Last reviewed 1 Oct 2026 · Facts as of 1 Oct 2026 · 7 min read
Functions of packaging
| Function | Meaning |
|---|---|
| Containment | Hold the product in convenient units |
| Protection | From physical damage, moisture, oxygen, light, odours, microbes, pests and tampering |
| Preservation | Extend shelf life (barrier, atmosphere, sterility) |
| Communication | Brand, ingredients, nutrition facts, date marking, instructions, legal information |
| Convenience | Easy to open, store, dispense, microwave, reseal |
| Marketing and sustainability | Appeal, recyclability, reduced waste |
Levels: primary package (in contact with the food), secondary (groups primary packs), tertiary (pallet loads, shipping containers).
Packaging materials
Glass
- Inert, impermeable, transparent, reusable/recyclable; withstands heat sterilisation; heavy and breakable. Used for jams, pickles, juices, sauces, baby food (twist-off metal lug caps with a vacuum seal).
Metals
| Material | Features |
|---|---|
| Tinplate (tin-coated steel) | Strong; used for canned foods; the tin coating protects against corrosion (internal lacquer for acid or sulphur-bearing foods — to avoid blackening and detinning); three-piece (welded side seam) and two-piece (drawn and wall-ironed) cans; double seam closure |
| Tin-free steel (TFS) | Chromium-coated, lacquered; cheaper |
| Aluminium | Light, corrosion-resistant, excellent barrier; cans for beverages, foil for laminates, trays |
Paper and paperboard
- Wrapping paper, kraft sacks, cartons (folding), corrugated fibreboard (CFB) boxes, moulded pulp trays; low cost, printable; poor moisture barrier (coating/laminating with plastic or wax needed). CFB boxes are the main transport pack for fresh produce (ventilation holes about 5 % of the surface, wet-strength, stacking strength tests).
Plastics
| Plastic | Properties and uses |
|---|---|
| LDPE (low-density polyethylene) | Flexible, heat-sealable, good moisture barrier, poor O₂ barrier; bags, liners, sealing layer |
| LLDPE | Stronger, tougher; stretch films |
| HDPE | Stiffer, better moisture barrier; bottles, crates, drums, carry bags |
| PP (polypropylene) | Clear (OPP/BOPP films), good moisture barrier, heat resistant (hot-fill, microwave); snack packs, tubs, closures |
| PET (polyethylene terephthalate) | Clear, strong, good O₂/CO₂ barrier; bottles for beverages, trays, films |
| PS (polystyrene) and EPS foam | Rigid; cups, trays; EPS cushions (EPS use is restricted in some jurisdictions) |
| PVC (polyvinyl chloride) | Clear; cling films, bottles (limited use); plasticiser migration concerns |
| PVDC (polyvinylidene chloride) | Excellent barrier to O₂, water, aroma (coatings, films) |
| EVOH (ethylene vinyl alcohol) | Excellent O₂ barrier (sensitive to moisture so sandwiched in multilayers) |
| Nylon (polyamide) | Good O₂ barrier, strength, puncture resistance; vacuum and retort packs |
| PLA and other biopolymers | Compostable/bio-based; limited barrier |
Laminates and multilayer films
- Combine layers (e.g., PET/Al foil/PE, BOPP/metallised BOPP/PE) to provide strength, barrier, printability and sealability.
- Retort pouches: PET/foil/CPP laminate that can withstand 121 °C.
- Aseptic cartons (e.g., Tetra Pak): paperboard (about 75 %), polyethylene (about 20 %), aluminium foil (about 5 %) in six layers — ambient shelf life of juice and milk (several months) after aseptic filling (UHT).
- Edible films and coatings: chitosan, starch, wax, protein, cellulose derivatives — used to extend the shelf life of fresh fruit (a growing technology).
Barrier properties and shelf life
| Property | Definition (units) | Importance |
|---|---|---|
| Water vapour transmission rate (WVTR) | Mass of water vapour passing through per unit area per day under a stated condition (g/m²·day at 38 °C, 90 % RH) | Dry foods (biscuits, spices, powders) vs moist foods |
| Oxygen transmission rate (OTR) | cm³ O₂ per m² per day (at 1 atm, 23 °C) | Fats, oils, nuts, colour, vitamin C |
| CO₂ and aroma transmission | — | Carbonated drinks, MAP, flavour |
| Light transmission | — | Photo-oxidation (milk, oil) |
| Mechanical strength | Tensile, tear, puncture, burst | Handling |
Worked ExampleExample — shelf life by moisture gain
A pouch of biscuits has an area of 0.04 m², a film with WVTR of 2.0 g/m²·day (under the test conditions, taken as the in-use condition) and can gain 1.0 g of water before the biscuits become unacceptable.
Water gain rate g/day; shelf life (very short). Changing to a metallised film of WVTR 0.3 g/m²·day gives . (Real shelf-life models use the driving humidity difference and the moisture-sorption isotherm of the product, giving a longer life than this simple estimate.)