阅读说明：本技术 一种用于保鲜板栗的壳聚糖-玉米醇溶蛋白涂膜及其制备方法 (Chitosan-zein coating film for keeping Chinese chestnuts fresh and preparation method thereof ) 是由 顾采琴 黄煜凯 朱冬雪 陈泽瑶 梁锃曦 于 2019-11-27 设计创作，主要内容包括：本发明属于农产品保鲜技术领域,具体公开了一种用于保鲜板栗的壳聚糖-玉米醇溶蛋白涂膜及其制备方法。所述用于保鲜板栗的壳聚糖-玉米醇溶蛋白涂膜,其包括以下质量份数的组分：壳聚糖3.0～5.0份、纳米纤维素0.5～2.5份、甘油1.0～3.0份、玉米醇溶蛋白0.1～0.9份、肉桂醛0.1～0.7份。因板栗壳富含纤维素和木质素,具有一定的疏水性,3％～5％的壳聚糖溶液难以完整地包裹在板栗壳表面。而在这基础上,添加0.1份～0.9份的玉米醇溶蛋白制得的壳聚糖-玉米醇溶蛋白溶液黏附性能得到改善,在板栗表面的黏附效果更好,能够完整的包裹板栗,提高保鲜效果。(The invention belongs to the technical field of agricultural product preservation, and particularly discloses a chitosan-zein coating film for preserving Chinese chestnuts and a preparation method thereof. The chitosan-zein coating for keeping Chinese chestnuts fresh comprises the following components in parts by weight: 3.0-5.0 parts of chitosan, 0.5-2.5 parts of nano-cellulose, 1.0-3.0 parts of glycerol, 0.1-0.9 part of zein and 0.1-0.7 part of cinnamyl aldehyde. Because the chestnut shells are rich in cellulose and lignin and have certain hydrophobicity, the 3-5% chitosan solution is difficult to completely wrap the surfaces of the chestnut shells. On the basis, the adhesion performance of the chitosan-zein solution prepared by adding 0.1-0.9 part of zein is improved, the adhesion effect on the surface of the Chinese chestnut is better, the Chinese chestnut can be completely wrapped, and the preservation effect is improved.)

1. A chitosan-zein coating for keeping Chinese chestnut fresh is characterized by comprising the following components in parts by weight:

2. a method for preparing the chitosan-zein coating film for fresh-keeping chestnuts according to claim 1, characterized by comprising the steps of:

dissolving chitosan, nano-cellulose and glycerol in an acetic acid solution to prepare a chitosan solution, then uniformly mixing the chitosan solution with an ethanol solution of zein, adding cinnamyl aldehyde, defoaming after uniform mixing to obtain a chitosan-zein nano coating solution, soaking Chinese chestnut fruits in the obtained chitosan-zein nano coating solution, and drying to obtain the preservative coating.

3. A method for preparing the chitosan-zein coating film for fresh-keeping chestnuts according to claim 2, characterized in that:

the concentration of chitosan in the chitosan-zein nano coating solution is 3-10 wt%; the concentration of the zein in the chitosan-zein nano coating solution is 0.1-0.9 wt%.

4. A method for preparing the chitosan-zein coating film for fresh-keeping chestnuts according to claim 2, characterized in that:

the volume ratio of the chitosan solution to the ethanol solution of zein is 5-10: 1-5.

5. The method of coating chitosan-zein film for fresh-keeping chestnuts according to claim 2, wherein:

the volume ratio of the chitosan solution to the ethanol solution of zein is 7-9: 1-3.

6. The method of coating chitosan-zein film for fresh-keeping chestnuts according to claim 2, wherein: the defoaming is ultrasonic defoaming, the power of the ultrasonic defoaming is 200-300W, and the ultrasonic time is 10-20 min.

7. The method of coating chitosan-zein film for fresh-keeping chestnuts according to claim 2, wherein: the Chinese chestnut is pretreated, and the specific process comprises the steps of selecting fresh and mature Chinese chestnuts without mechanical damage and plant diseases and insect pests, cleaning the Chinese chestnuts, soaking the Chinese chestnuts in a sodium metabisulfite solution for disinfection, and finally airing the Chinese chestnuts.

8. A fresh-keeping method of Chinese chestnut, specifically, after coating the Chinese chestnut with the chitosan-zein film of claim 1, storing in room temperature environment with relative humidity of 55% -95%.

Technical Field

The invention belongs to the technical field of agricultural product preservation, and particularly relates to a chitosan-zein coating film for preserving Chinese chestnuts and a preparation method thereof.

Background

Chinese chestnut, also known as chestnut, is known as the name of 'the king of dried fruit' and is a nut food with high nutritive value. The Chinese chestnut contains 51 to 60 percent of starch, wherein the content of protein is higher than that of rice, the variety of amino acids necessary for human bodies is complete, and the contained fat is mainly unsaturated fatty acid. In addition, the chestnut contains quite abundant minerals, especially contains outstanding potassium, and the potassium content is 4 times higher than that of the apple which is named to be rich in potassium. Modern medicine considers that the Chinese chestnut has certain medicinal value, sweet taste and warm nature, can invigorate spleen and tonify kidney, promote blood circulation to remove blood stasis, stop bleeding and relieve pain, eliminate damp-heat and has better prevention and treatment effects on hypertension, coronary heart disease and arteriosclerosis. In China, planting Chinese chestnuts becomes an important way for developing mountain economy and farmers in mountain areas to quickly lose poverty and become rich, and the Chinese chestnuts are also called 'iron stem crops' by the farmers in mountain areas and are good tree species produced in a greening and combining way. However, the Chinese chestnut belongs to recalcitrant seeds, has poor storage performance after being picked, is very sensitive to dehydration, and is very easy to cause weight loss, germination and serious mildew and deterioration if the storage conditions are improper. The economic loss of China caused by improper storage of Chinese chestnuts reaches billions of yuan every year, and a great deal of shock is caused to a plurality of chestnut farmers.

At present, the storage modes of Chinese chestnuts mainly comprise: sand storage, freezer storage, plastic film storage, and bract storage. Among them, sand storage, plastic film storage and storage with a bud are common among ordinary farmers. Although the sand storage method and the plastic film storage method have low cost, the Chinese chestnuts are easy to germinate and mildew due to large variation range of ground temperature, humidity and the like, and the regular inspection is needed, so the operation is complicated. The storage method with bracts is simple and labor-saving, but chestnuts are easy to germinate and are greatly influenced by insect pests. The cold storage method is simple and convenient to operate and good in effect, but the equipment cost is high, and the method is difficult to realize in ordinary farmers. The coating preservation technology has the advantages of low cost, convenient operation, good storage effect, easy popularization and the like, and has great development potential in the storage application of the Chinese chestnuts.

The film coating preservation is to coat a film on the surface of food in a wrapping or spraying way by using a film coating solution, and the film has certain barrier property, so that the contact between the food and air can be reduced, the water loss and moisture absorption of the food can be reduced, and the pollution of external microorganisms to the food can be reduced, thereby achieving the purpose of preserving the food. Chitosan is used as a natural polymer with good antibacterial and film-forming properties, has wide application in food coating preservation, but a single chitosan film lacks water resistance, and the coating preservation effect can be improved by compounding with other materials. Zein has good barrier property and has great potential as an oxygen-barrier and water-resistant fresh-keeping material, but a film prepared from single zein has poor mechanical property, so that the application development of the zein is limited. The data report that the film can be formed when the concentration of the chitosan reaches 2%, but when the Chinese chestnut film coating is carried out, the viscosity of the chitosan is too low when the concentration of the chitosan is 1.0%, 1.5%, 2.0% and 2.5%, the film coating effect is not good, and a complete film cannot be formed. If the concentration of the fructan exceeds 5.0%, the zein is easy to separate out due to excessive acidity caused by the need of adding acetic acid.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention mainly aims to provide a chitosan-zein coating film for keeping Chinese chestnuts fresh.

The invention also aims to provide a preparation method of the chitosan-zein coating film for keeping the Chinese chestnut fresh.

The invention further aims to provide a fresh-keeping method for the Chinese chestnut.

The purpose of the invention is realized by the following scheme:

a chitosan-zein coating for keeping Chinese chestnut fresh comprises the following components in parts by weight:

a preparation method of a chitosan-zein coating film for keeping Chinese chestnuts fresh comprises the following steps:

dissolving chitosan, nano-cellulose and glycerol in an acetic acid solution to prepare a chitosan solution, then uniformly mixing the chitosan solution with an ethanol solution of zein, adding cinnamyl aldehyde, defoaming after uniform mixing to obtain a chitosan-zein nano coating solution, soaking Chinese chestnut fruits in the obtained chitosan-zein nano coating solution, and drying to obtain the preservative coating.

The volume ratio of the chitosan solution to the ethanol solution of zein is 5-10: 1-5; preferably 7-9: 1-3, and more preferably 8: 2.

The volume fraction of the acetic acid solution is 0.05-4%, and preferably 2%; the volume fraction of the ethanol solution is 60-80%, and the preferred volume fraction is 70%.

The concentration of chitosan in the chitosan-zein nano coating solution is 3-10 wt%, and preferably 3-5 wt%. The concentration of the zein in the chitosan-zein nano coating solution is 0.1-0.9 wt%, preferably 0.1-0.5 wt%, and more preferably 0.3 wt%.

The defoaming is preferably carried out through ultrasonic defoaming, the power of the ultrasonic defoaming is 200-300W, and the ultrasonic time is 10-20 min.

The soaking time is preferably 1-3 min.

The Chinese chestnut is preferably pretreated firstly, and the specific process comprises the steps of selecting fresh and mature Chinese chestnuts without mechanical damage and plant diseases and insect pests, cleaning the Chinese chestnuts, soaking the Chinese chestnuts in a sodium metabisulfite solution for disinfection, and finally airing the Chinese chestnuts. Wherein the concentration of the sodium metabisulfite solution is 1.0-2.0 g/L, and the disinfection time is 0.5-1.5 min.

A fresh-keeping method of Chinese chestnut, after coating said chitosan-zein film on Chinese chestnut, store in the room temperature environment that the relative humidity is 55% -95%.

The unspecified temperature and the room temperature of the invention are both 20-25 ℃.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. because the chestnut shells are rich in cellulose and lignin and have certain hydrophobicity, the 3-5% chitosan solution is difficult to completely wrap the surfaces of the chestnut shells. On the basis, the adhesion performance of the chitosan-zein solution prepared by adding 0.1-0.9 part of zein is improved, the adhesion effect on the surface of the Chinese chestnut is better, the Chinese chestnut can be completely wrapped, and the preservation effect is improved.

2. Compared with the common chitosan-zein film, the composite film of the invention is added with the nano-cellulose, thus obviously reducing the water vapor transmission rate of the film by 15-25 percent compared with the film without the nano-cellulose.

3. Compared with a common chitosan-zein film, the composite film of the invention is added with the cinnamyl aldehyde, the compactness of the film is obviously increased, the water resistance of the film is improved, the water solubility of the film is reduced by 20-40% compared with the film without the cinnamyl aldehyde, and the water vapor transmission rate is reduced by 10-20%.

4. The prior research on the coating preservation of the Chinese chestnut is mainly to use refrigeration to assist preservation, but the invention has good preservation effect at room temperature and is suitable for common farmers without refrigeration equipment.

5. The chitosan-zein composite film prepared by the invention has obvious fresh-keeping effect on the normal-temperature storage of the picked Chinese chestnut fruits, can effectively reduce the water loss of the Chinese chestnuts, reduce the occurrence of the calcification of the Chinese chestnuts, has obvious inhibiting effect on Chinese chestnut mold, can observe the breakage and deformation of Chinese chestnut mold hypha treated by the film liquid, and obviously reduces the number of spores in multiple visual fields; after the Chinese chestnut is coated with the film, the Chinese chestnut is stored at normal temperature for 15 days, the mildew rate is reduced by 60 percent, and the calcification index is reduced by 57 percent.

6. The preparation method is simple and convenient, has wide raw material source and low cost, and is easy to popularize.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.