Soft-skin prawn and preparation method thereof

Abstract

The invention belongs to the field of aquatic product processing, and provides a soft-skin prawn preparation method, which specifically comprises: mixing prawns and a lactic acid bacteria fermentation broth according to a weight ratio of 1: 3, soaking for 2.5-3 h, softening the dried small shrimps, and reserving the chitin fiber skeleton of the shrimp shells; the preparation method comprises the following steps: by taking water as a base solution, adding 0.08 to 0.12 percent by weight of cysteine, 0.08 to 0.12 percent by weight of glutamic acid, 0.08 to 0.12 percent by weight of glycine, 0.08 to 0.12 percent by weight of alanine, 0.3 to 0.7 percent by weight of glucose, 0.008 to 0.012 percent by weight of astaxanthin and 0.003 to 0.007 percent by weight of ferrous sulfate to obtain cooking liquor; heating the cooking liquor to 70-85 DEG C, putting the prawns into the cooking liquor, and cooking for 15-40 minutes at a constant temperature; and drying until the water content of the prawns is 18-22%. The lactic acid bacteria are used as food-grade microorganisms and have softening and antibacterial effects under acidic conditions, (1) lactic acid, acetic acid and other organic acids generated by metabolism of the lactic acid bacteria can chemically react with calcium carbonate in shrimp shells to generate soluble calcium salt, so that the effect of softening the shrimp shells is achieved;

Description

Technical Field

[0001] This invention belongs to the field of aquatic product processing, specifically a soft-shelled shrimp and its preparation method. Background Technology

[0002] Shrimp meat is a high-protein, low-fat, high-quality aquatic product. The main components of the shrimp shell are chitin, protein, and calcium carbonate. Chitin and protein form a cross-linked network, which is then mineralized by calcium carbonate to form a dense and hard structure.

[0003] Drying is a key method for preserving and adding value to shrimp and expanding consumption scenarios. The main components of shrimp shells are chitin, protein, and calcium carbonate. However, dried shrimp face two main challenges in promotion: 1. The problem of shrimp shell softening: Since shrimp shells are difficult to chew and cannot be eaten directly, and are hard and difficult to peel, existing technologies have tried acid soaking or enzymatic hydrolysis to solve the problem of shrimp shell softening. However, acid soaking can easily lead to acidification and deterioration of shrimp meat and produce unpleasant odors. Enzymatic hydrolysis is difficult to control and has poor softening uniformity. In addition, both have the risk of chemical residues or uncontrolled enzyme activity.

[0004] 2. The taste of dried shrimp: Traditional shrimp drying process mainly uses direct steaming and then drying, which has obvious shortcomings: the meat is dry and coarse, the eating experience is poor, the flavor is monotonous and relies on external seasonings in the later stage, and the natural shrimp flavor is seriously lost.

[0005] Therefore, developing a process for preparing soft-skinned shrimp that is controllable, safe, natural, and has excellent taste and flavor has significant industrial application value. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a soft-shelled shrimp and its preparation method, aiming to overcome the shortcomings of traditional dried shrimp processing, such as hard shells, dry texture, and monotonous flavor, as well as the problems of strong off-flavors, high residue risk, and poor controllability in existing softening processes. It achieves multiple objectives, including gentle softening of the shrimp shell, preservation of tender meat, natural and mellow flavor, and stable color, resulting in a soft-shelled shrimp product with uniform quality that can be produced in a standardized manner.

[0007] According to a first aspect of the present invention, a method for preparing soft-shelled shrimp is provided, specifically comprising the following steps: Mix the shrimp with the lactic acid bacteria fermentation liquid at a weight ratio of 1:3. The mixing ratio is determined according to the expected shrimp flavor and can be 1:1, 1:2 or 1:3. Soak for 2.5-3 hours to soften the shrimp shell and retain the chitin fiber skeleton of the shrimp shell. The soaking time is determined according to the expected shrimp flavor and can be 2.5, 2.6, 2.7, 2.8, 2.9 or 3 hours. Using water as a base liquid, the following ingredients are added by weight percentage: 0.08-0.12% cysteine, 0.08-0.12% glutamic acid, 0.08-0.12% glycine, 0.08-0.12% alanine, 0.3-0.7% glucose, 0.008-0.012% astaxanthin, and 0.003-0.007% ferrous sulfate to obtain a cooking liquid. The proportions of amino acids, glucose, astaxanthin, and ferrous sulfate can be determined according to the desired shrimp flavor. Preferably, the following ingredients are added by weight percentage: 0.1% cysteine, 0.1% glutamic acid, 0.1% glycine, 0.1% alanine, 0.5% glucose, 0.01% astaxanthin, and 0.005% ferrous sulfate.

[0008] Heat the cooking liquid to 70-85℃, add the shrimp into the cooking liquid, and steam at a constant temperature for 15-30 minutes. Dry the shrimp until the moisture content is 18-22%.

[0009] The beneficial effects of the preparation method of the present invention are as follows: 1. The lactic acid bacteria of this invention, as food-grade microorganisms, have both softening and antibacterial effects under acidic conditions. ① The organic acids such as lactic acid and acetic acid produced by their metabolism can react chemically with the calcium carbonate in the shrimp shell to generate soluble calcium salts, thereby softening the shrimp shell. ② The lactic acid bacteria strains can secrete proteases to hydrolyze the protein matrix that connects chitin fibers. ③ Under acidic conditions, it also promotes the hydrolysis of chitin in the shrimp shell, causing chain breaking reactions to generate short-chain chitin, while retaining the chitin fiber skeleton of the shrimp shell, making the shrimp shell soft and edible, achieving the effect of eliminating the need for peeling without affecting the taste.

[0010] 2. During the steaming process of this invention, ferrous sulfate directionally catalyzes the Maillard reaction of complex amino acids and sugars, while also promoting the Maillard reaction of amino acid monomers and sugars in shrimp meat protein, thereby synergistically enhancing the flavor of shrimp. Astaxanthin effectively inhibits oxidative browning, forming an integrated effect of "flavor enhancement, color protection, and texture optimization," reducing dependence on exogenous flavorings.

[0011] Meanwhile, sulfur-containing amino acids such as cysteine ​​participate in disulfide bond recombination, further optimizing the soft cortex. Specifically, the building blocks of the protein include cysteine. During cooking, the cysteine ​​units in the protein undergo an oxidation reaction with the added cysteine, forming disulfide bonds for recombination, thereby changing the original structure of the protein and improving and optimizing the taste of shrimp.

[0012] 3. This invention avoids the problems of odor, residue and uniformity of existing softening processes; it uses food-grade raw materials throughout the process and has no harmful chemical additives, which meets the needs of healthy consumption.

[0013] 4. This invention has wide industrial applicability, simple process steps, no strong alkali or harmful chemical softeners added, and is easy for aquatic product processing enterprises to promote on a large scale, with significant economic and social benefits.

[0014] Furthermore, the preparation process of the lactic acid bacteria fermentation broth is as follows: brown sugar and brewer's yeast are added to water (preferably sterile water) as a nutrient substrate to obtain a culture medium, lactic acid bacteria are inoculated into the culture medium, and fermentation is carried out at 30-35℃ until the pH is 3.0~5.0 to obtain the lactic acid bacteria fermentation broth.

[0015] The beneficial effects of adopting the above-mentioned further technical solutions are that the construction of the "lactic acid bacteria + brown sugar + brewer's yeast" expansion system not only ensures the high activity of lactic acid bacteria to achieve shrimp shell softening, replacing the traditional mechanical, chemical and single enzymatic hydrolysis processes, but also improves the metabolic efficiency of the strain through the nutrient substrate of brewer's yeast, while giving the product a slight fermented umami flavor and avoiding the off-flavor problems caused by acid soaking / enzymatic hydrolysis.

[0016] Furthermore, the amount of brown sugar added is 5-8% of the total mass of the culture medium, and the amount of brewer's yeast added is 0.5-3%.

[0017] The beneficial effect of adopting the above-mentioned further technical solution is that it constructs a propagation system with a precise ratio of "lactic acid bacteria + brown sugar + brewer's yeast", and combined with precise pH control of 3-5, it ensures the high activity of lactic acid bacteria.

[0018] Furthermore, 0.1-0.3% by weight of trimethylamine oxide is added to the cooking liquid.

[0019] The beneficial effect of adopting the above-mentioned further technical solution is that the Maillard reaction of compound amino acids and sugars, combined with trimethylamine oxide, works synergistically with amino acids in shrimp meat to enhance the natural sweet flavor and reduce dependence on exogenous flavorings.

[0020] Furthermore, the lactic acid bacteria strain is Lactobacillus plantarum or Lactobacillus acidophilus, and the inoculation amount is 3-5% (v / v).

[0021] Furthermore, the drying is hot air drying at a temperature of 60-65℃ and an air velocity of 1.5-2m / s, or vacuum freeze drying at a vacuum degree of -0.08~0.1MPa and a sublimation temperature of -40~-30℃.

[0022] Furthermore, after constant-temperature steaming for 15-30 minutes, chitin undergoes thermoplasticization under humid and hot conditions. During hot air drying, the moisture evaporates, and the chitin molecular chain segments reform intermolecular hydrogen bonds in a mobile state, forming a disordered network cross-linked structure.

[0023] The beneficial effects of adopting the above-mentioned further technical solutions are that chitin undergoes thermoplasticization under humid and hot conditions. (1) Plasticizing effect of water: Water molecules, as hydrogen bond plasticizers, insert between chitin molecular chains and form new intermolecular hydrogen bonds with the hydroxyl (-OH) and amino (-NH2) groups of chitin, which can weaken the inherent strong hydrogen bonds between chitin molecules and cause the crystalline region to partially dissociate into the non-crystalline region; (2) Activating effect of heat: It provides kinetic energy for the molecular chain segments, so that the chitin molecular chain segments are in a mobile state, and the temperature (70-85℃) during cooking can induce activating effect. The non-crystalline region chain segments are relaxed (rotated, slipped), thereby realizing the transformation of chitin from a tight structure to a loose fiber network and achieving structural remodeling. This structural remodeling process is carried out simultaneously with the evaporation of water. (3) When the water evaporates during drying, the chitin molecular chain segments will re-form intermolecular hydrogen bonds in a mobile state. However, because the crystalline region is partially dissociated into a non-crystalline region in the early stage, the new hydrogen bond crosslinking sites are no longer the dense crystalline arrangement before thermoplasticization, but present a disordered and loose network crosslinking. When subjected to external force, the fibers can slightly slip and deform, making the shrimp shell exhibit a soft texture.

[0024] Furthermore, soaking for 2.5-3 hours softens the shrimp shells while preserving the chitin fiber skeleton, including: Step 1: Lactic acid bacteria ferment and metabolize to produce lactic acid and acetic acid, lowering the system pH to 3.0-5.0, preferably 3.5±0.2. This dissolves the calcium carbonate in the shrimp shell (specifically, it reacts with the calcium salts in the shell to form soluble calcium salts), exposing the proteins encased in the inorganic phase within the shell to the lactic acid bacteria fermentation broth. Simultaneously, the organic acids produced by lactic acid bacteria metabolism decompose the connective tissue between the shell and the meat. The connection between the shell and meat relies on connective tissue (mainly composed of collagen + a small amount of mucopolysaccharides and elastin). The lactic acid and acetic acid produced by the bacteria metabolize achieve a gentle decomposition of the connective tissue through a dual action of chemical degradation and structural swelling. Furthermore, the pH of the lactic acid bacteria-producing system is lowered. Stable at 3.5~5.0 (weakly acidic range), it acts on the collagen in connective tissue without causing denaturation of shrimp meat protein, preserving the tenderness, taste and nutrition of shrimp meat. The specific process is as follows: (1) Degradation of collagen by organic acids. Collagen relies on intermolecular hydrogen bonds, ionic bonds and covalent cross-linking bonds to maintain stability. The H⁺ dissociated from organic acids will destroy the hydrogen bonds and ionic bonds between collagen molecules, gently hydrolyze the peptide bonds of collagen (non-strong hydrolysis), degrade large-molecule collagen into small-molecule polypeptides, and gradually break the dense connective tissue fibers, so that the connection between the shrimp shell and the shrimp meat loses support and the peeling resistance is greatly reduced. (2) Swelling effect of organic acids. Organic acids penetrate into the fiber gaps of connective tissue with water molecules, causing the connective tissue to swell and soften, reducing the adhesion between the shrimp shell and the shrimp meat, and achieving easy physical peeling.

[0025] Step 2: Under acidic conditions, the lactic acid bacteria strain continuously secretes extracellular proteases, which hydrolyze the peptide bonds of the chitin-protein network structure in the shrimp shell, degrading the large protein molecules into polypeptides and amino acids. At the same time, the acidic conditions also promote the hydrolysis of chitin in the shrimp shell, causing a chain-breaking reaction to generate short-chain chitin, while retaining the chitin fiber skeleton, making the shrimp shell softer. Step 3: The dissolution of calcium carbonate and protein degradation occur simultaneously, while the acidic environment inhibits contamination by other bacteria.

[0026] The beneficial effects of adopting the above-mentioned further technical solutions are that the fermentation process is accompanied by the dissolution of calcium carbonate and the degradation of protein, which preserves the chitin fiber skeleton and makes it easy to adsorb the flavor components in the subsequent cooking liquid. The removal of calcium carbonate and protein between the chitin fiber skeletons also helps the subsequent cooking liquid to penetrate the shrimp shell and enter the shrimp meat, thus enhancing the natural freshness and aroma of the product.

[0027] Furthermore, before adding the shrimp to the cooking liquid, rinse the softened shrimp 2-3 times with water to remove the lactic acid bacteria and their metabolites attached to the surface. After rinsing, neutralize the shrimp by soaking in a baking soda solution (preferably food-grade baking soda) at 0.1%-0.3% of the shrimp's weight for 1-10 minutes. Baking soda is a weakly alkaline salt. A (dilute) solution is prepared and used to briefly soak the fermented shrimp meat. The HCO3⁻ released from sodium bicarbonate dissolving in water penetrates into the interfibrillary spaces of the shrimp meat, regulating the colloidal osmotic pressure of the muscle fibers. This allows a small amount of water to re-enter the muscle fibers, compensating for moisture loss during fermentation and preventing the shrimp meat from becoming dry. The weakly alkaline environment protects the spatial structure of actin and myosin in the shrimp muscle fibers, preventing slight denaturation due to prolonged acidity (after lactic acid bacteria fermentation, the surface of the shrimp meat / A small amount of lactic acid and acetic acid may remain in the gaps (the weakly acidic environment can easily cause slight oxidative denaturation of astaxanthin and protein in shrimp meat), preserving the tenderness and elasticity of shrimp meat. Through the synergistic effect of neutralizing acidity, adjusting the pH of the shrimp meat system, and slightly swelling muscle fibers, the potential quality problems of shrimp meat after lactic acid bacteria fermentation are solved, while enhancing the excellent taste, stabilizing the color and texture of shrimp meat, further optimizing the taste, and the whole process is gentle with no food additive residues. In addition, the baking soda residue in the shrimp is weakly alkaline, which can promote the Maillard reaction during the steaming process.

[0028] According to a second aspect of the present invention, a soft-shelled shrimp is provided, prepared by any of the methods described above, or obtained by any of the methods described above.

[0029] The beneficial effects of this invention are as follows: the chitin fiber skeleton of the shrimp shell is basically intact, the shrimp shell exhibits a soft texture, the Maillard reaction of complex amino acids and sugars generates natural flavor substances and an attractive color, and it can also be combined with trimethylamine oxide to work synergistically with the amino acids in the shrimp meat to enhance the natural sweet flavor and reduce the dependence on exogenous flavorings. Attached Figure Description

[0030] Figure 1 This is a flowchart of the preparation process of the present invention.

[0031] Figure 2 This is a schematic diagram illustrating the effect of soaking time in lactic acid bacteria fermentation broth on the softening of shrimp shells. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0033] Example 1 This embodiment provides a method for preparing soft-shelled shrimp, specifically including the following steps: 1. Preparation of Lactic Acid Bacteria Activation and Expansion Broth: Take 3L of sterile water, add 180g of brown sugar (6% of the total culture medium mass) and 15g of brewer's yeast (0.5% of the total culture medium mass), stir to dissolve, sterilize at 121℃ for 20 minutes, cool to 35℃, inoculate with 120mL of *Lactobacillus plantarum* inoculum (4% v / v), adjust the pH to 3.5, ferment at 32℃ for 48 hours, maintaining the pH stable at 3.3-3.7 to obtain the lactic acid bacteria fermentation broth. The lactic acid and acetic acid produced by lactic acid bacteria metabolism are both edible acids. These acidic substances can react with calcium carbonate in shrimp shells to form water-soluble calcium salts, and can also hydrolyze chitin fibers in shrimp shells. Simultaneously, the proteases secreted by the lactic acid bacteria strains work synergistically with the metabolically produced acids to enhance the hydrolysis of chitin proteins, causing the chitin fibers to break down into shorter chains, thus preserving the cellulose skeleton while optimizing the taste.

[0034] 2. Softening shrimp shells: Take 1 kg of fresh whiteleg shrimp, wash and remove impurities, then soak them in the above fermentation liquid at room temperature for 3 hours. Observe that the shrimp shells and shrimp meat are initially separated, and then take out the shrimp.

[0035] 3. Cleaning and neutralization: Rinse the shrimp three times with running water, then briefly soak them in a solution of 2g food-grade baking soda (0.2% of the shrimp's weight) for 5 minutes, then remove and drain the shrimp.

[0036] 4. Flavor Enhancement and Drying: ① Preparation of Flavor Cooking Liquid: Prepare 10kg of flavor cooking liquid, add 10g cysteine, 10g glutamic acid, 10g glycine, 10g alanine, 50g glucose, 1g astaxanthin, 0.5g ferrous sulfate, and 20g trimethylamine oxide, stir to dissolve, and heat to 85℃; ② Cooking: Place the shrimp in a constant temperature cooking chamber and cook for 20 minutes, then remove and drain; ③ Drying: Place in a 65℃ hot air drying oven at a wind speed of 1.8m / s and dry until the moisture content is 20%, obtaining the finished soft-shelled shrimp product. Ferrous sulfate directionally catalyzes the Maillard reaction between the complex amino acids, amino acid monomers in shrimp meat protein, and sugars to generate flavor substances, which enhances the flavor of the shrimp while further softening the shrimp shell and the bulkiness of the protein. The addition of astaxanthin effectively inhibits oxidative degeneration. The residual baking soda in the shrimp is weakly alkaline, which can promote the Maillard reaction during the cooking process.

[0037] This embodiment also provides a soft-shelled prawn prepared by the above method. The finished product is tested and found to have a soft and easy-to-peel shell that fits the prawn meat well. The meat is tender and not dry, with a rich natural prawn flavor, bright color without browning, no chemical residue, and a shelf life of up to 8 months.

[0038] Example 2 This embodiment provides a method for preparing soft-shelled shrimp, specifically including the following steps: Step 1: Preparation of lactic acid bacteria activation and expansion broth: Same as in Example 1.

[0039] Step 2, softening shrimp shells: Select tiger prawns as raw materials, adjust the soaking time of the prawns to 2.5 hours, and the rest is the same as in Example 1.

[0040] Step 3, Cleaning and Neutralization: Rinse the shrimp three times with running water, then briefly soak them in a solution made of 2g of food-grade baking soda (0.2% of the shrimp's weight) for 5 minutes. Remove the shrimp and drain.

[0041] Step 4, Flavor Enhancement and Drying: ① Preparation of Flavor Cooking Liquid: The composition is the same as in Example 1, except that trimethylamine oxide is not added, and the liquid is heated to 75°C; ② Cooking: The shrimp are placed in the liquid and cooked at a constant temperature for 20 minutes, then removed and drained; ③ Drying Treatment: The shrimp are dried to a moisture content of 18% using a vacuum freeze dryer at a vacuum degree of -0.09MPa and a sublimation temperature of -35°C to obtain the finished soft-skinned shrimp product.

[0042] This embodiment also provides a soft-skinned prawn prepared by the above method. The finished product test shows that the product has excellent crispness, prominent shrimp flavor, bright color, and complete retention of nutrients, making it suitable for high-end snack food scenarios.

[0043] Example 3 This embodiment provides a method for preparing soft-shelled shrimp, specifically including the following steps: Step 1: Mix shrimp and lactic acid bacteria fermentation broth at a weight ratio of 1:3, soak for 2.5-3 hours to soften the shrimp shells while preserving the chitin fiber skeleton. The preparation process of the lactic acid bacteria fermentation broth in this embodiment is as follows: Add brown sugar and brewer's yeast to water as a nutrient substrate to obtain a culture medium. Inoculate the culture medium with lactic acid bacteria strains, specifically *Lactobacillus plantarum* or *Lactobacillus acidophilus*, at an inoculation amount of 3% (v / v). Ferment at 30-35℃ until the pH reaches 4±0.2 to obtain the lactic acid bacteria fermentation broth. The amount of brown sugar added is 7% of the total mass of the culture medium, and the amount of brewer's yeast added is 2%.

[0044] Lactic acid bacteria fermentation broth softens shrimp shells while preserving the chitin fiber skeleton of the shrimp shell, including: Step 1: Lactic acid bacteria fermentation and metabolism produce lactic acid and acetic acid, which lowers the pH of the system to 3.0~5.0, dissolves the calcium carbonate in the shrimp shell, and exposes the proteins in the shrimp shell that are wrapped in the inorganic phase to the lactic acid bacteria fermentation liquid. At the same time, the organic acids produced by the metabolism of lactic acid bacteria decompose the connective tissue between the shrimp shell and the shrimp meat. Step 2: Under acidic conditions, the lactic acid bacteria strain continuously secretes extracellular proteases, which hydrolyze the peptide bonds of the chitin-protein network structure in the shrimp shell, degrading the large protein molecules into polypeptides and amino acids, while retaining the chitin fiber skeleton. Step 3: The dissolution of calcium carbonate and protein degradation occur simultaneously, while the acidic environment inhibits contamination by other bacteria.

[0045] Step 2: Using water as the base liquid, prepare 10 kg of flavor cooking liquid, and add 0.08% cysteine, 0.08% glutamic acid, 0.08% glycine, 0.08% alanine, 0.3% glucose, 0.008% astaxanthin, and 0.003% ferrous sulfate by weight percentage to obtain the cooking liquid. Trimethylamine oxide is also added to the cooking liquid at a weight percentage of 0.1%. The cooking liquid is heated to 70-85℃, and shrimp are added to the liquid. The mixture is then cooked at a constant temperature for 25 minutes. During this 25-minute cooking process, chitin undergoes thermoplasticization under moist heat. As the moisture evaporates during hot air drying, the chitin molecular chains reform in a mobile state, forming intermolecular hydrogen bonds and a disordered network cross-linked structure. In this embodiment, before adding the shrimp to the cooking liquid, the softened shrimp are rinsed 2-3 times with water, and then soaked in a sodium bicarbonate solution at 0.1%-0.3% of the shrimp's weight.

[0046] Step 3: After constant temperature steaming, dry the shrimp until the moisture content is 18-22%. The drying is done by hot air drying at a temperature of 60-65℃ and a wind speed of 1.5-2m / s, or by vacuum freeze drying at a vacuum degree of -0.08~0.1MPa and a sublimation temperature of -40~-30℃.

[0047] This embodiment also provides a soft-skinned shrimp prepared by the above method.

[0048] Comparative Example Take 1 kg of fresh whiteleg shrimp, wash them, and put them directly into salted boiling water (100℃) for 5 minutes. Remove them, drain them, and dry them with hot air at 65℃ until the moisture content is 20%. The finished shrimp shells are hard and difficult to peel, the meat is dry and tough, the flavor is monotonous with only saltiness, and the color is dark with browning.

[0049] Using Example 1 as the experimental group and the comparative example as the control group, the shelf life of shrimp was tested, as shown in Table 1 below. Table 1 (Detection temperature 35°C) Due to the initial antibacterial effect of lactic acid bacteria treatment and the antioxidant properties of Maillard reaction products, the microbial growth rate of the experimental group products was significantly slower than that of the control group, and the expected shelf life was extended to more than 8 months, which verified the advantages of this invention in ensuring product safety and shelf life.

[0050] Conclusion: The soft-shelled shrimp prepared by the method of this invention is significantly superior to products prepared by traditional methods in terms of shell softening, meat tenderness, and flavor richness, and also exhibits high quality stability.

[0051] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by any combination of the above-described technical features or their equivalents without departing from the inventive concept. For example, the above features may have similar functions to (but are not limited to) those disclosed in this application.

Claims

1. A method for preparing soft-shelled shrimp, specifically including the following steps: Mix shrimp and lactic acid bacteria fermentation liquid at a weight ratio of 1:3, soak for 2.5-3 hours to soften the shrimp shell and retain the chitin fiber skeleton of the shrimp shell. Using water as the base liquid, add 0.08-0.12% cysteine, 0.08-0.12% glutamic acid, 0.08-0.12% glycine, 0.08-0.12% alanine, 0.3-0.7% glucose, 0.008-0.012% astaxanthin, and 0.003-0.007% ferrous sulfate by weight percentage to obtain the cooking liquor; Heat the cooking liquid to 70-85℃, add the shrimp into the cooking liquid, and steam at a constant temperature for 15-40 minutes. The shrimp are dried until the moisture content is 18-22%.

2. The method for preparing soft-shelled shrimp according to claim 1, characterized in that, The preparation process of the lactic acid bacteria fermentation broth is as follows: brown sugar and brewer's yeast are added to water as a nutrient substrate to obtain a culture medium, lactic acid bacteria are inoculated into the culture medium, and fermentation is carried out at 30-35℃ until the pH is 3.0~5.0 to obtain the lactic acid bacteria fermentation broth.

3. The method for preparing soft-shelled shrimp according to claim 2, characterized in that, The amount of brown sugar added is 5-8% of the total mass of the culture medium, and the amount of brewer's yeast added is 0.5-3%.

4. The method for preparing soft-shelled shrimp according to claim 1, characterized in that, The cooking liquid also contains 0.1-0.3% by weight of trimethylamine oxide.

5. The method for preparing soft-shelled shrimp according to claim 1, characterized in that, The lactic acid bacteria strain is Lactobacillus plantarum or Lactobacillus acidophilus, and the inoculation amount is 3-5% (v / v).

6. The preparation method according to claim 1, characterized in that, The drying process is hot air drying at a temperature of 60-65℃ and an air velocity of 1.5-2m / s, or vacuum freeze drying at a vacuum degree of -0.08~0.1MPa and a sublimation temperature of -40~-30℃.

7. The preparation method according to claim 6, characterized in that, After being steamed at a constant temperature for 15-30 minutes, chitin undergoes thermoplasticization under humid and hot conditions. During hot air drying, the moisture evaporates, and the chitin molecular chain segments reform intermolecular hydrogen bonds in a mobile state, forming a disordered network cross-linked structure.

8. The preparation method according to claim 1, characterized in that, Soak for 2.5-3 hours to soften the shrimp shells while preserving the chitin fiber skeleton, including: Step 1: Lactic acid bacteria fermentation and metabolism produce lactic acid and acetic acid, which lowers the pH of the system to 3.0~5.0, dissolves the calcium carbonate in the shrimp shell, and exposes the proteins in the shrimp shell that are wrapped in the inorganic phase to the lactic acid bacteria fermentation liquid. At the same time, the organic acids produced by the metabolism of lactic acid bacteria decompose the connective tissue between the shrimp shell and the shrimp meat. Step 2: Under acidic conditions, the lactic acid bacteria strain continuously secretes extracellular proteases, which hydrolyze the peptide bonds of the chitin-protein network structure in the shrimp shell, degrading the large protein molecules into polypeptides and amino acids, while retaining the chitin fiber skeleton. Step 3: The dissolution of calcium carbonate and protein degradation occur simultaneously, while the acidic environment inhibits contamination by other bacteria.

9. The preparation method according to claim 1, characterized in that, Before adding the shrimp to the cooking liquid, rinse the softened shrimp 2-3 times with water, and then soak them in a baking soda solution of 0.1%-0.3% by weight of the shrimp.

10. A soft-skinned shrimp, characterized in that, Prepared by the method described in any one of claims 1-9.

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