Composite coating solution containing florists chrysanthemum extract as well as preparation method and application of composite coating solution

Abstract

The invention discloses a florists chrysanthemum extract-containing composite coating solution as well as a preparation method and application thereof, and relates to the technical field of composite materials. The invention discloses a composite film coating solution containing a florists chrysanthemum extract. The composite film coating solution is prepared by mixing the following components in percentage by weight: 2% of acetylated distarch adipate, 1.3% of chitosan, 1.25% of the florists chrysanthemum extract and glycerol. The preparation method disclosed by the invention is simple, excellent antioxidant activity and good antibacterial activity are achieved, and the prepared composite coating ADA / CS / GE shows good performance of inhibiting the number and growth speed of bacterial colonies and coliforms in a sample, inhibiting oxidation of lipid and protein, maintaining the pH level of the sample and reducing water evaporation of the sample; ultraviolet rays can be blocked, so that a sample can maintain better elasticity, chewiness and resilience. The raw materials of the composite coating disclosed by the invention are safe, non-toxic, green and edible, and do not affect the flavor of food.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and more specifically, relates to a composite coating solution containing chrysanthemum morifolium extract, a preparation method thereof, and an application thereof. Background Art

[0002] Since the central temperature of low-temperature cooked meat products does not exceed 85°C during cooking and sterilization, heat-resistant microorganisms in them are not easily killed and will multiply in large numbers during storage, thus causing the spoilage and deterioration of meat products, shortening the shelf life, and making it difficult to expand the sales range. Although traditional vacuum packaging and high-temperature sterilization can effectively extend the shelf life, they will squeeze the meat products, resulting in juice loss, affecting the taste and flavor, and reducing the sensory quality.

[0003] The coating preservation technology has been increasingly concerned in the field of food preservation. The coating can form a thin film barrier on the surface of food, effectively block the external environment, reduce juice loss, and the loaded active ingredients can inhibit the growth of microorganisms, delay oxidative spoilage, and enhance the preservation effect. The coating preservation technology is widely applied in fruits and vegetables, fresh meat, and aquatic products, but less in marinated and stewed meat products.

[0004] Chrysanthemum morifolium extract has biological activities such as antibacterial and anti-inflammatory properties, which may help inhibit the growth of microorganisms in food, thereby extending the shelf life of food. In addition, chrysanthemum morifolium extract also contains rich antioxidant components, which can slow down the oxidation process of food, maintain the freshness and nutritional value of food. Although chrysanthemum morifolium extract has shown certain potential in preservation, the current research on its specific application effects is relatively less. Therefore, in practical applications, further research and verification of the preservation effect of chrysanthemum morifolium extract are needed to determine its optimal usage conditions and applicable scope. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the technical problems to be solved by the present invention are as follows: to provide a composite coating solution containing chrysanthemum morifolium extract; to provide a preparation method of a composite coating solution containing chrysanthemum morifolium extract; to provide a composite coating containing chrysanthemum morifolium extract; to provide a preparation method of a composite coating containing chrysanthemum morifolium extract; to provide an application of a composite coating solution containing chrysanthemum morifolium extract; to provide an application of a composite coating containing chrysanthemum morifolium extract for food preservation.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A composite coating solution containing chrysanthemum morifolium extract is composed of the following components mixed in mass percentage concentration:

[0008] 1 - 5% acetylated distarch adipate, 0.4 - 1.6% chitosan, 0.3% - 1.5% extract of Flos Chrysanthemi morifolii Ramat., and glycerol.

[0009] Method for preparing a composite coating solution containing extract of Flos Chrysanthemi morifolii Ramat., the steps including:

[0010] 1) Prepare an acetylated distarch adipate solution with an acetylated distarch adipate concentration of 1 - 5% w / v;

[0011] 2) Prepare a chitosan solution with a chitosan concentration of 0.4 - 1.6% w / v;

[0012] 3) Mix the acetylated distarch adipate solution and the chitosan solution in a volume ratio of 3:7, stir evenly to prepare an acetylated distarch adipate / chitosan solution;

[0013] 4) Add glycerol and extract of Flos Chrysanthemi morifolii Ramat. to the mixed solution, with a glycerol concentration of 0.80% v / v and an extract of Flos Chrysanthemi morifolii Ramat. concentration of 0.3% - 1.5% w / v, to prepare an acetylated distarch adipate / chitosan / extract of Flos Chrysanthemi morifolii Ramat. coating solution.

[0014] The concentration of the acetylated distarch adipate is 2%, the concentration of the chitosan is 1.3%, and the concentration of the extract of Flos Chrysanthemi morifolii Ramat. is 1.25%.

[0015] A composite coating containing extract of Flos Chrysanthemi morifolii Ramat., which is composed of the following components mixed by mass percentage concentration:

[0016] 2% acetylated distarch adipate, 1.3% chitosan, 1.25% extract of Flos Chrysanthemi morifolii Ramat., and glycerol.

[0017] Method for preparing a composite coating containing extract of Flos Chrysanthemi morifolii Ramat., the specific steps including:

[0018] 1) Add acetylated distarch adipate to distilled water, with a concentration of 2% w / v, heat in a water bath at 80°C for 30 min to completely gelatinize it, and prepare an acetylated distarch adipate solution;

[0019] 2) Dissolve chitosan in an acetic acid solution with a volume ratio of 1%, with a concentration of 1.3% w / v, to prepare a chitosan solution;

[0020] 3) Mix the acetylated distarch adipate solution and the chitosan solution in a volume ratio of 3:7, stir evenly to prepare an acetylated distarch adipate / chitosan solution;

[0021] 4) Add glycerol and chrysanthemum extract to the mixed solution, with the glycerol concentration being 0.80% v / v and the chrysanthemum extract concentration being 1.25% w / v; homogenize the mixed solution at 8000 rpm for 1 min, and adjust the pH to 5.6 ± 0.1 using a sodium bicarbonate solution to prepare an acetylated distarch adipate / chitosan / chrysanthemum extract coating solution;

[0022] 5) Pour 20 mL of the film solution into a 90 mm plastic petri dish and dry it at room temperature for 48 h to obtain an acetylated distarch adipate / chitosan / chrysanthemum extract composite coating.

[0023] Application of the composite coating solution containing chrysanthemum extract in blocking water vapor and oxygen, and / or blocking ultraviolet rays, and / or food preservation, and / or inhibiting the growth of colonies and flora, and / or inhibiting protein oxidation, and / or maintaining the pH value of food, and / or inhibiting lipid oxidation.

[0024] Application of the composite coating containing chrysanthemum extract in blocking water vapor and oxygen, and / or blocking ultraviolet rays, and / or food preservation, and / or inhibiting the growth of colonies and flora, and / or inhibiting protein oxidation, and / or maintaining the pH value of food, and / or inhibiting lipid oxidation.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1) Apply the prepared ADA / CS / GE composite coating to the preservation of salted duck. The results show that the ADA / CS / GE composite coating significantly inhibits the number and growth rate of colonies and coliforms in the sample.

[0027] 2) Apply the prepared ADA / CS / GE composite coating to the preservation of salted duck. The results show that the ADA / CS / GE composite coating has an inhibitory effect on lipid oxidation.

[0028] 3) Apply the prepared ADA / CS / GE composite coating to the preservation of salted duck. The results show that the addition of chrysanthemum extract significantly enhances the inhibitory effect on protein oxidation.

[0029] 4) Apply the prepared ADA / CS / GE composite coating to the preservation of salted duck. The results show that the inherent antibacterial property of chrysanthemum extract effectively maintains the pH level of the duck meat sample.

[0030] 5) Apply the prepared ADA / CS / GE composite coating to the preservation of salted duck. The results show that during the entire storage period, the ADA / CS / GE group exhibits better elasticity, chewiness, and resilience.

[0031] 6) The ADA / CS / GE composite coating film prepared in this application was applied to the preservation of salted ducks. The results showed that as the storage time increased, the moisture content of the salted duck legs gradually decreased. Compared with the control group, the moisture content of the salted duck samples with the coating film decreased more slowly, indicating that the coating film could act as a barrier to reduce water evaporation. Description of the Drawings

[0032] Figure 1 It is a single-factor result diagram with the concentrations of acetylated distarch adipate, chitosan, and chrysanthemum extract as independent variables, and the DPPH scavenging rate, inhibition zone diameter, water vapor transmission rate, tensile strength, and elongation at break as dependent variables;

[0033] Figure 2 It is a response surface result diagram;

[0034] Figure 3 It is a finished product diagram of acetylated distarch adipate coating film (A), acetylated distarch adipate / chitosan coating film (B), and acetylated distarch adipate / chitosan / chrysanthemum extract composite coating film (C);

[0035] Figure 4 It is a result diagram of the water vapor transmission rate and oxygen transmission rate of the coating film;

[0036] Figure 5 It is a result diagram of the ultraviolet transmittance of the coating film;

[0037] Figure 6 It is a change diagram of the total phenolic content and DPPH scavenging rate of the composite coating film containing chrysanthemum extract;

[0038] Figure 7 It is a change diagram of the total number of colonies of salted duck legs under different treatment methods during storage;

[0039] Figure 8 It is a change diagram of the coliform group of salted duck legs under different treatment methods during storage;

[0040] Figure 9 It is a change diagram of TBARS of salted duck legs under different treatment methods during storage;

[0041] Figure 10 It is a change diagram of TVB-N of salted duck legs under different treatment methods during storage;

[0042] Figure 11 It is a change diagram of the protein carbonyl and total sulfhydryl content of salted duck legs under different treatment methods during storage;

[0043] Figure 12 It is a change diagram of the pH value of salted duck legs under different treatment methods during storage;

[0044] Figure 13Graph showing the changes in the texture properties of salted duck legs under different treatment methods during storage;

[0045] Figure 14 Graph showing the changes in the proton density weighted images of salted duck legs during storage. Specific implementation manners

[0046] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified in detail, the technical means used are all conventional means well known to those skilled in the art.

[0047] The acetylated distarch adipate used in this application was purchased from Hangzhou Prostar Starch Co., Ltd.; chitosan (degree of deacetylation 80%, molecular weight = 500,000) and glycerol were purchased from Shanghai Macklin Biochemical Co., Ltd.

[0048] The dried Gongju used in this application was purchased from Bozhou, Anhui, and pulverized using a pulverizer to obtain chrysanthemum powder.

[0049] The salted duck legs used in this application were provided by Nanjing Professor Huang Food Technology Co., Ltd.

[0050] Example 1

[0051] 1. Preparation of Gongju extract

[0052] Mix 10 g of chrysanthemum powder with 200 mL of 70% ethanol, stir for 10 min, then perform ultrasonic-assisted extraction at 480 W for 30 min at 40 °C, and filter using Watman No. 1 filter paper. Use a rotary evaporator to set at 40 °C to remove ethanol from the filtrate to obtain Gongju extract. The Gongju extract was freeze-dried to obtain a yellow powder and stored at -20 °C until use.

[0053] 2. Optimization of the composite coating formula

[0054] Through the BBD response surface experiment, with the concentration of acetylated distarch adipate at 1 - 5% (w / v), the concentration of chitosan at 0.4 - 1.6% (w / v), and the concentration of Gongju extract at 0.3% - 1.5% (w / v) as independent variables, and the DPPH scavenging rate, inhibition zone diameter, water vapor transmission rate, tensile strength, and elongation at break as dependent variables, the experimental data were fitted using a quadratic polynomial model:

[0055]

[0056] Among them, Yi represents the response, β0, βi, βij, βii are regression coefficients, and ei is the error term.

[0057] The results are as Figure 1 and2 As shown in 2 , by measuring the antioxidant, antibacterial, water vapor barrier and mechanical properties of the composite coating film, the optimal formula was determined as follows: the concentration of acetylated distarch adipate was 2% (w / v), the concentration of chitosan was 1.3% (w / v), and the concentration of Flos Chrysanthemi extract was 1.25% (w / v).

[0058] 3. Preparation of acetylated distarch adipate coating film (ADA)

[0059] 1) Add acetylated distarch adipate to distilled water at a concentration of 2% (w / v), and heat it in a water bath at 80 °C for 30 min to completely gelatinize it, thus preparing an acetylated distarch adipate solution.

[0060] 2) Add 0.8% (v / v) glycerol, stir evenly, and adjust the pH to 5.6 ± 0.1 using sodium bicarbonate solution to prepare an acetylated distarch adipate coating film solution.

[0061] 3) Pour 20 mL of the film solution into a 90 mm plastic petri dish and dry it at room temperature for 48 h to prepare an acetylated distarch adipate coating film (ADA).

[0062] 4. Preparation of acetylated distarch adipate / chitosan composite coating film (ADA / CS)

[0063] 1) Add acetylated distarch adipate to distilled water at a concentration of 2% (w / v), and heat it in a water bath at 80 °C for 30 min to completely gelatinize it, thus preparing an acetylated distarch adipate solution.

[0064] 2) Dissolve chitosan in 1% (v / v) acetic acid at a concentration of 1.3% (w / v) to prepare a chitosan solution.

[0065] 3) Mix the acetylated distarch adipate solution and the chitosan solution in a volume ratio of 3:7, stir evenly, and prepare an acetylated distarch adipate / chitosan solution.

[0066] 4) Add glycerol to the mixed solution, with the glycerol concentration being 0.80% (v / v), stir evenly, and adjust the pH to 5.6 ± 0.1 using sodium bicarbonate solution to prepare an acetylated distarch adipate / chitosan coating film solution.

[0067] 5) Pour 20 mL of the film solution into a 90 mm plastic petri dish and dry it at room temperature for 48 h to prepare an acetylated distarch adipate / chitosan coating film (ADA / CS).

[0068] 5. Preparation of acetylated distarch adipate / chitosan / Flos Chrysanthemi extract composite coating film (ADA / CS / GE)

[0069] 1) Add acetylated distarch adipate to distilled water at a concentration of 2% (w / v), and heat it in a water bath at 80 °C for 30 min to completely gelatinize it, thus preparing an acetylated distarch adipate solution.

[0070] 2) Dissolve chitosan in 1% (v / v) acetic acid at a concentration of 1.3% (w / v) to prepare a chitosan solution.

[0071] 3) Mix the acetylated distarch adipate solution and the chitosan solution in a volume ratio of 3:7, and stir evenly to prepare an acetylated distarch adipate / chitosan solution.

[0072] 4) Add glycerol and chrysanthemum extract to the mixed solution, with the glycerol concentration being 0.80% (v / v) and the chrysanthemum extract concentration being 1.25% (w / v). Homogenize the mixed solution at 8000 rpm for 1 min, and adjust the pH to 5.6 ± 0.1 using a sodium bicarbonate solution to prepare an acetylated distarch adipate / chitosan / chrysanthemum extract coating solution.

[0073] 5) Pour 20 mL of the membrane solution into a 90 mm plastic petri dish and dry it at room temperature for 48 h to obtain an acetylated distarch adipate / chitosan / chrysanthemum extract composite coating (ADA / CS / GE).

[0074] The results are as Figure 3 shown, Figure 3 A is the finished product of the acetylated distarch adipate coating (ADA), Figure 3 B is the finished product of the acetylated distarch adipate / chitosan coating (ADA / CS), Figure 3 C is the finished product of the acetylated distarch adipate / chitosan / chrysanthemum extract composite coating (ADA / CS / GE).

[0075] Example 2

[0076] 1. Water vapor transmission rate and oxygen transmission rate

[0077] 1) Water vapor transmission rate

[0078] Cover test tubes containing 5 g of silica gel with ADA, ADA / CS, and ADA / CS / GE membrane samples respectively, and place them in an environment at 20 °C. Record their weights after 5 days. The formula is as follows:

[0079] .

[0080] Among them, MVP is the water vapor transmission rate, W is the weight change (g), x is the membrane thickness (m), t is the time (s), S is the surface area of the membrane (m 2 ), and ΔP is the saturated vapor pressure at 20 °C.

[0081] 2) Oxygen transmission rate

[0082] Cover the ADA, ADA / CS, and ADA / CS / GE membrane samples on test tubes containing 8 g of deoxidizer (reduced iron powder:sodium chloride:activated carbon = 0.5:1.5:1), respectively. Record the initial weight of the test tubes, and then place the test tubes in a desiccator containing saturated barium chloride solution and weigh them every 24 h at 20 °C until the weight is constant.

[0083] 。

[0084] Among them, OP is the oxygen transmission rate, Δm is the weight increase of the test tube (g), t is the measurement time (h), and A is the exposed film surface area (m²).

[0085] The results are as Figure 4 shown. The water vapor transmission rates of the ADA, ADA / CS, and ADA / CS / GE coated films increase in turn. The results show that the addition of chitosan improves the water vapor transmission rate, and the addition of Flos Chrysanthemi extract has no significant effect on the water vapor transmission rate. The trend of the water vapor transmission rate and oxygen transmission rate of the coated films is similar. The results show that the addition of chitosan significantly improves the oxygen transmission rate, and the addition of Flos Chrysanthemi extract also significantly improves the oxygen transmission rate.

[0086] 2. Ultraviolet transmittance

[0087] Use a UV-visible spectrophotometer to measure the transmittance (%T) of the ADA, ADA / CS, and ADA / CS / GE membrane samples in the wavelength range of 200 nm - 800 nm, respectively.

[0088] The results are as Figure 5 shown. In the ultraviolet region (200 - 400 nm), the transmittance of the ADA coated film is close to 80%, while the transmittance of the ADA / CS coated film decreases, indicating that chitosan has specific ultraviolet absorption ability; while the transmittance of the ADA / CS / GE composite coated film is close to 0 in the range of 200 - 400 nm, and the ADA / CS / GE composite coated film shows excellent ultraviolet barrier ability, indicating that the addition of Flos Chrysanthemi extract significantly improves the ultraviolet barrier ability of the composite coated film.

[0089] 3. Total phenol content and DPPH scavenging rate

[0090] Add 0.5 mL of the ADA / CS / GE composite coated film solution to 4.5 mL of water or 95% ethanol, respectively, to prepare the ADA / CS / GE composite coated film aqueous solution (hydrophilic food simulant) and the ADA / CS / GE composite coated film ethanol solution (lipophilic food simulant), and store the solutions at 4 °C for 21 days.

[0091] 1) Total phenol content

[0092] Add Folin-Ciocalteu reagent (0.5 mL, 0.2 M) to the aqueous solution and ethanol solution of the ADA / CS / GE composite coating film respectively, react in the dark for 8 min, and then add 10% (w / v) of , and make up the volume to 10 mL with distilled water. After continuing the reaction for 2 h in the dark, measure the absorbance of the supernatant of the mixture at a wavelength of 765 nm to determine the total phenol content of the composite coating film. The results are expressed as mg GAE / 1 g DW (gallic acid equivalent).

[0093] 2) DPPH scavenging rate

[0094] Mix the prepared aqueous solution and ethanol solution of the ADA / CS / GE composite coating film with 0.1 mM DPPH ethanol solution respectively, and place them in the dark for 30 min. After centrifugation, measure the absorbance of the supernatant of the mixture at 517 nm.

[0095] The results are as Figure 6 shown. With the extension of storage time, the total phenol content in the coating film decreased significantly; in the hydrophilic food simulant, the total phenol content of the ADA / CS / GE coating film decreased from 0.075 mg GAE / mL to 0.066 mg GAE / mL; in the lipophilic food simulant, the total phenol content decreased from 0.070 mg GAE / mL to 0.061 mg GAE / mL ( Figure 6 A). The DPPH radical scavenging activity also decreased significantly during storage, but remained above 40% on the 21st day; in the hydrophilic food simulant, the DPPH radical scavenging activity of the ADA / CS / GE coating film decreased from 63.89% to 46.12%; in the lipophilic food simulant, it decreased from 60.70% to 43.98%. The results show that the ADA / CS / GE composite coating film has persistent and stable functional activities during storage ( Figure 6 B).

[0096] Example 3

[0097] Soak the salted duck legs in the ADA, ADA / CS and ADA / CS / GE coating solutions for 5 min respectively, then take them out and dry them at room temperature for 15 min, and repeat this process twice; then transfer them to a tray, cover them with plastic wrap, and store them in an environment of 4 °C. In the control group, the salted duck legs were directly placed on a tray, covered with plastic wrap, and stored in an environment of 4 °C. The experiment was repeated 5 times. Samples were taken on the 0th, 3rd, 6th, 9th, 12th, 15th, 18th, and 21st days of storage for index determination.

[0098] 1. Total number of colonies

[0099] Mix 25 g of deboned meat samples with skin under aseptic conditions with 225 mL of normal saline, and use a homogenizing beater to beat at medium speed for 2 min to mix evenly. Dilute the sample solution 10-fold, 100-fold, and 1000-fold with sterile normal saline. Using the pour plate method, evenly mix the appropriately diluted sample solution with plate count agar medium, and then incubate at 36 ± 1 °C for 48 ± 2 h before counting.

[0100] The results are as Figure 7 shown. During storage, the total number of colonies in the salted duck leg samples increased significantly. The control group had the fastest growth rate, followed by the ADA group and the ADA / CS group, while the ADA / CS / GE group had the slowest growth rate. The total number of colonies in the salted duck legs on the first day was 1.85 log CFU / g. According to the national food safety standard (GB 2726-2016), the allowable limit of the total number of colonies in cooked meat products is 4.0 log CFU / g. If the total number of colonies exceeds this value, the meat products will deteriorate; the control group, the ADA group, the ADA / CS group, and the ADA / CS / GE group reached this threshold on the 9th day, the 9th day, the 15th day, and the 18th day, respectively.

[0101] 2. Coliform bacteria

[0102] Use test strips (purchased from Guangdong DYNO Green Food Safety Technology Co., Ltd.), with an inoculation volume of 1 mL, and incubate at 36 ± 1 °C for 24 h before counting.

[0103] The results are as Figure 8 shown. The number of coliform bacteria in the salted duck legs increased with the extension of storage time. The control group and the ADA group had the fastest growth rate of coliform bacteria, and there was no significant difference between the two; the growth rate of the ADA / CS group was slightly slower, while the growth rate of the ADA / CS / GE group was the slowest; the number of coliform bacteria in the control group and the ADA group exceeded 1 log CFU / g on the 6th day, while the ADA / CS group and the ADA / CS / GE group exceeded this threshold on the 9th day and the 12th day, respectively. The results show that the antibacterial effect of the ADA / CS / GE group is better than that of the other three groups. At the end of storage, the number of coliform bacteria in the control group was 4.35 log CFU / g, the ADA group was 4.28 log CFU / g, the ADA / CS group was 3.22 log CFU / g, and the ADA / CS / GE group was 2.54 log CFU / g.

[0104] 3. TBARS

[0105] Mix 5 g of peeled and minced sample with 50 mL of 7.5% trichloroacetic acid solution and homogenize in an ice bath at 12,000 rpm for 30 s. After centrifuging at 8,000 rpm for 10 min, mix the supernatant with an equal volume of 0.02 mol / L thiobarbituric acid solution. React the mixture at 95 °C for 30 min and measure the absorbance at a wavelength of 532 nm. Establish a standard curve using 1,1,3,3-tetraethoxypropane. The results are expressed as milligrams of malondialdehyde (MDA) per kilogram of sample.

[0106] The results are as Figure 9 shown. As the storage time extended, the TBARS value of salted duck legs increased significantly. The growth rate of the ADA / CS / GE group was significantly lower than that of the other three groups. At the initial stage of storage, the TBARS value was 0.33 mg MDA / kg. By the end of storage, the TBARS values of the control group, ADA, ADA / CS, and ADA / CS / GE groups were 2.5, 2.3, 2.1, and 1.53 mg MDA / kg, respectively. Both the ADA / CS and ADA / CS / GE coatings inhibited lipid oxidation, and the ADA / CS / GE coating had a better effect.

[0107] 4. TVB-N

[0108] Mix 10 g of peeled and minced sample with 75 mL of distilled water in a distillation tube for 30 min, and add 1 g of magnesium oxide to the distillation tube. Measure using an automatic Kjeldahl apparatus. The results are expressed as milligrams per 100 grams.

[0109] The results are as Figure 10 shown. As the storage time increased, the TVB-N value of the sample also increased. The control group and the ADA group had the fastest growth rate, followed by the ADA / CS group, while the ADA / CS / GE group had the slowest growth rate. On day 0, the TVB-N value of the sample was 1.50 mg / 100 g, while on day 21, the TVB-N values of the control group, ADA, ADA / CS, and ADA / CS / GE groups were 11.29, 11.06, 8.16, and 5.78 mg / 100 g, respectively. On day 3, the TVB-N value of the ADA group was lower than that of the control group. Both the ADA / CS coating and the ADA / CS / GE coating significantly controlled the increase in the TVB-N value.

[0110] 5. Protein carbonyl and total sulfhydryl group content

[0111] 1) Protein carbonyl content

[0112] Measure using a protein carbonyl detection kit (purchased from Beijing Solarbio Science & Technology Co., Ltd.), and all steps are carried out according to the kit instructions.

[0113] The results are asFigure 11 As shown in Figure A, the initial carbonyl content in duck legs was 0.99 nmol / mg protein. With the increase of storage time, the carbonyl content in all groups increased. The growth rates of the control group and the ADA group were the fastest, followed by the ADA / CS group, while the growth rate of the ADA / CS / GE group was the lowest. On the 21st day, the carbonyl contents of the control, ADA, ADA / CS, and ADA / CS / GE groups reached 5.08, 5.00, 4.17, and 3.04 nmol / mg protein, respectively.

[0114] 2) Total sulfhydryl content

[0115] Mix 0.5 g of peeled sample with 9 mL of phosphate buffer (PBS, pH = 6.5) and homogenize thoroughly. Take 0.2 mL of the mixture and add it to 2.3 mL of 8 M urea and 0.25 mL of DTNB (10 mM DTNB dissolved in 20 mM PBS, pH = 8). Then keep the solution in the dark for 30 min and measure the absorbance at a wavelength of 412 nm.

[0116] The results are as Figure 11 shown in Figure B. The initial sulfhydryl content of the sample was 50.44 μmol / mg protein. The sulfhydryl content in all treatment groups decreased with time, but compared with the control group and the ADA group, the decrease rates of the ADA / CS group and the ADA / CS / GE group were significantly lower. The final sulfhydryl contents of the control, ADA, ADA / CS, and ADA / CS / GE groups decreased to 21.8, 21.59, 24.83, and 29.67 μmol / mg protein, respectively. The results indicate that the ADA / CS coating inhibited protein oxidation, and the addition of Gongju extract significantly enhanced this inhibitory effect.

[0117] 6. pH value

[0118] Measure the pH value using a pH meter.

[0119] The results are as Figure 12 shown. The pH value of the fresh sample was 6.5. During storage, the pH values of the control group and the ADA group changed more significantly, reaching 6.7 and 6.72 respectively at the end of storage, which were significantly higher than those of the ADA / CS group (pH = 6.44) and the ADA / CS / GE group (pH = 6.41). The inherent antibacterial properties of chitosan and Gongju extract effectively maintained the pH level of the duck meat samples.

[0120] 7. Texture properties

[0121] Measure the texture properties of the samples, such as hardness, elasticity, chewiness, and resilience, using a texture analyzer.

[0122] The results are as Figure 13As shown, during the late storage period, the hardness of the control group, ADA group, and ADA / CS group all increased. In addition, compared with other groups, the ADA / CS / GE group showed better elasticity, chewiness, and resilience throughout the storage period.

[0123] 8. Magnetic Resonance Imaging

[0124] The samples were analyzed using a low-field nuclear magnetic resonance analyzer. The water molecules in the salted duck leg samples are the main source of hydrogen protons. Nuclear magnetic resonance imaging technology generates hydrogen proton density images through the magnetic resonance signals of hydrogen protons, thereby analyzing the water content and distribution in the salted duck leg samples. Red and blue in the images represent high and low water content, respectively.

[0125] The results are as Figure 14 shown. As the storage time increased, the water content of the salted duck legs gradually decreased. Compared with the control group, the water content of the salted duck samples with coatings decreased at a slower rate, indicating that the coatings can act as a barrier to reduce water evaporation.

[0126] The above description is illustrative rather than restrictive for the present invention. Those of ordinary skill in the art understand that many modifications, variations, or equivalents can be made without departing from the spirit and scope defined by the appended claims, and all of them will fall within the protection scope of the present invention.

Claims

1. A composite coating solution containing a Gongju extract, characterized in that: It is composed of the following components in the following mass percentage concentrations: 1-5% acetylated distarch adipate, 0.4-1.6% chitosan, 0.3%-1.5% chrysanthemum extract and glycerol.

2. The method for preparing the composite coating solution according to claim 1, characterized in that the steps include: 1) preparing an acetylated distarch adipate solution, wherein the concentration of acetylated distarch adipate is 1-5% w / v; 2) preparing a chitosan solution with a chitosan concentration of 0.4-1.6% w / v; 3) mixing the acetylated distarch adipate solution and the chitosan solution in a volume ratio of 3:7, stirring evenly, to prepare an acetylated distarch adipate / chitosan solution; 4) Glycerin and Gongju extract were added into the mixed solution, the concentration of glycerin was 0.80% v / v, and the concentration of Gongju extract was 0.3%-1.5% w / v, to prepare acetylated distarch adipate / chitosan / Gongju extract coating solution.

3. The method for preparing the composite coating solution according to claim 2, characterized in that: The concentration of the acetylated distarch adipate is 2%.

4. The method for preparing the composite coating solution according to claim 2, characterized in that: The chitosan concentration is 1.3%.

5. The method for preparing the composite coating solution according to claim 2, characterized in that: The concentration of the Gongju extract is 1.25%.

6. A composite coating containing a Gongju extract, characterized in that: It is composed of the following components in the following mass percentage concentrations: 1-5% acetylated distarch adipate, 0.4-1.6% chitosan, 0.3%-1.5% chrysanthemum extract and glycerol.

7. The composite coating containing the Gongju extract according to claim 6, characterized in that: It is composed of the following components in the following mass percentage concentrations: 2% acetylated distarch adipate, 1.3% chitosan, 1.25% chrysanthemum extract and glycerol.

8. The method for preparing the composite coating containing the Gongju extract according to claim 6, characterized in that: The specific steps include: 1) Acetylated distarch adipate was added to distilled water at a concentration of 2% w / v, and heated in a water bath at 80°C for 30 min to completely gelatinize the water, thereby preparing an acetylated distarch adipate solution; 2) dissolving chitosan in a 1% by volume acetic acid solution to a concentration of 1.3% w / v to prepare a chitosan solution; 3) mixing the acetylated distarch adipate solution and the chitosan solution in a volume ratio of 3:7, stirring evenly, to prepare an acetylated distarch adipate / chitosan solution; 4) Glycerin and Gongju extract were added to the mixed solution, the concentration of glycerin was 0.80% v / v, and the concentration of Gongju extract was 1.25% w / v; the mixed solution was homogenized at 8000 rpm for 1 min, and the pH was adjusted to 5.6±0.1 with sodium bicarbonate solution to prepare acetylated distarch adipate / chitosan / Gongju extract coating solution; 5) Pour 20 mL of the film solution into a 90 mm plastic culture dish and dry at room temperature for 48 h to obtain the acetylated distarch adipate / chitosan / gongju extract composite coating.

9. The use of the composite coating solution containing Gongju extract as described in claim 1 in blocking water vapor and oxygen, and / or blocking ultraviolet rays, and / or preserving food, and / or inhibiting the growth of colonies and bacterial colonies, and / or inhibiting protein oxidation, and / or maintaining the pH value of food, and / or inhibiting lipid oxidation.

10. Use of the composite coating containing Gongju extract as described in claim 6 in blocking water vapor and oxygen, and / or blocking ultraviolet rays, and / or preserving food, and / or inhibiting the growth of bacterial colonies and flora, and / or inhibiting protein oxidation, and / or maintaining the pH value of food, and / or inhibiting lipid oxidation.

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