A method of packaging that removes air from the package before sealing is known as vacuum packaging. The method involves automatic or manually placing of items inside the plastic film, removing air and then sealing the package. The intention behind removing air inside the package is to remove all the oxygen inside the package so as to increase shell life of the food products and flexible package form helps to decrease volume of the content and the package.
Barrier shrink bags decreases atmospheric oxygen, reducing the growth of fungi and aerobic bacteria and avoiding evaporation of volatile components. Thereby, food industries have widely adopted this packaging technology, which is further boosting the growth of global barrier shrink bags market. This type of packaging is also used to store dry foods over long period of time. The dry foods include nuts, cereals, cured meats, smoked fish, potato chips, coffee, cheese, etc. Another type of barrier shrink packaging is short term packaging, which is used to store fresh food such as meats, liquids and vegetables as this packaging obstructs bacteria growth.
Barrier shrink bags significantly decreases the bulk of non-food items such as clothing and bedding. These can be stored in vacuum bags with the help of domestic vacuum cleaner or a staunch vacuum sealer. This technology is also used to compact household waste. Vacuum packaging products by using plastic bags, bottles, mason jars and canisters are also available for household use.
For delicate food items such as potato chips, which are likely to be crushed by vacuum packaging process, an alternative process is available i.e. removal of oxygen and filling interior with nitrogen gas. This has similar effect of hindering deterioration owing to removal of oxygen.
The extent of shelf life improved by the vacuum bag is totally depends upon the structure of the material used. A standard vacuum bag consists of a PA/PE form, where PA is referred to puncture structure as well as PE is to sealing. A category of the vacuum bag, high barrier shrink bags includes utilization of additional layers, so as to prevent oxygen penetrability and thereby improved protection of shelf life. Ethylene vinyl chloride (EVOH) and polyvinylidene chloride (PVDC) are the two materials that are used in the production of high barrier shrink bags. Shelf life indication is likely to be efficiently measured by number of cubic centimetre of oxygen will permeate through 1 square meter of material over 24-hour time period. A research states that a standard PA/PE bag permits on average 100 cubic centimetres, PADC permits on average more than 10 and EVOH on average 1 cubic centimetre. The structure of multi-layer bags have the capacity to utilize strong oxygen-barrier materials for improved shelf life protection. A best example of EVOH is the PremiumPack structure, which is based on high barrier shrink material.
Various sealer procedure based on different machines are used for packaging of products. Here are several machines and its procedure.
A bag is being attached to the vacuum machine. The machine will remove the air inside the bag and will seal the package. The whole process is done externally. Further, a heat sealer is often utilized to seal the pack.
Single Vacuum Chamber Machine
Such type machine needs entire package to be placed inside the machine. As soon as the product is placed inside the machine, the package is closed and air is removed. The heat seal inside the machine seal the package. The air is automatically filled inside the machine with the help of a vent placed at the outside of the machine. The oncoming air pressure removes remaining air from the bag.
Double Vacuum Chamber Machine
The double vacuum chamber machine needs entire package to be placed inside the chamber. As soon as the product is placed on the seal bar inside the machine, the lid is closed and air is removed. Rest of the process in similar to the single vacuum chamber machine. The basic difference between these two is size of the package used for packaging. Generally, medium side packages are sealed inside the double vacuum chamber machines.
Several other sealing machines are also available in the market. However these two are used in small scale industries for sealing small and medium size packages.