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FAT is a controversial subject in food science. We have all been told from an early age that it is unhealthy and something we should try to eat less of. But as we have said in ¿ìè¶ÌÊÓƵ before, the science that led us to fear it is deeply flawed, and many studies have found that cutting down on fat brings no clear health benefits.

In fact, fats are an essential part of our diet, a vital aid to cooking and key to what makes many of our favourite foods, such as chocolate, so enjoyable. To make smarter use of them, it helps to know a bit about their chemistry.

Animal and vegetable fats are composed mainly of triglycerides, molecules with three fatty acid chains joined onto a type of alcohol called glycerol. If the bonds between carbon atoms in the chains are all single ones, it is a saturated fat. If there are any double bonds, it is an unsaturated fat. An unsaturated fat with one double bond is monounsaturated; with more, it is polyunsaturated. Saturated fats are generally solid at room temperature, while unsaturated fats are liquid.

In unsaturated fats, the double-bonded carbon atoms can react with oxygen in the air. This oxidation reaction produces compounds that taste bad, gradually turning the fat rancid. The process is accelerated by light, so it is a good idea to keep oils in opaque containers or cupboards.

All fats can be heated much hotter than water can without evaporating, which makes them very useful for cooking. However, heating them accelerates oxidation and produces various chemicals that may harm our health. But these products don’t reach concerning levels unless you reuse the same oil several times.

Some believe you shouldn’t use olive oil for high-heat cooking, but studies have shown that both ordinary and extra virgin olive oil are and . This is partly because they have a higher ratio of monounsaturated to polyunsaturated fat, so they oxidise less easily. They also have higher levels of antioxidants than other oils, which helps prevent the fat molecules from oxidising.

Deep-frying in hot oil is great for making delicious, crispy foods, but we can also use flavourful fats to cook foods slowly and gently, a technique called confit. The word comes from the French for preserved. Pieces of meat, such as pork (pictured), would be cooked submerged in fat and then stored in the fat to prevent spoiling.

The slow and gentle cooking in fat also keeps meat moist and helps to break down connective tissue, making it very tender. But vegetables can benefit from an extended bath in warm oil too.

To make confit parsnips, place parsnips, garlic and extra virgin olive oil in a baking dish and cover with foil. Cook in a fan oven at 160°C (320°F) for an hour, or until tender. You can reuse the oil, but don’t reheat it multiple times.

Sam Wong is assistant news editor and self-appointed chief gourmand at ¿ìè¶ÌÊÓƵ. Follow him @samwong1

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