In order to protect the environment, many edible packaging films and biodegradable films have been developed in the United States, Japan and other countries.
Polysaccharides are cellulose-based polysaccharides. Celluloid? Cellophane?, biodegradable but inedible, sensitive to moisture. Commonly used nitrocellulose-wax? NC-W? mixed polyvinylidene chloride? PVDC? coating and metallized polyester composite film. Thus, its water vapor permeability is as low as that of high density polyethylene, and the blocking performance against oxygen and grease is not affected by changes in relative humidity. NC-W coated celluloid is fully biodegradable and PVDC coated celluloid can degrade into PVDC chips.
Cellulose acetate. It is a thermoplastic material that has a weak barrier to grease. Because it is breathable, it does not fog when wrapping certain foods with high moisture content. It is also mineralizable and, although inedible, biodegradable. Chemically modified cellulose. As a raw material for edible and biodegradable films, cellulose can be expanded by chemical modification, such as methyl cellulose, MC?, hydroxypropyl methylcellulose, HPMC, and hydroxypropyl cellulose. Materials such as HPC® and carboxymethylcellulose® CMC® are moderately strong, flexible, and odorless. They are good grease blocking materials, but their ability to block moisture is weak.
For example, when MC or HPMC is made into a composite film with solid fat such as beeswax or fatty acid, their water vapor permeability can be lowered and used in many foods to block water, oxygen or grease. MC or HPMC can also be used for the coating of tablets and can be made into a package of food ingredient powder. Another chemically modified cellulose ethyl cellulose, which also has a weak barrier to water, is a good blocking material for fats and oils. Starch-based polysaccharides, amylose, high amylose and hydroxypropanol high amylose can be injection molded into a film from aqueous solution, and mechanical properties are inferior to synthetic polymers. Amylose, hydroxypropanol starch and dextrin can be eaten, but the use of starch film is limited by the influence of moisture, and is often used to coat foods to block oxygen and grease, and to maintain the appearance and texture of the food. Starch composite. Starch and polyvinyl alcohol? PVOH? is a material that is made into a thermoplastic synthetic polymer. It is biodegradable and has some properties superior to pure starch.
It can replace low-density polyethylene when the mechanical properties are strict and the moisture-blocking performance is not high. Some starch-PVOH composites can replace polystyrene to make disposable tableware. Other polysaccharide materials. Alginate has the property of protecting the moisture of the coated food by its own moisture, and can well block oxygen and oil, delay the oxidation of food and fat, and maintain the color and fragrance of food. Carrageenan. Antibacterial agents can be added to coat foods, which can antibacterial, heat preservation, slow oxidation and maintain the integrity of food. Pectin. It also has the property of protecting the moisture of the coated food with its own moisture, and can be used for freezing food, candy and preserved fruit to prevent sticking together. Chitosan. It is extracted from shell waste and is biodegradable and is not yet approved as a food ingredient in the United States. The chitosan film is a clear, strong, flexible material with excellent oxygen barrier properties. Microbial polysaccharides. For example, fungicidal polysaccharides and fructans are edible and biodegradable materials, which have good oxygen barrier properties and can be used for coating foods and medicines.
Protein collagen. At relatively low temperatures, its ability to block oxygen is excellent, but if the relative temperature rises, its oxygen permeability will also rise very quickly. It has been widely used to make sausages instead of natural casings, and can be eaten with sausages; it can also be used to package frozen meat pieces, which will melt when the meat is thawed or cooked. gelatin. The gelatin coating is edible and can block the infiltration of oxygen, moisture and oil, and can be used as a carrier for antibacterial agents. Gelatin capsules can also be used to wrap low-fat oils and foods. Other protein materials. Such as zein, wheat gluten, soy protein, whey protein isolate and casein, its mechanical properties are similar to collagen membrane, but second to celluloid. Therefore, its use as a biodegradable film is limited, but it can be used as an edible coating for foods. Among them, zein is the most widely used, and wheat gluten and soy protein are used as raw materials for replacing animal casing materials such as gelatin.
Microbial polyester? Polyhydroxyalkanoate? Such as polytrihydroxybutyrate-3 hydroxyvalerate? PHB/V? is a thermoplastic material that is fully biodegradable and has good oxygen, moisture and aroma properties. It can be used to make beverage bottles, coatings for milk packaging, etc.
Polylactic acid (PLA)
It is a thermoplastic material that is biodegradable and widely used in pharmaceutical products. PLA is easily hydrolyzed to lactic acid and can be repolymerized, thus facilitating recycling. Studies have shown that modifying its molecular weight and crystallinity allows it to have many properties similar to plastics such as polystyrene, polyethylene, polypropylene, and polyvinyl chloride. Several companies in the United States and Japan are developing PLA polymers to expand their use. In addition to medical supplies, there are also disposable products for the catering industry, packaging bags for self-selected food stores, compostable garbage bags and agricultural cover films. .
Experts believe that the sensory properties of food coatings, microbial stability and the economics of edible films need to be further studied.
Environmentally friendly packaging material BOPS is used in food packaging. Plastic pallets are widely used in food packaging, especially for quick-frozen foods, frozen foods, biscuit linings and other packaging. In the past, food trays were mainly made of materials such as PS (polystyrene), PVC (polyvinyl chloride) and PP (polypropylene). However, it has been scientifically proven that PS, PVC and PP contain different levels of harmful substances.
Thus, a safer and environmentally friendly packaging material BOPS (biaxially oriented polypropylene) has been used internationally for the production of food packaging boxes. BOPS has several characteristics: good optical properties, good transparency and gloss in freezing and water vapor (-40 ~ 90 ° C); strong, high recovery value, safe recovery or incineration; odorless , does not produce odor transfer; low cost.
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