Processing
Cultivation
1. Macadamia trees require rich soil, about 50 in (130 cm) of rain per year, and temperatures that are not only frost-free but that vary within a limited range. The soil must also drain well, so not all tropical zones are suited to macadamias as a crop.
2. The flowering of the trees occurs over a four-to-six-month period. Consequently, the nuts mature at different times over the course of the year. They are also biennial, so alternate years produce light then heavy crops from a single tree.
3. Ripened and unripen nuts look identical, so producers either wait until the nuts fall to the ground or they harvest infrequently, approximately five or six times a year. The nuts are harvested through a complicated process that includes gathering by hand, shaking the trees and picking the fallen nuts, or picking them with a mechanical picker. Blowers are sometimes used to blow the nuts and fallen leaves into windrows so they can be collected by machine.
Processing in the Factory
1. The harvested macadamias are fed into large hoppers and then into a de-husker made of double rollers that strip the husk away. The husked nut has a moisture content of about 25%, and it has to be dried and cured to reduce its moisture content to about 1.5%.
2. Drying is done in a greenhouse, and curing is accomplished by heating the nuts to 104- 122° F (40-50° C). Some processors store the nuts in netted bags during drying so the heated air can move freely through the nuts. The lower moisture helps later in processing in separating the kernel from the shell.
3. To shell the nuts, they are passed through steel rollers that counter-rotate and are carefully spaced and engineered to conform to the size of the macadamias. An alternative process uses a cracking machine equipped with rotating knives that pin the nuts against a wedge shape and crack them.
4. In the Kenya, sorting is done mechanically using manual labor although in some instances advanced optical selectors are used to speed up the process. At this stage, grading and sorting of different styles is also carried out through the necessary equipment.
5. Processed macadamia nuts are vacuum packaged whether for local or foreign markets where they have various uses depending on the end -use industries.
