Preservative for fresh tilapia mossambica blocks and preparation method thereof

Abstract

The invention provides a fresh tilapia mossambica block preservative and a preparation method thereof, the fresh tilapia mossambica block preservative comprises the following raw materials: natural plant extract, modified biological polysaccharide, organic acid, natural antibacterial peptide, a humectant, deionized water and the like, and propolis extract and astaxanthin can be selected to enhance the effect; wherein the natural plant extract is corncob, zingiber mioga and tartary buckwheat bran extract; the modified biological polysaccharide is obtained by modifying chitosan quaternary ammonium salt, laminarin, cell wall polysaccharide and carboxylic acid. The fresh-keeping agent is prepared through ultrasonic mixing, multilayer electrostatic deposition and other technologies, through the synergistic effect of all the raw materials, a multilayer coating structure is formed through electrostatic deposition, microbial growth can be inhibited, gas exchange can be controlled, water loss can be reduced, the fresh-keeping period of tilapia mossambica blocks can be effectively prolonged, and the quality of the tilapia mossambica blocks can be kept.

Description

Technical Field

[0001] The invention relates to the technical field of aquatic product preservation, and in particular to a preservative for fresh tilapia pieces and a preparation method thereof. Background Art

[0002] Tilapia is a freshwater farmed fish that is the focus of scientific research and cultivation in the world's aquaculture industry. It has the advantages of fast growth, high yield, omnivorous diet, and few diseases. It is an important freshwater farmed species and export-earning aquatic product in my country. However, during the process of fishing, transportation, processing and sales, tilapia is prone to spoilage due to the growth and reproduction of microorganisms, fat oxidation, protein decomposition, etc., which affects its quality and shelf life.

[0003] At present, the main preservation methods for fresh tilapia pieces include low-temperature preservation, controlled atmosphere preservation, coating preservation, chemical preservative preservation, etc. Although low-temperature preservation can effectively inhibit the growth of microorganisms and the activity of enzymes, it has high energy consumption and is difficult to maintain a constant low temperature during transportation and sales. The cost of controlled atmosphere preservation is high and strict requirements are placed on packaging materials and equipment; although coating preservation has the advantages of simple operation and low cost, the existing coating materials have problems such as poor film-forming properties, high air permeability, and insufficient antibacterial properties, making it difficult to achieve the ideal preservation effect. Although chemical preservatives have significant preservation effects, there are chemical residues and safety issues, which may pose a potential threat to human health; although some existing preservatives can play a certain preservation role in a short period of time, as the storage time increases, the preservation effect gradually weakens and cannot effectively maintain the quality of fresh fish, such as freshness, taste, and nutritional content. For example, some traditional preservatives, such as some chemical synthetic preservatives, may pose certain safety hazards and potential threats to human health if used excessively or in long-term contact; preservatives may leave residues in the fish, affecting food safety. Moreover, they have a single function and can only inhibit the growth of microorganisms or slow down oxidation, which cannot comprehensively solve the quality deterioration problem faced by fresh fish during storage, transportation and sales. It also affects the quality of fish. While playing a preservation role, some preservatives may change the original flavor, color and texture of the fish, affecting consumer acceptance.

[0004] Therefore, it is particularly important to develop a safe, effective, environmentally friendly and cost-effective fresh tilapia fillet preservative. In the prior art, although a variety of natural preservative ingredients have been applied in the field of food preservation, the formula and preparation process still need to be further optimized to meet the specific preservation needs of fresh tilapia fillets in order to improve the preservation effect and meet market demand. Summary of the invention

[0005] In view of this, the present invention provides a preservative for fresh tilapia pieces and a preparation method thereof to solve the above problems.

[0006] The technical solution of the present invention is achieved as follows: a preservative for fresh tilapia pieces: comprising the following raw materials in parts by weight: 20-40 parts of natural plant extracts, 10-30 parts of modified biopolysaccharides, 5-15 parts of organic acids, 0.5-2 parts of natural antimicrobial peptides, 2-5 parts of moisturizers, and 3-8 parts of deionized water; the natural plant extracts are corn cob extracts, radix strychnifolia extracts, and buckwheat bran extracts in a mass ratio of (14-28):(7-9):(22-32); the modified biopolysaccharides are biopolysaccharides modified with carboxylic acids to obtain fat-soluble biopolysaccharides; the biopolysaccharides are chitosan quaternary ammonium salts, laminarin, and cell wall polysaccharides in a mass ratio of (5-10):(2-8):(1-3).

[0007] Furthermore, a preservative for fresh tilapia pieces comprises the following raw materials in parts by weight: 30 parts of natural plant extract, 20 parts of modified biopolysaccharide, 10 parts of organic acid, 1.5 parts of natural antimicrobial peptide, 3 parts of moisturizer, and 5 parts of deionized water.

[0008] Furthermore, a preservative for fresh tilapia pieces also includes the following raw materials in parts by weight: 4-8 parts of propolis extract and 2-7 parts of astaxanthin.

[0009] Furthermore, the organic acid is selected from one or more of phytic acid, lactic acid, acetic acid, ascorbic acid or citric acid.

[0010] Furthermore, the natural antimicrobial peptides are protamine peptide, nisin and melittin in a mass ratio of (11-15):(8-12):(2-4), and the average molecular weight is ≤1 kDa.

[0011] Furthermore, the moisturizing agent is selected from one or a combination of glycerin, propylene glycol, sorbitol, maltitol, sodium hyaluronate, and sodium carboxymethyl cellulose.

[0012] Furthermore, the modification method of the modified biopolysaccharide comprises the following steps:

[0013] A. Polysaccharide dissolution: Add the biopolysaccharide to deionized water and stir at 40-60°C and 300-500 rpm for 2-4 hours until dissolved to form a uniform and transparent polysaccharide solution. The mass volume ratio of the biopolysaccharide to deionized water is 1:20-50 g / mL, and set aside.

[0014] B. Activation: Carboxylic acid, N,N-dicyclohexylcarbodiimide DCC and 4-dimethylaminopyridine DMAP are mixed in a molar ratio of 1:(1.2-1.5):(0.1-0.2), and then a solvent is added to the mixture and stirred at 200-300 rpm in an ice water bath at 0-5°C for 30-60 minutes to form a carboxylic acid solution. The ratio of the carboxylic acid to the solvent is 1 mmol:2-5 mL, and the solvent is dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0015] C. Esterification: Add the activated carboxylic acid solution dropwise into the dissolved polysaccharide solution to make the volume ratio of the carboxylic acid solution to the polysaccharide solution be 1:2-5, react at 40-60°C with a stirring speed of 300-500 rpm for 12-24 hours, purify and dry to obtain fat-soluble biopolysaccharide.

[0016] Furthermore, the carboxylic acid is stearic acid or palmitic acid.

[0017] Furthermore, a method for preparing a preservative for fresh tilapia pieces comprises the following steps:

[0018] S1. Preliminary mixing: taking the natural plant extract and astaxanthin according to the above weight parts, ultrasonically mixing them, the ultrasonic power is 50-100 W, the ultrasonic frequency is 20-40 kHz, the ultrasonic time is 5-15 min, the ultrasonic temperature is 20-40 ° C, grinding to a particle size of 10-100 μm, and obtaining a mixed material for standby use;

[0019] S2, secondary mixing: first add deionized water into the reaction container, add organic acid, natural antimicrobial peptide, and propolis extract in sequence while stirring at 300-500 rpm with a magnetic stirrer, and stir until completely dissolved to obtain solution I;

[0020] S3, one layer of deposition: the above mixture is spread on the electrode plate, solution I is sprayed under the action of the electrostatic field to form droplets of 10-50 μm, and the droplets are deposited on the surface of the powder while stirring, the spraying rate is 0.5-1 mL / h, and the deposition is 1-3 hours to obtain a deposition layer I;

[0021] S4, second layer deposition: using a spray gun to deposit the fat-soluble biopolysaccharide on the deposition layer I under the action of an electrostatic field, with a powder feeding rate of 0.1-0.5 g / min and a deposition time of 10-15 min to obtain a deposition layer II;

[0022] S5, three-layer deposition: finally, the moisturizer is deposited on the surface of the deposition layer II according to the above method, with a spraying speed of 0.3-0.5 mL / h and a deposition time of 5-10 min to obtain a deposition layer III. The solution system with the deposited powder is filtered and centrifuged to separate the undeposited solution, excess powder, etc. The product after deposition is collected as the preservative.

[0023] Furthermore, the environment temperature of the three electrostatic depositions is 20-25° C., the relative humidity is 40%-60%, the electrostatic deposition voltage is 5-30 kV, and the current is 0.1-1.0 mA.

[0024] The corncob extract is prepared by mixing corncob powder and hot water, extracting the mixture by ultrasonic wave, centrifuging and concentrating the supernatant, mixing the concentrate with anhydrous ethanol, filtering, and drying to obtain the corncob extract.

[0025] The extract of the radix sibiricum is prepared by taking dried radix sibiricum rhizomes as raw materials through a hot extraction method and filtering, concentrating, drying and other steps to obtain the desired radix sibiricum extract.

[0026] The tartary buckwheat bran extract is prepared by crushing and sieving the tartary buckwheat bran, adding cellulase for enzymolysis, and obtaining the tartary buckwheat bran extract.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Highly effective antibacterial and fresh-keeping agent: The preservative combines a variety of effective ingredients such as natural plant extracts, modified biopolysaccharides, organic acids, and natural antimicrobial peptides. These ingredients work synergistically to effectively inhibit the growth of microorganisms and enzymatic hydrolysis of tilapia fillets during storage, and have inhibitory and killing effects on a variety of bacteria and fungi. The average molecular weight of ≤1kDa makes it easier for it to exert its antibacterial effect, effectively inhibit the growth of microorganisms, delay the spoilage of tilapia fillets, significantly extend the shelf life, and maintain the freshness and nutritional value of the fish fillets.

[0029] (2) Antioxidation and quality maintenance: The natural plant extracts and astaxanthin in the formula have strong antioxidant properties, which can effectively inhibit fat oxidation in tilapia fillets and reduce the generation of odor and rancidity; propolis extract is rich in a variety of bioactive ingredients, which synergizes with astaxanthin to further enhance the antioxidant effect and maintain the color, flavor and nutritional value of the fish fillets; in addition, the moisturizer helps maintain the moisture content of the tilapia fillets, prevents the taste from deteriorating and nutritional loss due to water loss, and maintains the quality and taste of the fish fillets.

[0030] (3) Advantages of multi-layer coating structure: The three-layer deposition structure formed by electrostatic deposition technology allows the various components of the preservative to be distributed and act in an orderly and stable manner. The first layer of deposition mixes natural plant extracts with astaxanthin, which first exerts antioxidant and preliminary antibacterial effects; the second layer of fat-soluble biopolysaccharides can form a physical barrier to prevent the invasion of external oxygen, moisture and microorganisms; the third layer of moisturizer further locks in moisture and maintains the moistness of the fish pieces. This multi-layer structure works synergistically to provide comprehensive and long-lasting freshness protection for tilapia pieces.

[0031] (4) High safety: All ingredients of the preservative are derived from natural substances, without chemical synthetic preservatives, and are friendly to human health and the environment, meeting the requirements of modern consumers for food safety and environmental protection. DETAILED DESCRIPTION

[0032] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0033] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0034] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0035] Example 1

[0036] A preservative for fresh tilapia pieces: comprising the following raw materials in parts by weight: 20 parts of natural plant extract, 10 parts of modified biopolysaccharide, 5 parts of phytic acid, 0.5 parts of natural antimicrobial peptide, 2 parts of glycerol, and 3 parts of deionized water;

[0037] The natural plant extracts are corn cob extract, radix strychnifolia extract and buckwheat bran extract in a mass ratio of 14:7:22;

[0038] The natural antimicrobial peptides are protamine peptide, nisin and melittin in a mass ratio of 11:8:2;

[0039] The modified biopolysaccharide is obtained by modifying biopolysaccharide with stearic acid to obtain a fat-soluble biopolysaccharide, wherein the biopolysaccharide is chitosan quaternary ammonium salt, laminarin and cell wall polysaccharide in a mass ratio of 5:2:1;

[0040] The modification method of the modified biopolysaccharide comprises the following steps:

[0041] A. Polysaccharide dissolution: Add the biopolysaccharide to deionized water and stir at 40°C and 300 rpm for 2 h until dissolved to form a uniform and transparent polysaccharide solution. The mass volume ratio of the biopolysaccharide to deionized water is 1:20 g / mL and set aside.

[0042] B. Activation: Stearic acid, N,N-dicyclohexylcarbodiimide DCC and 4-dimethylaminopyridine DMAP were mixed in a molar ratio of 1:1.2:0.1, and then a solvent was added to the mixture and stirred at 200 rpm in an ice water bath at 0°C for 30 min to form a stearic acid solution, wherein the ratio of stearic acid to solvent was 1 mmol:2 mL, and the solvent was dimethyl sulfoxide (DMSO);

[0043] C. Esterification: Add the activated stearic acid solution dropwise into the dissolved polysaccharide solution to make the volume ratio of stearic acid solution to polysaccharide solution 1:2, react at 40°C with a stirring speed of 300 rpm for 12 hours, purify and dry to obtain fat-soluble biopolysaccharide.

[0044] Example 2

[0045] A preservative for fresh tilapia pieces: comprising the following raw materials in parts by weight: 40 parts of natural plant extract, 30 parts of modified biopolysaccharide, 15 parts of lactic acid, 2 parts of natural antimicrobial peptide, 5 parts of propylene glycol, and 8 parts of deionized water;

[0046] The natural plant extracts are corn cob extract, radix strychnifolia extract and buckwheat bran extract in a mass ratio of 28:9:32;

[0047] The natural antimicrobial peptides are protamine peptide, nisin and melittin in a mass ratio of 15:12:4;

[0048] The modified biopolysaccharide is obtained by modifying biopolysaccharide with palmitic acid to obtain a fat-soluble biopolysaccharide, wherein the biopolysaccharide is chitosan quaternary ammonium salt, laminarin and cell wall polysaccharide in a mass ratio of 10:8:3;

[0049] The modification method of the modified biopolysaccharide comprises the following steps:

[0050] A. Polysaccharide dissolution: Add the biopolysaccharide to deionized water and stir at 60°C and 500 rpm for 4 h until dissolved to form a uniform and transparent polysaccharide solution. The mass volume ratio of the biopolysaccharide to deionized water is 1:50 g / mL and set aside.

[0051] B. Activation: palmitic acid, N,N-dicyclohexylcarbodiimide DCC and 4-dimethylaminopyridine DMAP were mixed in a molar ratio of 1:1.5:0.2, and then a solvent was added to the mixture and stirred at 300 rpm in an ice water bath at 5°C for 60 minutes to form a palmitic acid solution. The ratio of palmitic acid to solvent was 1 mmol:5 mL, and the solvent was N,N-dimethylformamide (DMF).

[0052] C. Esterification: Add the activated palmitic acid solution dropwise into the dissolved polysaccharide solution to make the volume ratio of palmitic acid solution to polysaccharide solution 1:5, react at 60°C with a stirring speed of 500 rpm for 24 hours, purify and dry to obtain fat-soluble biopolysaccharide.

[0053] Example 3

[0054] A preservative for fresh tilapia pieces: comprising the following raw materials in parts by weight: 30 parts of natural plant extract, 20 parts of modified biopolysaccharide, 10 parts of organic acid, 1.5 parts of natural antimicrobial peptide, 3 parts of moisturizer, and 5 parts of deionized water;

[0055] The natural plant extracts are corn cob extract, radix strychnifolia extract and buckwheat bran extract in a mass ratio of 21:8:27;

[0056] The natural antimicrobial peptides are protamine peptide, nisin and melittin in a mass ratio of 12:10:3;

[0057] The modified biopolysaccharide is obtained by modifying biopolysaccharide with stearic acid to obtain a fat-soluble biopolysaccharide, wherein the biopolysaccharide is chitosan quaternary ammonium salt, laminarin and cell wall polysaccharide in a mass ratio of 8:6:2;

[0058] The modification method of the modified biopolysaccharide comprises the following steps:

[0059] A. Polysaccharide dissolution: Add the biopolysaccharide to deionized water and stir at 50°C and 400 rpm for 3 h until dissolved to form a uniform and transparent polysaccharide solution. The mass volume ratio of the biopolysaccharide to deionized water is 1:35 g / mL and set aside.

[0060] B. Activation: Stearic acid, N,N-dicyclohexylcarbodiimide DCC and 4-dimethylaminopyridine DMAP were mixed in a molar ratio of 1:1.3:0.1, and then a solvent was added to the mixture, stirred at 250 rpm in an ice water bath at 3°C ​​for 50 min to form a stearic acid solution, wherein the ratio of stearic acid to solvent was 1 mmol:3 mL, and the solvent was dimethyl sulfoxide (DMSO);

[0061] C. Esterification: Add the activated stearic acid solution dropwise into the dissolved polysaccharide solution to make the volume ratio of the stearic acid solution to the polysaccharide solution be 1:3, react at 50°C with a stirring speed of 400 rpm for 18 hours, purify and dry to obtain the fat-soluble biopolysaccharide;

[0062] The above examples 1-3 adopt the following preparation method:

[0063] S1, preliminary mixing: taking the natural plant extract and astaxanthin according to the above weight parts, ultrasonically mixing them, the ultrasonic power is 80W, the ultrasonic frequency is 30kHz, the ultrasonic time is 10min, the ultrasonic temperature is 30°C, and grinding them to a particle size of 50μm to obtain a mixed material for standby use;

[0064] S2, secondary mixing: first add deionized water into the reaction container, add organic acid, natural antimicrobial peptide, and propolis extract in sequence while stirring with a magnetic stirrer at 400 rpm, and stir until completely dissolved to obtain solution I;

[0065] S3, one layer of deposition: the above mixture is spread on the electrode plate, solution I is sprayed under the action of the electrostatic field to form 30 μm droplets, and the droplets are deposited on the surface of the powder while stirring, the spraying rate is 0.8 mL / h, and the deposition is carried out for 2 hours to obtain a deposition layer I;

[0066] S4, second layer deposition: the fat-soluble biopolysaccharide is deposited on the deposition layer I using a spray gun under the action of an electrostatic field, with a powder feeding rate of 0.3 g / min and a deposition time of 13 min to obtain a deposition layer II;

[0067] S5, three-layer deposition: finally, the moisturizing agent is deposited on the surface of the deposition layer II according to the above method, the spraying speed is 0.4mL / h, the deposition time is 8min, and the deposition layer III is obtained, which is filtered and centrifuged. The ambient temperature of the above three electrostatic depositions is 22°C, the relative humidity is 50%, the electrostatic deposition voltage is 20kV, and the current is 0.5mA. The solution system with the deposited powder is separated from the undeposited solution, excess powder, etc., and the product after deposition is collected as the preservative.

[0068] Example 4

[0069] A preservative for fresh tilapia pieces: comprising the following raw materials in parts by weight: 30 parts of natural plant extract, 20 parts of modified biopolysaccharide, 10 parts of organic acid, 1.5 parts of natural antimicrobial peptide, 3 parts of moisturizer, and 5 parts of deionized water;

[0070] The natural plant extracts are corn cob extract, radix strychnifolia extract and buckwheat bran extract in a mass ratio of 21:8:27;

[0071] The natural antimicrobial peptides are protamine peptide, nisin and melittin in a mass ratio of 12:10:3;

[0072] The modified biopolysaccharide is obtained by modifying biopolysaccharide with stearic acid to obtain a fat-soluble biopolysaccharide, wherein the biopolysaccharide is chitosan quaternary ammonium salt, laminarin and cell wall polysaccharide in a mass ratio of 8:6:2;

[0073] The modification method of the modified biopolysaccharide comprises the following steps:

[0074] A. Polysaccharide dissolution: Add the biopolysaccharide to deionized water and stir at 50°C and 400 rpm for 3 h until dissolved to form a uniform and transparent polysaccharide solution. The mass volume ratio of the biopolysaccharide to deionized water is 1:35 g / mL and set aside.

[0075] B. Activation: Stearic acid, N,N-dicyclohexylcarbodiimide DCC and 4-dimethylaminopyridine DMAP were mixed in a molar ratio of 1:1.3:0.1, and then a solvent was added to the mixture, stirred at 250 rpm in an ice water bath at 3°C ​​for 50 min to form a stearic acid solution, wherein the ratio of stearic acid to solvent was 1 mmol:3 mL, and the solvent was dimethyl sulfoxide (DMSO);

[0076] C. Esterification: Add the activated stearic acid solution dropwise into the dissolved polysaccharide solution to make the volume ratio of the stearic acid solution to the polysaccharide solution be 1:3, react at 50°C with a stirring speed of 400 rpm for 18 hours, purify and dry to obtain the fat-soluble biopolysaccharide;

[0077] The above-mentioned Example 4 adopts the following preparation method:

[0078] S1, preliminary mixing: taking the natural plant extract and astaxanthin according to the above weight parts, ultrasonically mixing them, the ultrasonic power is 50W, the ultrasonic frequency is 20kHz, the ultrasonic time is 5min, the ultrasonic temperature is 20°C, and grinding them to a particle size of 10μm to obtain a mixed material for standby use;

[0079] S2, secondary mixing: first add deionized water into the reaction container, add organic acid, natural antimicrobial peptide, and propolis extract in sequence while stirring with a magnetic stirrer at 300 rpm, and stir until completely dissolved to obtain solution I;

[0080] S3, one layer deposition: the above mixture is spread on the electrode plate, solution I is sprayed under the action of the electrostatic field to form 10 μm droplets, and the droplets are deposited on the surface of the powder while stirring, the spraying rate is 0.5 mL / h, and the deposition is 1 h to obtain a deposition layer I;

[0081] S4, second layer deposition: the fat-soluble biopolysaccharide is deposited on the deposition layer I using a spray gun under the action of an electrostatic field, with a powder feeding rate of 0.1 g / min and a deposition time of 10 min to obtain a deposition layer II;

[0082] S5, three-layer deposition: finally, the moisturizing agent is deposited on the surface of the deposition layer II according to the above method, the spraying speed is 0.3mL / h, the deposition time is 5min, and the deposition layer III is obtained, which is filtered and centrifuged. The ambient temperature of the above three electrostatic depositions is 20°C, the relative humidity is 40%, the electrostatic deposition voltage is 5kV, and the current is 0.1mA. The solution system with the deposited powder is separated from the undeposited solution, excess powder, etc., and the product after deposition is collected as the preservative.

[0083] Example 5

[0084] A preservative for fresh tilapia pieces: comprising the following raw materials in parts by weight: 30 parts of natural plant extract, 20 parts of modified biopolysaccharide, 10 parts of organic acid, 1.5 parts of natural antimicrobial peptide, 3 parts of moisturizer, and 5 parts of deionized water;

[0085] The natural plant extracts are corn cob extract, radix strychnifolia extract and buckwheat bran extract in a mass ratio of 21:8:27;

[0086] The natural antimicrobial peptides are protamine peptide, nisin and melittin in a mass ratio of 12:10:3;

[0087] The modified biopolysaccharide is obtained by modifying biopolysaccharide with stearic acid to obtain a fat-soluble biopolysaccharide, wherein the biopolysaccharide is chitosan quaternary ammonium salt, laminarin and cell wall polysaccharide in a mass ratio of 8:6:2;

[0088] The modification method of the modified biopolysaccharide comprises the following steps:

[0089] A. Polysaccharide dissolution: Add the biopolysaccharide to deionized water and stir at 50°C and 400 rpm for 3 h until dissolved to form a uniform and transparent polysaccharide solution. The mass volume ratio of the biopolysaccharide to deionized water is 1:35 g / mL and set aside.

[0090] B. Activation: Stearic acid, N,N-dicyclohexylcarbodiimide DCC and 4-dimethylaminopyridine DMAP were mixed in a molar ratio of 1:1.3:0.1, and then a solvent was added to the mixture, stirred at 250 rpm in an ice water bath at 3°C ​​for 50 min to form a stearic acid solution, wherein the ratio of stearic acid to solvent was 1 mmol:3 mL, and the solvent was dimethyl sulfoxide (DMSO);

[0091] C. Esterification: Add the activated stearic acid solution dropwise into the dissolved polysaccharide solution to make the volume ratio of the stearic acid solution to the polysaccharide solution be 1:3, react at 50°C with a stirring speed of 400 rpm for 18 hours, purify and dry to obtain the fat-soluble biopolysaccharide;

[0092] The above-mentioned Example 5 adopts the following preparation method:

[0093] S1, preliminary mixing: taking the natural plant extract and astaxanthin according to the above weight parts, ultrasonically mixing them, the ultrasonic power is 100 W, the ultrasonic frequency is 40 kHz, the ultrasonic time is 15 min, the ultrasonic temperature is 40 ° C, grinding to a particle size of 100 μm, to obtain a mixed material, and set aside;

[0094] S2, secondary mixing: first add deionized water into the reaction container, add organic acid, natural antimicrobial peptide, and propolis extract in sequence while stirring with a magnetic stirrer at 500 rpm, and stir until completely dissolved to obtain solution I;

[0095] S3, one layer deposition: the above mixture is spread on the electrode plate, solution I is sprayed under the action of the electrostatic field to form 50 μm droplets, and the droplets are deposited on the surface of the powder while stirring, the spraying rate is 1 mL / h, and the deposition is 3 hours to obtain a deposition layer I;

[0096] S4, second layer deposition: the fat-soluble biopolysaccharide is deposited on the deposition layer I using a spray gun under the action of an electrostatic field, with a powder feeding rate of 0.5 g / min and a deposition time of 15 min to obtain a deposition layer II;

[0097] S5, three-layer deposition: finally, the moisturizing agent is deposited on the surface of the deposition layer II according to the above method, the spraying speed is 0.5mL / h, the deposition time is 10min, and the deposition layer III is obtained, which is filtered and centrifuged. The ambient temperature of the above three electrostatic depositions is 25°C, the relative humidity is 60%, the electrostatic deposition voltage is 30kV, and the current is 1.0mA. The solution system with the deposited powder is separated from the undeposited solution, excess powder, etc., and the product after deposition is collected as the preservative.

[0098] Comparative Example 1

[0099] The difference between this comparative example and Example 3 is that a preservative for fresh tilapia chunks comprises the following raw materials in parts by weight: 15 parts of natural plant extract, 35 parts of modified biopolysaccharide, 3 parts of organic acid, 3 parts of natural antimicrobial peptide, 1 part of moisturizer, and 12 parts of deionized water.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 3 is that the natural plant extracts are sage extract, tea polyphenols and rosemary extract in a mass ratio of 21:8:27.

[0102] Comparative Example 3

[0103] The difference between this comparative example and Example 3 is that the biopolysaccharide in the preservative of the fresh tilapia pieces is not modified.

[0104] Comparative Example 4

[0105] The difference between this comparative example and Example 3 is that the biopolysaccharide is chitosan, sodium alginate and carrageenan in a mass ratio of 8:6:2.

[0106] Comparative Example 5

[0107] The difference between this comparative example and Example 3 is that the preservative does not undergo the three-layer electrostatic deposition step. Specifically, natural plant extracts, modified biopolysaccharides, organic acids, natural antimicrobial peptides, 3 parts of moisturizers, deionized water, propolis extracts, and astaxanthin are fully ultrasonically mixed, with an ultrasonic power of 80 W, an ultrasonic frequency of 30 kHz, an ultrasonic time of 50 min, and an ultrasonic temperature of 30° C. to obtain the preservative.

[0108] Effect test

[0109] 1. Experimental methods:

[0110] (I) Processing of Tilapia Blocks: Fresh tilapia was slaughtered, the head, tail, viscera and scales were removed, the fish were rinsed with distilled water, and cut into fish blocks of uniform size (5 cm×5 cm×2 cm). The fish blocks were randomly divided into 10 groups, each with 15 blocks. The preservatives of Examples 1-5 and Comparative Examples 1-5 of the present invention were diluted to 10 times the volume by adding deionized water, and then sprayed on the surfaces of the 10 groups of experimental fish blocks respectively to evenly cover the surfaces of the fish blocks.

[0111] (ii) Storage conditions: Place the packaged tilapia pieces in a refrigerated environment at 4°C to simulate cold chain storage conditions.

[0112] 2. Index determination:

[0113] On the 0th, 5th and 15th days of storage, the following indicators were measured for 10 groups of fish pieces:

[0114] 1. Determination of total bacterial count: According to GB4789.2-2016 "National Food Safety Standard Food Microbiology Examination Colony Count Determination", determine the total bacterial count on the surface of the fish block.

[0115] 2. Determination of volatile basic nitrogen (TVB-N) content: The semi-micro Kjeldahl method was used to determine the TVB-N content in fish fillets.

[0116] 3. Determination of thiobarbituric acid (TBA) value: The TBA value in the muscle tissue of fish blocks was determined by TBA colorimetry to reflect the degree of fat oxidation.

[0117] 4. Juice loss rate (%) = ((m1-m2) / m1) × 100%; m1 represents the mass of the tilapia block before the fresh-keeping treatment, that is, the initial mass, and m2 represents the mass of the tilapia block after the fresh-keeping treatment, that is, the final mass.

[0118] 3. Results and data

[0119] Table 1: Initial fish block data

[0120]

[0121] Table 2: Result data of 5-day storage

[0122]

[0123] Table 3: Result data of 10-day storage

[0124]

[0125]

[0126] Table 4: Result data of 15-day storage

[0127]

[0128] As can be seen from the above results, after 5, 10 and 15 days of preservation, the total bacteria count of the embodiment group is generally lower than that of the comparative group, especially in Example 3, whose total bacteria count increases the slowest, indicating that its preservation method is the most effective. The TVB-N value of the embodiment group increases relatively slowly, among which the TVB-N value of Example 3 increases the least, indicating that its preservation method can better maintain the freshness of the fish pieces. The TVB-N value of the comparative group increases rapidly, reflecting a faster deterioration rate. In all groups, the TBA value increases over time, but the growth rate of the embodiment group is relatively small, especially in Example 3, whose TBA value increases the slowest, indicating that its preservation method can better inhibit lipid oxidation. The juice loss rate reflects the water retention capacity of the fish pieces during storage. The juice loss rate of the embodiment group is generally lower than that of the comparative group, among which the juice loss rate of Example 3 is the lowest, indicating that its preservation method can better maintain the moisture of the fish pieces. The juice loss rate of the comparative group is high, especially after long-term storage, such as 15 days, the juice loss is particularly obvious. In the example group, Example 3 showed the best effect in terms of total bacteria count, TVB-N value, TBA value and juice loss rate, indicating that its preservation method is the most superior.

[0129] Comparison between Example 3 and Comparative Example 1 shows that the raw material ratio of the preservative of the present invention plays a better role in the preservation process.

[0130] Compared with Comparative Example 2, Example 3 of the present invention selects natural plant extracts of corn cob extract, radix schizonepeta extract and buckwheat bran extract to mix with astaxanthin, wherein the corn cob extract is used as a biofilm carrier to indirectly improve the preservation effect of fish chunks; the radix schizonepeta extract may extend the shelf life of fish chunks through its antioxidant, anti-inflammatory and antibacterial properties; and the buckwheat bran extract directly exhibits strong antibacterial properties and significant preservation effects.

[0131] Compared with Comparative Examples 3 and 4, the present invention has scientifically selected chitosan quaternary ammonium salt, laminarin and cell wall polysaccharide combinations, which have good antibacterial, antioxidant and film-forming properties. The modified biopolysaccharides enhance their antibacterial properties, can inhibit the growth of bacteria on the surface of tilapia blocks, extend the shelf life, enhance their antioxidant properties, help reduce oxidation reactions in tilapia blocks, reduce fat oxidation and odor generation; esterification modification can optimize the molecular structure of polysaccharides and improve their film-forming properties. Good film-forming properties help to form a tight and lasting protective film on the surface of tilapia blocks, help to maintain the moisture of tilapia blocks, prevent water loss, further block the influence of external factors on the fish blocks, and maintain their freshness and quality;

[0132] Compared with Comparative Example 5, Example 3 prepares a mixture and a solution I respectively, deposits the solution I on the mixture, and then uses the modified biopolysaccharide and the humectant to use electrostatic deposition in sequence, so that the preservative forms a multi-layer coating structure, provides a physical barrier, prevents external air, moisture and microorganisms from directly contacting the fish block, reduces the invasion and reproduction of microorganisms, and thus delays the corruption and deterioration of the fish block. This structure makes it difficult for adverse external factors to penetrate through layers of barriers, and provides a more stable and safe storage environment for the fish block; at the same time, the preservative ingredients are slowly and continuously released, and can be gradually released to the surface of the fish block within a certain period of time, play a preservative role, and thus extend the shelf life.

[0133] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preservative for fresh tilapia pieces, characterized in that: The invention comprises the following raw materials in parts by weight: 20-40 parts of natural plant extracts, 10-30 parts of modified biopolysaccharides, 5-15 parts of organic acids, 0.5-2 parts of natural antimicrobial peptides, 2-5 parts of moisturizers, and 3-8 parts of deionized water; the natural plant extracts are corn cob extracts, radix strychnifoliae extracts, and buckwheat bran extracts in a mass ratio of (14-28):(7-9):(22-32); the modified biopolysaccharides are fat-soluble biopolysaccharides obtained by modifying biopolysaccharides with carboxylic acids; and the biopolysaccharides are chitosan quaternary ammonium salts, laminarin, and cell wall polysaccharides in a mass ratio of (5-10):(2-8):(1-3).

2. A preservative for fresh tilapia pieces as claimed in claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 30 parts of natural plant extract, 20 parts of modified biopolysaccharide, 10 parts of organic acid, 1.5 parts of natural antimicrobial peptide, 3 parts of moisturizer and 5 parts of deionized water.

3. The preservative for fresh tilapia pieces as claimed in claim 1, characterized in that: The invention also comprises the following raw materials in parts by weight: 4-8 parts of propolis extract and 2-7 parts of astaxanthin.

4. The preservative for fresh tilapia pieces as claimed in claim 1, characterized in that: The organic acid is selected from one or more of phytic acid, lactic acid, acetic acid, ascorbic acid or citric acid.

5. The preservative for fresh tilapia pieces as claimed in claim 1, characterized in that: The natural antimicrobial peptides are protamine peptide, nisin and melittin in a mass ratio of (11-15):(8-12):(2-4), and the average molecular weight is ≤1 kDa.

6. The preservative for fresh tilapia pieces as claimed in claim 1, characterized in that: The moisturizing agent is selected from one or a combination of glycerin, propylene glycol, sorbitol, maltitol, sodium hyaluronate, and sodium carboxymethyl cellulose.

7. The preservative for fresh tilapia pieces as claimed in claim 1, characterized in that: The modification method of the modified biopolysaccharide comprises the following steps: A. Polysaccharide dissolution: Add the biopolysaccharide to deionized water and stir at 40-60°C and 300-500 rpm for 2-4 hours until dissolved to form a uniform and transparent polysaccharide solution. The mass volume ratio of the biopolysaccharide to deionized water is 1:20-50 g / mL, and set aside. B. Activation: Carboxylic acid, N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are mixed in a molar ratio of 1:(1.2-1.5):(0.1-0.2), and then a solvent is added to the mixture and stirred at a speed of 200-300 rpm in an ice water bath at 0-5°C for 30-60 minutes to form a carboxylic acid solution, wherein the ratio of the carboxylic acid to the solvent is 1 mmol:2-5 mL, and the solvent is dimethyl sulfoxide or N,N-dimethylformamide; C. Esterification: Add the activated carboxylic acid solution dropwise into the dissolved polysaccharide solution to make the volume ratio of the carboxylic acid solution to the polysaccharide solution be 1:2-5, react at 40-60°C with a stirring speed of 300-500 rpm for 12-24 hours, purify and dry to obtain fat-soluble biopolysaccharide.

8. The preservative for fresh tilapia pieces as claimed in claim 7, characterized in that: The carboxylic acid is stearic acid or palmitic acid.

9. The method for preparing a preservative for fresh tilapia pieces as claimed in claim 1, characterized in that: The following steps are involved: S1. Preliminary mixing: taking the natural plant extract and astaxanthin according to the above weight parts, ultrasonically mixing them, the ultrasonic power is 50-100 W, the ultrasonic frequency is 20-40 kHz, the ultrasonic time is 5-15 min, the ultrasonic temperature is 20-40 ° C, grinding to a particle size of 10-100 μm, and obtaining a mixed material for standby use; S2, secondary mixing: first add deionized water into the reaction container, add organic acid, natural antimicrobial peptide, and propolis extract in sequence while stirring at 300-500 rpm with a magnetic stirrer, and stir until completely dissolved to obtain solution I; S3, one layer of deposition: the above mixture is spread on the electrode plate, solution I is sprayed under the action of the electrostatic field to form droplets of 10-50 μm, and the droplets are deposited on the surface of the powder while stirring, the spraying rate is 0.5-1 mL / h, and the deposition is 1-3 hours to obtain a deposition layer I; S4, second layer deposition: using a spray gun to deposit the fat-soluble biopolysaccharide on the deposition layer I under the action of an electrostatic field, with a powder feeding rate of 0.1-0.5 g / min and a deposition time of 10-15 min to obtain a deposition layer II; S5, three-layer deposition: finally, the moisturizer is deposited on the surface of the deposition layer II according to the above method, with a spraying speed of 0.3-0.5 mL / h and a deposition time of 5-10 min to obtain a deposition layer III. The solution system with the deposited powder is filtered and centrifuged to separate the undeposited solution, excess powder, etc. The product after deposition is collected as the preservative.

10. The method for preparing a preservative for fresh tilapia pieces according to claim 1, characterized in that: The environment temperature of the three electrostatic depositions is 20-25° C., the relative humidity is 40%-60%, the electrostatic deposition voltage is 5-30 kV, and the current is 0.1-1.0 mA.

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