Oils and fat-containing items are perishable and can be spoiled when exposed to oxygen. This is because oil and fats are reactive and can react with oxygen easily and get oxidised. To prevent oxidation, these items are flushed with nitrogen gas. Nitrogen is an inert gas and cannot react with oils or fats easily. So, food items with oils and fats are kept in packets having nitrogen gas that increases the shelf life and makes these items last for a long time.