Analysis and Research on the application of the mo

Analysis and Research on the application of green food packaging (Part 2)

as we all know, at present, food packaging is a major player in the packaging industry, accounting for about 70% of the packaging industry. Therefore, the waste of food packaging is also the biggest pollution to the environment. In order to better store food and avoid the pollution of packaging waste to the environment, the application of green packaging of food is inevitable

green packaging materials

broadly speaking, green packaging materials are recyclable packaging materials that are harmless to human health, have a good protective effect on the ecological environment in the process of production, manufacturing, use and recycling

1. Reusable and recycled packaging materials

reusable packaging, such as glass bottle packaging of beer, beverages, soy sauce, vinegar, etc., can be used repeatedly. Sweden and other countries implement the reuse of polyester beverage bottles and PC milk bottles for more than 20 times

recycled packaging, such as polyester bottles, can be regenerated by physical and chemical methods after recycling. Physical method refers to the direct and thorough purification and crushing, without any pollutant residue, and the treated plastic can be directly used in the production of recycled packaging containers. Chemical method means that after crushing and washing the recycled PET bottles, depolymerization agents such as methanol water, ethylene glycol or diethylene glycol are used to depolymerize pet completely or partially into oligomers under the action of alkaline catalysts, and then the monomers or oligomers are re polymerized into regenerated PET resin packaging materials after purification

2. Edible packaging materials

they occupy a place in the market

developing edible packaging materials is the best way to solve the contradiction between food packaging waste and environmental protection. The goal of developing edible packaging is to make a packaging film that does not affect the flavor of the packaged food, and this packaging film is edible. For example, we are familiar with glutinous rice paper used in candy packaging and corn baking cups used in ice cream packaging

pullulan resin, which has been put into industrial production in the 1970s, is an odorless, amorphous, amorphous white powder, and is a non-ionic, non reducing stable polysaccharide. Because it is easy to dissolve in water, it can be used as viscous, neutral and non separable non gelatinized aqueous solution. Its 5% - 10% aqueous solution can be made into a film with a thickness of 0.01mm after drying or hot pressing. This film is transparent, colorless, tasteless, non-toxic, tough, high oil resistance, edible, and can be used as food packaging. Its gloss, strength and folding resistance are better than those of films made of high amylose

there is also an edible fresh-keeping film, which has developed into a multi-component edible film with multiple functional properties made of a variety of biological macromolecules (proteins and polysaccharides) and lipids. This composite film mainly forms a stable emulsion through the interaction between different molecules, and then dries to volatilize the solvent to form a porous, transparent or semitransparent three-dimensional complex structure film. This porous complex structure makes the film have obvious water resistance and certain optional permeability. Therefore, it has broad application prospects in the food industry, especially in the fresh-keeping of fruits and vegetables

3. Degradable packaging material

degradable packaging material refers to a kind of plastic whose chemical structure changes at a specific time and in a specific environment. Degradable plastics not only have the functions and characteristics of traditional plastics, but also can be split and degraded in the natural environment through the action of ultraviolet light in the sun or microorganisms in soil and water after the service life is completed, and finally re-enter the ecological environment in the form of non-toxic and return to nature

degradable plastics are generally divided into synthetic photodegradable plastics, photodegradable plastics with photosensitizers, biodegradable plastics, and multifunctional degradable plastics combined with a variety of degradable plastics. According to the degradation environmental conditions, degradable plastics can be divided into photodegradable plastics, biodegradable plastics (fully biodegradable plastics and partially biodegradable plastics), chemical degradable plastics (oxidative degradable plastics and water degradable plastics), and composite degradable plastics composed of the above three kinds of degradable plastics

among synthetic photodegradable plastics, polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) are the most produced. Their properties are similar to polyethylene and polypropylene, and their price is about 10 times that of polyethylene. The degradation principle is that the polymer absorbs ultraviolet light to produce photoinitiation, which weakens the bond energy, splits the long chain into fragments with lower molecular weight, and reduces the physical properties. The fragments with lower molecular weight are further oxidized in the air, producing free radical chain breaking and further degraded into carbon dioxide and water

in the process of plastic processing, adding a small amount of photosensitizer can turn ordinary plastics into photodegradable plastics. This method is simpler and cheaper than copolymerization synthesis method. Photodegradable plastics are mainly used as beverage bottles, shopping bags, garbage bags, mulching films, etc. in foreign countries. Photodegradable plastics researched and developed in China are mainly used for mulching films. In recent years, photodegradable plastics for new disposable fast food boxes have been developed. Because photodegradable plastics can be degraded only under the condition of sunlight irradiation, they are greatly restricted by geographical environment and climatic conditions, so it is difficult to achieve accurate time control, and the buried part cannot be degraded, so the large-scale promotion and application is limited

polymers synthesized from petroleum are difficult to be decomposed by ordinary microorganisms under natural conditions. Both synthetic polymers and natural polymers containing genes prone to hydrolysis have high biodegradability. In China, the incomplete biodegradable plastics mixed with starch and polyolefin plastics are mostly studied. The degradation principle of this kind of plastic is that the starch particles are eroded and consumed by fungi and bacteria first, so as to weaken the strength of the plastic. At the same time, after contacting with some salts in the soil, peroxide is formed by self oxidation, which promotes the breaking of the molecular chain of the polymer in the plastic. They promote and complement each other. Bacteria consume starch, which increases the surface area of the plastic and is conducive to self oxidative degradation. Over and over, the polymer chain gradually breaks and shortens, reducing the strength of the plastic until the molecular weight of the polymer is reduced to the extent that it can be metabolized by microorganisms

4. Paper packaging material

the raw material of paper is mainly natural plant fiber. Factor 5: the force value sensor of electronic tensile testing machine will decay quickly in nature, will not pollute the environment, and can also be recycled for papermaking. In addition to the advantages of light weight, low price and shock resistance, pulp molded products also have the characteristics of good air permeability, which is conducive to the preservation of fresh food. In the international commodity circulation, they are widely used in the turnover bags of fragile, fragile and extrusion resistant items such as eggs, fruits and glass products

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