As a packaging material, glass has numerous positive functional characteristics; it is potentially reusable, highly recyclable, strong, transparent, can be formed into a wide variety of shapes, and is chemically resistant and inert. In hygienic and safe glass packaging, premium products remain completely fresh and retain their true flavour over long periods. No other packaging material can compete with the outstanding properties of glass.
Glass is airtight. This means that mineral water in glass bottles retains its carbon dioxide content for a long time, which is why the shelf life for mineral water in PET bottles is about 40% shorter than for mineral water in glass bottles.
The general composition of glass, if manufactured from 100% virgin materials, is:
• Silica sand (SiO2) 68–73%
• Soda ash (Na2CO3) 12–15%
• Limestone (CaCO3) 10–13%
• Alumina (Al2O3) 1.5–2.0%
• Other metal oxides ~1% (e.g. for colouring).
Many foods that are packaged in glass are then heat processed and for these it is usual to hot-fill the containers (fill at 80°C or above). Glass has to be heated and cooled carefully to avoid the risk of breakage and therefore it is usual to pre-sterilise containers before hot filling.
Most foods that are packaged in glass are either liquids, such as drinks and syrups or thicker pastes such as sauces, chutneys.
Glass bottles packaging
