Macadamia oil

Macadamia oil (or macadamia nut oil) is the non-volatile oil collected from the nuts of the macadamia (Macadamia integrifolia), a native Australian plant. It is used in food as a frying or salad oil, and in cosmetic formulations as an emollient or fragrance fixative. Macadamia integrifolia is an Australian tree with holly-like leaves that grows well in a moist organic soil and can withstand temperatures as low as −4.4 °C (24 °F). Seedlings bear in 5–7 years. The fruit is borne in a case enclosing an extremely hard spherical nut. The kernel is whitish, sweet and eaten raw or roasted. The flowers are white to cream and the leaves are in whorls of three. Propagation is by seed, grafting or air layering. It is grown commercially. Common names of the trees are the Australian nut or the Queensland nut. Species that are “smooth shelled macadamia” are called Macadamia integrifolia and “rough shelled macadamia” are called Macadamia tetraphylla. Macadamia ternifolia is also the name used for M. integrifolia. Macadamia integrifolia is native to Australia where it grows in rain forests and close to streams. Macadamia tetraphylla is native to Southeastern Queensland and Northeastern New South Wales. The oil content ranges from 65% to 75% and sugar content ranges from 6% to 8%. These factors result in variable colors and texture when the nuts are roasted under the same conditions. Macadamia oil is liquid at room temperature. The refined oil is clear, lightly amber-colored with a slightly nutty smell. It has a specific gravity of 900–920 and a flash point of over 300 °C (572 °F). Oil accumulation does not commence until the nuts are fully grown and the shell hardens. It accumulates rapidly in the kernel during late summer when the reducing sugar content decreases. The composition of mature, roasted and salted macadamia nuts is shown. As with many oil seeds, the protein is low in methionine. Fresh kernels contain up to 4.6% sugar, mostly non-reducing sugar.