Macadamia nuts: benefits, varieties, nutritional values and where to find them.

Healthy and balanced , Magazine

Published : 02/08/2021

Macadamia nuts

One of the most delicious types of dried fruit is undoubtedly the macadamia nut: with their sweet, delicate taste and buttery texture, macadamia nuts are a temptation to be eaten with care due to their high fat content. Delicious either au naturel or roasted briefly in the oven, they can also be used in both sweet and savoury recipes, providing creaminess or crunchiness depending on how you choose to use them.

Let's find out more about these fruits from Australia!

Botanical aspects

The macadamia nut is the fruit of the perennial plant called macadamia, a member of the Proteaceae family, native to the south-eastern Pacific, which includes more than ten species, although the classification is not yet complete. The two most common species of Macadamia are the smooth-shelled Macadamia integrifolia and the rough-shelled Macadamia tetraphylla, which are also the only two plants that produce commercially important fruit. Both are large evergreen plants growing to heights of more than 20 metres which, because of their dense, hemispherical crowns, are often found as shade plants in gardens in Queensland and New South Wales. The macadamia nut plant grows very slowly and comes into full production about ten years after planting, but it can produce fruit for over a century. In Australia, flowering begins during the cold season when the days are short (May). The leaves have a similar elliptical shape, more pointed in Macadamia tetraphylla and slightly more rounded in Macadamia integrifolia. The flowers grow in clusters of 40-50 flowers, but in reality about 15 fruits usually develop from these huge clusters.

The fruits

The fruit is globular in shape and can reach a diameter of 25 millimetres. It is enclosed in a greenish-brown fibrous vegetable “shell” (husk) about 3 mm thick, which opens naturally along a groove once the fruit is ripe. The fruit inside the husk can be either a single spherical nut or, in some cases, there can even be two hemispherical nuts. The seed is a nut consisting of a very leathery woody shell and a kernel made up of two large hemispherical cotyledons (embryonic leaves) and a small root inserted between them.

Production and processing

As with all types of nuts, the processing of macadamia nuts involves several steps:

Harvesting stage: the nuts fall in Australia between March and September each year. They are harvested from the ground at regular intervals either by means of harvesters or by hand.
Smalling stage: this is the stage where the outer fibrous part is removed. It is essential that this is removed within 24 hours from the harvesting to prevent the inner kernel from overheating and to facilitate drying. The empty husks are used as a natural fertilizer, while the seeds are sent to the next stage of processing.
Drying phase: in this phase the walnut is dried while still in its shell. At the time of harvesting, the nuts have a moisture content of 30% and the seed fills the entire shell. The drying phase takes about three weeks during which the moisture content drops to about 1.5% and the kernel shrinks. The removal of the water makes it easier to remove the shell without damaging the kernel and improves the shelf life of the product.
Shelling: the shell of the macadamia nut is very strong and many different methods have been used to break it without damaging the kernel inside. The most commonly used cracking systems are systems that have a fixed plate and a moving cutting blade, or roller systems that break the shell by compression. After breaking the shell, the nuts must be separated from the shell fragments and this can be done by sieving or electronic or manual sorting.
Sizing stage: shelled nuts are sorted according to size. Classification is made on the basis of the size of the fruit (diameter) or fragments and the percentage of whole fruit. These classes are referred to as 'Style' (Style 0 has 95% whole fruit with a diameter of <20mm and="" is="" the="" highest="" quality="" class="" style="" 8="" contains="" fruit="" up="" to="" 4mm="" in="" size="" li="" data-mce-style="">
Packaging stage: macadamia nuts contain a lot of unsaturated fats and are therefore particularly susceptible to oxidative rancidity. To avoid this, they must be vacuum or inert gas packed and the packaging must be impermeable to moisture and oxygen. Macadamia nuts can also be roasted or fried before packaging.

Producing countries and varieties

All species classified to date are native to eastern Australia, with the exception of Macadamia hildebrandii that is native to Indonesia (Sulawesi), but have then spread to several tropical countries. In Australia and Hawaii Macadamia integrifolia is most common, while in South Africa and New Zealand Macadamia tetraphylla is best known.

Nutritional values

Macadamia nuts, like all dried fruits and oilseeds, have a high energy value and are cholesterol-free. Their high fat content gives them excellent satiety and their very high monounsaturated fat content, around 78% of the total fruit composition, is the highest of any natural oil on the market - including olive oil. They also have a good content of minerals (manganese, selenium, copper, magnesium, phosphorus, potassium) and vitamins (B1, B6). The oil is extracted exclusively by cold pressing and filtration and is used in both the food and cosmetics industries because of its high moisturising and penetrating power.

Curiosities

Macadamia trees are very long-lived plants that can survive for more than a hundred years: in the Brisbane Botanic Garden there is a specimen that was planted in 1858.

Although many people think that “macadamia” is the geographical area of origin, the name of the genus Macadamia is actually a tribute to the famous Australian scientist John McAdam, a colleague of the British botanist Ferdinand von Mueller who was the first to describe this plant. The macadamia nut was discovered and classified between 1828 and 1860.

The same plant can be called with several different names:

_ Queensland nut, the North-Eastern region of Australia where it originated;

_ Bauple nut, from the name of Mount Bauple located in Australian Queensland, where the first varieties of edible nuts were found;

_ Jindilli or Kindal Kindal, the two names given by Australian natives to these fruits long before Australia was discovered by European explorers;

_ Hawaii nut, as this archipelago is the greatest producer of macadamia nuts after Australia;

_ and also Bush nut and Maroochi nut.