Fresh-keeping and anti-browning coating film, and preparation method and application thereof

Abstract

The application discloses a kind of preservative anti-browning coating film and preparation method and application thereof, belong to edible film technical field, a kind of preservative anti-browning coating film, according to mass fraction, its raw materials include the following components: chitosan quaternary ammonium salt 1.5-2.5 parts, glycerol 0.8-1.2 parts, glutathione 0.25-0.75 parts, citral 0.5-1.0 parts, anhydrous ethanol 8-12 parts and distilled water 88-92 parts.The application uses chitosan quaternary ammonium salt as main film-forming material, glutathione and citral are compounded as main raw materials to prepare preservative anti-browning coating film, the coating film has good antioxidant and antibacterial performance, is used for the surface of waxy rice and Chinese yam, can effectively prevent the browning of waxy rice and Chinese yam, can also inhibit the growth of bacteria and mould, thereby prolongs its shelf life, maintains its nutritional and appearance quality.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of edible film, and particularly relates to a fresh-keeping and browning-preventing coating film and a preparation method and application thereof. BACKGROUND

[0002] Dioscorea is a total name of grassy liana plants of the Dioscoreaceae and Dioscorea, which is rich in starch, polysaccharide, mucin and polyphenols and has high nutritional efficacy and is widely used in Chinese food and traditional medicinal diet. Dioscorea is extremely susceptible to mechanical damage in the process of transportation and storage, so that the surface of the dioscorea is exposed to air, thereby leading to browning and spoilage, which not only affects the edible quality and nutritional value of the dioscorea, but also hinders the further popularization and application and large-scale production of the dioscorea. Therefore, how to control the browning and prevent the spoilage of the dioscorea is a key technical problem to be solved by relevant production enterprises.

[0003] At present, the main methods for preserving dioscorea include cold storage and air conditioning preservation, but the dioscorea may be frozen, the taste and quality of the dioscorea may be reduced and molds may grow on the surface of the dioscorea when the cold storage time is too long; the air conditioning preservation needs to be realized by means of professional equipment and technical means and has high cost, therefore, research and development of a fresh-keeping technology which can effectively prevent the browning of dioscorea, inhibit the growth of bacteria and molds and is economical, convenient and fast is a current research focus. SUMMARY

[0004] In view of the deficiencies of the prior art, the application provides a fresh-keeping and browning-preventing coating film and a preparation method and application thereof.

[0005] One of the technical solutions provided by the application is as follows:

[0006] A fresh-keeping and browning-preventing coating film, according to mass parts, raw materials of the fresh-keeping and browning-preventing coating film include the following components: 1.5-2.5 parts of chitosan quaternary ammonium salt, 0.8-1.2 parts of glycerol, 0.25-0.75 parts of glutathione, 0.5-1.0 parts of citral, 8-12 parts of anhydrous ethanol and 88-92 parts of distilled water.

[0007] Further, according to mass parts, raw materials of the fresh-keeping and browning-preventing coating film include the following components: 2.0 parts of chitosan quaternary ammonium salt, 1.0 part of glycerol, 0.5 part of glutathione, 0.75 part of citral, 10 parts of anhydrous ethanol and 90 parts of distilled water.

[0008] The second technical solution provided by the application is as follows:

[0009] A preparation method of the fresh-keeping and browning-preventing coating film, including the following steps:

[0010] The chitosan quaternary ammonium salt, the distilled water, the anhydrous ethanol and the glycerol are mixed and stirred under heating conditions until completely dissolved to obtain a chitosan quaternary ammonium salt solution;

[0011] Glutathione and citral are added to the chitosan quaternary ammonium salt solution, and after mixing, vacuum low-temperature magnetic stirring film crosslinking is carried out to obtain a film-forming solution;

[0012] The film-forming solution is subjected to ultrasonic degassing to prepare the fresh-keeping and browning-preventing coating film.

[0013] By adding a certain amount of ethanol, the ethanol molecules are wrapped in the high-molecular mesh pores of the chitosan quaternary ammonium salt solution, so that the ethanol molecules are limited by physical steric hindrance and are difficult to escape from the system by diffusion. In addition, during the heating process, the movement ability of the chitosan quaternary ammonium salt molecular chain is enhanced, and further crosslinking is formed through hydrogen bonds to form a more dense network, further "imprisoning" the ethanol molecules. When the coating solution acts on the surface of the food, the system is separated from the heating condition, the intermolecular force is weakened, and the volatility of ethanol is dominant. A volatile gradient is formed to accelerate the overall evaporation rate of the solvent, which carries out rapid evaporation of water, so that the film-forming time of the coating film is shortened to 3.67 min.

[0014] Further, the temperature of the heating is 60 DEG C, and the time is 15-45 min.

[0015] Further, the vacuum degree of the vacuum low-temperature magnetic stirring film crosslinking is -0.06 MPa, the temperature is 25-35 DEG C, and the time of the magnetic stirring is 40-80 min.

[0016] The vacuum low-temperature magnetic stirring film crosslinking method is adopted, which has a significant advantage in improving the film performance and fresh-keeping effect compared with the traditional normal pressure crosslinking. In a vacuum environment, the interference of air molecules is eliminated to create more uniform conditions for the crosslinking reaction in the film structure. At the same time, oxygen is effectively excluded to avoid side reactions caused by oxidation during the crosslinking process, thereby ensuring the performance and structural integrity of the film material and significantly improving the stability and service life of the film.

[0017] Further, the time of the ultrasonic degassing is 10-20 min, and the power is 200-400 W.

[0018] The third technical solution provided by the application is as follows:

[0019] The application provides an application of the fresh-keeping and browning-preventing coating film to the fresh-keeping of a waxy yam.

[0020] The fourth technical solution provided by the application is as follows:

[0021] A fresh-keeping method of a waxy yam, the fresh-keeping and browning-preventing coating film is sprayed on the surface or damaged part of the waxy yam, and after a thin film is formed on the surface of the waxy yam, the waxy yam is stored at low temperature; or the waxy yam is soaked in the fresh-keeping and browning-preventing coating film, and after a thin film is formed on the surface of the waxy yam, the waxy yam is stored at low temperature.

[0022] Further, the low temperature is 2-5 DEG C.

[0023] The citral and glutathione have synergistic antioxidant effect and realize sustained effect, and the two are compounded with other ingredients in the film to crosslink, and the sustained antioxidant effect is achieved through the slow release effect. As a fat-soluble substance, citral can capture free radicals through conjugated double bonds, and embed into the cell membrane to inhibit lipid peroxidation; glutathione is a water-soluble sulfhydryl tripeptide, which can directly reduce active oxygen with sulfhydryl, and regenerate other antioxidants, and the two form a three-dimensional antioxidant network of 'fat-soluble-water-soluble' and 'direct-indirect'. In terms of slow release and long-acting antioxidant, citral can inhibit the activity of polyphenol oxidase by combining with polyphenol oxidase, and glutathione can capture o-quinone generated by the reaction to block browning; the two can be regenerated by mutual reduction after oxidation, and can cycle to play a role; at the same time, citral stabilizes the cell membrane, glutathione maintains the intracellular reducing state, delays tissue deterioration, and synergistically induces the expression of endogenous antioxidant enzymes, realizes long-acting protection of the waxy yam through the multiple mechanisms of 'enzyme inhibition-circulation-membrane protection-promotion'.

[0024] Compared with the prior art, the present application has the following advantages and technical effects:

[0025] The chitosan quaternary ammonium salt used in the present application can interact with glutathione and citral through hydrogen bonds, van der Waals forces and electrostatic attraction to form a good crosslinked structure. The chitosan quaternary ammonium salt provides a basic skeleton and cationic properties, and the cationic properties refer to the property of a substance molecule or group having a positive charge (cation), which is usually caused by the protonation or permanent electrification of groups such as amino and quaternary ammonium groups in the molecular structure, and the cationic properties of the chitosan quaternary ammonium salt are derived from the quaternary ammonium group (-N + (CH3)3), which can be combined with the negatively charged components in the system through electrostatic interaction to form an 'ionic bond bridge', promote the crosslinking between molecular chains, and make the film structure more compact. Glutathione participates in crosslinking and stabilizes the film structure through the action of sulfhydryl, and citral increases the crosslinking degree and improves the mechanical properties, water resistance and oxygen permeability of the film through Schiff base reaction, and the chitosan quaternary ammonium salt used in the present application has good film-forming property and good antibacterial property.

[0026] The chitosan quaternary ammonium salt is used as the main film-forming material, and glutathione and citral are compounded as the main raw materials to prepare the preservative and browning prevention coating film, which has good antioxidant and antibacterial properties, and is used on the surface of waxy yam, which can effectively prevent the browning of waxy yam, inhibit the growth of bacteria and mold, and prolong the shelf life and maintain the nutritional and appearance quality of the waxy yam. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] In the embodiments of this invention, unless otherwise specified, "parts" refers to "parts by mass".

[0033] Example 1: A method for preparing a preservative and anti-browning coating

[0034] Weigh out 2.0 parts of chitosan quaternary ammonium salt, 1.0 part of glycerol, 0.5 parts of glutathione, 0.75 parts of citral, 10 parts of anhydrous ethanol, and 90 parts of distilled water according to the specified weight. The specific preparation method is as follows:

[0035] S1. Mixing of film-forming materials: In a 100mL beaker, add distilled water, anhydrous ethanol and glycerol respectively, and stir magnetically at 60℃ for 30min until completely dissolved to prepare a chitosan quaternary ammonium salt solution. Then add glutathione and citral to the solution and mix thoroughly.

[0036] S2. Crosslinking: the prepared solution of step S1 was crosslinked completely under the conditions of vacuum degree -0.06 MPa and temperature 30℃ for 60 min by vacuum magnetic stirring to prepare a film-forming solution;

[0037] S3. Degassing: the film-forming solution obtained in step S2 was placed in an ultrasonic cleaning machine to remove bubbles by ultrasonic treatment (300 W, 15 min) to prepare a fresh-keeping and browning-preventing coating film.

[0038] Example 2: A preparation method of a fresh-keeping and browning-preventing coating film

[0039] According to mass parts, 1.5 parts of chitosan quaternary ammonium salt, 1.0 part of glycerol, 0.5 part of glutathione, 0.75 part of citral, 12 parts of absolute ethanol, and 88 parts of distilled water were weighed, and the specific preparation method was as follows:

[0040] S1. Mixing of film-forming materials: chitosan quaternary ammonium salt was added into a 100 mL beaker, and distilled water, absolute ethanol, and glycerol were added respectively, and magnetic stirring was performed at 60℃ for 30 min until complete dissolution to prepare a chitosan quaternary ammonium salt solution, and then glutathione and citral were added respectively and mixed thoroughly;

[0041] S2. Crosslinking: the prepared solution of step S1 was crosslinked completely under the conditions of vacuum degree -0.06 MPa and temperature 30℃ for 60 min by vacuum magnetic stirring to prepare a film-forming solution;

[0042] S3. Degassing: the film-forming solution obtained in step S2 was placed in an ultrasonic cleaning machine to remove bubbles by ultrasonic treatment (300 W, 15 min) to prepare a fresh-keeping and browning-preventing coating film.

[0043] Example 3: A preparation method of a fresh-keeping and browning-preventing coating film

[0044] According to mass parts, 2.5 parts of chitosan quaternary ammonium salt, 0.8 part of glycerol, 0.25 part of glutathione, 0.5 part of citral, 8 parts of absolute ethanol, and 92 parts of distilled water were weighed, and the specific preparation method was as follows:

[0045] S1. Mixing of film-forming materials: chitosan quaternary ammonium salt was added into a 100 mL beaker, and distilled water, absolute ethanol, and glycerol were added respectively, and magnetic stirring was performed at 60℃ for 30 min until complete dissolution to prepare a chitosan quaternary ammonium salt solution, and then glutathione and citral were added respectively and mixed thoroughly;

[0046] S2. Crosslinking: the prepared solution of step S1 was crosslinked completely under the conditions of vacuum degree -0.06 MPa and temperature 30℃ for 60 min by vacuum magnetic stirring to prepare a film-forming solution;

[0047] S3. Degassing: the film-forming solution obtained in step S2 was placed in an ultrasonic cleaning machine, and bubbles were removed by ultrasonic treatment (400 W, 20 min) to prepare the fresh-keeping and browning-preventing coating film.

[0048] Example 4 A method for preparing a fresh-keeping and browning-preventing coating film

[0049] According to the mass parts, 2.5 parts of chitosan quaternary ammonium salt, 1.2 parts of glycerol, 0.75 parts of glutathione, 1 part of citral, 8 parts of absolute ethanol, and 92 parts of distilled water were weighed, and the specific preparation method was as follows:

[0050] S1. Mixing of film-forming materials: chitosan quaternary ammonium salt was added into a 100 mL beaker, and distilled water, absolute ethanol, and glycerol were added respectively, and the mixture was stirred at 60°C for 45 min until completely dissolved to prepare a chitosan quaternary ammonium salt solution. Then, glutathione and citral were added respectively, and the mixture was thoroughly mixed;

[0051] S2. Crosslinking: the prepared solution in step S1 was crosslinked under the conditions of vacuum degree -0.06 MPa and temperature 35°C by vacuum magnetic stirring for 80 min to prepare a film-forming solution.

[0052] S3. Degassing: the film-forming solution obtained in step S2 was placed in an ultrasonic cleaning machine, and bubbles were removed by ultrasonic treatment (400 W, 20 min) to prepare the fresh-keeping and browning-preventing coating film.

[0053] Comparative Example 1 A method for preparing a fresh-keeping and browning-preventing coating film

[0054] According to the mass parts, 2.5 parts of chitosan quaternary ammonium salt, 1.2 parts of glycerol, 0.75 parts of glutathione, 1 part of citral, 8 parts of absolute ethanol, and 92 parts of distilled water were weighed, and the specific preparation method was as follows:

[0055] S1. Mixing of film-forming materials: chitosan quaternary ammonium salt was added into a 100 mL beaker, and distilled water, absolute ethanol, and glycerol were added respectively, and the mixture was stirred at 60°C for 45 min until completely dissolved to prepare a chitosan quaternary ammonium salt solution. Then, glutathione and citral were added respectively, and the mixture was thoroughly mixed;

[0056] S2. Crosslinking: the prepared solution in step S1 was crosslinked under the conditions of vacuum degree -0.06 MPa and temperature 35°C by vacuum magnetic stirring for 80 min to prepare a film-forming solution.

[0057] S3. Degassing: the film-forming solution obtained in step S2 was placed in an ultrasonic cleaning machine, and bubbles were removed by ultrasonic treatment (400 W, 20 min) to prepare the fresh-keeping and browning-preventing coating film.

[0058] Comparative Example 2 A method for preparing a fresh-keeping and browning-preventing coating film

[0059] The same as Comparative Example 1, except that the vacuum low-temperature magnetic stirring film crosslinking method was replaced by the traditional normal pressure crosslinking method.

[0060] According to the mass parts, 1.5 parts of chitosan quaternary ammonium salt, 1.0 part of glycerol and 100 parts of distilled water are weighed, and the specific preparation method is as follows:

[0061] S1. Mixing of film-forming material: chitosan quaternary ammonium salt is added with distilled water and glycerol in a 100 mL beaker, and stirred at 60°C for 30 min to completely dissolve, to prepare a chitosan quaternary ammonium salt solution;

[0062] S2. Crosslinking: The solution prepared in step S1 is crosslinked at 45°C under normal pressure and magnetic stirring for 60 min to prepare a film-forming solution;

[0063] S3. Degassing: The film-forming solution obtained in step S2 is placed in an ultrasonic cleaning machine, and the bubbles are removed by ultrasonic (200W, 5min) to prepare a fresh-keeping and browning-preventing coating film.

[0064] Preparation method of a kind of fresh-keeping and browning-preventing coating film

[0065] The same as example 1, the only difference is that no citral is added.

[0066] According to the mass parts, 2.0 parts of chitosan quaternary ammonium salt, 1.0 part of glycerol, 0.5 part of glutathione, 10 parts of anhydrous ethanol and 90 parts of distilled water are weighed, and the specific preparation method is as follows:

[0067] S1. Mixing of film-forming material: chitosan quaternary ammonium salt is added with distilled water, anhydrous ethanol and glycerol in a 100 mL beaker, and stirred at 60°C for 30 min to completely dissolve, to prepare a chitosan quaternary ammonium salt solution, and then add glutathione and mix well;

[0068] S2. Crosslinking: The solution prepared in step S1 is crosslinked at a vacuum degree of-0.06MPa and a temperature of 30°C under vacuum and magnetic stirring for 60 min to completely crosslink to prepare a film-forming solution;

[0069] S3. Degassing: The film-forming solution obtained in step S2 is placed in an ultrasonic cleaning machine, and the bubbles are removed by ultrasonic (200W, 15min) to prepare a fresh-keeping and browning-preventing coating film.

[0070] Preparation method of a kind of fresh-keeping and browning-preventing coating film

[0071] The same as example 1, the only difference is that no glutathione is added.

[0072] According to the mass parts, 2.0 parts of chitosan quaternary ammonium salt, 1.0 part of glycerol, 0.75 part of citral, 10 parts of anhydrous ethanol and 90 parts of distilled water are weighed, and the specific preparation method is as follows:

[0073] S1. Mixing of film-forming materials: The chitosan quaternary ammonium salt was added with distilled water, anhydrous ethanol and glycerol in a 100 mL beaker, respectively, and stirred magnetically at 60°C for 30 min until completely dissolved to prepare a chitosan quaternary ammonium salt solution, and then citral was added and mixed thoroughly;

[0074] S2. Crosslinking: The solution prepared in step S1 was crosslinked completely under the conditions of vacuum degree -0.06 MPa and temperature 30°C by vacuum magnetic stirring for 60 min to prepare a film-forming solution;

[0075] S3. Degassing: The film-forming solution obtained in step S3 was placed in an ultrasonic cleaning machine to remove air bubbles by ultrasonic treatment (200 W, 15 min) to prepare a fresh-keeping and browning-preventing coating film.

[0076] Comparative Example 5

[0077] The same as in Example 1, except that the vacuum low-temperature film crosslinking method was replaced by the traditional normal-pressure crosslinking method.

[0078] The chitosan quaternary ammonium salt 2.0 parts, glycerol 1.0 part, glutathione 0.5 part, citral 0.75 part, anhydrous ethanol 10 parts and distilled water 90 parts were weighed according to the mass fraction, and the specific preparation method was as follows:

[0079] S1. Mixing of film-forming materials: The chitosan quaternary ammonium salt was added with distilled water, anhydrous ethanol and glycerol in a 100 mL beaker, respectively, and stirred magnetically at 60°C for 30 min until completely dissolved to prepare a chitosan quaternary ammonium salt solution, and then glutathione and citral were added and mixed thoroughly;

[0080] S2. Crosslinking: The solution prepared in step S1 was crosslinked completely under the conditions of vacuum degree -0.06 MPa and temperature 30°C by vacuum magnetic stirring for 60 min to prepare a film-forming solution;

[0081] S3. Degassing: The film-forming solution obtained in step S2 was placed in an ultrasonic cleaning machine to remove air bubbles by ultrasonic treatment (200 W, 15 min) to prepare a fresh-keeping and browning-preventing coating film.

[0082] Performance test

[0083] The film-forming time of the coating films prepared in Examples 1-4 and Comparative Examples 1-5 was investigated, and the tensile strength, water vapor transmission rate and oxygen transmission rate of each film were tested.

[0084] The film-forming time was measured by taking equal amounts of the coating films prepared under different conditions and uniformly coating them on the surface of yam, and timing. When the coating film on the glass flat plate was almost not sticky to the hand (or glove) when touched, it was determined that a film had been formed. Each group of samples was measured repeatedly for 3 times, and the average value was taken. The test results are shown in Table 1.

[0085] The test method of tensile strength is as follows: the prepared coating liquid is poured into a 15x15cm flat dish, dried in a vacuum oven at 35℃, cut into 90x20mm long strips, the initial clamping distance of the Universal TA texture analyzer is set to 50mm, the thickness of the preservative film is measured with a micrometer, the tensile speed is 0.5mm / min, each group of samples is measured three times, and the average value is taken, and the test results are shown in Table 1.

[0086] Table 1

[0087]

[0088] As can be seen from Table 1, the tensile strength of the preservative and browning prevention coating prepared by the present application can reach 22.67MPa, which is increased by 78.93% compared with the pure quaternary ammonium salt chitosan coating (Comparative Example 1), the water vapor permeability is 30.55g / (m 2 ·24h), which is reduced by 45.12% compared with the pure quaternary ammonium salt chitosan coating (Comparative Example 1), the oxygen permeability coefficient is 1.19x10 -4 g / m 2 s, which is reduced by 55.76% compared with the pure quaternary ammonium salt chitosan coating (Comparative Example 1), effectively blocking the transmission of water and oxygen.

[0089] The coatings prepared by Examples 1-4 and Comparative Examples 1-5 are respectively sprayed to the damaged parts of waxy rice and yam, and a layer of film is formed on the surface, and then placed in a refrigerator at 4℃ for storage, and PE film is wrapped around the damaged parts of waxy rice and yam as a control group. The oxidation and browning of waxy rice and yam, DPPH and ABTS free radical scavenging rate, browning degree and ΔE in each example, comparative example, control group and blank group (CK, the damaged part of waxy rice and yam is not treated) are investigated.

[0090] Among them, the determination method of browning degree is as follows: 2g of yam is ground into homogenate at 4℃, distilled water is added at a mass ratio of 1:10, centrifuged at 4000r / min for 10min at 4℃, the supernatant is incubated at room temperature for 5min, the absorbance value A410nm at 410nm is measured, and the browning degree is represented by A410nmx10, and the investigation results are shown in Table 2.

[0091] The determination method of ΔE is as follows: the NS810 type spectrophotometer is used to measure the L* value, a* value and b* value of the brittle yam block at multiple points, and the average value is analyzed, and the investigation results are shown in Table 2.

[0092] Table 2

[0093]

[0094] It can be seen from Table 2 that the film formed by the preservative and browning prevention coating prepared by the application has a DPPH and ABTS free radical scavenging rate of 90.06% and 85.88% respectively, which is 3.65 times and 3.61 times higher than that of the blank group (CK) respectively, and prolongs the storage period of the waxy yam by 8-10 days. Compared with the blank group and the PE film control group, the browning degree of Example 1 is reduced by 57.39% and 51.49% respectively. Compared with the blank group and the control group (PE), the ΔE value of Example 1 is reduced by 46.28% and 43.90% respectively.

[0095] The reducing sugar content, titratable acid content, soluble solid content and vitamin C content of the waxy yam in each example, comparative example, control group and blank group were investigated.

[0096] Among them, the reducing sugar content is determined according to GB 5009.7-2016; the titratable acid content is determined according to GB 12456-2021; the soluble solid content is determined according to NY / T 2637-2014; and the vitamin C content is determined according to GB 5009.86-2016. The investigation results are shown in Table 3.

[0097] Table 3

[0098]

[0099] Bacteriostatic test:

[0100] The bacteriostatic performance of the preservative and browning prevention coating prepared in Example 1, the control group and the blank group was investigated, and the test method was as follows:

[0101] The inhibition effect on bacteria was tested by GB 15979-2024 method;

[0102] The inhibition effect on mold was tested by GB 15979-2024 method;

[0103] The inhibition effect on yeast was tested by GB 15979-2024 method;

[0104] The calculation formula of the bacteriostatic rate is

[0105] In the formula: Y is the bacteriostatic rate;

[0106] N c The average number of colonies of the blank group, unit: CFU / mL;

[0107] N s The average number of colonies of the test sample, unit: CFU / mL.

[0108] The test results show that the bacteriostatic rates of the fresh-keeping and browning-preventing coating prepared in Example 1 on bacteria, molds and yeasts are 71.34%, 65.66% and 64.88% respectively; the bacteriostatic rates of the control group on bacteria, molds and yeasts are 33.78%, 28.98% and 27.87% respectively.

[0109] Fresh-keeping test

[0110] The waxy yam is packaged by using the fresh-keeping and browning-preventing coating prepared in Example 1 and the control group (PE film) respectively.

[0111] The packaging method of the fresh-keeping and browning-preventing coating is that the fresh-keeping and browning-preventing coating is sprayed on the surface of the waxy yam to form a thin film on the surface, and then the waxy yam is stored in a cold storage at 4 DEG C, four waxy yams are processed in parallel, and the average value of the test results is taken;

[0112] The packaging method of the PE film is that the PE film is wrapped on the surface of the waxy yam, and after one layer of wrapping, the waxy yam is stored in a cold storage at 4 DEG C, four waxy yams are processed in parallel, and the average value of the test results is taken;

[0113] At the same time, four waxy yams without packaging are stored in a cold storage at 4 DEG C as a blank group (CK), and the average value of the test results is taken.

[0114] At 0, 4, 8 and 12 days, the waxy yams packaged by using the fresh-keeping and browning-preventing coating of Example 1, the PE film and without packaging are taken out from the cold storage, the number of bacteria in the epidermal part of the waxy yam per gram of sample, i.e. CFU / g, is determined by the method of GB 4789.2-2022, and the test results are shown in Table 4.

[0115] Table 4

[0116]

[0117] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A preservative and anti-browning coating, characterized in that, The raw materials, by weight, include the following components: 1.5-2.5 parts of chitosan quaternary ammonium salt, 0.8-1.2 parts of glycerol, 0.25-0.75 parts of glutathione, 0.5-1.0 parts of citral, 8-12 parts of anhydrous ethanol, and 88-92 parts of distilled water; The method for preparing the preservation and anti-browning coating includes the following steps: Chitosan quaternary ammonium salt, distilled water, anhydrous ethanol and glycerol are mixed and stirred under heating until completely dissolved to obtain a chitosan quaternary ammonium salt solution. Glutathione and citral were added to the chitosan quaternary ammonium salt solution, and after mixing, the mixture was subjected to vacuum low-temperature magnetic stirring for membrane cross-linking to obtain a film-forming solution. The film-forming liquid was degassed by ultrasonication to prepare the fresh-preserving and anti-browning coating film. The vacuum degree of the crosslinked vacuum low-temperature magnetic stirring membrane is -0.06MPa, the temperature is 25-35℃, and the magnetic stirring time is 40-80min.

2. The preservative and anti-browning coating according to claim 1, characterized in that, The heating temperature is 60℃, and the time is 15-45 minutes.

3. The preservative and anti-browning coating according to claim 1, characterized in that, The ultrasonic degassing time is 10-20 minutes, and the power is 200-400W.

4. The application of the preservative and anti-browning coating according to any one of claims 1-3 in the preservation of glutinous rice yam.

5. A method for preserving glutinous rice yam, characterized in that, The preservation and anti-browning coating of any one of claims 1-3 is sprayed onto the surface or damaged part of the glutinous rice yam, and a thin film is formed on the surface of the glutinous rice yam before it is stored at low temperature; or the glutinous rice yam is soaked in the preservation and anti-browning coating, taken out, and a thin film is formed on the surface of the glutinous rice yam before it is stored at low temperature.

6. The method for preserving glutinous rice yam according to claim 5, characterized in that, The low temperature is 2-5℃.

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