Oil

Oil

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From
Encyclopedia of Food and Cookery

Oils are distinguished from fats in that they are liquid at room temperature. Edible oils are processed from many seeds, nuts and fruits including olives, peanuts, sunflower seeds, coconuts, walnuts, pumpkin seeds, grape seeds, avocados, sesame seeds, corn, cotton seeds and soybeans.

There are some edible oils of animal origins, but these are mostly used in manufacturing rather than in the kitchen.

Cold-pressed or unrefined oils have been extracted simply by pressing, and retain their full natural flavour. Refined oils, the majority of those available, have been processed to make them relatively flavourless and odourless, and to keep well. Ideally, buy oil in quantities that you will use within a month or two. Delicate salad oils such as walnut, grape seed or pumpkin seed, and other cold‑pressed oils, should always be stored in the refrigerator. Cooking oils should be stored, tightly sealed, in a cool place away from light. Do not mix together used and unused oil or else the flavour will spoil.

Types of oil: There are three basic types of oil: polyunsaturated, mono-unsaturated and saturated. They differ from each other in their chemical structure. There is some controversy about the different effects of these oils on health, and it is widely believed that the use of polyunsaturated oils, as well as fats, is preferable to that of saturated ones to help control blood fats (cholesterol and triglycerides), which are a risk factor in the development of heart disease and strokes.

Polyunsaturated oils include sunflower, safflower, maize, soybean and many blended vegetable oils. Mono-unsaturated oils are usually fairly neutral in context. They include olive and peanut oils. Saturated oils are mostly of animal origin; coconut oil, however, is saturated.

Ways to use oils: Salad dressings and sauces: Olive oil is the queen of salad oils and is indispensable for pasta sauces. Its flavour varies in character and strength from one country and from one type of olive to another. A trick for developing a fruity flavour is to keep a few black olives in a bottle of oil. The finest olive oil is virgin oil, from the first cold pressing of the olives. It is sometimes blended with the less expensive, blander oil from later pressings to improve its flavour.

Peanut oil or polyunsaturated all-purpose oils, such as sunflower, safflower, corn or blended oils, can be used in salad dressings and sauces, although they will contribute little to the flavour. You may like to mix them half-and-half with olive oil.

Aromatic oils, such as walnut, grape seed, pumpkin seed and avocado, give subtle flavour variations to salad dressings.

Cakes and breads: Oil is used instead of butter or margarine in some cakes and breads, but it cannot be substituted for these in other recipes. All-purpose oils such as the polyunsaturated ones are suitable; the flavour of olive oil is usually too strong, although it is occasionally called for.

Frying: The best oils for frying are those which can be heated to fairly high temperatures before beginning to smoke (a sign that the oil is starting to break down and will spoil the flavour of the food; it is also very close to its ‘flash’ point – when it will burst into flames). Peanut oil (much used in Chinese cooking), corn oil, safflower oil, sunflower and most blended oils are suitable.

So-called ‘solid oils’ (oils which have been processed to make them solid at room temperature), are much less expensive than polyunsaturated oils; they are recommended by manufacturers for deep-frying and perform particularly well, although the processing makes them more saturated than before.

Olive oil breaks down at high temperatures so can be used for frying only at moderate heat; it is not, therefore, suitable for deep-frying. But its lovely flavour makes it ideal for lightly frying vegetables or for the gentle cooking of onion, which is the first step in so many dishes. Olive oil is also used for Ratatouille and other Mediterranean dishes which are simmered in oil rather than fried. Mustard seed oil, which has a distinctive flavour, is often used to fry the onions, garlic and spices when preparing a curry.

Heat oil for frying slowly to the correct temperature. If it is not hot enough, too much will be absorbed by the food, and if it is overheated, it will not only spoil the flavour but can be dangerous. If overheated oil should catch alight, smother the flames by sprinkling with flour (don’t thrown on too much at once as this may cause oil to splash); or cover the pan with a lid and leave so that flames will extinguish from lack of air. Do not use water as this will only spread the flames. After use, strain the oil through a sieve lined with a disposable cloth and store it, tightly sealed, in the refrigerator or a very cool place. The ‘smoke’ point of the oil is gradually lowered with use.

Oil that smells burnt or looks dark should be discarded. Solid oil or peanut oil, properly used, should last for about 3–5 fryings. Polyunsaturated oils are less robust and will probably last for only 1–2 fryings.

Sautéing and browning casserole meat: Use only a little oil, and heat slowly until it just begins to give off a haze, then add food (which should be well dried or floured) immediately. If you are cooking several batches, wipe pan out quickly with paper towels and use fresh oil for each batch.

Shallow-frying: Usually used for food which is floured or coated with batter or crumbs. Put in enough oil to come halfway up the pieces of food. Be sure the container is deep enough to allow oil to boil up when food is added. Heat slowly until the oil just begins to give off a haze and add food immediately.

Frying with butter and oil: A mixture of butter and oil is often used for sautéing and shallow-frying – the butter contributes its distinctive and fine flavour, while the oil with its higher smoking point protects the butter from burning. Heat oil slowly until it just begins to give off a haze, add butter and, as soon as foaming subsides, add food.

For sautéing, use equal quantities of oil and butter unless otherwise instructed. For shallow-frying, use rather more oil and less butter.

Deep-frying: Use a depth of oil sufficient to float the food, but never fill pan more than halfway up as oil will boil up when you add food. Have pieces of food of uniform size so that they cook evenly. A frying basket helps to add and remove food all together so that none is overdone. Heat oil slowly to required temperature – for most deep-frying, this is 180°C on a kitchen thermometer, or when a cube of day-old bread turns golden and crisp in 1 minute.

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