Oils play a significant part in the diet of most of British people. Used in baking, In dressing, for sauteing and frying, their quaility and nutritional value is an important but easily overlooked consideration when a healthy diet

Composition of oils

Oils are fats whitch are in liquard state when at room temputure .fats and oils conist of a monicules of glycerol plus three molicules of fatty acids. The chemical stucture of the faty acids determines wheather it is saturated or unsaturated. 'Saturated' indicates the absence of double chemical bonds so that the molocules can not contain any more hydrogen atoms, i.e they are saturated with with hydrogen.

Oils are unsaturated and are further catagorised into monosaturates e.g olive oil, and polyunsaturates e.g safflower oil, corn oil, and sunflower oil and soya oil. Polyunsaturates contain the smallest number of hydrogen atoms.

Function of Oils

Fats are required in the diet as they provide the structural components of the cell walls of all tissues. They also act as carriers for the soluble vitamins A, D, E and K.

Whilst an excess of saturated fat in the diet can lead to raised cholestrol levels and heart-related diseases, poly unsaturated fats can actually lower cholestrol levels. Some oils contain essential fatty acids, a deficiancy of which can lead to heart disease, acne and eczema. Mono unsaturates have actually been found to reduce cholestrol levels.

Extraction of Oils

Oil is liberated from the raw material by mechanical pressure (or in the case of refined oils, chemical solvents).

Where a product is soft, it is cold pressed. So keeping vitamin destruction to a minimum.

Harder products such as safflower are expeller processed. Extraction rates from pressings are low and the oil has a higher nutritional value. It also retains its characteristic smell and taste.

Uses of Oils

The root of the word "oil" is "olive" and olive oil is arguably the finest of all oils.

Olive Oil - the strength of its flavour lends itself to use as a salad dressing (add a little lemon juice or vinegar for extra "tang") or as a condiment with jacket potatoes, pizzas and hot vegetables. It can also be used in casseroles and in sauces. Olive oil is comparetively pricey, but this is not suprising when you consider that on average a tree produces 10 kilos of fruit and it takes 5 kilos of fruit to make 1 kilo of oil.

Corn Oil - Use in baking or in salads.

Sesame oil - A favorite in Far Eastern cookery. It is usually fairly pungent in flavour, so is best used in small quantitys. A brilliant oil in for stir-frys and marinades.

Nut oils are becoming increasingly popular and are particuarly good in salad dressing or hot or cold vegetable dishes. Almond oil is cheaper than hazelnut or walnut and is somewhat cheaper, making ideal for use in cakes and pastries.

How to Choose your Oil

Commercial oils are highly processed, which means that much of the nutritional value is destroyed. Quality natural oils are only obtained by "cold pressing". This is a purely mechanical process, during which temperatures are maintained at a low level. There is no chemical or heat treatment.

Mechanical Pressing - Has an acidity of less than 1%. Likely to be the product of just one country or region. Flavour will be strong.

Extra Virgin First Pressed - This is the purest and finest oil and is extracted from the first pressing.

Extra Virgin Cold Pressed - Low pressure pressing. High quality.

Pure - Oil extracted from the third or fourth pressing and refined. The refining process includes washing with caustic soda, bleaching, fine filtering and deoderising at high temperatures. These processes can remove minerals and vitamin E which is a natural anti-oxidant and prevents rancidification.

Light - Last pressing. The mildest flavour.

General Comments

Exposure of oils to the atmosphere causes them to turn rancid. Apart from rendering the oil unpalatable, rancidity also destroys vitamins A, C, E and B6. Oil should therefore be kept in a cool place and customers should be advised to refridgerate after opening.

Oils should be cooked slowly and gently. If the oil begins to smoke, the composition of the oil changes and essential fatty acids are destroyed. Oils high in mono-unsaturated fats tend to be more stable when heated than poly-unsaturates, making them more suitable for cooking - eg peanut, avacado, almond, olive and palm.