Plastic products are very commonly used today. It is used for a wide variety of things including transportation, clothing, construction, infrastructure and food packaging. However, not all plastic resins are suitable for food packaging. Food grade plastic is the kind of plastic material approved by authorities like the Food and Drug Administration for contact with food and drink substances. Such plastic substances are called food contact substances. Other materials are prone to leach chemicals into the food or react with it to produce harmful toxins. To make sure that food packaging is not only effective but also healthy, it is necessary to know which plastic resins are safe.
Food packaging must adhere to the protocols set by the Food Safety and Standards Act of 2006. There are general requirements for packaging like containers which may be used for food. Plastics that come in contact with food must conform to the Indian Standards Specification when used to store food articles partly or wholly. According to these regulations and the definitions of the Bureau of Indian Standards, the plastics given below may be used in contact with food.
- IS 10146 (Specification for Polyethylene in contact with foodstuffs)
- IS 10142 (Specification for Styrene Polymers in contact with foodstuffs)
- IS 10151 (Specification for Polyvinyl Chloride (PVC), in contact with foodstuffs)
- IS 10910 (Specification for Polypropylene in contact with foodstuffs)
- IS 11434 (Specification for Ionomer Resins in contact with foodstuffs)
- IS 11704 (Specification for Ethylene Acrylic Acid (EAA) copolymer);
- IS 12252 (Specification for Poly alkylene terephathalates (PET))
- IS 12247 (Specification for Nylon 6 Polymer)
- IS 13601 (Ethylene Vinyl Acetate (EVA))
- IS 13576 (Ethylene Metha Acrylic Acid (EMAA)
Additional requirements for specific food items are enumerated in different sections of the act.
A good way to spot food grade plastic material is to check the plastic material’s resin identification code or RIC. Resin identification code is a uniform set of symbols that appear on plastic products. It is used to identify the plastic resin used to make the product. The RIC of a plastic product can be seen within a triangle. There are 7 numbers, each denoting one grade. 1 stands for polyethylene terephthalate (PET), 2 for high density polyethylene (HDPE), 3 for polyvinyl chloride (PVC) and so on.
Here is a list of commonly used food grade plastic resins-
- Polyethylene Terephthalate (PET)
- High Density Polyethylene (HDPE)
- Low Density Polyethylene (LDPE)
- Polypropylene (PP)
- Polycarbonate (PC)
Polyethylene Terephthalate or PET
Polyethylene terephthalate, generally known as PET, is one of the most commonly available thermoplastic polymers in the market. It is used for several applications including packaging and textiles. Over 80 million metric tonnes of PET is produced every year. Over 90% of PET produced each year is used to make bottles or fibers. The monomer unit of polyethylene terephthalate is the polycarbonate compound ethylene terephthalate C10H8O4. Ethylene terephthalate is the product of the esterification reaction between ethylene glycol and terephthalic acid. Polycondensation creates the polymer PET. PET can exist as both amorphous and semi crystalline, with each form having its own physical properties.
The RIC code of PET is 1. It is the most recyclable plastic produced. PET has high strength and flexibility. It is resistant to water and wear. It has exceptional dimensional stability and impact strength. Another desirable feature of PET is its chemical resistance. These features make PET an ideal choice for food storage. It is used on a large scale to make bottles, beverages, sheets and films, trays and much more.
High Density Polyethylene or HDPE
High density polyethylene is a commonly used thermoplastic polymer. It is used to make a wide variety of products including pipes, bottles and synthetic lumber. It is also extensively used in packaging in products like milk, juice, soda, water and so on. The resin identification code of HDPE is 2. The monomer molecule of HDPE is ethylene. Over 60 million metric tonnes of HDPE is produced every year as of 2022.
HDPE is tough, rigid and low cost. It has good tensile strength and impact strength. HDPE has a high melting point and is resistant to cracking and weathering. HDPE has a linear structure with little branching, hence it has a higher molecular strength. It is one of the most stable and inert forms of plastic. It does not absorb a lot of moisture. Due to these desirable physical properties HDPE is used to produce several food contact products like containers, bottles, bags, jugs and so on.
Polypropylene or PP
Polypropylene is a thermoplastic polymer produced by the chain growth polymerization of propylene. It also goes by the name polypropene. The resin identification code of polypropylene is 5. It is crystalline in form and its physical properties like high melting point and high thermal resistance make it an excellent choice to make containers suitable for microwave machines and dishwashers.
Polypropylene is rigid and resistant to several external things. It has good water resistance and fatigue resistance as well as electrical resistance. It is cost effective and fairly recyclable, hence it is a great choice to make food contact substances. It is used to make fibes, food containers, utensils and other dishware like trays. It can also be used to make blister sheets to store food items.
Low Density Polyethylene or LDPE
Low density polyethylene is a thermoplastic polymer made from the monomer ethylene by free radical polymerization reaction. LDPE is lightweight, flexible and tough. It has great corrosion resistance. It does not have high temperature compatibility but does have good chemical properties. Unlike HDPE, LDPE has more branches in its structure, this is why it has low density and great flexibility.
LDPE is a good insulator, it is resistant to a wide variety of chemicals like alcohols, acids and alkalis at dilute concentration. It is quite cost effective. It is used to make several common packaging materials like bread bags, covers, lids, and six pack rings. LDPE is also used to produce several lab equipment.
Polycarbonate or PC
Polycarbonate is a transparent thermoplastic polymer known for its very high impact strength. It is amorphous in nature and has high dimensional stability. It is a good insulator and has just as much transmission capacity as does glass. It is widely used in food packaging as well as industrial applications. Another great thing about polycarbonate is its moderate chemical resistance. It is resistant to chemicals like alcohol, aliphatic hydrocarbons and dilute acids. However it reacts with aromatic and halogenated hydrocarbons and alkali.
Nevertheless, polycarbonate is great for making rigid containers for water and other beverages. It can also be used for other food products.