From Minor Oil Crops, FAO Agricultural Bulletin No. 94
by the Food And Agriculture Organization of the United Nations
Macademia Nuts
I. GENERAL
Common name
Macadamia Nuts
Botanical name
Macadamia intergrifolia
Macadamia tetraphylla
Family
Proteaceae
Other names
Queensland nut, Australian nut, bopple nut, bauple nut, popple nut, kindal kindal, boombera, burrawang (Aboriginal)
Cultivation conditions
Macadamia
is indigenous to coastal rainforests of South Queensland and the
northern river districts of New South Wales, Australia (Cavaletto). It
has since been introduced to many- other countries, particularly in
Africa.
The trees cannot tolerate frost and are suited best to areas where there are alternate wet and dry seasons (Cavaletto).
Major producing countries
HAWAII, AUSTRALIA, USA, Kenya, Guatemala, Costa Rica, Malawi, Zimbabwe, South Africa, Brazil, Fiji.
In 1978 Hawaii, for example, produced 9 500 tonnes of inshell nuts (Rosengarten).
Description and yield
Two species of the family produce edible nuts, M. tetraphylla known as rough shell macadamia and M. intergrifolia
known as smooth shelled macadamia. The fully mature nut consists of a
nearly round nut in hard spherical brown testa, or shell, about 25 mm
in diameter and 2-3 mm thick which is in turn surrounded by a fibrous
green pericarp some 2 to 4 mm thick. Normally only one nut develops in
each fruit. The tree begins to bear fruit when it is about 6-7 years
old and has a lifespan of approximately 60 years. Trees can yield
between 27 - 68 kg of nuts per year (Cavaletto). Nuts have an oil
content of 60% (Maefalane).
Main uses
The
kernels are mainly sold whole as high value edible nuts. Macfalane and
Harris (NRI, 1981) show that reject kernels can be processed to yield
an edible oil. The shell is used as a mulch or, if mixed with pineapple
and molasses, for animal feed (Woodroof). It can also be used as a
source of fuel. Some industrial units use the shell to fire their
boilers. (calorific value 10,000 BTU/lbs) (Rosengarten). The oil
extraction process produces an oilcake which is suitable as a feed for
non ruminant animals (Macfalane). The hull powder is used as a filler
in the plastics industry (Woodroof).
II. AGRICULTURAL ASPECTS
Cultivation
Macadamia trees are usually grown in plantations, especially in Hawaii where there has been extensive research into the crop.
Trees
can be grown from seedlings but it is suggested that this type of
planting yields low oil content as there are too many variations in
productivity and kernel quality.
A preferred method of planting
is by grafting trees of selected varieties. New grafting methods have
reduced propagation from 2 years to 1 year and have also increased
success from 66.8% - to 94.8% (Campo-Dall'Orto).
Varieties
10
Spp of Macadamia have been identified, M. intergrifolia and tetraphylla
are the only two that produce edible oil nuts. In Hawaii 9 selections
of intergrifolia have been used for creating varieties. The rough
shelled M. tetraphylla has less desirable processing characteristics
than intergrifolia.
It is not really grown for commercial
purposes. The varieties used are: (HAES 246) Keauhou, (HAES 333)
Ikaika, (HAES 508) Kakea, (HAES 660) Kcaau, (HAES 344) Ka'u, (HAES 741)
Mauka, (HAES 800) Makai, (HAES 294) Purvis, and (HAES 788) Pahala
(Cavaletto).
Listed below is a summary of insect pests which attack Macadamia, taken from different sources.
Peoudotheraptus wayi
Maladera matrida
Monolepta australis
Cryptoblabes gnidiella larvae
Spectrobates ceratoniae
Crytophlebia leucotreta
Nezara spp.
Erysichton lineata
Ulonemia spp.
Toxoptera aurantii
Amblypelta nitida
Cryptophlebia ombrodelta
Damage from rats can also be serious, cases have been noted where 50% of the crop has been lost as a result of rat infestation.
Major diseases noted: In Taiwan 1982, extensive root decay in macadamia was noted, caused by Ganoderma tucidum and Kretzschmania clavus (Ann). Phytophthora cinnamomi has been noted to cause trunk canker disease in Australia (Pegg).
Harvesting period
About
215 days after flowering, the nuts mature and fall to the ground.
Harvesting extends over a seven month period, therefore several
harvests are required.
In general, harvesting in the northern
hemisphere occurs between August and February while harvesting in the
southern hemisphere takes place between March and September
(Cavaletto). During the main harvest, nuts are gathered at intervals of
2 weeks. For the rest of the harvest period they are collected once a
month (Woodroof).
Harvesting methods
Harvesting
is usually by manual collection of the nuts from the ground. Picking is
generally avoided as there is great difficulty in distinguishing
between immature and mature fruits (Grimwood). In Hawaii, to provide a
smooth surface for the nuts to fall upon, some areas are covered with
volcanic cinders. Mechanical harvesting methods have been developed.
For example, an inexpensive tractor mounted nut recovery attachment has
been designed. Experiments show that it is 90% efficient and can
replace 30 hand pickers (Paquin). Other methods use nets hung between
trees to catch the falling nuts. This is not often used as the nets are
expensive and are often contaminated with fallen leaves (Cavaletto).
III. POST HARVEST TREATMENT. PRESERVATION, STORAGE
Pre-treatment
The
husks are removed and the nuts are dried within 24 hours of harvest.
Failure to do so initiates undesirable physiological activity which
causes fermentation and spoilage.
For the production of edible
nuts it is important to dry the nuts from an initial moisture content
of 45% to between 5% - 1.5%. This is done by passing air through the
nuts for a week, followed by an application of low heat (38 deg C - 54
deg C), for an additional 7-10 days (Cavaletto). At a smaller scale
nuts are placed 2-3 deep in trays which have good air circulation and
these are left to dry for about 2-3 weeks (Rosengarten).
If
stored in bulk, respiratory activity results in increased temperatures
and creates high relative humidity. In such conditions lipolysis and
moulds become storage problems. The nuts should be stored in a
rainproof shelter or drying shed (Rosengerten).
Simple drying racks can be made from 1.27-0.635 cm meshed cloth stapled to a light wooden frame (Rosengarten).
IV. PROCESSING
Processing methods
A
range of technical options exist for shelling, or decorticating, the
nut". These range from simple hand methods, through to machines that
apply pressure with a rotating rubber tyre (Cavaletto), to large
commercial crackers. Walnut decorticators have teen used with some
success in Hawaii, but are expensive (Woodroof). Other machines use
counter rotating steel rollers. Experiments in Hawaii have been
successful in showing that flame drying can be used to decrease the
macadamia nutshell moisture below that of the kernel so causing it to
become brittle and easy to crack (Tang).
After the nuts have
been removed from their shells they are graded. Fresh nuts are placed
into a saline bath of specific gravity 1.024.
If they float they
are placed into a water bath. The nuts that rise to the surface are
classed as grade I nuts and are packaged as "Top Quality Edible Nuts".
Those that sink are classed as grade II nuts and are sold whole for
edible purposes.
The nuts that sink during the first immersion
are placed into another saline bath which has a specific gravity of
1.15. If they float they are graded as Grade III and are used for oil
extraction. The debris, such as shells, usually sink at this stage.
Those nuts falling into Grade III can account for about 25% of the nuts processed (Macfalane).
Oil extraction
Oil
is extracted from reject grade III nuts using small expellers and finds
use as cooking oil, and by the cosmetic industry. (Anon). It has been
shown that it is necessary to add a proportion of fibre in the form of
press cake to the feed of kernels to obtain good extraction rates
(Macfalane). In Malawi the oil is made into soap.
Major fatty acids of oil
| Myristic acid | 0.7% | | Palmitic acid | 9.1% | | Palmitoleic acid | 21.9% | | Stearic acid | 2.2% | | Oleic acid | 59.9% | | Linoleic acid | 1.9% | | Arachidonic acid | 1.8% | | Eicosenoic acid | 2.0% |
(Source: Cavaletto)
A high oleic acid to low linoleic acid ratio suggests that the oil is quite stable to oxidative deterioration (Macfalane).
The oil extracted using expellers is pale yellow in colour and has a taste and smell similar to unprocessed macadamia nuts (Macfalane).
Equipment
Decorticators,
driers, saline bath. An expeller with a throughput of about 25 kg/hr
has been recommended for small scale production (Macfalane).
Additional
information was unidentifiable for the following areas: agricultural
aspects, planting period, major pests and diseases; processing and oil
extraction, nomenclature of products.
Bibliography
Anon, "Macadamia Beauty Products", Chemist & Druggist, 1984, 221, no. 5402, P.87.
Ann, P.J. KO, W.H. "Root Rot of Macademia Caused by Ganoderma tucidum and Kretzschmania clavus in Taiwan", Journal of Agricultural Research China, 37, 4, pp. 424429, 1988.
Campo-Dall'Orto,
K.A. Ojima, M. Barbosa, W. Sabino, J. C. Rigitario, O. "Early Grafting
of Macadamia Seedlings", Bragantia, Instituto Agronomico de Campinas
Brazil, 45, 2, pp. 289-295, 1988.
Cavaletto,
C.G. "Macadamia Nuts", pp.542-559, "Tropical and Subtropical Fruits,
Composition, Properties and Uses", Edited by NAGY, S. Shaw, P. E. AVI
Publications Company, 1980.
Cavaletto, C.G. "Handbook of Tropical Foods", pp.362-392, Edited by CHAN, H. T. Marcel Dekker Inc.
Croix,
E.A.S. la. "Thindwa, H.Z. "Macadamia Pests in Malawi. IV. Control of
Bugs and Borers", Tropical Pest Management, 32, 2, 1986.
Golberg,
A.M. Yathom, S. Almogi-Labi, A. Fridland-Wunder, G. "Diurnal and
Seasonal Occurrence, Feeding Habits and Mating Behaviour of Maladera
matrida Adults in Israel", Phytopareeitica, 17, 2, pp. 81-89, 1989.
Grimwood, B.E. "The Processing of Macadamia Nuts", pp. 3-4, Tropical products Institute, July 1971.
Ironside, D.A. "The Macadamia Flower Caterpilla", Queenland Agricultural Journal, 104,1, 1978.
Macfalane,
N. Harris, R.V. "Macadamia Nuts as an Edible Oil Source", Edited by
PRYDE, E.H. PRINCEN, L.H. MUKNERJEE, X.D. American Oil Chemists
Society, 1981.
Macfalane, N. Harris, R.V. "Extraction of Macadamia Oil Using a Small Expeller", Tropical 8cience, Vol 23, 3, pp. 205-215, 1986.
Meulen,
T. van der, "The Coconut Stink Bug Gets Out of Hand", Information
Bulletin, Citrus and Subtropical Fruit Research Institute South Africa,
202, 1989.
Paquin, D,G, Laing, T. "Sweeping Efficiencies of a
Macadamia Nut Harvester on Difficult Orchard Surfaces", Journal of
Agricultural Engineering Research, 45, 2, pp. 8999, 1990.
Pegg, K.G. "Macadamia Trunk Canker Disease", Queensland Agricultural Journal, 99, 11, pp. 595-596, 1973.
Queensland
Department of Primary Industries Entonomy branch, "Macadamia Summary of
Insect Control Recommendations", Queensland Agricultural Journal, 101,
3, pp.286-290, 1978.
Rosengarten, F. "The Book of Edible Nuts", Walker and Co New York, 1984.
Sarig,
Y. Grosz, F. Rasis, S. "The Development of a Mechanical nut Cracker for
Macadamia Nuts", Journal of Agricultural research, 25, 4, pp. 367-374,
1980.
Tang, G.P. "Flash Drying Macadamia Nuts for Improved Kernel
Extraction", Transactions of the A.S.A.E. (American Society of
Agricultural Engineers), 25, 6, pp. 1733-1736, 1982.
Treverrow, N. "Monolepta Beetle", Agfacts, No 42, Agricultural Research Centre Wollongbar, New South wales Australia, 1986.
Woodroof, J.G. "Tree Nuts, Production, Processing, Products, Vol 1.", pp.313-337, AVI Publications Company, 1967.
Wysoki, M. "New Records of Lepidopterus Pests of Macadamia in, Israel", Phytoparesitica, 14,2, 1986.
Further Reading
Principals of Extraction
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Smooth Shell Macadamia Page
Rough Shell Macadamia Page
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