If you tend to store your cooking oil beside the cooker, leave jars of nuts on the kitchen counter top or eat foods past their use by date then you may be unintentionally damaging your health. Here is some practical advice on the storage of various types of fats to prevent damage to fats, a term called fat oxidation.
Fats are generally solid at room temperature (example butter) and oils are liquid at room temperature (example olive oil). Fats and oils perform many life-supporting functions in each cell of our body. Fats add a lot of the flavour to the foods and they also serve as a concentrated source of energy and calories. Fats and oils provide essential fat soluble vitamins such as A, D, E and K. Fats may exert positive and negative effects on our health e.g. too much saturated fat can cause heart disease, yet healthy types of oils can benefit to lower cholesterol.
Foods which contain 100% fat such as butter and vegetable oils and foods which contain high amounts of fat e.g. nuts, seeds, avocados, crisps, biscuits are prone to oxidation. When air, light, heat or moisture interacts with the exposed fat it can become damaged or rancid. Rancid fat is caused by the resulting chemical reactions, which produces off- flavours and off-odours. There are many studies which have shown that consuming oxidised fat is linked with an elevated risk of developing heart disease and other health conditions.
Preventing Fat Damage
Oxidative rancidity occurs in fats and oils that contain unsaturated fatty acids; mostly because unsaturated fats (salmon and rapeseed oil) are a little less stable than saturated fats (butter). Heat, light and oxygen are the main factors which speed up oxidative rancidity. All foods containing fat will become rancid over time but it is possible to delay the process with some forward thinking in the kitchen. Processed foods contain preservatives which prevent the fat for “going off”. Once foods have exceeded their use by date, the level of preservatives and anti-oxidants can rapidly decline, therefore it becomes difficult to prevent the natural process of fat oxidation in biscuits, cakes etc.
Fats exposed to air can trigger oxidation and rancidity therefore always keep those oils in bottles that are tightly capped. A tightly capped bottle will help prevent your oil from being unnecessarily exposed to oxygen. Always replace the lid on a tub of spread at the table and never leave butter uncovered in the fridge once taken out of the foil packaging. If storing oily type fish e.g. salmon, rainbow trout or mackerel in the fridge, ensure it is well wrapped up in foil and use double freezer bags when freezing.
Protection from light is also important when it comes to your food oils. It is best to purchase oils in bottles made from darker tinted glass (usually dark brown or dark green bottles). All cooking oils should be stored in a cupboard that is lightproof, therefore storage in display glass cabinets are unsuitable. It is best not to leave nuts or seeds in glass storage jars in the kitchen – whilst they may look pretty on display, the healthy fat in such foods can be destroyed over time.
A constant exposure to heat can speed up fat oxidation. Cooking oils, spreads, butters, omega 3 supplements etc should never be stored next to your cooker, hob or oven as the heat damages the fat. All solid fats e.g. butters and spreads should be stored in the fridge and never left out on the table after meals as the higher room temperature can spark fat rancidity. Foods such as nuts, seeds and avocados can be stored in the fridge if you have room or alternatively kept in the cooler room of the house. Cooking oils may be stored in the fridge or the coolest area of the kitchen.
It is important to take some time to consider how you store your fats within the home, take the above steps to minimize fat damage and avoid consuming out of date high fat foods.