Growing and Processing Macadamias

Growing and Processing Macadamias

Creating the world’s finest nut takes patience, skill and lots of loving attention. It can take 10 to 15 years before a macadamia tree reaches maturity and maximum yield. Mature trees grow to heights of between 12 and 15 metres and have shiny dark green leaves.

Macadamias are mostly grown in northern New South Wales and south-eastern Queensland thanks to their sub-tropical climates. Recently there have also been significant increases in plantings of trees in the Bundaberg and surrounding regions, as well as the Clarence Valley in the NSW Northern Rivers region. These locations have all the perfect conditions for growing this native Australian nut because of all the factors influencing macadamia growth and productivity, temperature is the most important. Optimum growth occurs between 20-25OC.

Macadamias are prolific producers with each tree bearing sprays (racemes) of long, delicate, sweet-smelling white or pink blossoms. Each spray of 40-50 flowers produces from four to 15 ‘nutlets’, which will eventually ripen into nuts. Flowering occurs in early spring with nuts forming in early summer and, by early autumn, clusters of plump green nuts appear. The nuts grow encased in a hard, woody shell, which is protected by a green-brown fibrous husk. Shell hardening takes place in early December followed by rapid oil accumulation in late December and January. Between March and September, the mature nuts fall to the ground and are harvested regularly with purpose built harvesters. The fibrous outer husk of the macadamia is removed within 24 hours of harvest to reduce heat respiration and facilitate drying. The husk material is usually recycled as organic mulch.

From tree to me - the macadamia life cycle

Fortunately, when the nuts fall, their precious cargo is protected by an incredibly hard shell. Careful drying is a critical step in macadamia processing to maximise quality of the end product. At harvest the nuts have a moisture content of up to 30%. Drying can take up to three weeks and reduces the moisture content to around 1.5%. The kernel shrinks away from the inside of the shell and allows the shells to be cracked without damaging the kernel. Cracking machines have been developed to crack the tough shell of the macadamia without damaging the kernel inside. These machines have either a fixed blade and cutting blade, or a combination of rollers and a base plate to compress the shell.

The seven steps for macadamia harvesting and processing

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Supported by Hort Innovation and Macadamia Fund

This website has been partly funded by Hort Innovation, using the macadamia research and development levy and contributions from the Australian Government.