the core temperature is ≤-18℃, vacuum pack and store in a -18℃ cold storage.

[0047] Example 3

[0048] This embodiment provides a method for preparing shrimp-based food products, with the following specific steps:

[0049] 1. Cleaning and grading: Select 12kg of fresh prawns, rinse with 10℃ water, remove the shrimp whiskers and legs, and mechanically remove the shells to collect 7.5kg of shrimp meat and 4.5kg of shrimp by-products; soak the shrimp meat in 4℃ ice water for 5min, take it out and centrifuge at 800r / min for 2min, drain the water to obtain 7.3kg of shrimp meat.

[0050] 2. Preparation of shrimp by-product compound extract: 4.5 kg of shrimp by-products were crushed to 5-10 mm, 13.5 kg of water (material-to-liquid ratio 1:3) was added, the pH was adjusted to 6.5, 18 g of neutral protease was added, and the mixture was enzymatically hydrolyzed in a 50℃ constant temperature water bath for 2.5 h with intermittent stirring (50 r / min, stirring once every 30 min); the hydrolysate was ultrasonically extracted at 250 W and 40℃ for 25 min, filtered through a 100 mesh, and 10.2 kg of filtrate was collected. The filtrate was then concentrated under vacuum (-0.08 MPa, 50℃) to 2.04 kg to obtain the shrimp by-product compound extract. The astaxanthin content was detected by HPLC method described in Example 1 and was 0.035 mg / g. The extract was stored at 4℃ for later use.

[0051] 3. Preparation of compound preservative solution: At 4℃, add 0.09 kg of gellan gum, 0.18 kg of pullulan, and 0.09 kg of propylene glycol alginate to 120 kg of deionized water and stir at 500 rpm for 20 min until dissolved; add 3.0 kg of shrimp by-product compound extract and continue stirring at 500 rpm for 15 min; then add 0.09 kg of potassium citrate and 0.03 kg of sodium phytate in sequence, stir for 5 min, adjust the pH to 4.5 with citric acid, add 0.025 kg of transglutaminase, and stir for 3 min to obtain 123.415 kg of compound preservative solution, which should be prepared and used immediately.

[0052] 4. Preservation soaking treatment: Put 7.3kg of shrimp meat into the compound preservation solution (material-liquid ratio 1:2), soak at 4℃ for 18 minutes, and stir once every 6 minutes at 30r / min.

[0053] 5. Freezing and storage treatment: Drain the shrimp naturally for 10 minutes, spread them flat on a silicone tray, pre-freeze at -10℃ for 5 minutes, tunnel-freeze at -40℃ until the core temperature is ≤-18℃, vacuum pack and store in a -18℃ cold storage.

[0054] Comparative Example 1 (Shrimp By-product-free Complex Extract)

[0055] The difference between this comparative example and Example 1 is that no shrimp by-product extract is added to the composite preservation liquid, while the remaining steps and parameters are completely consistent with Example 1.

[0056] Comparative Example 2 (without ultrasonic extraction step)

[0057] The difference between this comparative example and Example 1 is that the shrimp by-product extraction only uses an enzymatic hydrolysis process, and the ultrasonic extraction step is removed. The remaining steps and parameters are completely consistent with those of Example 1.

[0058] Comparative Example 3 (without glutamine transaminase)

[0059] The difference between this comparative example and Example 1 is that no transglutaminase is added to the compound preservation solution, while the remaining steps and parameters are completely consistent with Example 1.

[0060] Performance test results

[0061] The shrimp products prepared in Examples 1-3 and Comparative Examples 1-2 were stored at -18℃, and their sensory quality, TVB-N content, and polyphenol oxidase (PPO) activity were tested at 0 days, 30 days, 60 days, and 90 days, respectively. The detection methods and results are as follows:

[0062] (a) Detection methods

[0063] 1. TVB-N content determination: Semi-micro nitrogen determination method was used (according to GB 5009.228-2016 "National Food Safety Standard - Determination of Volatile Basic Nitrogen in Food"). Take 5.0g of shrimp sample, homogenize, add 50mL of ammonia-free distilled water, shake for 30min, let stand for 10min, filter and collect the supernatant; take 10mL of the supernatant and inject it into the reaction chamber of the distillation apparatus, add 5mL of magnesium oxide suspension, steam distill, absorb the distillate with 20mL of boric acid absorption solution (containing mixed indicator), stop distillation when the volume of the distillate reaches 100mL; titrate with 0.01mol / L hydrochloric acid standard solution to the endpoint, and calculate the TVB-N content (unit: mg / 100g).

[0064] 2. Polyphenol oxidase (PPO) activity assay: The catechol colorimetric method was used. 2.0 g of shrimp sample was added to 10 mL of phosphate buffer (0.05 mol / L, pH 6.8), homogenized in an ice bath, and centrifuged at 8000 r / min for 20 min at 4℃. The supernatant was used as the crude enzyme solution. The reaction system contained 2.5 mL of phosphate buffer, 1.0 mL of 0.1 mol / L catechol solution, and 0.5 mL of crude enzyme solution. The blank control group was replaced with boiled and inactivated crude enzyme solution. After reacting in a constant temperature water bath at 30℃ for 10 min, 1.0 mL of 2 mol / L hydrochloric acid was added to terminate the reaction. The absorbance (OD value) was measured at 420 nm. One unit of enzyme activity (U) was defined as a change in absorbance of 0.01 per minute. The PPO activity inhibition rate was calculated as: inhibition rate = (OD value of control group - OD value of sample group) / OD value of control group × 100%.

[0065] (II) Test Results

[0066] Table 1. Performance Test Results

[0067]

[0068] Note: 1. Sensory quality evaluation is based on a comprehensive judgment of three dimensions: color, meat firmness, and odor; 2. TVB-N content that meets the GB 2733-2015 standard (≤25mg / 100g) is considered qualified; 3. Comparative Example 3 lacks transglutaminase, resulting in insufficient cross-linking of the film-forming substrate, making the film easy to fall off, thus weakening the preservation effect compared to the Example.

[0069] As can be seen from Table 1: (1) Shrimp by-product compound extract (containing astaxanthin) is the core component that ensures long-term and stable preservation effect: Comparing Examples 1-3 with Comparative Example 1 (without shrimp by-product extract), it can be seen that the TVB-N content of the sample without shrimp by-product extract exceeded the national standard after 60 days of storage, the PPO activity inhibition rate dropped sharply to 35%, and obvious blackening and off-odor appeared; while the sample of the example with added shrimp by-product extract, after 90 days of storage, the TVB-N content was still ≤24.3mg / 100g, the PPO activity inhibition rate was ≥70.8%, and the sensory quality remained good. This difference fully demonstrates that the synergistic effect of multiple components such as astaxanthin and active peptides in the extract can build an efficient antioxidant and antibacterial barrier, solving the problems of short shelf life and fluctuating effect of traditional preservation technology.

[0070] (2) The ultrasonic extraction step is crucial to improving the activity of the by-product extract: Compared with Example 1, the TVB-N content (32.5 mg / 100 g) of Comparative Example 2 (without ultrasonic extraction step) was significantly higher than that of Example 1 (23.1 mg / 100 g) after 90 days of storage, and the PPO activity inhibition rate (52.0%) was 20.4 percentage points lower than that of Example 1. This indicates that ultrasonic extraction can effectively break the cell structure of shrimp by-products, improve the dissolution rate of active ingredients such as astaxanthin, ensure that the extract has sufficient preservation activity, and lay the foundation for subsequent synergistic preservation.

[0071] (3) The cross-linking effect of transglutaminase can enhance the preservation stability and film adhesion: The sample of Comparative Example 3 (without transglutaminase) was prone to film detachment because the film-forming substrate could not be fully cross-linked. As a result, the TVB-N content reached 35.8 mg / 100g after 90 days of storage, the PPO activity inhibition rate was only 55.3%, the meat was loose and obvious blackening occurred; while the sample of Example 1 relied on the dense network film structure formed by transglutaminase catalysis to firmly lock the active ingredients, avoid the failure of the preservation barrier, and maintain the firmness of the shrimp meat, thus achieving a dual guarantee of preservation effect and sensory quality.

[0072] (4) The composite system of the present invention has a significant synergistic effect: The test data of Examples 1 to 3 show that the combination of film-forming substrate, shrimp by-product extract, transglutaminase and food-grade regulator can achieve synergistic effect of "physical barrier + active preservation + structural reinforcement". Compared with the comparison ratio with the absence of a single component, it can significantly extend the shelf life of shrimp under -18℃ cold storage conditions, and there are no harmful residues throughout the process, taking into account both safety and industrial application value.

[0073] In summary, this invention solves industry pain points such as unstable shrimp preservation effects and waste of by-product resources through the synergistic design of high-value utilization of shrimp by-products and composite preservation system. The process is controllable, the effect is significant, and it has broad prospects for industrial application.

[0074] Meanwhile, this invention, through the synergistic effect of shrimp by-product compound extract (containing astaxanthin), transglutaminase, film-forming substrate, and regulators, can significantly improve the freshness stability and film adhesion of shrimp, extend shelf life, and the process is controllable, making it suitable for industrial production.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing shrimp-based food products, characterized in that, Includes the following steps: (1) Cleaning and grading: Rinse the shrimp with water below 10℃, remove the shrimp whiskers and legs, then use a mechanical sheller to separate the shrimp shell and shrimp meat to obtain shrimp meat. Soak the shrimp meat in ice water at 0~4℃ for 5 minutes to remove surface mucus and blood. After taking it out, use a centrifuge (speed 800r / min, time 2min) to drain the surface water. (2) Place the drained shrimp obtained in step (1) into the compound preservation liquid with a material-to-liquid ratio of 1:2 (mass ratio), soak at 0-4℃ for 18 minutes, and stir once every 6 minutes (30r / min). (3) Drain the shrimp meat obtained in step (2) naturally for 8-10 minutes until there are no drips on the surface. Then spread it evenly on a silicone tray and put it into a -10℃ cold storage for pre-freezing for 5 minutes. Then tunnel-freeze it at -35~-40℃ until the core temperature of the shrimp meat is ≤-18℃. After vacuum sealing, store it in a -18℃ cold storage.

2. The method for preparing a shrimp food product according to claim 1, characterized in that, The method for preparing the composite preservative solution is as follows: Under a low temperature environment of 0-4℃, gellan gum, pullulan polysaccharide, and propylene glycol alginate are added sequentially to deionized water, and stirred at a low speed of 300-500 r / min for 20-25 min until completely dissolved to obtain a film-forming base solution. Then, shrimp by-product composite extract is added to the film-forming base solution, and stirred at a low speed for 15-20 min until fused. Potassium citrate and sodium phytate are added sequentially, and stirred for 5-8 min. The pH is adjusted to 4.0-4.

5. Finally, transglutaminase is added, and stirred at a low speed for 3-5 min to obtain the composite preservative solution.

3. The method for preparing a shrimp food product according to claim 2, characterized in that: The compound preservative solution should be prepared and used immediately, and stored at 0-4℃ for no more than 12 hours.

4. The method for preparing a shrimp food product according to claim 2, characterized in that, The preparation method of the active extract of shrimp by-products is as follows: Shrimp heads and shells collected during the separation of shrimp meat are washed and drained, and crushed to a particle size of 5-10 mm using a crusher. Then, water is added to the crushed by-products at a material-to-liquid ratio of 1:3 (mass ratio), and the pH is adjusted to 6.0-6.

5. Then, 0.4% neutral protease is added, and the enzyme is hydrolyzed at a constant temperature of 45-50℃ for 2.5 h, with stirring once every 30 min (speed 50 r / min). The hydrolysate is then transferred to an ultrasonic extraction device, and the ultrasonic power is set to 250 W and the temperature to 40℃ for 25 min. Finally, the obtained hydrolysate is filtered through a plate and frame filter (100 mesh) to remove residues. The filtrate is then sent to a vacuum concentration device (vacuum degree -0.08 MPa, temperature 50℃) and concentrated to 1 / 5 of the original volume to obtain the active extract of shrimp by-products, which is then refrigerated at 4℃ for later use.

5. The method for preparing a shrimp food product according to claim 4, characterized in that: The composite preservative solution, by total mass, comprises: 1.5-2.5% of the shrimp by-product composite extract, 0.015-0.025% of the transglutaminase, 0.06-0.09% of gellan gum, 0.12-0.18% of pullulan polysaccharide, 0.06-0.09% of the propylene glycol alginate, 0.07-0.09% of the potassium citrate, 0.02-0.03% of the sodium phytate, with deionized water as the balance.

6. The method for preparing a shrimp food product according to claim 2, characterized in that: The compound preservative solution has a pH of 4.0-4.5, is prepared at a low temperature of 0-4℃ and is stirred at a low speed throughout the process, with a stirring rate of 300-500 r / min.

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