Refrigerate after opening
Encyclopedia
The term refrigerate after opening is an instruction on commercial preserved food products to cool the container after it has been opened and the contents exposed to open air.
Moist foods are commonly preserved using canning
and vacuum sealing to kill off any bacteria and molds, and to prevent further growth by removing oxygen. Dry-product containers are often preserved with heating and filling the empty container spaces with an inert nonreactive gas
such as nitrogen
.
Once opened for consumption, the product is immediately exposed to atmospheric oxygen and floating dust particles containing bacteria and mold spores, and all protections from the preservation process are immediately lost. At room temperature, mold and bacteria growth resumes almost immediately, and warmer temperatures can lead to an explosion of growth that rapidly degrades the food product. This organism growth can result in the accumulation of poisonous bacterial substances in the food product such as botulin, that lead to food poisoning, sickness, or death.
Cooling the food product to a temperature just above freezing in a refrigerator
is generally required to slow the growth of these organisms. This cooling can permit foods to remain safely edible for up to two weeks after opening.
Simply loosening the lid of a vacuum-packed food product to break the seal is enough to permit the bacteria and mold growth to resume. The amount of air inhaled into the container when the seal is broken is small, but sufficient to permit slow growth of contaminating and decomposing organisms.
This seal is extremely important to the safe preservation of the food product. That is why most preserved screw-top food products use a domed metal cover that emits an audible popping sound as the container is opened. The dome is held down by the vacuum seal and will not make a popping sound when the cover is pressed on a properly sealed container.
Moist foods are commonly preserved using canning
Canning
Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container. Canning provides a typical shelf life ranging from one to five years, although under specific circumstances a freeze-dried canned product, such as canned, dried lentils, can last as...
and vacuum sealing to kill off any bacteria and molds, and to prevent further growth by removing oxygen. Dry-product containers are often preserved with heating and filling the empty container spaces with an inert nonreactive gas
Inert gas
An inert gas is a non-reactive gas used during chemical synthesis, chemical analysis, or preservation of reactive materials. Inert gases are selected for specific settings for which they are functionally inert since the cost of the gas and the cost of purifying the gas are usually a consideration...
such as nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
.
Once opened for consumption, the product is immediately exposed to atmospheric oxygen and floating dust particles containing bacteria and mold spores, and all protections from the preservation process are immediately lost. At room temperature, mold and bacteria growth resumes almost immediately, and warmer temperatures can lead to an explosion of growth that rapidly degrades the food product. This organism growth can result in the accumulation of poisonous bacterial substances in the food product such as botulin, that lead to food poisoning, sickness, or death.
Cooling the food product to a temperature just above freezing in a refrigerator
Refrigerator
A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...
is generally required to slow the growth of these organisms. This cooling can permit foods to remain safely edible for up to two weeks after opening.
Simply loosening the lid of a vacuum-packed food product to break the seal is enough to permit the bacteria and mold growth to resume. The amount of air inhaled into the container when the seal is broken is small, but sufficient to permit slow growth of contaminating and decomposing organisms.
This seal is extremely important to the safe preservation of the food product. That is why most preserved screw-top food products use a domed metal cover that emits an audible popping sound as the container is opened. The dome is held down by the vacuum seal and will not make a popping sound when the cover is pressed on a properly sealed container.
External links
- How long does food keep in the pantry? http://www.demesne.info/Home-Maintenance/Pantry.htm
- Do jars always have to pop? http://en.allexperts.com/q/Food-Safety-Issues-767/2008/4/jars-pop.htm
- http://www.drgreene.com/21_442.html