阅读说明：本技术 一种天然保鲜膜及其制备方法 (Natural preservative film and preparation method thereof ) 是由 刘建强 徐鸿嘉 潘莹 陈倩怡 魏霖涛 钟钰瑜 李宝红 李思 彭新生 陈金香 杨倩 于 2019-11-14 设计创作，主要内容包括：本发明具体涉及一种天然保鲜膜的制备方法,包括步骤：取虾头外壳晾干、粉碎并过筛,然后加入EDTA溶液进行搅拌,过滤洗涤；将得到的滤渣烘干,加入过氧化氢溶液,在水浴中浸泡,脱色,洗净烘干,得到甲壳素白色粉末；往得到的甲壳素中添加氢氧化钠的水溶液,升温至80～100℃反应,过滤,转入氢氧化钠的乙醇溶液中,在回流温度下反应,过滤,用蒸馏水洗至中性,烘干粉碎,制得壳聚糖；将壳聚糖制备成溶液,溶于醋酸的水溶液中,于水浴加热搅拌,加入甘油,取出后冷却至室温,搅拌均匀,涂抹于玻璃平板上,干燥得到天然保鲜膜。相比于现有技术,该方法处理周期短且费用低,获得的天然保鲜膜具备良好的抗氧化、锁水保鲜作用。(The invention particularly relates to a preparation method of a natural preservative film, which comprises the following steps: taking the shrimp head shell, airing, crushing and sieving, then adding an EDTA solution, stirring, filtering and washing; drying the obtained filter residue, adding a hydrogen peroxide solution, soaking in a water bath, decolorizing, cleaning and drying to obtain white chitin powder; adding an aqueous solution of sodium hydroxide into the obtained chitin, heating to 80-100 ℃ for reaction, filtering, transferring into an ethanol solution of sodium hydroxide, reacting at a reflux temperature, filtering, washing with distilled water to be neutral, drying and crushing to obtain chitosan; preparing chitosan into a solution, dissolving the solution in an aqueous solution of acetic acid, heating and stirring the solution in a water bath, adding glycerol, taking out the solution, cooling the solution to room temperature, uniformly stirring the solution, coating the solution on a glass flat plate, and drying the glass flat plate to obtain the natural preservative film. Compared with the prior art, the method has short treatment period and low cost, and the obtained natural preservative film has good antioxidant and water-locking preservation effects.)

1. The preparation method of the natural preservative film is characterized by comprising the following steps:

s1, taking the shrimp head shells, airing, crushing, sieving, adding an EDTA solution, stirring, filtering and washing;

s2, drying the filter residue obtained in the step S1, adding a hydrogen peroxide solution with the volume ratio concentration of 10%, soaking in a water bath at 30-40 ℃, decolorizing, cleaning and drying to obtain white powder, namely chitin;

s3, adding an aqueous solution of sodium hydroxide into the chitin obtained in the step S2, heating to 80-100 ℃, reacting for 2-4 h, filtering, transferring into an ethanol solution of sodium hydroxide, reacting for 2-4 h at a reflux temperature of 80-90 ℃, filtering, washing with distilled water to be neutral, drying and crushing to obtain chitosan;

s4, preparing chitosan into a solution, dissolving the solution in an aqueous solution of acetic acid, heating and stirring the solution in a water bath at 55-65 ℃ for 25-35 min, adding glycerol, taking out the solution, cooling the solution to room temperature, uniformly stirring the solution, coating the solution on a glass flat plate, and drying the solution to obtain the natural preservative film.

2. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S1, the sieving operation is specifically sieving through a 50-75 mesh sieve.

3. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S1, the EDTA solution has a concentration of 0.01mol/L, pH value of 13.

4. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S1, stirring for 20-30 min under the conditions of ultrasonic frequency of 60kHz and power of 180W.

5. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S2, the drying temperature is 40-60 ℃.

6. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S3, the concentration of the aqueous solution of sodium hydroxide is 12 mol/L.

7. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S4, the solution prepared from chitosan has a mass concentration of 2-3.5%.

8. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S4, the aqueous solution of acetic acid contains 2% by volume of acetic acid.

9. The method for preparing a natural preservative film according to claim 1, characterized in that: in step S4, the drying temperature is 50-70 ℃ and the drying time is 3-5 h.

10. A natural preservative film is characterized in that: the preparation method is adopted to prepare the compound of the formula I and the formula II.

Technical Field

The invention belongs to the technical field of preservative films, and particularly relates to a natural preservative film and a preparation method thereof.

Background

At present, common preservative film products in the market mainly comprise three types of preservative films, namely Polyethylene (PE), polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC). The three types of the preservative films are all polymerized by using petroleum extracted ethylene as a master batch, and at present, white pollution is increasingly serious, and the preservative films sold in the market are not easy to decompose in the environment due to poor degradability, so that the environment-friendly performance is poor. In addition, the preservative films also have the problems of plasticizer safety, insufficient standard, high cost, fewer preservative films prepared by new raw materials and new processes, and the like.

The chitosan has rich resources and simple extraction, has the advantages of good film forming property, safety, high transparency, biocompatibility, safety, environmental protection and the like, and simultaneously has broad-spectrum antibacterial property, thereby being a biodegradable material approved by the State food and drug administration. And chitosan is hydrophilic macromolecule, reduces the evaporation of food water, and achieves the effect of keeping the sensory quality of food. Therefore, chitosan becomes one of the materials for preparing the degradable preservative film. Chitosan is a semi-synthetic high molecular amino polysaccharide, which is obtained by deacetylating chitin to a certain degree. Chitin is widely distributed and mainly exists in shells of crustaceans, inner bones of mollusks, cell walls of microorganisms such as algae and the like. At present, methods for extracting chitin from shrimp shells mainly comprise an acid-base method, an enzyme method and a fermentation method, a large amount of waste liquid is generated in the processing process of the methods, the defects of large environmental pollution, long treatment period, high treatment cost and the like exist more or less, and 0.5t of hydrochloric acid and 250t of fresh water are consumed to extract 1t of chitin, so that a large amount of resources are consumed.

Disclosure of Invention

One of the objects of the present invention is: aiming at the defects of the prior art, the preparation method of the natural preservative film is provided, the treatment period is short, the treatment cost is low, and the obtained natural preservative film has good effects of oxidation resistance and water locking preservation.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a natural preservative film comprises the following steps:

s1, taking the shrimp head shells, airing, crushing, sieving, adding an EDTA solution, stirring, filtering and washing;

s2, drying the filter residue obtained in the step S1, adding a hydrogen peroxide solution with the volume ratio concentration of 10%, soaking in a water bath at 30-40 ℃, decolorizing, cleaning and drying to obtain white powder, namely chitin;

s3, adding an aqueous solution of sodium hydroxide into the chitin obtained in the step S2, heating to 80-100 ℃, reacting for 2-4 h, filtering, transferring into an ethanol solution of sodium hydroxide, reacting for 2-4 h at a reflux temperature of 80-90 ℃, filtering, washing with distilled water to be neutral, drying and crushing to obtain chitosan;

s4, preparing chitosan into a solution, dissolving the solution in an aqueous solution of acetic acid, heating and stirring the solution in a water bath at 55-65 ℃ for 25-35 min, adding glycerol, taking out the solution, cooling the solution to room temperature, uniformly stirring the solution, coating the solution on a glass flat plate, and drying the solution to obtain the natural preservative film.

As an improvement of the preparation method of the natural preservative film, in step S1, the sieving operation is specifically sieving with a 50-75 mesh sieve. Preferably, the powder is sieved through a 60-mesh sieve.

As an improvement of the preparation method of the natural preservative film, in step S1, the concentration of the EDTA solution is 0.01mol/L, pH value is 13.

As an improvement of the preparation method of the natural preservative film, in step S1, stirring is carried out for 20-30 min under the conditions that the ultrasonic frequency is 60kHz and the power is 180W.

As an improvement of the preparation method of the natural preservative film, in step S2, the drying temperature is 40-60 ℃.

As an improvement of the preparation method of the natural preservative film, in step S3, the concentration of the aqueous solution of sodium hydroxide is 12 mol/L.

In step S4, the solution prepared from chitosan has a mass concentration of 2-3.5%.

As an improvement of the preparation method of the natural preservative film, in step S4, the aqueous solution of acetic acid contains 2% by volume of acetic acid.

As an improvement of the preparation method of the natural preservative film, in the step S4, the drying temperature is 50-70 ℃, and the drying time is 3-5 hours.

Another object of the invention is: provides a natural preservative film which is prepared by the preparation method described in any section of the specification.

Compared with the prior art, the invention has the beneficial effects that:

1) according to the invention, Ethylene Diamine Tetraacetic Acid (EDTA) is used as a decalcifying agent instead of hydrochloric acid, so that on one hand, the decalcifying effect is better than that of hydrochloric acid, the treatment period is effectively shortened, and on the other hand, the chitin obtained by the EDTA treatment method has higher quality, so that the preservative film has better quality. In addition, EDTA can be recovered, so that the resource consumption is reduced, and the production cost is reduced.

2) The invention extracts chitin from the shrimp head shell, the chitin is deacetylated to obtain high molecular polymer chitosan, and the chitosan is prepared into solution, the solution has the characteristics of high transparency, good film forming property, safety and no toxic or side effect, and the prepared preservative film also has the advantages of high transparency, safety and no toxic or side effect.

3) The chitosan prepared by the method is hydrophilic macromolecule, reduces the evaporation of food water, and the prepared natural preservative film has good effects of oxidation resistance, water locking and preservation, and can keep the sensory quality of food.

Drawings

FIG. 1 is FT-IR spectra of chitosan of example 1 of the present invention and standard chitosan.

Detailed Description

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