Processing Macadamia Nuts
Hi-tech meets bush nut
The technology used for preparing macadamia nuts for the market is constantly being improved. Sophisticated machines process the nuts with speed and efficiency. The major concerns of processors are kernel damage, contamination, product availability and distribution.
From farm to factory
Most macadamia nut processing plants are situated close to growing districts. The nut-in-shell farm produce is delivered to the plant where it is stored in silos.
Some growers incorporate their own processing plant adjacent to the orchard. Large plants such as the Macadamia Processing Company at Alphavale are owned by the growers. MPC is Australia’s largest and has some 240 shareholder/growers.
Processing takes place from about April to November when the factory ceases operation until the next season begins. Many of the employees are happy to have a four month holiday.
During down-time the plant machinery is cleaned, serviced and upgraded ready for next years crop.
drying of the nuts-in-shell is a critical step in the processing of macadamias. At harvest, moisture content of the nuts is approximately 30% and the kernel fills the entire shell, but after about 3 weeks of drying this is reduced to around 1.5% and the kernel shrinks away from the shell. The shell can then be cracked without damaging the kernel and nut-in-shell storage life is prolonged. Nuts can be stored in their shell for up to two years.
The macadamia industry have finally cracked the age-old problem of dispensing with the nut shell and retrieving a whole kernel.
Modern machines have been perfected to crack the nuts without damaging the kernel. There are two main types in use: the fixed plate with cutting blade and combination rollers and base plate to compress the shell.
Many methods are employed for separating the kernel from broken shell, including hand sorting, screens, flotation, air separators and state of the art electronic colour sorters. These sorters differentiate between the dark brown colour of shell and the creamy colour of kernel and remove the shell fragments with a burst of compressed air. A final hand sorting inspection is carried out, to remove poor quality kernel.
Grading of styles and qualities is usually achieved using rotating screens. Quality is maintained, by accredited processors, in accordance with ISO 9002 standards.
Macadamia nuts are either dry or oil roasted. Several different types of oil are used including vegetable, coconut, peanut and, of course, macadamia oil.
The good oil
A very important by-product of macadamias is the extraction of cold-pressed oil. Although costly in comparison to other vegetable oils, it is becoming a favourite as a salad and cooking oil.
This high performance oil could very well be ‘the Champagne of oils’.
Produce is constantly monitored through chemical analysis to ensure the correct balance of nutrients is present and that pesticide and other chemical residues are within industry safety standards. Test are also conducted for bacterial analysis.
Long-life storage is another positive attribute of macadamia nuts and this can be further enhanced by the use of nitrogen flushed, vacuum sealed containers that prevent oxidisation and rancidity. A variety of glass, metal, foil and plastic containers are used. The unbroken shell of the macadamia is also an excellent storage container.