Jan Bilton: Endless ways with cracker of a nut

Walnuts are one of the oldest known sources of food.

Walnuts are one of the oldest sources of food known to man. The so-called European walnut is one of half a dozen species and is indigenous to Persia. The Phoenicians traded walnuts. The Romans sanctified them, naming them julgas regia in honour of Jupiter, their king.

The trees were introduced to Britain in the 16th century where they were called walnuts because, in the language of the day, "wal" meant "foreign".

Walnut trees flourish in temperate climates and start bearing nuts six to eight years after being planted and continue to produce for about a century.

In New Zealand, small green fruits arrive about January and before the inner shell is formed, they are often gathered to turn into ketchup or to pickle. The walnuts turn black and these vinegary morsels are excellent served with roasted pork or on antipasto platters with cheese.

We enjoy walnuts as nibbles, in salads, baking and desserts but in many European countries they are simmered with poultry, used as a stuffing or ground and turned into soups or sauces.

Walnuts contain 52 to 70 per cent oil and more than 90 per cent of this is as unsaturated fatty acids - the good oil that helps lower levels of cholesterol in the blood. They are great brain food - walnuts in their shells even look like brains!

They're also high in omega-3, protein, minerals and fibre and have been found to help reduce the risk of type 2 diabetes.

Walnuts will keep fresh in their shells in a cool place for many months. When shelled, I believe they are best refrigerated or frozen to keep their fabulous nutty flavour and, in warmer climes, to prevent them from becoming rancid. It is not necessary to rub off the papery skin as this is where many of the antioxidants are stored.

Take care when toasting walnuts. Excessive heat can damage the heart-friendly fats so keep toasting temperature to 180C or under and bake them for no more than 10 minutes.