The walnut has long been one of the world’s most prized nuts. It fetched high prices in ancient Rome, where it was thrown at weddings as other cultures might throw rice or confetti. These esteemed nuts were thought to have been domesticated thousands of years ago in an area stretching across north-east Turkey, the Caucasus and northern Iran. They were introduced to England from Gaul, and their English name derives from the old English wealhhnutu, meaning ‘foreign nut’.
Today, walnut trees can be found growing across many temperate regions of the world, including France, Italy, China, Japan and Argentina. The US state of California is the world’s biggest producer of walnuts. In Australia, they are grown in the Riverina district of New South Wales, Victoria’s Ovens Valley and areas of Tasmania and South Australia. The Australian walnut industry has been bolstered recently by management investment schemes, and at present its annual production is 500 tonnes, expected to reach 22,000 tonnes in five years. The Australian walnut season runs from April to May.
In the same family as pecans and other hickory nuts, there about 21 species of walnut, though it is rarely sold by variety in Australia. Most commonly available are the darkly-coloured American walnuts, which have a strong flavour and an ability to withstand cooking, unlike other varieties such as the milder Persian walnut.
In south-west France, walnuts are known by their varieties – typically Corne, Mabot and Grandjean, and the hazelnut-sized noix noisette.
Walnuts have a smooth, green outer husk, which splits as it matures to bear the hard, oval creamy-brown shell within. The shell then dries out and hardens, making it easier to crack, revealing the brain-like kernel (in fact, the word for walnut in Afghanistan means ‘four brains’) which splits into two halves.
Walnuts are harvested at varying stages throughout maturation and even green walnuts may be eaten in their entirety. The green fleshy skin is used in France to make a liqueur originally formulated by the Chartreuse monks, while in parts of Europe and Asia they are pickled or made into sauces and jams. In the Middle East and Greece, half-ripe walnuts are preserved in a heavy syrup and used to accompany desserts. In Italy, Nocino, or walnut liqueur, is produced by infusing black and other walnuts in brandy for two years.
For the production of walnut oil, nuts are stored for up to three months, allowing their milky juices to run clear, then pressed. The oil can be used in salad dressings or to drizzle over roasted vegetables.
How to buy, store…
Walnuts become rancid quite quickly because of their high oil content and are best bought as required.
Anna Del Conte writes in Secrets from an Italian Kitchen, “…old walnuts first develop a piquant taste that tickles your tongue unpleasantly, and later they become rancid. A single piece of rancid walnut can ruin your dish.”
Whole nuts may be stored for up to three months. Shelled nuts are best stored in an airtight container and refrigerated to slow their deterioration.
Walnuts are used in sweet preparations such as cakes, biscuits and confectionary – one of the most well known is baklava. They also appear in many savoury dishes, like the famous Waldorf salad, as well as in stuffings and sauces, or blended into soups. Of course, they can be simply eaten raw or toasted, sometimes as an accompaniment to cheese. Some recipes call for the nuts to be peeled. To do this, blanch them in boiling water, then remove as much of the papery skin as possible with a small knife.
* For a walnut, pear and radicchio salad, combine sliced pear, toasted walnuts, thinly sliced celery and torn radicchio leaves. Mix walnut oil and red wine vinegar and season to taste, drizzle over salad and toss to combine.
* For a fig and walnut dessert, cut figs in half, scatter with coarsely chopped walnuts and drizzle with honey, then place under a hot grill until the nuts are toasted. Combine thick natural yoghurt with honey, to taste, and serve with figs.
* For an apple and walnut crumble, melt butter in a saucepan, add thinly sliced apple, the juice of an orange, brown sugar and a cinnamon quill, cook until just tender, remove the quill and spoon into individual ovenproof dishes. Preheat oven to 200C. Using equal quantities of plain flour and brown sugar and half the amount of butter, combine flour and sugar with coarsely chopped walnuts and a pinch of ground cinnamon and coarsely rub through butter. Scatter over fruit. Bake at 200C for 20 minutes or until golden.
* For roasted beetroot and goat’s cheese tart, preheat oven to 180C. Place trimmed baby beetroot in an oven tray, drizzle with verjuice and olive oil, season to taste, cover with foil and roast for an hour or until tender. Cool. Using a prepared tart shell, spread base with soft goat’s curd and scatter with a mixture of coarsely chopped walnuts, thyme and finely grated lemon rind. Slice the beetroot thinly lengthways and arrange on top of the goat’s cheese, drizzle with pan juices, return to the oven for 10 minutes to warm through and serve with a rocket salad.
* For spiced walnuts, sift icing sugar and mixed spice into a bowl, add walnuts and toss to coat nuts, shaking off any excess. Place the nuts on a lightly oiled oven tray, drizzle with a little Cointreau or brandy and roast at 200C for 10 minutes or until caramelised and golden. Cool. Store in an airtight container.
Walnuts are great with:
Apples, bitter greens, blue cheese, celery, chocolate, cream, croûtons, dates, duck, figs, garlic, goat’s cheese, honey, mussels, nuts, oranges, pears, potatoes, quinces and verjuice.