The following is an overview of the types and characteristics of plastics most commonly used for food packaging.
1) Polyethylene Terephthalate (PET) - recycling code "01"
PET belongs to the polyester family. It is best known as a material for disposable and recyclable bottles for carbonated beverages. In addition, thin PET films are often used as outer packaging for fresh fruit.
PET is resistant to oils, fats, alcohols and dilute acids. It can also be coated with other plastics or aluminium, and can be used as a vapour-deposited or composite material.
PET can be crystalline or transparent. In the transparent form, it is used for packaging food products such as ice cream. In this case, however, it is not very mechanically resistant. The use temperature is between -40°C and +60°C.
Semi-crystalline PET is less transparent but more stable. It is harder, more flexible and has a higher barrier to oxygen and carbon dioxide, with use temperatures between -20°C and +120°C.
The fully crystalline PET is opaque and is often used for microwaveable dishes.
Pure PET is fully recyclable, which gives it an ecological advantage over other plastics.
2) Polyethylene (PE) - recycling code "02" and "04"
Polyethylene is the most commonly used plastic because of its malleability and relatively low cost. One of its advantages is that PE is highly resistant to acids, alkalis, oils and fats and can therefore be used as a container for a wide variety of products.
Different production methods can be used to produce high density polyethylene (HD-PE = high density polyethylene, recycling code "02") or low density polyethylene (LD-PE = low density polyethylene, recycling code "04").
LD-PE is transparent and much more flexible than HD-PE. LD-PE is widely used in the food industry, mostly in combination with other packaging film materials such as adhesive film. In addition, LD-PE is often used, for example, as a barrier layer for the inner lining of milk cartons. HD-PE, on the other hand, is milk white and much stronger than LD-PE. It is mainly used for packaging solid food products and for the production of carrier bags.
Depending on the type, polyethylene retains its properties over a temperature range of -60°C to +85°C, making it an excellent choice for freezer bags and containers. On the other hand, it is less used for packaging food to be heated in a microwave or as a cooking bag.
Since polyethylene has a high gas permeability, it can only be used for modified atmosphere packaging in laminated form (in combination with composite film).
3) Polyvinyl chloride (PVC) - recycling code "03"
Polyvinyl chloride (PVC) is a plastic that has a very wide range of applications, but above all in the non-food sector. In its original form, it is hard and brittle, but can be made flexible and malleable by adding plasticisers. It is also very resistant to acids, alkalis, alcohol and oil.
In the food industry, rigid PVC is used to make bottles of edible oils and vinegar or to package chocolates and sweets, among other things. No plasticising chemicals are added to rigid PVC.
For example, soft PVC is used to make shrink film. It shrinks under heat to protect and stabilise the contents during transport and storage. It is often used to package pallets or PET drinks bottles. PVC films are also still used commercially as packaging for fresh food and as inner rings for the inner ring of the screw of jars.
However, the use of the critical hormone-hosting flatates as plasticisers in the packaging of fatty foods is prohibited.
The added plasticisers used in food packaging pose a risk because they are not chemically integrated into the structure of the plastic and can evaporate or leach into the food, reducing the importance of PVC in the food industry. Nowadays, for example, the fresh-keeping film used in households is made entirely of polyethylene, which does not contain plasticisers, and blue-coloured, PVC-free lids are available for jars.
4) Polypropylene (PP) - recycling code "05"
Polypropylene is chemically similar to polyethylene, but stronger and more heat resistant. Good fat and
is one of the most commonly used plastics in food packaging because of its moisture barrier properties.
Depending on the production process, it is used for containers or foils, such as dairy cups, bottle caps, baking foils and trays. Application temperatures range from 0°C to 100°C. Due to the maximum continuous use temperature, PP can be used to make microwaveable heat-resistant containers. However, at temperatures below 0°C, the plastic usually becomes brittle. PP is relatively easy to recycle.
5) Polystyrene (PS) - recycling code "06"
Polystyrene was previously used mainly for disposable drinking cups, coffee cup spout lids or disposable cutlery, and is now used to package yoghurt pots, honey, coffee cream, pastries and confectionery.
As expanded polystyrene (expanded polystyrene foam = ESP) - also known as Styrofoam - polystyrene is used to package fish, meat, fruit, vegetables and takeaway food in restaurants and buffets.
Polystyrene is very cheap compared to other plastics. In addition, it has high water vapour and gas permeability, is odourless and tasteless, which is particularly advantageous for storing fruit, vegetables, meat and fish. The continuous use temperature is between -10°C and +70°C.
However, polystyrene can also leach styrene, which is known to be carcinogenic and endocrine disrupting.
6) Other plastics: polycarbonate (PC) and polyamide (PA)
Polycarbonateis the reaction product of carbonic acid dichloride (phosgene), diphenyl carbonate and bisphenol A. High in strength and difficult to break, polycarbonate was used in sterilizable baby bottles until 2011. It is still found in water dispensers, drinking bottles, microwave ovens and kitchen equipment. Bisphenol A Its use in the food industry is now declining due to its hormone-like effects.
Polyamidesare polymers based on peptide bonds. A well-known representative of the group of polyamides is nylon. Most polyamides have high strength and toughness and are easy to process industrially. It is used for films, sausage casings and as a sealant in combination with other plastics, for example as a middle layer in PET beer bottles. Together with polyethylene, multilayer films are produced for vacuum packaging oxygen-sensitive foods such as ham, cheese or sausages.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
