Page 10 - Curriculum Visions Dynamic Book

Uses for inert nitrogen
For many purposes nitrogen can be thought of as an inert gas. This means that it does not react easily with other gases or liquids.
At first this might seem to be a very unpromising property for a gas, but in fact it has found many applications, in food packaging, food preservation and light bulbs.
In each case nitrogen is used because it doesn’t react. For example, nitrogen gas is used in some forms of food processing to prevent oxygen getting to the food and causing it to spoil. Nitrogen gas in light bulbs is designed to make the filaments last much longer.
Preserving food freshness
Food spoils because of the presence
of oxygen (which reacts with the food
to produce new, less tasty, chemical compounds). One way of preserving the freshness of food therefore is to fill the space above the food with nitrogen, which replaces the oxygen and does not react with the food at all. (Sometimes nitrogen is called an antioxidant,
i.e. it keeps food from oxidising.) Food can be frozen at very low
temperatures using nitrogen. During the freezing process, the food does not have time to spoil as it would when frozen slowly in air.
Other foods that are prepared by roasting could be severely altered
by the presence of oxygen in the air. For example, the flavour of roasting coffee will be lost in air, so coffee is roasted in an oven containing nitrogen.
Some snack foods are filled with nitrogen for this reason. Look for the inflated foil bags of crisps and other snacks.
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 The puffed up packaging that is used for some foods is not just
to make the food appear to occupy more volume than it really does. The bag contains
inert nitrogen, used to prevent the food from spoiling and, in the case
of delicate foods like crisps, to help to prevent the packaging from being
crushed and the crisps breaking.