阅读说明：本技术 一种用于指示食品新鲜度的疏水薄膜的制备方法 (Preparation method of hydrophobic film for indicating freshness of food ) 是由 邹小波 翟晓东 石吉勇 李志华 黄晓玮 孙悦 张俊俊 杨志坤 于 2020-03-23 设计创作，主要内容包括：本发明属于食品智能包装技术领域,具体涉及一种用于指示食品新鲜度的疏水性薄膜的制备方法；方法为：将姜黄素、疏水性高分子粒和塑化剂搅拌混合,得到姜黄素-疏水高分子粒混合料；混合均匀,随后加入到双螺杆挤出机中,设置加热温度,通过口膜和切粒机进行挤出造粒,形成姜黄素-疏水高分子复合粒料；然后再加入到挤出吹膜机中,设置加热温度、冷却风风量和吹胀比制备成姜黄素-疏水高分子膜；本发明利用利用熔融挤出吹膜法将姜黄素包埋在低密度聚乙烯膜中,制备成一种疏水性薄膜,具有机械性能好,安全无毒、制备简单的优点；且该膜对碱性气体具有响应,因此在指示食品新鲜度方面具有良好的应用前景。(The invention belongs to the technical field of intelligent food packaging, and particularly relates to a preparation method of a hydrophobic film for indicating food freshness; the method comprises the following steps: stirring and mixing curcumin, hydrophobic polymer particles and plasticizer to obtain a curcumin-hydrophobic polymer particle mixture; uniformly mixing, adding into a double-screw extruder, setting the heating temperature, and performing extrusion granulation through a mouth film and a granulator to form curcumin-hydrophobic polymer composite granules; then adding the curcumin-hydrophobic polymer film into an extrusion film blowing machine, and setting the heating temperature, the cooling air quantity and the blowing ratio to prepare the curcumin-hydrophobic polymer film; the curcumin is embedded in the low-density polyethylene film by utilizing a melt extrusion film blowing method to prepare the hydrophobic film, and the curcumin-coated film has the advantages of good mechanical property, safety, no toxicity and simple preparation; and the film has response to alkaline gas, so the film has good application prospect in the aspect of indicating food freshness.)

1. A preparation method of a hydrophobic film for indicating food freshness is characterized by comprising the following specific steps:

(1) preparing curcumin-hydrophobic polymer particle mixed material particles: stirring and mixing curcumin, hydrophobic polymer particles and a plasticizer according to a certain mass ratio to obtain curcumin-hydrophobic polymer particle mixed material particles;

(2) preparing curcumin-hydrophobic polymer composite particles: uniformly mixing the curcumin-hydrophobic polymer particle mixture obtained in the step (1), adding the mixture into a double-screw extruder, setting a certain heating temperature, and carrying out extrusion granulation through a mouth film and a granulator to form curcumin-hydrophobic polymer composite granules;

(3) preparing a curcumin-hydrophobic polymer composite membrane: and (3) adding the curcumin-hydrophobic polymer composite granules prepared in the step (2) into an extrusion film blowing machine, and setting a certain heating temperature, cooling air quantity and blowing ratio to prepare the curcumin-hydrophobic polymer film.

2. The method for preparing the hydrophobic film for indicating the freshness of food according to claim 1, wherein in the step (1), the mass ratio of the curcumin to the hydrophobic polymer particles is 0.1-10: 100.

3. the method for preparing the hydrophobic film for indicating food freshness of claim 1, wherein in the step (1), the ratio of the plasticizer to the hydrophobic polymer particles is 0-10: 100.

4. The method for preparing a hydrophobic film for indicating food freshness according to claim 1, wherein in step (1), the hydrophobic polymer material is one or more of polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer or polypropylene film-blowable polymer material.

5. The method for preparing a hydrophobic film for indicating food freshness according to claim 1, wherein in the step (1), the plasticizer is phthalate, aliphatic dibasic acid ester, aliphatic acid ester, polyol ester or polyol.

6. The method for preparing a hydrophobic film for indicating food freshness according to claim 1, wherein in the step (2), the extruder is set to a heating temperature of 80-170 ℃.

7. The preparation method of the hydrophobic film for indicating food freshness according to claim 1, wherein in the step (3), the certain heating temperature is set to be 95-170 ℃, the cooling air volume is 0-4L/s, and the blow-up ratio is 1-3.

8. A curcumin-hydrophobic polymer film prepared by the method according to any one of claims 1 to 7 is used for visual detection of food freshness.

Technical Field

The invention belongs to the technical field of intelligent food packaging, and particularly relates to a preparation method of a hydrophobic film for indicating food freshness.

Background

Food quality and safety are directly related to food safety. With the development of socioeconomic, people put higher demands on food safety. The quality of food is susceptible to factors such as ambient temperature, humidity, light and gas composition. Since these environmental factors are often difficult to control during the distribution of food products, the actual shelf life of the food product is often difficult to determine and predict. Therefore, it is of great significance to develop a technology capable of indicating the quality of food in real time.

Intelligent food packaging is a packaging technology that has emerged in the last two decades. It generally refers to reflecting the quality of the food product with sensors, indicators or data carriers or the like placed inside the package. At present, most of intelligent packaging materials reported at home and abroad mainly comprise oxygen and carbon dioxide indicators, sulfide sensors, pH sensors and the like.

Spoilage of food products produces many non-neutral volatile gases, including basic gases (e.g., biogenic amines) and acidic gases (e.g., carbon dioxide, acetic acid, hydrogen sulfide, etc.). A gas sensor disposed within the interior of the food package is capable of reacting with the non-neutral volatile gas to produce a response signal indicating the freshness of the food product. Typically, colorimetric gas sensors are composed of an indicator and a base material for immobilizing the indicator. Many documents report the use of chemically synthesized pigments such as pH indicators to prepare films for indication of food freshness. However, the chemically synthesized pigment has certain biological toxicity, which is not beneficial to the application of the chemically synthesized pigment in the field of food packaging.

In recent years, more and more studies have been made to try to replace the chemically synthesized pigments with edible natural pigments (such as anthocyanins and curcumin). Curcumin is an edible yellow pigment extracted from rhizome of Curcuma longa L of Zingiberaceae, and is acidic polyphenol. In food production, the coloring agent is mainly used for coloring products such as sausage products, cans, sauced and marinated products and the like. Curcumin is insoluble in water, soluble in ethanol and propylene glycol, and soluble in glacial acetic acid and alkali solution. It is reddish brown in alkaline condition, and yellow in neutral or acidic condition. Modern chemistry therefore exploits this property as an acid-base indicator. In addition, curcumin has certain thermal stability and can be oxidized and decomposed at a temperature of more than 180 ℃. Therefore, the curcumin as an indicator has wide application prospect; for example, the patent "an edible packaging film indicating rancidity of food and a method for preparing the same" (publication No. CN108314792A) reports a method for preparing a film in which anthocyanins are immobilized in whey protein, the film having a color response to acid gases and being capable of indicating rancidity of food. Patent "curcumin/PVA/tara gum NH₃Preparation method of intelligent response film "(publication No. CN106117577A) reports a preparation method of a film in which curcumin is embedded in hydrophilic polyvinyl alcohol and tara gum, and the film responds to alkaline gas ammonia gas and can be used for indicating the putrefaction of food. However, these studies have a disadvantage that these films are formed by embedding natural pigments with a hydrophilic base material, and thus the films easily absorb moisture in a high humidity environment, thereby causing swelling of the films, uneven dispersion of pigments, and migration and elution of pigments from the films to the environment. The uncontrollable pigment uneven distribution or pigment migration and dissolution phenomenon can seriously affect the indicating function of the film. Therefore, it is very important to solve the stability of the film under high humidity.

Disclosure of Invention

The invention aims to overcome the defects and provides a preparation method for fixing safe and nontoxic edible pigment in a macromolecular hydrophobic film and application of the film in intelligent food packaging. In particular to a preparation method for embedding curcumin in a hydrophobic polymer film by using a melt extrusion film blowing method and a using method of the film.

In order to achieve the above purpose, the specific steps are as follows:

(1) preparing curcumin-hydrophobic polymer particle mixed material particles: stirring and mixing curcumin, hydrophobic polymer particles and a plasticizer in a certain mass ratio to obtain a curcumin-hydrophobic polymer particle mixture;

(2) preparing curcumin-hydrophobic polymer composite particles: uniformly mixing the curcumin-hydrophobic polymer particle mixture prepared in the step (1), adding the mixture into a double-screw extruder, setting a certain heating temperature in the extruder, and carrying out extrusion granulation through a mouth film and a granulator to form curcumin-hydrophobic polymer composite granules;

(3) preparing a curcumin-hydrophobic polymer composite membrane: and (3) adding the curcumin-hydrophobic polymer composite granules prepared in the step (2) into an extrusion film blowing machine, and setting a certain heating temperature, cooling air quantity and blowing ratio to prepare the curcumin-hydrophobic polymer film.

Preferably, the mass ratio of the curcumin to the hydrophobic polymer particles in the step (1) is 0.1-10: 100.

preferably, the dosage ratio of the plasticizer to the hydrophobic polymer particles in the step (1) is 0-10: 100.

Preferably, the hydrophobic polymer material in the step (1) is one or more of polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer or polypropylene polymer material capable of being blown into a film, and a mixture thereof.

Preferably, the plasticizer in step (1) is phthalate, aliphatic dibasic acid ester, fatty acid ester, polyol ester or polyol.

Preferably, the extruder in the step (2) is set to have a certain heating temperature of 80-170 ℃.

Preferably, the certain heating temperature set in the step (3) is 95-170 ℃, the cooling air volume is 0-4L/s, and the blow-up ratio is 1-3.

The hydrophobic polymer material used in the invention conforms to the materials specified in GB/T30768- & 2014 & lt & ltpaper for food packaging and plastic composite films and bags & gt; the plasticizer meets the regulation of GB 9685-2016 (Standard for sanitary use of additives for food containers and packaging materials). The mass ratio of the plasticizer to the hydrophobic polymer particles is not more than the highest concentration of the additives specified in GB 9685-20016 sanitation Standard for use of additives for food containers and packaging materials.

The invention has the beneficial effects that:

(1) the invention adopts safe and edible curcumin as an indicator, and the indicator is embedded in a hydrophobic polymer film by a melt extrusion film blowing method; the low-density polyethylene film is a breathable and waterproof film and is one of common plastic films for food packaging; it has the advantages of good mechanical property, safety, no toxicity and simple preparation; the invention utilizes the advantages of the two, and the curcumin is embedded in the low-density polyethylene film by a melt extrusion film blowing method to prepare the hydrophobic film, and the film has response to alkaline gas, so the curcumin film has good application prospect in the aspect of indicating food freshness.

(2) The prepared film adopts a melt extrusion film blowing method, and the method is suitable for industrial mass production; in addition, the prepared film is safe and nontoxic, can be directly used in the field of food packaging, and is relatively economical in cost.

(3) Curcumin embedded in the hydrophobic polymer film can not be dissolved out under high humidity, and the stability of the film in a high humidity food packaging environment is ensured.

(4) The film prepared by the invention has good response to alkaline gas, but no response to acid-base ions in the solution, so that the film can be used as a gas sensor under high humidity.

(5) The film prepared by the invention can react with gas volatilized in the food spoilage process to quickly generate macroscopic color, so that the freshness of the food can be detected in real time, without damage and in situ.

Drawings

Fig. 1 is a low density polyethylene-curcumin film prepared using an extrusion blown film process in example 1.

In fig. 2, a is the color change of ethanol-water solution of curcumin at different pH; b is ultraviolet-visible spectrum of ethanol-water solution of curcumin under different pH values; figure C is the color at different pH of the prepared low density polyethylene-curcumin film described in example 1; figure D is a uv-vis spectrum of leachate at different pH for the prepared low density polyethylene-curcumin film described in example 1; wherein the inset is the absorbance at 420nm of the uv-vis spectrum at different pH for the prepared low density polyethylene-curcumin films described in example 1.

Fig. 3 is a photograph of the low density polyethylene-curcumin film prepared as described in example 1 before and after reaction with ammonia gas.

Fig. 4 a is a graph of uv-vis spectrum change and color (inset) change before and after reaction of the prepared low density polyethylene-curcumin film described in example 1 with ammonia gas at different relative humidities; and the diagram B is a schematic diagram of the reaction of curcumin and ammonia gas.

Fig. 5 is a color change of the prepared low-density polyethylene-curcumin film for real-time indication of fish freshness described in example 1; wherein the upper left outer film is the film placed outside the package and the lower left inner film is the film placed inside the package.

The specific implementation mode is as follows: