Edible composite film coating liquid as well as preparation method and application thereof

Abstract

The invention relates to the technical field of meat preservation, in particular to edible composite film coating liquid as well as a preparation method and application thereof. The method comprises the following steps: preparing a water-phase solution from oyster peptide, uniformly mixing the water-phase solution with soybean oil through vortex oscillation and magnetic stirring, carrying out high-speed shearing and ultrasonic emulsification to obtain an oyster peptide nano-emulsion, taking chitosan as a coating material, and adding the oyster peptide nano-emulsion, an acerola cherry extract and Nisin to improve the functional activity and nutritional supplement value of the coating liquid. According to the invention, the bad flavor of the oyster peptide can be covered, and the slow release of the antioxidant activity function of the oyster peptide can be realized. The edible film coating liquid is good in dispersity, high in stability and remarkable in oxidation resistance and antibacterial effect. The fresh-keeping effect is excellent, protein decomposition and lipid oxidation of the conditioned steak can be effectively delayed, the storage time is prolonged, meanwhile, the quality and flavor are kept, and the fresh-keeping agent has wide application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of meat preservation, and in particular to an edible composite coating liquid and a preparation method and application thereof. Background Art

[0002] With the accelerated pace of modern life and consumers' increasing requirements for food safety, health and quality, the market demand for fresh prepared meat products continues to grow. However, such products are susceptible to protein and lipid oxidation and microbial growth and reproduction during the refrigeration process, resulting in quality deterioration, which in turn shortens the shelf life of the product, seriously affecting consumers' eating experience and the market competitiveness of the product.

[0003] Although traditional chemical preservatives can extend the shelf life of products to a certain extent, their potential health risks make consumers cautious about them, which in turn promotes the research and application of safer and greener natural preservatives. In recent years, natural preservatives have been favored for their safety, non-toxicity, and green environmental protection. Among them, the coating preservation technology loaded with nanoemulsions has become a research hotspot due to its low cost and significant effect. However, there are still few natural coating preservative products that can be truly applied to processed meat products. On the one hand, although most plant essential oil nanoemulsions have been improved in the form of emulsions, it is still difficult to completely cover up the irritating odor that is continuously released, which not only affects the characteristic flavor of the processed meat products themselves, but also affects the consumer's eating experience. On the other hand, the effects of some natural preservatives are relatively single, and they cannot meet the needs of high-end meat products such as processed steaks for comprehensive preservation effects, such as inhibiting microbial growth, anti-oxidation, and maintaining texture characteristics.

[0004] When preparing nanoemulsions, surfactants are usually added to stabilize the emulsions. Chemically synthesized emulsifiers are prone to cause consumers' concerns about safety, making the development of natural substances to play an emulsifying role a research hotspot. Although protein-based nanoemulsions meet the emulsification needs to a certain extent, peptide-based nanoemulsions have higher antioxidant activity, faster interfacial adsorption capacity, lower allergy and higher nutritional value. Therefore, the research on peptide-based nanoemulsions has developed rapidly in recent years. In addition to certain emulsifying properties, polypeptide molecules may also contain specific bioactive peptides, which may have multiple physiological functions in the human body, such as promoting digestion, enhancing immunity, and anti-oxidation. Therefore, compared with simple protein-based nanoemulsions, peptide-based nanoemulsions can provide additional nutritional value and bioactive functions while providing partial emulsification functions. However, the current research and application of peptide-based nanoemulsions in the preservation of conditioned meat products is still relatively limited. How to apply this technology to the preservation of conditioned meat products still needs further exploration.

[0005] As a small molecule oligopeptide, oyster peptide has the ability to scavenge free radicals and resist lipid peroxidation in vivo, and is an ideal raw material for preparing peptide-based nanoemulsions. However, when oyster peptide is directly used, there are problems such as poor flavor release and insufficient stability. Nisin, as a natural biological antimicrobial peptide, is widely used in the food industry. However, Nisin has a narrow antibacterial spectrum and only has an inhibitory effect on most Gram-positive bacteria, which limits its application to a certain extent. In addition, Nisin's performance in antioxidant properties is not ideal, and its single use makes it difficult to deal with problems such as oxidation and deterioration that may occur during food processing and storage. Chitosan, as a natural polysaccharide, has the characteristics of low price, wide source, good film-forming property and antibacterial effect, and is widely used as a carrier for loading active ingredients. However, the preservation effect of a single chitosan coating is limited, and it usually needs to be combined with other bioactive substances to further improve its preservation effect.

[0006] At present, the existing technology has many defects in the preservation of conditioned meat products, especially in the single function of natural preservatives, the pungent smell of nanoemulsions, the safety of emulsifiers, the improvement of comprehensive preservation performance, and the stability and functionality of coatings. Therefore, it is urgent to develop a new, safe and efficient preservation technology to solve the defects in the existing technology. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides an edible composite coating liquid and a preparation method and application thereof.

[0008] The present invention provides an innovative fresh-keeping solution to solve the problems of single function of the preservative in the prior art, difficulty in masking the bad flavor, poor stability and insufficient safety, and at the same time, it aims at the difficult problems of water loss, corruption, protein and lipid oxidation that are easy to occur in the storage process of conditioned meat products. The present invention uses chitosan as a coating matrix, and adds oyster peptide nanoemulsion, acerola cherry extract and Nisin as functional substances to prepare an edible fresh-keeping coating liquid. The oyster peptide nanoemulsion masks its bad flavor through a physical barrier, thereby improving the stability and biological activity of the oyster peptide. Acerola cherry extract is rich in antioxidant components and can further enhance the antioxidant activity of the fresh-keeping coating. Nisin, as a natural antibacterial peptide, can inhibit the growth and reproduction of microorganisms. The present invention discovers and utilizes the synergistic effect of the three to construct a fresh-keeping system based on antioxidant peptides-plant extracts-antibacterial peptides, which significantly enhances the antioxidant and antibacterial activity of the fresh-keeping coating.

[0009] In the first aspect, the present invention provides an application of an oyster peptide nanoemulsion in an edible composite coating liquid, and the preparation of the oyster peptide nanoemulsion includes the following steps: mixing and stirring oyster peptide with water to obtain an aqueous phase solution; mixing the aqueous phase solution with soybean oil and vortexing and magnetically stirring; then performing shearing treatment and ultrasonic crushing treatment; the edible composite coating liquid contains the oyster peptide nanoemulsion, acerola cherry extract, Nisin and chitosan. In the present invention, oyster peptide is used to prepare an aqueous phase solution, which is evenly mixed with soybean oil by vortexing and magnetic stirring, and then subjected to high-speed shearing and ultrasonic emulsification to obtain an oyster peptide nanoemulsion, and oyster peptide nanoemulsion, acerola cherry extract and Nisin are added to the coating material such as chitosan to enhance the functional activity and nutritional supplement value of the coating liquid. The present invention adopts nanoemulsification technology, which not only successfully masks the bad flavor of oyster peptides, but also realizes the sustained release of the antioxidant activity function of oyster peptides. Combined with coating preservation technology, the prepared edible coating liquid has good dispersibility, strong stability, and significant antioxidant and antibacterial effects. The preparation method of the present invention is simple, and the components can synergize with each other after being compounded in a reasonable proportion, so that the preservation effect is better; it can not only effectively delay the protein decomposition and lipid oxidation of the conditioned steak, prolong the storage time, but also maintain its excellent quality and flavor at the same time, and has broad application prospects in the field of meat preservation.

[0010] Preferably, the average particle size of the oyster peptide nanoemulsion is 185-245 nm, and the PDI value is 0.28-0.39. The average particle size and PDI value of the oyster peptide nanoemulsion prepared by the present invention are low, the emulsion system is stable, and the droplets are evenly dispersed. The oyster peptide nanoemulsion has a smaller particle size and good system stability, and can better prepare an edible composite coating liquid with excellent performance.

[0011] Preferably, in the oyster peptide nanoemulsion, the average particle size is preferably 195-225 nm, and the PDI value is preferably 0.33-0.38; further preferably, the average particle size of the oyster peptide nanoemulsion is 207.7±8.3 nm, and the PDI value is 0.369±0.022.

[0012] In a second aspect, the present invention provides a method for preparing an edible composite coating liquid comprising an oyster peptide nanoemulsion, comprising the following steps: 1) Mix oyster peptide and water and stir to obtain an aqueous phase solution.

[0013] 2) The aqueous phase solution and soybean oil are mixed and vortexed and magnetically stirred; and then sheared and ultrasonically crushed to obtain an oyster peptide nanoemulsion.

[0014] 3) The oyster peptide nanoemulsion, acerola cherry extract, Nisin and chitosan coating liquid are mixed and stirred, and bubbles are removed after high-speed homogenization to obtain an edible composite coating liquid containing the oyster peptide nanoemulsion.

[0015] The edible composite coating liquid containing oyster peptide nanoemulsion provided by the present invention, first, by constructing a nanoemulsion, effectively masks the bad flavor of oyster peptides, and at the same time improves its stability and biological activity. Secondly, the synergistic effect of acerola cherry extract and Nisin is combined to further enhance the antioxidant and antibacterial effects of the coating liquid. Finally, using chitosan as the coating matrix not only improves the film-forming and barrier properties of the coating, but also helps to achieve effective slow release of bioactive ingredients such as oyster peptide nanoemulsion, acerola cherry extract and Nisin, and because chitosan itself has certain antibacterial properties, the antibacterial effect of the fresh-keeping coating is further enhanced. Therefore, the fresh-keeping coating liquid based on antioxidant peptides-plant extracts-antibacterial peptides constructed by the present invention has broad application prospects in the preservation of conditioned meat products.

[0016] Preferably, in step 1), the molecular weight of the oyster peptide is 400-3000 Da, the mass concentration of the oyster peptide in the aqueous solution is 0.5%-15%, preferably 3%-10%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. and any value or range therebetween; and / or, the stirring time is 20-50 min.

[0017] Preferably, in step 2), the shearing treatment is performed after adding Tween, and the Tween is Tween 20 and / or Tween 80, preferably Tween 20; preferably, the volume ratio of the soybean oil to the aqueous phase solution is 4-25:75-96, and the addition amount of the Tween 20 is 0.2%-2% (w / v).

[0018] Further preferably, in step 2), the vortex oscillation time is 1 to 5 min, and the magnetic stirring time is 5 to 20 min; and / or, the rotation speed of the shearing treatment is 8500 to 15000 rpm, and the shearing treatment time is 5 to 16 min. More preferably, the rotation speed of the shearing treatment is 12500±1500 rpm, and the shearing treatment time is 12±4 min.

[0019] Further preferably, in step 2), the ultrasonic power of the ultrasonic crushing treatment is 15-21 kHz; the ultrasonic crushing treatment procedure is running for 4-7s and resting for 4-7s; and / or the ultrasonic temperature is preferably 18-22°C; and / or the total ultrasonic duration of the ultrasonic crushing treatment is 7-20 min. More preferably, the ultrasonic power of the ultrasonic crushing treatment is 18±2kHz; the ultrasonic crushing treatment procedure is running for 5±1 s and resting for 5±1 s; preferably the ultrasonic temperature is 20±1.5°C, and preferably the total ultrasonic duration of the ultrasonic crushing treatment is 15-20 min.

[0020] Preferably, in step 3), the preparation of the chitosan coating liquid comprises the following steps: mixing chitosan with glacial acetic acid solution and magnetically stirring to obtain a chitosan solution, adding edible glycerol to the chitosan solution, and continuing stirring to obtain a chitosan coating liquid.

[0021] Preferably, the mass concentration of chitosan in the chitosan coating solution is 0.8-3.5%; and / or the concentration of the glacial acetic acid solution is 0.4%-2.5% (v / v); the magnetic stirring is magnetic stirring at 25-50°C for 40-70 min; 0.8%-3% (v / v) edible glycerol is added to the chitosan solution and stirring is continued for 4-16 min.

[0022] Preferably, in step 3), the speed of the high-speed homogenization is 8000-14000 rpm, and the time is 2-8 min. In the present invention, by high-speed homogenization at 8000-14000 rpm for 2-8 min, and then using an ultrasonic cleaner to remove bubbles, an edible composite coating liquid containing oyster peptide nanoemulsion with a more uniform and stable system and better performance can be further obtained.

[0023] Preferably, in step 3), the mass ratio of the oyster peptide nanoemulsion, acerola cherry extract and Nisin is 1-10: 0.5-5: 0.02-0.8, preferably 1-8: 0.5-4: 0.03-0.7, and more preferably 2-3: 0.5-1: 0.3-0.5. In the present invention, a fresh-keeping system based on antioxidant peptides-plant extracts-antibacterial peptides is constructed. Especially at the preferred ratio, the oyster peptide nanoemulsion, acerola cherry extract and Nisin can produce good synergistic effects in anti-oxidation and antibacterial through complementary performance, and can better exert the synergistic fresh-keeping effect.

[0024] Further preferably, 1-10% (w / w) of the oyster peptide nanoemulsion, 0.5-5% (w / w) acerola cherry extract and 0.02-0.8% (w / w) Nisin are added to the chitosan coating solution, preferably 1-8% (w / w) of the oyster peptide nanoemulsion, 0.5-4% (w / w) acerola cherry extract and 0.03-0.7% (w / w) Nisin, more preferably 2-3% (w / w) of the oyster peptide nanoemulsion, 0.5-1% (w / w) acerola cherry extract and 0.3-0.5% (w / w) Nisin.

[0025] As a preferred embodiment, 2±0.2 parts by mass of chitosan are weighed and dissolved in 1% glacial acetic acid solution, magnetically stirred to obtain a chitosan solution, edible glycerol is added as a plasticizer, and stirring is continued to obtain a chitosan coating liquid; the ratio of chitosan, glacial acetic acid and edible glycerol is 2g:99mL:1mL. 2.5±0.2 parts by mass of the oyster peptide nanoemulsion, 1±0.2 parts by mass of acerola cherry extract and 0.4±0.2 parts by mass of Nisin are added to 100±0.5 parts by mass of the chitosan coating liquid, stirred evenly and homogenized, and bubbles are removed using an ultrasonic cleaner to obtain an edible composite coating liquid containing oyster peptide nanoemulsion.

[0026] In a third aspect, the present invention further provides an edible composite coating liquid, which is prepared by the above-mentioned preparation method.

[0027] In a fourth aspect, the present invention also provides an application of the above-mentioned edible composite coating liquid, characterized in that the edible composite coating liquid is used as a preservative and texture retainer for the antibacterial preservation and quality maintenance of refrigerated prepared meat products.

[0028] The beneficial effects of the present invention are at least: 1) The oyster peptide nanoemulsion prepared by the present invention exhibits the characteristics of uniform particle size and good stability, and can effectively adhere to the surface of the processed meat product to form a protective layer.

[0029] 2) Oyster peptides not only have the ability to scavenge DPPH and ABTS free radicals, but also have the advantages of safety and high nutritional value. In addition, the presence of multiple short peptides can improve the emulsification stability of the emulsion. When oyster peptides exist in the form of nanoemulsions, they can not only mask the bad flavor through physical barriers, reduce the loss of peptides and improve their stability. More importantly, they can effectively control the sustained release of antioxidant active ingredients and effectively inhibit the lipid peroxidation reaction caused by free radicals during the storage of meat products, and have certain application value in the preservation of meat products.

[0030] 3) The present invention constructs a fresh-keeping system based on antioxidant peptides-plant extracts-antibacterial peptides. The edible composite coating liquid containing oyster peptide nanoemulsion prepared by the preferred method not only has excellent stability, but also its antibacterial activity and antioxidant activity surpass those of the composite coating liquids prepared by the existing methods including other embodiments and comparative examples of the present invention.

[0031] 4) The present invention compounds acerola cherry extract, Nisin and oyster peptide nanoemulsion. Based on the fence theory, the ingredients produce good synergistic antioxidant and antibacterial effects, have good biocompatibility and sustained release of active ingredients, and further enhance the preservation effect.

[0032] 5) When the edible composite coating liquid containing oyster peptide nanoemulsion prepared by the preferred method provided by the present invention is applied to the refrigeration process of the prepared steak, the total colony count, TBARS and TVB-N value are significantly reduced compared with the uncoated prepared steak in the control group, which effectively delays the protein decomposition, lipid oxidation and microbial reproduction of the prepared steak and prolongs the shelf life; at the same time, the juice loss rate of the prepared steak is reduced by 33.78% on the 14th day of refrigeration, which slows down the destruction of the protein structure of the beef tissue, and helps the prepared steak maintain a good texture quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 The average particle size and PDI diagram of the three oyster peptide emulsions OPE1, OPE2 and OPE3 in the examples of the present invention.

[0035] Figure 2 The PCA diagram (A) and radar diagram (B) are the masking effects of the oyster peptide nanoemulsion OPE3 on undesirable flavors in the examples of the present invention.

[0036] Figure 3 This is a comparison chart of the antioxidant activities of the coating solutions provided by Examples 2 to 6 of the present invention and Comparative Examples 1 to 2.

[0037] Figure 4 The embodiment of the present invention provides the change in the total number of colonies of the cooked steak under different coating treatments during refrigeration.

[0038] Figure 5 The volatile basic nitrogen changes of cooked steaks under different coating treatments during cold storage provided by the embodiments of the present invention.

[0039] Figure 6 The fat oxidation of cooked steaks under different coating treatments during refrigeration provided by the embodiments of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0042] If no specific technology or conditions are specified in the examples of the present invention, the technology or conditions described in the literature in the field or the product instructions are used. If the manufacturer of the devices, instruments, reagents, etc. is not specified, they are all conventional products that can be purchased through regular channels. The experimental reagents and raw materials involved are all commercially available, and the reagents are all analytically pure products.

[0043] In the embodiment of the present invention, the vitamin C content of the acerola cherry extract used is ≥17%; the Nisin used is a polypeptide substance produced by nisin, composed of 34 amino acid residues, and has a potency of ≥900 IU / mg. The purity of the oyster peptide used is ≥95%, and the molecular weight is less than 3000 Da.

[0044] Example 1: Preparation of oyster peptide nanoemulsion (1) Preparation steps of oyster peptide nanoemulsion: Control 1: 2 g of oyster peptide was dissolved in 40 mL of deionized water and stirred at room temperature for 30 min to fully dissolve it to obtain an aqueous solution with a concentration of 5%; 2 mL of soybean oil and 18 mL of the above aqueous solution were fully mixed by vortex oscillation (3 min) and magnetic stirring (15 min), and then 0.14 g of Tween 20 was added, and then a high-speed disperser was used for shearing at 12500 rpm for 12 min to obtain an oyster peptide emulsion, namely OPE1.

[0045] Control 2: 2 g of oyster peptide was dissolved in 40 mL of deionized water and stirred at room temperature for 30 min to fully dissolve it to obtain an aqueous solution with a concentration of 5%; 2 mL of soybean oil and 18 mL of the above aqueous solution were fully mixed by vortex oscillation (3 min) and magnetic stirring (15 min), and then 0.14 g of Tween 20 was added, and then ultrasonically crushed at 18 kHz for 15 min, the ultrasonic temperature was 20°C, and the cycle was 5 s of operation and 5 s of interval, to obtain oyster peptide emulsion, namely OPE2.

[0046] 2 g of oyster peptide was dissolved in 40 mL of deionized water and stirred at room temperature for 30 min to fully dissolve it to obtain an aqueous solution with a concentration of 5%; 2 mL of soybean oil and 18 mL of the above aqueous solution were fully mixed by vortex oscillation (3 min) and magnetic stirring (15 min), and then 0.14 g of Tween 20 was added. Then, a high-speed disperser homogenizer was used for shear treatment at 12500 rpm for 12 min, and then ultrasonically crushed at 18 kHz for 15 min. The ultrasonic temperature was 20°C, and the cycle was 5 s of operation and 5 s of interval, so that oyster peptide nanoemulsion, namely OPE3, was obtained.

[0047] (2) Average particle size and PDI value of oyster peptide nanoemulsion: The average particle size and PDI value of the prepared emulsion were measured using a Malvern nanoparticle size analyzer. Figure 1 As shown, the average particle size of the oyster peptide nanoemulsion OPE3 prepared in this embodiment is 207.7±8.3 nm, and the PDI value is 0.369±0.022. The average particle size and PDI value of the oyster peptide nanoemulsion OPE3 prepared in this embodiment are the lowest, the emulsion system is stable, and the droplets are evenly dispersed. Therefore, the nanoemulsion prepared by the present invention has a smaller particle size and good system stability, so the preparation method of OPE3 is selected to prepare a composite coating liquid containing oyster peptide nanoemulsion.

[0048] (3) Emulsion masks the adverse flavor effects of oyster peptides The flavor changes of oyster peptide powder OP and the above-mentioned oyster peptide nanoemulsion OPE3 were measured by electronic nose. The analysis results are as follows: Figure 2 A and 2B. Figure 2 As shown in A, the contribution rates of the first principal component (PC1) and the second principal component (PC2) in the PCA analysis are 98.83% and 0.64%, respectively, and the total contribution rate is 99.47%. In the PCA analysis, the data points of each group are distributed in their respective regions without overlap. It is worth noting that the oyster peptide powder sample OP is located in the right quadrant, while the oyster peptide nanoemulsion sample OPE3 is located in the left quadrant, indicating that there is a significant difference in the flavor of the oyster peptide sample OP and the oyster peptide nanoemulsion sample OPE3, and the electronic nose can successfully distinguish the samples. Figure 2 B The results showed that nitrogen oxides and sulfides represented by W1W, W5S and W2W were the main sources of oyster peptide undesirable flavor substances, and oyster peptide nanoemulsion OPE3 had a significant masking effect on these undesirable flavors.

[0049] Example 2: Preparation of oyster peptide nanoemulsion-chitosan coating solution (1) The oyster peptide nanoemulsion was prepared using the method and steps of OPE3 in Example 1.

[0050] (2) Weigh 2 g of chitosan and dissolve it in 99 mL of 1% glacial acetic acid solution. Stir magnetically at 45 °C for 60 min to obtain a chitosan solution. Add 1 mL of edible glycerol as a plasticizer and continue stirring for 8 min to obtain a chitosan coating solution.

[0051] (3) Add 2.5 g of the oyster peptide nanoemulsion prepared in step (1) to the chitosan coating liquid, stir evenly and homogenize at 11,000 rpm for 4 min. Finally, use an ultrasonic cleaner to remove bubbles to obtain an oyster peptide nanoemulsion-chitosan coating liquid.

[0052] Example 3: Preparation of edible composite coating liquid containing oyster peptide nanoemulsion (1) The oyster peptide nanoemulsion was prepared using the method and steps of OPE3 in Example 1.

[0053] (2) Weigh 2 g of chitosan and dissolve it in 99 mL of 1% glacial acetic acid solution. Stir magnetically at 45 °C for 60 min to obtain a chitosan solution. Add 1 mL of edible glycerol as a plasticizer and continue stirring for 8 min to obtain a chitosan coating solution.

[0054] (3) Add 2.5 g of the oyster peptide nanoemulsion prepared in step (1), 1 g of acerola cherry extract and 0.4 g of Nisin to the above 100 g of chitosan coating liquid, stir evenly and homogenize at 11000 rpm for 4 min, and finally use an ultrasonic cleaner to remove bubbles to obtain an edible composite coating liquid containing oyster peptide nanoemulsion.

[0055] Comparative Example 1 The only difference between this comparative example and Example 2 is that no oyster peptide nanoemulsion is added.

[0056] Comparative Example 2 The only difference between this comparative example and Example 3 is that no acerola cherry extract is added.

[0057] Comparative Example 3 The only difference between this comparative example and Example 3 is that Nisin is not added.

[0058] Example 4 The same method for preparing an edible composite coating liquid containing oyster peptide nanoemulsion as in Example 3 is adopted, except that in step (3), 1 g of the oyster peptide nanoemulsion prepared in step (1), 0.5 g of acerola cherry extract and 0.07 g of Nisin are added to 100 g of the chitosan coating liquid.

[0059] Example 5 The same method for preparing an edible composite coating liquid containing oyster peptide nanoemulsion as in Example 3 was adopted, except that in step (3), 8 g of the oyster peptide nanoemulsion prepared in step (1), 1.5 g of acerola cherry extract and 0.53 g of Nisin were added to 100 g of the chitosan coating liquid.

[0060] Example 6 The same method for preparing an edible composite coating liquid containing oyster peptide nanoemulsion as in Example 3 is used, except that in step (1): instead of using the method and steps of OPE3 in Example 1 to prepare the oyster peptide nanoemulsion, the oyster peptide nanoemulsion used is prepared by the following method: 2 g of oyster peptide is dissolved in 40 mL of deionized water, and stirred at room temperature for 30 min to fully dissolve it, to obtain an aqueous phase solution with a concentration of 5%; 2 mL of soybean oil and 18 mL of the aqueous phase solution are fully mixed by vortex oscillation (3 min) and magnetic stirring (15 min), and then 0.14 g of Tween 20 is added, and then a high-speed dispersing homogenizer is used for shearing treatment at 8500 rpm for 5 min, and then ultrasonically crushed at 15 kHz for 8 min, the ultrasonic temperature is 20°C, and the cycle is 4 s of operation and 4 s of rest, to obtain the oyster peptide nanoemulsion, namely OPE4.

[0061] Test Example 1 This test example uses the DPPH free radical scavenging rate to determine the antioxidant effect of the coating liquids of Examples 2 to 6 and Comparative Examples 1 to 2. The greater the DPPH free radical scavenging rate, the stronger the antioxidant activity of the coating liquid. Figure 3As shown, compared with Comparative Example 1, Example 2 can significantly improve the antioxidant activity of the coating liquid by adding oyster peptide nanoemulsion. Compared with Comparative Examples 1~2 and Example 2, Examples 3~6 all significantly improve the antioxidant activity of the coating liquid to varying degrees. It can be seen from the measurement that Example 3 has the highest antioxidant activity, not only because the acerola cherry extract is rich in vitamin C and polyphenol compounds that can block free radical chain reactions, but also because different active substances are reasonably proportioned to produce an ideal synergistic effect, which greatly improves the antioxidant activity of the coating liquid and has application prospects in inhibiting protein and lipid oxidation. In addition, the average particle size and PDI value of the oyster peptide nanoemulsion OPE4 prepared in Example 6 are significantly larger than those of OPE3 used in Example 3, the emulsion system is less stable, and the antioxidant activity of Example 6 is lower than that of Example 3. The edible composite coating liquid containing oyster peptide nanoemulsion prepared in the embodiments of the present invention, especially in Example 3, has excellent antioxidant effect.

[0062] Test Example 2 This test example verifies the antibacterial activity of the coating solution provided by Examples 2 to 6 and Comparative Examples 1 and 3. Specific steps and methods: Select a total colony count of 1.0×10 6 CFU / g of beef was sampled and homogenized, and the bacterial solution was retained for later use. 100 μL of the above bacterial solution was applied to the nutrient agar plate. 10 μL of the coating solution prepared in Comparative Example 1, Comparative Example 3 and Examples 2 to 6 was taken on the filter paper and placed on the plate containing the bacterial solution. Sterile water was used as the control group and placed in a 37°C incubator for 48 h. After taking out, the diameter of the inhibition zone was measured.

[0063] Table 1 Antibacterial effects of different coating solutions

[0064] As shown in Table 1, Comparative Example 1 also has a certain antibacterial ability, because the positive charge on the surface of chitosan attracts the negative charge on the surface of the microorganism, causing the cell to rupture and die, thereby achieving the purpose of antibacterial. Compared with Comparative Example 1, Comparative Example 3 and Example 2, Examples 3 to 6 all significantly improve the antibacterial activity of the coating liquid to varying degrees, thereby broadening the antibacterial spectrum of the coating liquid, enhancing the antibacterial performance, and better inhibiting the growth of microorganisms. In particular, the diameter of the antibacterial circle of Example 3 is the largest, because Nisin can destroy the structural integrity of the microorganism, thereby directly leading to the death of the microorganism, and the vitamins and flavonoids contained in the acerola cherry extract can inhibit the growth of enzymes in the cell. After the components are reasonably compounded, the purpose of synergistic antibacterial is achieved. The edible composite coating liquid containing oyster peptide nanoemulsion prepared in the embodiment of the present invention has a good antibacterial effect, and the effect of Example 3 is the best.

[0065] Application Example 1 In this application example, the coating liquid provided in Comparative Example 1 and Examples 2-3 is applied in the refrigeration process of preparing steak.

[0066] (1) First, cut the beef tenderloin into uniform slices weighing 70 g and about 1.5 cm thick. Then add salt, sugar, monosodium glutamate, sodium pyrophosphate and other auxiliary materials and water for vacuum tumbling and marinating for 2.5 h, tumbling for 20 min each time, and resting for 10 min.

[0067] (2) A coating liquid was prepared according to the preparation method described in Examples 2-3 and Comparative Example 1; and the prepared steaks in step (1) were soaked in different coating agents for 20 min, and the prepared steaks without any soaking treatment were used as a control group, and then the surface was dried at 25° C. in a sterilized forced air drying oven for 30 min.

[0068] (3) The processed steaks treated in step (2) were packaged in a high oxygen modified environment and stored in a refrigerator at 4°C. Samples were taken on the 1st, 3rd, 6th, 8th, 10th, 12th and 14th day to determine the total colony count, volatile basic nitrogen, TBARS value and juice loss rate.

[0069] (4) Determination of total colony count: Determine in accordance with GB 4789.2-2022 National Food Safety Standard Food Microbiology Examination Determination of Total Colony Count.

[0070] (5) Determination of volatile basic nitrogen content (TVB-N): Determination shall be carried out in accordance with GB 5009.228-2016 National Food Safety Standard Determination of Volatile Basic Nitrogen in Food.

[0071] (6) Determination of thiobarbituric acid reactants (TBARS): Take 5 g of meat sample and chop it into small pieces. Add 50 mL of 7.5% trichloroacetic acid solution and shake it for 30 min. Then filter it through double-layer filter paper. Take 5 mL of the filtrate and mix it evenly with 5 mL of 0.02 M TBA solution. Keep it in a water bath at 90°C for 35 min. Then quickly cool it to room temperature in an ice bath. Add 5 mL of chloroform. Shake it and let it stand for stratification. Then take the upper layer of liquid and record the absorbance at 532 nm and 600 nm. Calculate the TBARS value.

[0072] (7) Determination of juice loss rate: The juice loss rate is calculated by measuring the ratio of the difference in the mass of the meat block sampled each time to the mass of the meat block before refrigeration and expressed as a mass fraction.

[0073] (8) Changes in the total number of colonies in cooked steaks treated with different coatings during refrigeration Figure 4As shown. During the storage process, the prepared steak will undergo a series of changes. The growth and reproduction of microorganisms can cause the prepared steak to spoil. Therefore, monitoring the changes in the total number of colonies in the coated prepared steak during the storage period can reflect the inhibitory effect of the coating liquid on the spoilage of the prepared steak. Figure 4 It can be seen that the total number of colonies in the conditioned steaks of each treatment group gradually increased with the extension of the refrigeration time. During the entire refrigeration period, the total number of colonies in the conditioned steaks treated with the coating (including comparative example 1 and embodiments 2-3) was significantly lower than that in the control group, indicating that the coating treatment had a certain inhibitory effect on the growth of microorganisms. On the 8th day of refrigeration, the total number of colonies in the conditioned steaks not treated with the coating in the control group was 6.05 log CFU / g, which exceeded the national standard limit, indicating that the conditioned steaks were spoiled. In contrast, the total number of colonies in the conditioned steaks treated with comparative example 1 reached the threshold value (6.00 log CFU / g) on ​​the 9th day of refrigeration, entering the corruption stage. Compared with the control group, the extended shelf life of the conditioned steaks treated with comparative example 1 may be because the amino groups in the chitosan molecules are positively charged after protonation, which produces electrostatic attraction with the negative charges on the surface of the microbial cells, causing the cell membrane to rupture and promote cell death, thereby delaying the corruption process. On the 10th day of refrigeration, the total colony count of the conditioned steak treated with Example 2 was close to the threshold value (6.00 log CFU / g), indicating that the oyster peptide nanoemulsion loaded in the chitosan coating liquid can control the biological activity sustained release rate of the oyster peptide to a greater extent, and interact with chitosan to delay the rate of increase of the total colony count. On the 12th day of refrigeration, the total colony count of the conditioned steak treated with Example 3 was only 5.66 log CFU / g, which was 26.01%, 22.68% and 18.21% lower than that of the control group, comparative example 1 and example 2, respectively. It was not until the 13th day of refrigeration that the total colony count of the conditioned steak treated with Example 3 reached the corruption threshold, and on the 14th day, the total colony count of the conditioned steak treated with Example 3 was 6.42log CFU / g. Therefore, Example 3, by virtue of its unique combination of oyster peptide nanoemulsion, acerola cherry extract and Nisin chitosan coating, not only exerts the synergistic effect of each bioactive component in antibacterial and anti-oxidation, but also forms a coating with a tight and uniform structure, and has good barrier properties and sustained release function of bioactive substances. Therefore, the edible composite coating liquid containing oyster peptide nanoemulsion represented by the embodiment of the present invention has a good antibacterial and fresh-keeping effect, especially Example 3 has the best effect. The coating is used for conditioning steak, effectively inhibiting the growth and reproduction of microorganisms, and significantly prolonging the shelf life of the conditioned steak. Compared with the control group, its shelf life is extended by 5 to 6 days.

[0074] (9) Changes in volatile basic nitrogen of cooked steaks under different coating treatments during cold storage Figure 5TVB-N is an alkaline nitrogen-containing substance produced by the decomposition of protein by spoilage bacteria in meat. Protein provides rich nutrition for the growth of microorganisms, and its decomposition degree is an important indicator for evaluating the quality of cooked steak. Figure 5 It can be seen that the TVB-N values ​​of the four groups of conditioned steaks showed an overall upward trend with the refrigeration time, which directly reflects the growth and reproduction of microorganisms and their process of gradually decomposing the protein in the meat into alkaline nitrogen-containing products. The TVB-N value of the conditioned steaks in the control group that were not coated increased most significantly, and was significantly higher than that of Comparative Example 1 and Examples 2-3 from the third day of refrigeration. The TVB-N value of the conditioned steaks in the control group that were not coated exceeded the corruption threshold (20 mg / 100 g) on ​​the 8th day of refrigeration, indicating that the conditioned steaks had been corrupted and were not suitable for consumption. The TVB-N value of the conditioned steaks treated in Comparative Example 1 reached the threshold (20 mg / 100 g) on ​​the 9th day of refrigeration, and corruption occurred; compared with the control group, the shelf life of the conditioned steaks treated in Comparative Example 1 was relatively extended, which may be because chitosan effectively inhibited the growth of microorganisms, thereby reducing the oxidative deamination of nitrogen-containing compounds by microorganisms. On the 10th day of refrigeration, the TVB-N value of the conditioned steak treated in Example 2 was close to but still did not exceed the spoilage threshold, indicating that the addition of oyster peptide nanoemulsion can effectively slow down the protein oxidation rate during refrigeration. In particular, the oyster peptide nanoemulsion loaded in the chitosan coating liquid can control the sustained release of the antioxidant activity of oyster peptides to a greater extent, and more effectively inhibit the production of alkaline substances, thereby delaying the spoilage of the conditioned steak. During the entire storage period, compared with the control group, comparative example 1 and example 2, the TVB-N value of the conditioned steak treated in Example 3 was always significantly lower than that of the other three groups, and the rate of increase was slow. It was not until 13 days of refrigeration that the TVB-N value of the conditioned steak treated in Example 3 reached the spoilage threshold, and on the 14th day, the TVB-N value of the conditioned steak treated in Example 3 was 22.92 mg / 100 g. The results show that the addition of acerola cherry extract and Nisin in the embodiments of the present invention not only enhances the antioxidant and antibacterial properties of the coating liquid, but also produces a certain synergistic effect, promotes the gradual release of active ingredients, thereby more effectively inhibiting the production of amines by microorganisms and better slowing down the oxidative decomposition rate of protein. Therefore, the embodiments of the present invention, especially Embodiment 3, show better preservation effect on prepared steaks.

[0075] (10) Fat oxidation of steaks treated with different coatings during refrigeration Figure 6 As shown. Fat oxidation is a series of complex chemical reactions in which fatty acids interact with oxygen through auto-oxidation, photo-oxidation and enzymatic oxidation pathways. This process is not only accompanied by the release of unpleasant odors, but also causes the rancidity and quality deterioration of the cooked steak, seriously affecting the quality of the cooked steak. Figure 6The changes in TBARS values ​​of the conditioned steaks in different treatment groups during storage at 4°C for 14 days are shown. During the 14-day cold storage process, the TBARS value of the conditioned steaks in the control group that were not coated increased sharply from 0.392 mg / kg to 1.771 mg / kg. This significant increase directly reflects that the conditioned steaks in the control group that were not coated had serious fat oxidation, accompanied by a significant rancid smell, which seriously damaged the quality of the conditioned steaks. In contrast, the TBARS value of the conditioned steaks treated with coatings (including Comparative Example 1 and Examples 2-3) increased slowly under the same cold storage conditions. This is attributed to the coating treatment that constructed a dense protective barrier on the surface of the conditioned steaks, which reduced the oxygen permeability to a certain extent, thereby inhibiting lipid oxidation and delaying the spoilage of the conditioned steaks. Compared with Comparative Example 1, loading the oyster peptide nanoemulsion into the chitosan coating (Examples 2 and 3) can significantly reduce the TBARS value of the conditioned steaks during cold storage. On the 10th day of storage, the TBARS value of the conditioned steak treated in Example 2 was only 0.778 mg / kg, which was 29.26% and 14.87% lower than that of the control group and comparative example 1, respectively; and as the refrigeration time increased, the TBARS value of the conditioned steak treated in Example 2 remained significantly lower than that of the control group and comparative example 1. This result shows that the composite coating of oyster peptide nanoemulsion and chitosan can effectively inhibit fat oxidation and rancidity, which is mainly related to the sustained release of the antioxidant activity of oyster peptide nanoemulsion in the chitosan film liquid. After 14 days of refrigeration, the TBARS value of the conditioned steak treated in Example 3 still did not exceed 1 mg / kg, and the TBARS value of the conditioned steak treated in Example 3 was significantly reduced by 48.34%, 36.72% and 24.72% compared with the control group, comparative example 1 and example 2, respectively. This significant effect reveals the synergistic mechanism between the active ingredients such as vitamin C in the acerola cherry extract in the embodiment of the present invention and the oyster peptide nanoemulsion and Nisin. These ingredients can not only chelate metal ions, but also scavenge hydroxyl radicals and peroxyl radicals, effectively inhibiting free radical chain reactions, thereby synergistically slowing down the fat oxidation rate of the cooked steak, which helps to extend the refrigeration time of the cooked steak.

[0076] (11) The changes in juice loss rate of steaks under different coating treatments during refrigeration are shown in Table 2.

[0077] Table 2 Changes in juice loss rate of cooked steaks under different coating treatments during cold storage

[0078] As shown in Table 2, the juice loss rate of the conditioned steaks treated with the control group, comparative example 1 and embodiment 3 all showed an upward trend with the extension of the refrigeration time, but the juice loss rate of the conditioned steaks treated with the coating in comparative example 1 and embodiment 3 was always lower than that in the control group. On the 8th day of refrigeration, the juice loss rate of the conditioned steaks in the control group that were not treated with the coating reached 6.04%, and the juice loss was serious, while the juice loss rates of the conditioned steaks treated with comparative example 1 and embodiment 3 were only 5.43% and 4.84%, respectively, which were significantly lower than the juice loss rate of the control group, indicating that the coating significantly reduced the permeability of the conditioned steak tissue cell membrane, thereby improving the water retention of the conditioned steak. During the entire refrigeration period, the juice loss rate of the steak treated with Example 3 was lower than that of the other groups. On the 14th day of refrigeration, the juice loss rate of the steak treated with the coating of Example 3 was only 6.39%, which was 33.78% lower than that of the control group and 17.97% lower than that of the comparative example 1, respectively, indicating that the coating solution of the present invention has a significant inhibitory effect on the juice loss of the steak, among which Example 3 has the best effect. The oyster peptide nanoemulsion is loaded on chitosan to form a thin film on the surface of the steak, blocking the contact between the steak and the spoilage microorganisms in the external environment. At the same time, it has a synergistic effect with the acerola cherry extract and Nisin, further inhibiting the growth and reproduction of spoilage microorganisms in the steak, significantly reducing the juice loss rate of the steak, slowing down the destruction of the protein structure of the beef tissue, and helping the steak to maintain a good texture quality.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An application of oyster peptide nanoemulsion in an edible composite coating liquid, characterized in that: The preparation of the oyster peptide nanoemulsion comprises the following steps: mixing oyster peptide with water and stirring to obtain an aqueous phase solution; mixing the aqueous phase solution with soybean oil and vortexing and magnetically stirring; and then performing shearing treatment and ultrasonic crushing treatment; the edible composite coating liquid contains the oyster peptide nanoemulsion, acerola cherry extract, Nisin and chitosan.

2. The use according to claim 1, characterized in that: The average particle size of the oyster peptide nanoemulsion is 185-245 nm, and the PDI value is 0.28-0.

39.

3. A method for preparing an edible composite coating liquid containing oyster peptide nanoemulsion, characterized in that: The following steps are involved: 1) Mixing oyster peptide with water and stirring to obtain an aqueous solution; 2) mixing the aqueous phase solution and soybean oil, vortexing and magnetically stirring; and then performing shearing treatment and ultrasonic crushing treatment to obtain oyster peptide nanoemulsion; 3) The oyster peptide nanoemulsion, acerola cherry extract, Nisin and chitosan coating liquid are mixed and stirred, and bubbles are removed after high-speed homogenization to obtain an edible composite coating liquid containing the oyster peptide nanoemulsion.

4. The preparation method according to claim 3, characterized in that: In step 1), the molecular weight of the oyster peptide is 400-3000 Da, and the mass concentration of the oyster peptide in the aqueous solution is 0.5%-15%; preferably, the mass concentration is 3%-10%; And / or, the stirring time is 20 to 50 min.

5. The preparation method according to claim 3 or 4, characterized in that: In step 2), the volume ratio of the soybean oil to the aqueous solution is 4-25:75-96; And / or, the shearing treatment is performed after adding Tween, wherein the Tween is Tween 20 and / or Tween 80; preferably, the added amount of the Tween 20 is 0.2% to 2% (w / v); And / or, the vortex oscillation time is 1 to 5 min, and the magnetic stirring time is 5 to 20 min; And / or, the rotation speed of the shearing treatment is 8500-15000 rpm, and the time of the shearing treatment is 5-16 min.

6. The preparation method according to any one of claims 3 to 5, characterized in that: In step 2), the ultrasonic power of the ultrasonic crushing treatment is 15-21 kHz; the program of the ultrasonic crushing treatment is running for 4-7 seconds and resting for 4-7 seconds; and / or, the ultrasonic temperature is 18-22°C; And / or, the total ultrasonic duration of the ultrasonic fragmentation treatment is 7 to 20 min.

7. The preparation method according to any one of claims 3 to 6, characterized in that: In step 3), the preparation of the chitosan coating liquid comprises the following steps: mixing chitosan with glacial acetic acid solution and magnetically stirring to obtain a chitosan solution, adding edible glycerol to the chitosan solution, and continuing to stir to obtain a chitosan coating liquid; preferably, the mass concentration of chitosan in the chitosan coating liquid is 0.8-3.5%; And / or, in step 3), the speed of the high-speed homogenization is 8000-14000 rpm, and the time is 2-8 min.

8. The preparation method according to any one of claims 3 to 7, characterized in that: In step 3), the mass ratio of the oyster peptide nanoemulsion, acerola cherry extract and Nisin is 1-10: 0.5-5: 0.02-0.8, preferably 1-8: 0.5-4: 0.03-0.

7.

9. An edible composite coating liquid, characterized in that: The method is prepared according to any one of claims 3 to 8.

10. The use of the edible composite coating liquid according to claim 9, characterized in that: The edible composite coating liquid is used as a preservative and texture retainer for the antibacterial preservation and quality maintenance of refrigerated prepared meat products.

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