Macadamia

Macadamia trees are evergreen, reaching 10 to 15 metres, with glossy leathery leaves and long hanging clusters of small cream or pink flowers. The fruit is a green husk that splits as it dries to release a single round seed with an extremely hard, glossy brown shell. Inside is a creamy-white kernel about the size of a large marble. The flavour is mild, sweet and buttery with a crisp yet tender bite. Macadamias are sold in the shell (with a special cracker), as raw or dry-roasted kernels, salted or plain, chopped, as nut butter, as cold-pressed oil and as milk. They are often chocolate-coated or candied.

The genus is native to the coastal rainforests of south-eastern Queensland and northern New South Wales in Australia, where two of the cultivated species originate. For thousands of years the nuts were gathered by Aboriginal peoples, who called them names such as kindal kindal. The tree was formally described by European botanists in the 1850s and named Macadamia in honour of the Scottish-Australian chemist John Macadam, a friend of the botanist Ferdinand von Mueller. Commercial domestication is very recent compared with most nuts: the first orchards were planted in Australia in the 1880s and in Hawaii around the same period, and modern cultivars come from only a few generations of selection.

For Aboriginal peoples of the Australian east coast the macadamia was a prized food, eaten raw or roasted and traded between groups. European settlers initially treated the tree as an ornamental curiosity. Seeds were carried to Hawaii in the 1880s, where the tree was first planted as a windbreak and shade for sugar cane. Only in the 1920s and 1930s did Hawaiian growers begin to select superior trees and develop the nut as a commercial crop, helped by the work of agricultural stations that grafted improved varieties.

By the mid-twentieth century Hawaii dominated world supply, and macadamias became linked with tropical tourism, appearing in gift boxes and chocolates. Plantings then spread to California, Costa Rica, Guatemala, Brazil, Malawi, Kenya, South Africa and Australia itself, which rebuilt a major industry in the 1960s onward. Today South Africa and Australia are among the leading producers, with growing volumes from China and Kenya. Because the trees take many years to come into full bearing and the shells are so hard, the nuts have long been among the most expensive tree nuts, and the crop remains associated with premium snacking and baking.

Macadamia kernels are eaten as snacks, roasted and salted, or added to cookies, most famously white chocolate and macadamia biscuits. They are chopped over salads, blended into pestos and dairy-free cheeses, ground into pastry fillings and pressed for nut butter and milk. The oil, with a high monounsaturated fat content, is used for finishing dishes and for light cooking, and is also a common ingredient in cosmetics, skin and hair products. The hard shells are burned as fuel or ground into mulch. In traditional Australian bush food the nuts were eaten raw, and the trees are still valued in gardens for their shade and flowers.

Macadamias are dominated by monounsaturated fat, mostly oleic acid, and contain relatively little protein or carbohydrate. Small clinical studies suggest that replacing some saturated fat in the diet with macadamias can modestly lower LDL cholesterol, although the evidence base is limited and the nuts are very energy dense. They provide thiamine, manganese, magnesium and copper, plus small amounts of fibre. They are not a significant source of calcium or vitamin C. A handful of about 30 grams fits easily into a balanced eating pattern for most people, but portions should be moderated by anyone watching calorie intake.