Zwitter-ion nano-cellulose composite fresh-keeping liquid as well as preparation method and use method thereof

Abstract

The invention provides a zwitter-ion nanocellulose composite fresh-keeping liquid and a preparation method and a use method thereof, and the preparation method comprises the following steps: adding chloroacetic acid into a chitosan solution, mixing, stirring and heating to obtain carboxymethyl chitosan; the preparation method comprises the following steps: adding glycidyl trimethyl ammonium chloride into a carboxymethyl chitosan solution, mixing, stirring and heating in a dark environment to obtain combined modified chitosan; adding a cellulose raw material into the ammonium persulfate solution, mixing, stirring and heating to obtain oxidized cellulose; adding ethylenediamine and carbodiimide into the oxidized cellulose dispersion liquid, mixing, stirring and heating to obtain a combined modified cellulose solution, and sequentially carrying out mechanical grinding and high-pressure homogenization on the combined modified cellulose solution to obtain a combined modified nano cellulose solution; uniformly mixing the combined modified chitosan and the combined modified nanocellulose solution to obtain a precursor solution; and adding a genipin cross-linking agent into the precursor solution, mixing, stirring and heating to obtain the zwitterionic nanocellulose composite fresh-keeping liquid.

Claims

1. A method for preparing a zwitterionic nanocellulose composite fresh-keeping liquid, characterized in that: The preparation method comprises: (I) dispersing chitosan in a complex solvent, mixing uniformly to obtain a chitosan solution, adding chloroacetic acid to the chitosan solution, mixing, stirring and heating to react, centrifuging, washing and drying after the reaction is completed to obtain carboxymethyl chitosan; dispersing carboxymethyl chitosan in deionized water to obtain a carboxymethyl chitosan solution, adding glycidyl trimethyl ammonium chloride to the carboxymethyl chitosan solution, mixing, stirring and heating in a light-proof environment to react, and after the reaction is completed, dialyzing, evaporating, concentrating and freeze-drying the reaction product to obtain a combined modified chitosan; (II) adding a cellulose raw material to an ammonium persulfate solution, mixing, stirring and heating to react, centrifuging and washing after the reaction is completed to obtain oxidized cellulose; dispersing the oxidized cellulose in an MES buffer to obtain an oxidized cellulose dispersion, adding ethylenediamine and carbodiimide to the oxidized cellulose dispersion, mixing, stirring and heating to react, washing after the reaction is completed to obtain a combined modified cellulose solution, and mechanically grinding and high-pressure homogenizing the combined modified cellulose solution in sequence to obtain a combined modified nanocellulose solution; (III) uniformly mixing the combined modified chitosan obtained in step (I) and the combined modified nanocellulose solution obtained in step (II) to obtain a precursor solution; adding a genipin crosslinking agent to the precursor solution, stirring and heating the mixture to react, and filtering after the reaction to obtain the zwitterionic nanocellulose composite fresh-keeping solution.

2. The preparation method according to claim 1, characterized in that: In step (I), the deacetylation degree of the chitosan is 85-92%; The composite solvent is composed of isopropanol and deionized water in a volume ratio of (2.5-3):1; The solid-liquid ratio of the chitosan to the composite solvent is 1 g: (15-20) mL; The molar ratio of the chloroacetic acid to the chitosan in the chitosan solution is 1:(1.5-1.8); The mixing and stirring time of the chloroacetic acid and chitosan solution is 2 to 4 hours; The mixing and stirring speed of the chloroacetic acid and chitosan solution is 300-500 rpm; The heating temperature for mixing and stirring the chloroacetic acid and chitosan solution is 50-60° C.; During the mixing and stirring of the chloroacetic acid and chitosan solutions, 5-8 wt % sodium hydroxide solution is added dropwise to the mixture of the chloroacetic acid and chitosan solutions to control the pH value of the mixture within the range of 8.8-9.2; After the reaction of the chloroacetic acid and chitosan solution is completed, the reaction product solution is cooled to 10-15° C. in an ice water bath, and then a 0.5 mol / L dilute hydrochloric acid solution is added dropwise to a pH value of 5-5.5; The centrifugal speed is 5000-8000 rpm; The centrifugation time is 20 to 30 minutes; The drying temperature is 40-50°C; The drying time is 12 to 16 hours.

3. The preparation method according to claim 1, characterized in that: In step (I), the mass fraction of carboxymethyl chitosan in the carboxymethyl chitosan solution is 3-5wt%; Before adding glycidyl trimethylammonium chloride to the carboxymethyl chitosan solution, 0.1 mol / L sodium hydroxide solution is added dropwise to the carboxymethyl chitosan solution to adjust the pH value thereof to 8 to 9; The molar ratio of the glycidyl trimethylammonium chloride to the carboxymethyl chitosan in the carboxymethyl chitosan solution is (1-1.2):1; The mixing and stirring time of the glycidyl trimethylammonium chloride and carboxymethyl chitosan solution is 2 to 3 hours; The mixing and stirring speed of the glycidyl trimethylammonium chloride and carboxymethyl chitosan solution is 300-400 rpm; The heating temperature for mixing and stirring the glycidyl trimethylammonium chloride and carboxymethyl chitosan solution is 40-45° C.; During the mixing and stirring of the glycidyl trimethylammonium chloride and carboxymethyl chitosan solutions, a 0.1 mol / L sodium hydroxide solution is added dropwise to the mixed solution of the glycidyl trimethylammonium chloride and carboxymethyl chitosan solutions to control the pH value of the mixed solution within the range of 7 to 7.5; The dialysis uses a dialysis bag with a molecular weight cut-off of 8000 to 14000Da; The dialysis time is 48 to 72 hours; The evaporation concentration temperature is 40-50°C; The evaporation and concentration is performed until the solid content of the reaction product is 15-20%; The freeze drying temperature is -45 to -30°C; The freeze-drying time is 24 to 36 hours.

4. The preparation method according to claim 1, characterized in that: In step (II), the cellulose raw material includes any one of bleached hardwood pulp, bleached softwood pulp or cotton, or a combination of at least two thereof; The concentration of the ammonium persulfate solution is 0.5 to 1.5 mol / L; The ratio of the cellulose raw material to the ammonium persulfate solution is 1 g: (15-25) mL; The mixing and stirring time of the cellulose raw material and the ammonium persulfate solution is 2 to 4 hours; The mixing and stirring speed of the cellulose raw material and the ammonium persulfate solution is 500-600 rpm; The heating temperature for mixing and stirring the cellulose raw material and the ammonium persulfate solution is 70-80° C.; The centrifugal speed is 5000-10000 rpm; The centrifugation time is 10 to 20 minutes; The washing is performed with a dilute hydrochloric acid solution with a pH of 4.5 to 5.5 for 2 to 3 times.

5. The preparation method according to claim 1, characterized in that: In step (II), the pH value of the MES buffer is 4.5 to 5.5; The mass fraction of oxidized cellulose in the oxidized cellulose dispersion is 3 to 5 wt %; The amount of ethylenediamine added is 10-15 wt% of the mass of the oxidized cellulose in the oxidized cellulose dispersion; The added amount of the carbodiimide is 20-30 wt% of the mass of the oxidized cellulose in the oxidized cellulose dispersion; The mixing and stirring time of the oxidized cellulose dispersion, ethylenediamine and carbodiimide is 8 to 12 hours; The rotation speed of mixing and stirring the oxidized cellulose dispersion, ethylenediamine and carbodiimide is 400-500 rpm; The heating temperature for mixing and stirring the oxidized cellulose dispersion, ethylenediamine and carbodiimide is 50-60°C.

6. The preparation method according to claim 1, characterized in that: In step (II), the mechanical grinding process is carried out in a colloid mill or a refiner; The mechanical grinding time is 5 to 20 minutes; The pressure of the high-pressure homogenization is 80-100 MPa; The high pressure homogenization is performed 3 to 5 times; The solid content of the combined modified nanocellulose solution is 1-2 wt %.

7. The preparation method according to claim 1, characterized in that: In step (III), the ratio of the mass of the combined modified chitosan to the dry weight of the combined modified nanocellulose in the combined modified nanocellulose solution is 1:(2-4); The amount of the genipin cross-linking agent added is 0.5-0.8wt% of the total mass of the precursor solution; The mixing and stirring time of the precursor solution and the genipin cross-linking agent is 8 to 12 hours; The mixing and stirring speed of the precursor solution and the genipin cross-linking agent is 300-400 rpm; The heating temperature for mixing and stirring the precursor solution and the genipin cross-linking agent is 35 to 45° C.; During the mixing and stirring process of the precursor solution and the genipin crosslinking agent, 0.1 mol / L sodium hydroxide solution is added dropwise to the mixed solution of the precursor solution and the genipin crosslinking agent to control the pH value of the mixed solution within the range of 8 to 9; The filtration uses a microporous filter membrane with a pore size of 0.22 to 0.45 μm.

8. A zwitterionic nanocellulose composite fresh-keeping liquid prepared by the preparation method according to any one of claims 1 to 7.

9. A method for using the zwitterionic nanocellulose composite fresh-keeping liquid according to claim 8, characterized in that: The method of use includes: The fruits and vegetables to be preserved are soaked in a zwitterionic nanocellulose composite preservation liquid for at least one time, and after soaking, the fruits and vegetables are taken out and naturally air-dried to form a preservation coating on the surface of the fruits and vegetables.

10. The method of use according to claim 9, characterized in that: The single soaking time is 5 to 60 seconds; The soaking is performed 2 to 5 times.

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