In order to protect the environment, the United States, Japan and other countries have successively developed many edible packaging films and biodegradable films.
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. In this way, its water vapor permeability is as low as that of high-density polyethylene, and the blocking properties of oxygen and grease are also not affected by changes in relative humidity. The NC-W coated cellophane is fully biodegradable and the PVDC coated cellophane can be degraded to PVDC.
Cellulose acetate. It is a thermoplastic material and has weak barrier properties to grease. Because of its breathability, it does not produce fog when wrapped in foods with high moisture content. It can also be mineralized, though not edible but biodegradable. Chemically modified cellulose. Cellulose is a raw material for edible and biodegradable films, and its use can be expanded by chemical modification, such as methylcellulose?MC?, hydroxypropylmethylcellulose? HPMC?, hydroxypropylcellulose? HPC? and carboxymethyl cellulose? CMC? materials, moderate strength, flexibility, transparency, odorless, is a good oil blocking material, but their ability to block moisture is weak.
If MC or HPMC is made into a composite film with solid fat such as beeswax or fatty acids, their water vapor permeability can be reduced and they can be 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 food packaging powder bags. Another chemically modified cellulose, ethylcellulose, also has weaker barrier properties to water, but it is a good blocking material for grease. Starch-based polysaccharides, amylose, high amylose, and hydroxypropanol high amylose starches can be injection molded into films from aqueous solutions, with mechanical properties inferior to synthetic polymers. Amylose, hydroxypropanol starch and dextrin are all edible, but the use of a starch film is restricted due to the influence of moisture, and they are mostly used for coating foods to block oxygen and grease, and maintain the appearance and organization of foods. Starch composites. Blended with starch and polyvinyl alcohol (PVOH), it is a thermoplastic synthetic polymer material that is biodegradable and has some properties superior to pure starch.
It can replace low-density polyethylene when the mechanical performance requirements are strict and moisture-blocking performance requirements are not high, and some starch-PVOH composites can replace polystyrene to make disposable tableware. Other polysaccharide materials. The alginate has the property of protecting the coated food from moisture loss by its own moisture, and can well block oxygen and grease, delay oxidation of the food oil, and maintain the color and flavor of the food. Carrageenan. Antibacterial agents can be used to coat foods, which can resist bacteria and heat, slow down oxidation and maintain food integrity. Pectin. It also has the property of protecting the moisture of the coated food with its own moisture, and can be used for frozen food, candy, preserved fruit, etc. to prevent sticking together. Chitosan. It is extracted from shell waste and is biodegradable. It is currently not approved as a food ingredient in the United States. Chitosan films are clear, strong, and flexible materials that have excellent oxygen barrier properties. Microbial polysaccharides. For example, Pullulan and fructan are edible and biodegradable materials, which have good oxygen barrier properties and can be used for the coating of foods and pharmaceuticals.
Protein collagen. At relatively low temperatures, its oxygen barrier properties are excellent, but if the relative temperature rises, its oxygen permeability will also increase rapidly. It has been widely used to replace natural casings to make sausages and can be eaten together 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 wrap low moisture foods and pharmaceuticals. Other protein materials. Such as corn protein, wheat gluten, soy protein, whey protein isolate and casein, etc., its mechanical properties and collagen membrane similar, but after celluloid. Therefore its use as a biodegradable membrane is limited, but it can be used as an edible coating for foods. Among them, corn protein is most widely used, and wheat gluten, soybean protein and the like are mostly used as vegetable raw materials that can replace animal casing raw materials such as gelatin.
Microbial polyesters Polyhydroxyalkanoates such as polytrihydroxybutyrate-3-hydroxyvalerate PHB/V are thermoplastic materials that are fully biodegradable and have good oxygen, moisture, and fragrance barrier properties. Can be used to make beverage bottles, milk packaging coatings.
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 re-polymerized, making it easy to recycle. Studies have shown that modification of its molecular weight and crystallinity can make it have many properties similar to polystyrene, polyethylene, polypropylene, polyvinyl chloride and other plastics. Several companies in the U.S. and Japan are developing PLA polymers to expand their use. In addition to medical products, there are disposable products for the food and beverage industry, packaging bags for self-selected food malls, compostable garbage bags, and agricultural cover films. .
Experts believe that further research is needed on the organoleptic properties of food coatings, microbial stability, and economics of edible films.
Environmentally Friendly Packaging Materials BOPS Used in Food Packaging Production Plastic trays are now 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). But recently scientifically confirmed that PS, PVC, PP three kinds of packaging materials contain different levels of harmful substances.
As a result, a more environmentally friendly packaging material, BOPS (biaxially oriented polypropylene), has begun to be used in the production of food packaging boxes internationally. BOPS has several characteristics: good optical properties, can maintain good transparency and gloss in freezing and vapor (-40～90°C); strong, high recovery value, safe recovery or incineration; odorless No odor transfer; low cost.
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