Nuts in general.

Introduction.

Nuts have been part of the human diet for a long time and remains have been found in archaeological sites dating back to before 10,000 BC. The discarded husks found at these sites illustrate one of the positive features of nuts that allow nuts to be stored for extended periods of time. Nuts are a concentrated food and recent research suggests that some early civilisations relied on nuts as a staple food before cereal grains.
A nut may be defined as a hard, dry, single-seeded fruit, partially or totally enclosed in a husk that remain with the fruit as it ripens. A layman’s definition of a nut would be a seed or fruit with an edible kernel inside a shell. A good example of a nut would be a walnut, chestnut or hazelnut. The term nut is applied to many hard-shelled fruits that may be stored dry but many of these are not true nuts. The peanut (groundnut), for example, is not a true nut it is a legume. The almond is actually the pit of a drupe like fruit and the Brazil nut is actually a seed. The common nuts of commerce are the Brazil nut, cashew nut, chestnut, coconut, hazelnut, kola nut, litchi nut, macadamia nut, pecan, pine nut, pistachio and walnut.
Almonds, hazelnuts, pine nuts, chestnuts and walnuts form a significant part of the traditional Mediterranean diet (which is considered to be very healthy). They also appear to provide a protective effect on both fatal heart attacks and non-fatal ischaemic heart disease1 in people who consume them regularly.
Peanuts are commonly included in the tree nut group because their composition, particularly their fatty acid profile, is similar to tree nuts. It should be remembered that peanuts are legumes. The pod develops above the ground and it is slowly pushed into the soil as it develops. In nutritional surveys peanuts are often included in the same grouping as nuts.
In some parts of the world nuts are extremely important to the diets of local cultures e.g. coconut in the tropical Pacific islands. While in Korea chestnuts play a role similar to potatoes in some Western cultures. In many other regions of the world nuts are regarded as less important as staple foods but more important to decorate food, to provide important tastes or as a delicacy. Most of the lesser-known nuts (Table 1) are restricted to traditional diets usually within relatively narrow regional boundaries. Only two of the lesser-known nuts of warm climates, macadamia and pistachio have developed into commercial crops.
The production of edible tree nuts (not including coconut) is estimated to be 1.6 million tons on a shelled basis. This is made up of chestnuts (28%), walnuts (21%), almonds (13%), hazelnuts (11%), pecans (7%), cashew nut (5%), pistachio nuts (3%) with all the other nuts masking up the remaining (12%). The world production figures of nuts are notoriously inaccurate, as large amounts of nuts are known to be consumed without passing through commercial trade channels. It is possible that up to 40% of world production is not accounted for.

Composition and nutritive value of nuts.

Because nuts are not major items of the diet little analysis of their composition has been carried out. Table 1 shows the mean composition of the proximate constituents of many of the common nuts.A feature of nuts is their high content of oil and protein. Macadamia nuts appear to have the highest levels of total oil while peanuts contain the highest levels of protein.Chestnuts are an exception as they have a high carbohydrate content low protein and moderate total fat content.

Table 1. Composition of some of the major commercial nuts (g/100 g edible nut).

Almond
Brazil
Cashew
Chestnut
Hazelnut
Hickery
Lychee
Maca-damia
Pecan
PinePignolias
nutsPinon
Pistachio
Blackwalnut
English walnut
Water (%)
4.7
4.6
5.2
8.4
5.8
3.3
22.3
3.0
3.4
5.6
3.1
5.3
3.1
3.5
Energy (Cal)
598
654
561
377
634
673
277
691
687
552
635
594
628
651
Protein (g)
18.6
14.3
17.2
6.7
12.6
13.2
3.8
7.8
9.2
31.1
13.0
19.3
20.5
14.8
Fat (g)
54.2
66.9
45.7
4.1
62.4
68.7
1.2
71.6
71.2
47.4
60.5
53.7
59.3
64.0
Carbohydrates(g)
19.5
10.9
29.3
78.6
16.7
12.8
70.7
15.9
14.6
11.6
20.5
19.0
14.8
15.8
Fiber (g)
2.6
3.1
1.4
2.5
3.0
1.9
1.4
2.5
2.3
0.9
1.1
1.9
1.7
2.1
Ash (g)
3.0
3.3
2.6
2.2
2.5
2.0
2.0
1.7
1.6
4.3
2.9
2.7
2.3
1.9
Calcium (mg)
234
186
38
52
209
tr
33
48
73
-
12
131
tr
99
Phosphorus (mg)
504
693
373
162
337
360
181
161
289
-
604
500
570
380
Iron (mg)
4.7
3.4
3.8
3.3
3.4
2.4
1.7
2.0
2.4
-
5.2
7.3
6.0
3.1
Sodium (mg)
4
1
15
12
2
-
3
-
tr
-
-
-
3
2
Potassium (mg)
773
715
464
875
704
-
1100
264
603
-
-
972
460
450
Vitamin A (IU)
0
tr
100
-
-
-
-
0
130
-
30
230
300
30
Thiamin (mg)
0.24
0.96
0.43
0.32
0.46
-
-
0.34
0.86
0.62
1.28
0.67
0.22
0.33
Riboflavin (mg)
0.92
0.96
0.43
0.32
0.46
-
-
0.34
0.86
0.62
1.28
0.67
0.22
0.33
Niacin (mg)
3.5
1.6
1.8
1.2
0.9
-
-
1.3
0.9
-
4.5
1.4
0.7
0.9
Vitamin C (mg)
tr
-
-
-
tr
-
-
0
2
-
tr
0

Fatty acid content.

Most nuts are rich in monounsaturated fat (oleic acid) while walnuts are also high in two polyunsaturated fatty acids linoleic and a-linolenic acids (Table 2).Monounsaturated and polyunsaturated fatty acids are known to have a cholesterol lowering effect when consumed in a reasonable amount in the diet.Macadamia nuts are interesting as they contain a very low content of polyunsaturated fatty acids combined with a very high content of monounsaturated fatty acids (Table 3).

Table 2. Fatty acid content of common nuts.


Dietary fibre.

The dietary fibre contents of nuts are moderately high ranging from 5-9% by weight. Dietary fibre is known to have cholesterol-lowering properties.

Protein.

Nuts are a good source of protein ranging from 14-26%; they also contain high levels of the essential acid arginine and low levels of lysine.Table 3 shows the amino acid composition of some of the common nuts.A high ratio of lysine to arginine appears to have an atherogenic effect on animals and people so food containing high levels of arginine is to be preferred.Arginine is used to make protein in the body but it also can be degraded to nitric oxide.Nitric oxide is a potent endogenous vasodilator with similar action to nitro-glycerine (nitro-glycerine is the compound given to people who have some blockage in the arteries supplying the heart and have cardiac pain when they exercise).Nitric oxide helps to relax smooth muscle in the walls of the arteries.Nitric oxide also appears to inhibit platelet aggregation which helps to prevent the development of atherogenic plaques (this is the first stage in the formation of a blockage in the arteries.

Table 3. Amino acid composition of some commonly consumed nuts.


Vitamin E.

Nuts are an excellent source of the antioxidant vitamins particularly the a-tocopherols. In contrast walnuts contain about 290 mg/g oil` l-tocopherol.Antioxidant vitamins protect low-density lipoprotein (LDL) cholesterol from oxidation to atherogenic products.The basic function of tochopherols is to trap free radicals thus preventing the oxidation of unsaturated fatty acids in the tissues.Note that nut oils contain reasonable amounts of unsaturated fatty acids. Other plant sterols Nut oils like other plant oils contain no cholesterol but they do contain a range of plant or phytosterols.Sitosterol is found in the largest amounts in nut oils.Phytosterols are known to act as antioxidants, which is important in maintaining the stability of the oil during storage.In the digestive tract it appears that the phytosterols combine with cholesterol from other foods eaten at the same time, and prevent the cholesterol from being absorbed.This has the positive effect of reducing blood cholesterol levels. Minerals Nuts contain a good range of essential minerals and are high in copper. Peanuts, walnuts and almonds range from 0.8-1.2 mg/100g.Western diets appear to be low in copper and it has been suggested that eating 28 g nuts (two of the little packets served on airlines) would add 0.37 mg copper to the daily intake.If a person has a low copper intake this increase would have a positive reducing effect on blood cholesterol levels and slow the development of arteriosclerosis. Nuts are a good source of magnesium.In the USA, for instance, up to 75% of the people consume less than the recommended daily intake of 300 mg Mg/day.There appears to be an inverse relationship between magnesium intake and coronary heart disease mortality in some populations.The regular consumption of almonds, cashews and hazelnuts would considerably help to meet the requirement for Mg. Epidemiological evidence In a prospective study among approximately 34,000 members of the Seventh-Day Adventist Church in California there was an association between the intake of some foods and the risk of developing heart disease.About 45% are vegetarians and they consume more nuts than the rest of the population.The regular consumption of nuts reduced the incidence of heart disease.The American Nurses Health Study (84,409 nurses) carried out over 14 years also showed that their risk of coronary heart disease was considerably reduced if they ate nuts regularly.Other studies in Australia and New Zealand have shown that frequent consumption of nuts is associated with a reduced risk of both fatal coronary heart disease and non-fatal myocardial infarction.Most studies show a significant reduction of blood cholesterol occurs but many of the other factors mentioned above may also have a positive effect. Summary Most nuts contain a significant amount of fat. Nuts contain high levels of monounsaturated and polyunsaturated fats making them a healthy food to eat. Regular consumption of nuts reduces blood cholesterol levels and the risk of coronary heart disease.


Lesser-known nuts.

Lesser known nuts that are edible.

Almondettes
(Buchanania lanzan Spreng. Family Anacardiaceac) Southern AsiaThese are related to the pistachio nut; medium-sized tree; black, single-seeded fruits; pear-shaped kernels, 1 cm, eaten raw or roasted, delicious (combination of almond and pistachio flavour); 51.8% oil, 12.1 % protein, 21.6% starch, 5% sugars.
Bunya nut(Araucaria bidwillii, Family Araucariaceae) Australia It is a large pine tree its large cones contain starchy nuts, 5 x 3 cm, usually roasted, flavour resembles chestnuts.
Candle (Tung) nut(Aleuriles spp., Family Euphorbiaceae) China, Southeast Asia, Indonesia
An attractive tree with a fleshy fruit, containing a single nut, globular 3 cm; hard thick shell; soft, oily white kernel (5 g); must be cooked, moderately poisonous when eaten raw.
Galip nut (Canarium indicum L., Family Burseraccae, also including related Java almond, C.commune and Pili nut, C. ovatum Engl.) Philippines, Moluccas, Papua New Guinea
A tall, buttressed tree; roundish, dehiscent fruit bearing a single 5.5 x 2 cm nut, triangular in cross-section, 3 g, delicious, sweet almond-like flavour; 70-80% oil, 13% protein, 7% starch; remove testa before eating raw or roasted.
Lotus seeds (Nelumbo nucifera Gaertn., Family Nymphaceae) Asia
Water lilies are revered by Buddhists; white, single-seeded carpals embedded in flat-topped, fleshy receptacle which dries when mature so that the 1 cm seeds rattle in their cavity; bitter green embryos must be removed before eating; eaten raw before fully ripe; nutty flavour, roasted or boiled when mature; rich in vitamin C, 58% carbohydrate (starchy), 17% protein, 2.5% fat
Macadamia nut (Macadamia integrifolia Maiden and Betche, M. tetraphylla, Family Proteaceae), Queensland, Australia
An evergreen tree adapted to the fringes of subtropical rainforests; spherical kernel enclosed by a thick, stony shell in a fibrous single-sutured husk; high oil content (> 72%); distinctive, delicate flavour
Okari nut (Terminalia kaernbachii Warb., Family Combretaceae, also T. catappa L., the tropical almond) Papua New Guinea, Southeast Asia, India. A tall tree, leaves clustered at twig tips; flattened, ellipsoid fruit; stony endocarp, encloses white kernel consisting of a leaf-like coiled cotyledon 8 x 2 cm, 1.5-10 g; almond flavour; contain about 50% sweet, colourless, non-drying edible oil; eaten raw or roasted
Oyster nuts (Tefflairia pedata (sm. ex Sims) Hook, Family Cucubitaceae) Tropical East Africa A woody stemmed climbing vine, dioecious; large (< 15 kg), deeply ridged, dehiscent gourds containing up to 140 pale yellow seeds (nuts) enclosed in a strong, bitter-tasting, fibrous husk; nuts are flat and circular (34 x 1.5 cm thick), washed, sun-dried and dehusked before eating, raw or roasted; palatable, flavour similar to Brazil nuts; nutritious, 62% fat, 27% protein, rich edible oil.
Pandanus nuts (various species, Pandanus jiulianettii Martelli, Family Pandanaceae) Papua New Guinea.
A dioecious 'screw' pine; large, dense multiple fruit up to 16 kg; individual fruits separate easily, up to 10 cm long, 1.5 cm in diameter; sweet coconut taste; oily endosperm; normally roasted.
Paradise (Sapucaia) nut(Lecythis usitata Miers., Family Lecythidaceae) Brazil, Guyana
A tall Amazon rainforest tree, related to Brazil nut but with superior, sweet delicate flavour (Note some species are poisonous); large, dehiscent woody fruits containing 30-40 irregular, oblong nuts resembling Brazil nuts but more rounded with a thinner, softer shell, white, creamy textured kernel highly nutritious, 62% fat, 20% protein; eaten raw or roasted; edible oil.
Pistachio nut (Pistacia vera L., Family Anacardiaceae) Central Asia, the Middle East and Mediterranean basin
A small, deciduous, dioecious tree; resin ducts through all tree organs; bunches of nuts near shoot tips; harvesting at the correct stage of maturity is critical; fleshy hull surrounds dehiscent, bony shell which encloses the kernel; high in carbohydrates mainly sucrose (16%), oil, mainly unsaturated (55%) and essential amino acids (25%).
Quandong(Santalum acuminatum Sprague and Surnmerhayes, Family Santalaceae) Australia
Small, semiparasitic trees of desert regions; globular, edible, fleshy fruits; kernel enclosed in pitted, stony shell; oily; harsh aromatic flavour; nutritious, 60% fat, 25% protein; generally roasted.
Souari nut (Caryocar nuciferum L., Family Caryocaraceae) Brazil, Guianas
An attractive, large tree; fruits round, soft wooded capsules, 15 cm diameter containing two to five large, brown, kidney-shaped nuts up to 5 cm long; edible yellow pulp surrounding nut; kernel enclosed in hard, woody, warty shell up to 1 cm thick, hard to crack; kernel has soft, white, sweet, almond-like flavour; eaten raw or roasted; edible oil.
Tahiti (Polynesian) chestnut(Inocarpus fagiferus (Parkinson) Fosberg., Family Leguminosae) Pacific Islands A moderate sized tree; stout, kidney-shaped, nondehiscent, single-seeded pod borne in terminal clusters; fleshy nuts, boiled or roasted when nearly ripe, taste like chestnuts, palatable, sometimes hard to digest; staple food on some islands; moderately nutritious, 80% starch, 10% protein, 7% fat. Tallow nuts (Ximenia americana L., Family Olacaceae Widespread throughout the Tropics
A densely branched shrub. Usually deciduous; egg-shaped, juicy, fleshy fruits contains large, oily seed; white kernels. Palatability varies; nutritious, rich in protein and oil; eaten raw or roasted; used to make cooking oil.
Water chestnut, Chinese water chestnut (Trapa spp., Family Trapaceae) Tropical Africa, Central Europe, Eastern Asia
An aquatic plant; not a true nut; hard-shelled, woody fruit with four woody, spiny horns contains a single large white starchy kernel; eaten raw, roasted or boiled; 16% starch, 3% protein, not particularly nutritious.

Health Benefits of New Zealand Nuts.


The positive advantages of consuming nuts in the diet are well known to vegetarians. Identifying the advantages for everybody is a little more difficult. There is, however, a nutritional survey that has been in progress for a number of years in the USA. It involves surveying the dietary habits, lifestyle and health outcomes of a very large number of American nurses (84,409 at the start of the study. The Nurses' Health Study, as it is called has shown that those nurses who consumed nuts five or more times a week had a 50% reduction in risk of coronary heart disease compared to those who never consumed nuts. This epidemiological study showed that the regular consumption of nuts in the diet without any complicated dietary modification could have a positive effect. The Nurses’ Health Study is based in the USA and the common nuts consumed there are walnuts, hazelnuts, peanuts, pecans and pine nuts. Unfortunately the nurses were not asked to give details of which nuts they commonly consumed.More recently a number of researchers have supplemented the diets of patients suffering from high blood cholesterol levels with walnuts or almonds (Sabaté et al 1993; Abbey et al, 1994; Chisholm et al, 1998). These experiments have shown that adding nuts in relatively small amounts to the diets of people with high blood cholesterol levels can reduce the blood cholesterol levels by as much as 14%. This reduction should have a significant effect on the long-term health cardiovascular outcomes of people with high blood cholesterol. So far all of these experiments have been carried out in outpatient clinics and they have involved giving additional dietary advice (such as cutting down fat intake and not eating so much!).There seems to be scope to encourage ordinary people (that is people who are not attending Lipid Clinics) to consume nuts in the diet more regularly. An experiment carried out by Savage and McNeil at Lincoln last year showed that feeding walnuts to students did have the effect of reducing blood cholesterol levels. These experiments should encourage people to consume a more healthy diet containing fresh New Zealand grown nuts.Studies at Lincoln have shown that the composition of nuts varies widely between cultivars and also between different varieties of nuts. It is possible that some varieties of nuts and some cultivars may have a more beneficial effect on the lipid profile than others. This paper will discuss the different compositions of nuts commonly consumed in New Zealand and suggest which of the many constituents may have the positive effects observed so far. While it is clear that nuts have a positive role in human nutrition, it will not be easy to identify which constituents have the more important effects.

Walnut.


Many of the species of trees in the family Juglandaccae, which include walnuts and pecans, produce a valuable edible, oil-rich nut.Walnuts are common, large, forest deciduous trees found primarily in temperate areas, but also in subtropical regions, mainly in eastern North America, Central America, western South America and eastern Asia.Walnuts belong to the genus Juglans, which consists of about 15 species.The most important species is the Persian or English walnut (J. regia L.).It was probably moved by migrating populations from ancient Persia to Greece and later distributed throughout the Roman Empire.The early colonists from the UK took seeds to North America, and the settlers called the resulting trees 'English walnuts' to distinguish them from the native American Black walnuts.English walnuts are cultivated commercially in the USA, France, Italy, Yugoslavia, Poland, Germany, Czechoslovakia, Bulgaria, Turkey, Chile, northern India, China and Australia.The second principal variety is the Black walnut (J. nigra L.), which is native to the USA and is found distributed along the coast, west to Michigan and throughout most of the midwestern states of USA.A third walnut variety, less important from a commercial standpoint is the butternut (J.cinerea L.).This tree is native to eastern regions of North America.
Commercial importance

Although the most important and best-known commercial species is English walnut, many commercial varieties of different species are grown, and the production of nuts is over 90,000 t/year.The nuts of all species are edible, and the young green fruits (before the nuts harden) are also eaten pickled in vinegar.The mature nuts can be eaten raw or salted, and are excellent for dessert, in ice creams and sweets, and are also used in baking and confectionery.Although the black walnut has a richer flavour than the English walnut, it is not as popular because its shell is much thicker and harder to remove without breaking the kernels.The kernel forms 42-60% of the nut.Walnut oil makes a good salad oil, and can also be used in the preparation of soap, and as a drying oil in paints. The defatted walnut cake can be used as an animal feed.
The walnut shells, when reduced to a powder of various mesh sizes, have found applications as fillers in synthetic resin adhesives, plastics and industrial tiles.About 50% of the annual production of walnut shell is used in the plastics industry alone.The shell powder is also used as a drilling mud in oil fields, and as an abrasive for polishing metal castings.Dyes prepared from walnut shells and leaves are still used in Turkey, and the high tannin content of green walnut shells is useful in leather manufacture.A pharmaceutical grade of activated charcoal can be prepared from the non-edible parts of the fruit.Various parts of the walnut tree, such as bark, leaves, shells, fruits and kernels, have been used in folk medicine throughout the world.The timber of walnuts, particularly of the English and black walnut varieties, possesses excellent mechanical strength and very good shock resistance, and hence it is much valued for veneers, furniture, and gunstocks.

Anatomy of the fruits and seeds.
The walnuts are usually tall, broad-headed, deciduous trees that grow from 10-50 m in height.They have rough barks, and compound pinnate leaves that exude an aromatic fragrance when crushed or bruised, a property that varies in degree from one species to another.
The English walnut is a large, deciduous tree attaining over 30 m in height and a trunk of 6 m in girth; the bark is grey, smooth on young trees and fissuring with age.The staminate (male) flowers of this species are borne on twigs of the previous season's growth, and the pistillate (female) flowers, usually few, are borne on the twigs of the current season's shoots.Pollination occurs naturally via the wind, but numerous cultivated varieties have been recently developed by other means.The green fruit is 3.7-5.0 cm in length with a subglobose, gland-dotted and glabrous structure.The fruit is a drupe which means that it consists of an outer layer and an inner nut, inside which is the single seed containing at least 60% oil.When the seed is ripe, the husk opens and the ovoid-shaped stone falls to the ground.The surface of the stone is wrinkled, showing the suture of the carpels in the median vertical plane.The seed consists mainly of two large cotyledons storing fatty substances.The black walnut tree grows up to 50 m in height and has brownish bark with fissuring.The drupelike fruits are solitary or in pairs, 2.5-5.0 cm in length, globose, oblong and pointed at the apex, or slightly pyriform with a thick husk.The nut is oval or oblong, slightly flattened 3.0-3.8 cm in diameter, and deeply divided on the outer surface into thin or thick, often interrupted, irregular ridges.

Chemical and nutritional composition.
Properties of the oil Walnut oil is produced from the inedible nuts rejected during shelling.The oils from the different species of walnut bear a close resemblance to each other in terms of both physical and chemical characteristics.They are light yellow in colour with a greenish tinge and have a delicate nutty odour.
Fat ContentThe walnut kernels generally contain about 60% oil, but vary from 52% to 70% depending on the variety.The major constituents of the oil are triglycerides.Free fatty acids, diglycerides, monoglycerides, sterols, sterol esters, phosphatides and vitamins are present in minor quantities.The triglyceride moiety of the oil is a mixture of triunsaturated and nonsymmetrical diunsaturated glycerides that form up to 83-95% of the total fraction.The number 2 position of the triglyceride contains primarily linoleic acid.The fatty acids of the walnut oil are predominantly (> 93%) unsaturated and consist mainly of linoleic and oleic acids (Table 1).The linoleic acid content in English walnut is higher than that in black walnut.Walnut oil has also been found to contain at least 29 volatile components, such as terpenes, alcohols and carbonyls, and the characteristic odour of the oil is attributable to the collective effect of a number of constituents.
Table 1. Fatty acid composition of walnut oil.
Palmitic16:0
2.37
Palmitoleic16:1
0.05
Margaric17:0
0.04
Stearic18:0
2.0
Oleic18:1
19.9
Linoleic18:2
28.3
Linolenic18:3
1.9
Arachidic20:4
0.04
Eicosenoic22:6
1.0
Energy Content.
Walnut kernels are a good source of energy.Black walnut kernels provide more energy (3318 kJ/100 g) than English walnuts (2730 kJ/100 g).

Protein content.
Walnut kernels contain about 14.5-24% of protein, and this rises to 61-66% in dry, defatted cake. Walnut cake contains more arginine and less lysine than does casein and soya bean meal.The walnut kernel protein contains all the common amino acids, and glutamic acid (1.28 g/100 g of kernel) is the main amino acid, followed by arginine (0.85-1.19 g/100 g of kernel).The essential amino acid composition is given in Table 2. In addition to the common amino acids, walnut kernels also contain a sulphur amino acid, taurine (2-aminoethanesulphonic acid) in concentrations of about 15-46 nmol/g, depending on the variety.In humans, taurine deficiency may lead to a decreased electroretinogram and to pigmentary degeneration of the retina.Walnut kernels have the potential to replace meat as a source of dietary taurine.

Table 2. Essential amino acid content of walnut kernels (g/100g)
Arginine
2.3
Histidine
0.4
Isoleucine
0.73
Leucine
1.3
Lysine
0.3
Methionine
0.25
Phenylanine
0.8
Threonine
0.5
Tryptophan
0.18
Valine
0.9

Carbohydrates.
The total carbohydrate content in English and black walnut kernels varies from 15.6-19.9 and 13-16 g/100g, respectively.The fibre content in both the varieties is about 2 g/100 g of kernel.Some varieties of walnut kernels contain large amounts of sugar(s).VitaminsWalnut kernels are a good source of vitamins.English walnuts contain more vitamin A (380 iu/100 g) than black walnut (30-140 iu/100 g), while the latter is a richer source (0.48?0.93 mg/100 g) of thiamin than English walnuts (0.28 mg).The contents of riboflavin (0.11-0.14 mg/100 g) and nicotinic acid (0.6-1.2 mg/100g) are almost same for all the varieties of walnut.The richest sources of vitamin C are the immature fruits or their green hulls.Unripened or green walnuts are reported to have a very high vitamin C content (1300?3000 mg/100 g), (40?50 times as high as oranges or lemons!) but these reports have yet to be verified.Dry walnut kernels are reported to contain only 2?3 mg/100 g after ripening.Walnuts contain about 200 mg /g-tocopherol and 15mg a-tocopherol/ g of nut; the d isomer is present in very minute quantities.Walnut kernels also contain vitamin K1 (0.9-1.1 mg/100 g).Phenolic AcidsIn foods phenolic acids has been associated with astringency, discoloration, inhibition of enzyme activity, and antioxidant properties.Defatted kernels are found to contain some phenolic acids, namely phenylacetic, protocatechuic, syringic, vanillic, gallic, caffeic and ferulic acids, in very small quantities ranging from 0.02-0.20 g/g of kernels.Pectic SubstancesWalnuts contain about 2% on the dry matter basis pectic substances.These make up a component of dietary fibre and have a positive nutritional value such as hypocholesterolaemic effects (lowering blood cholesterol), increased excretion of faecal sterols and the capacity to bind bile salts.Pectic substances may also slow down the absorption of soluble carbohydrates, causing a smaller increase in the postprandial level of blood sugar; hence walnut kernels could play a role in the design of pectic-rich diets designed to lower blood cholesterol levels and lower the possibility of heart disease.MineralsWalnuts are considered to be a good source of dietary minerals. The English and black walnuts contain almost similar quantities of minerals, except calcium, which is present only in moderate amounts in black walnuts.Potassium, phosphorus, magnesium and iron are found in significant quantities in these nuts.The mineral composition of walnuts is given in Table 4.

Table 4. Mineral content of walnut kernels (mg/100 g).
Calcium
Trace-108
Chloride
14-30
Copper
0.9-3.2
Iron
2.1-7.6
Magnesium
132-137
Manganese
2.4-2.7
Phosphorus
309-380
Potassium
328-606
Sodium
2-17
Sulphur
120-140
Zinc
2.3-3.6
Industrial uses of walnut oilWalnut oil is similar to linseed oil in composition, and its drying properties have been extensively used in paints and artists' colours from early times.English walnut oil contains more linoleic acid and has more active drying properties than black walnut oil.Walnut oil can also be used in the manufacture of soaps, varnishes, alkyd resins and styrenated oils.Since the 1940’s walnut oil has been consumed as a speciality food oil in salads.
Handling and storageRancidity is one of the first signs of deterioration in walnuts this is because they are rich in oil containing unsaturated fatty acids.High temperature and humidity, as well as sunlight, favour the development of rancidity in kernels, and the best storage conditions are therefore low temperature, low humidity and little or no light.Aflatoxin contamination presents another problem.In general, as the potential for aflatoxin production occurs during the harvest period after the nuts have begun to dry; the nuts must therefore pass quickly through this critical moisture content stage.Storage of the nuts under proper temperature and humidity will prevent further contamination.
The optimum moisture level for the storage of walnuts is 3.5±0.3 %, and stability of the shelled nuts is significantly reduced at higher or lower moisture levels.Very elaborate machinery is used for cleaning, grading, bleaching, cracking and packaging of edible tree nuts, including walnuts.Skin colour of the nuts is very important, and methods such as the photometric estimation of absorbance of a methanol extract of the whole nuts are useful for determining the rate of darkening of walnuts at regular intervals during storage.Walnuts are bleached for market by dipping them for 5-10 seconds in an aqueous solution of bleaching powder and sodium carbonate, with a small amount of sulphuric acid to clear the liquid.In another method, walnuts are exposed to ethylene (1 part ethylene to 1000 parts air) to preserve the natural colour of the kernel.This treatment prevents the hulls from sticking and staining the shells.After hulling and washing, the walnuts are placed in bins and dried with warm air (not over 43°C) to reduce the moisture content.The best storage conditions for walnuts are 0-2°C, accompanied by ventilation with air of relative humidity in the range 65-75%.

Almonds.

Almonds are part of the species Prunus,which includes peaches, apricots, cherries and other stonefruit. In 1768, the cultivated almond was redesignated as Prunus dulcis, for "sweet" almond. In 1801, Batsch renamed the species Prunus amygdalus, later Prunus amygdalus Batsch was used as the official name for almond. In 1964, the International Botanical Congress proposed Prunus dulcis as the official name of the cultivated sweet almond.

Anatomy of the fruits and seeds.
Almond trees are well proportioned and may grow up to 10 metres. The flowers are white, slightly tinged with pink; they may be up to 5cm across, with a reddish calyx, and are borne singly or in pairs on short stalks. The yellowish-green fruits are downy, oval drupes, slightly furrowed along on one side. The fruit dries and splits to show the stone which contains 1-2 edible seeds – the almond kernels.Almonds are not self-fertile and they require two varieties blossom at the same time to produce fruit. Almonds are grown commercially only in the regions free from early spring frosts as the blossoms open early in spring, before the leaves appear (especially in young specimens). In other regions, they are grown as ornamental plants.

Commercial importance.
Almond is a major commercial tree nut crop of the world. Since 1950, almonds have become the most important tree nut crop in the World with production of 350,000 to 400,000 tonnes. In any given year, California produces about 70% of the world’s supply of almonds. In New Zealand, almonds are not grown on a commercial scale and most of the produce is imported. Almonds imported in shell from Australia (10,000 kg) and the United States (31,145kg) had a value of $NZ 210,933 VFD (value for duty) or $NZ 220,174 CIF (cost including freight). The amount of shelled almonds is greater, with a total of 622,959kg imported, mainly from the United States (569,099kg) with a value of $NZ VFD $3,919,837 or CIF $4,122,307.The cultivated almond traces its origins to the deserts and lower mountain slopes of central and southwest Asia, and spread by human populations along trade routes and near ancient cities. By 4,000 BC, almonds were in use in nearly every ancient civilization. The geographical range of the cultivated almonds corresponds to the three stages of cultural evolution: (1) Asiatic (Southwest and Central Asia). (2) Mediterranean (countries bordering both sides of the Mediterranean Sea), and (3) Californian (central valleys of California, parts of Australia, central Chile and areas of South Africa). Today Mediterranean sources (except for Spain, which is the second-largest almond producer after California) no longer play an important role in the international trade in almonds.

Chemical and Nutritional Composition.
Fat content.

Almonds contain about 54% oil (table 1), but the amount can be as high as 62% depending on the variety. Almonds are a rich source of unsaturated fatty acids, mainly Oleic acid and the essential fatty acid linoleic acid. The saturated fatty acid content of almonds is very low (about 10 %), with and palmitic acid the main saturated fatty acid. There are 8 minor fatty acids present in the almond kernel (C10:0, C12:0, C14:0, C15:0, C17:0, C17:1, C18:3, C20:0).

Table 1. Mean total oil and fatty acid composition of almonds

almonds
Total oil %
54.3
16:0 palmitic
7.0
16:1 palmitoleic
0.03
18:0 stearic
2.3
18:1 D9 oleic
61.5
18:1D11 oleic
1.2
18:2 linoleic
27.2
18:3 linolenic
0.3
20:1
0.1

Tocopherol Content
Almonds contain a high level of a- tocopherols (table 2).Table 2 Mean total and individual tocopherol contents (mg/g oil) of almonds

tocopherol
a
b
g
almonds
215.2
151.8
3.1
60.3

Plant Sterols
The mean total sterol contents of almonds are shown in table 3. Campesterol ranged from 137 to 172 mg/g lipids, stigmasterol ranged 6 to 121 mg/g lipids, sitosterol 1310 to 2052 mg/g lipids and D5- avenasterol ranged from 369 to 445mg/g lipids.
Table 3 Mean composition of desmethylsterols (mg/g lipids) in oil extracted from almonds

Total sterols
campesterol
stigmasterol
sitosterol
D5 Avenasterol
almonds
2307
154.8
63.3
1681.1
407.3

Amino acids.
Almonds contain a significant amount of various amino acids (Table 4). Glutamic acid was found to be the most predominant amino acid (22-24 %), followed by arginine (9-11 %) and aspartic acid (11 %). These three amino acids made up over 40% of the total amino acid composition in almonds.

Table 4. Amino acid content of almonds (g/100g nuts). (blue denotes essential amino acids)
Amino acids
Almonds – amino acid g/100g of nuts
Tryptophan
0.19
Threonine
0.68
Isoleucine
0.69
Leucine
1.47
Lysine
0.60
Methionine
0.19
Cysteine
0.28
Phenylalanine
1.15
Tyrosine
0.53
Valine
0.80
Arginine
2.47
Histidine
0.59
Alanine
1.00
Aspartic Acid
2.73
Glutamic acid
5.17
Glycine
1.47
Proline
0.97
Serine
1.00

Mineral and Vitamin content.
At only 5% moisture, nutrients are quite concentrated in almonds. When compared with cashews, hazelnuts, macadamias, pecans, and walnuts, almonds rank highest in content for the essential micronutrients like calcium, magnesium, phosphorus and potassium (Table 5). Almonds are a good source of Niacin, Riboflavin, Thiamin, B6, pantothenic acid, Vitamin C, Folacin and Vitamin E.

Table 5. Composition of almonds per 100g tree nuts.
Nutrient (units)
Almonds – nutrients in 100g of tree nuts
Calories (kcal)
578
Protein (g)
21
Total fat (g)
51
Saturated fat (g)
4
Monounsaturated fat (g)
32
Polyunsaturated fat (g)
12
Carbohydrate (g)
20
Fiber (g)
12
Calcium (mg)
248
Iron (mg)
4
Magnesium (mg)
275
Phosphorus (mg)
474
Potassium (mg)
728
Sodium (mg)
1
Zinc (mg)
3
Copper (mg)
1
Manganese (mg)
3
Selenium (mcg)
8
Vitamin C (mg)
0
Thiamin (mg)
0.2
Riboflavin (mg)
0.8
Niacin (mg)
4
Pantothenic acid (mg)
0
Vitamin B6 (mg)
0.1
Folate (mcg)
29
Vitamin B12 (mcg)
0
Vitamin A IU
10
Vitamin A (mcg) RE
1
Vitamin E mg
26

Harvesting, Handling and Storage.
Almonds should be harvested as soon as possible after maturity to avoid loss in quality and to minimise fungal attack and insect infection. Indices for determining maturity include splitting, separation of hull from the shell and drying of hulls and kernels. Almond harvesting can be done manually by shaking the trees or mechanically by shakers. After about a week of drying, the nuts are picked up and then the hulls are separated from the in-shell product.Almonds have a relatively long shelf life in comparison to other nutmeats due to their relatively low polyunsaturated profile, high tocopherol content, and structural location of the oil. Prolonged exposure to direct sunlight should be avoided as it darkens the skin and reduces the shelf life. Since almonds readily absorb odours, they should never be exposed to pungent odours from onions, fresh fruits, fish, cheeses, paint, chemicals or other compounds. Almonds should be preferably stored at 32-40 0F with 65-70% relative humidity for maximum shelf life although cold storage is advised for long-term storage.

Hazelnuts.

Anatomy of the fruits and seeds.
The hazelnut or filbert is part of the genus Corylus (corylaceae) which is made up of deciduous tree and shrubs, made up of ten or more species from temperate regions of the northern hemisphere. The most commonly grown species branch from the ground up, others have a well developed trunk. The branches are tough and supple and the toothed leaves broad, heart-shaped and strongly veined.
Hazelnut plants are monoecious - with separate male and female flowers grow on the same plant and open at different times. The male part is in the slender, pendulous catkins that shed the pollen before the leaves expand, the female in small green clusters at the tip of the branches. Most are self sterile which means that pollen must be obtained from another plant. The flowers are primitive and the females have no petals sepals or ovary, only 2 receptive styles and it takes months to complete post fertilisation.
The female flower develop into the fruit (the hazelnuts), each enclosed in a fringed green husk and ripening in summer. The fuzzy outer husk opens as the nut ripens, revealing a hard, smooth shell. Hazelnuts are harvested between late summer and early autumn, when the mature nut turns from bright green to shades of hazel. The fruits are round achenes, growing in clusters of 2-4, are surrounded by a bell-shaped enclosure, irregularly dentate. Bushes begin to bear from their3rd to 5th year but may take 10 to reach potential. C.avellana (cobnut hazel) is a deciduous, dense shrub or tree which grows up to 7 metres tall and produces greenish brown catkins which are borne in winter.C.colurna (Turkish hazel) is a deciduous, conical tree which grows to between 7 – 20m and has long, yellow catkins are borne in late winter.

Commercial importance.
Hazelnuts are believed to have originated in Asia, then extended into Europe. Today, the main hazelnut producing countries are Turkey, Spain, Italy, and the U.S. (although 99% of the US hazelnut crop is produced in Oregon’s Willamette Valley). Oregon ranks third in world hazelnut production, behind Turkey (the worlds largest hazelnut producer, accounting for more than three-quarters of annual worldwide production) and Italy.

Chemical and nutritional composition.
Protein content.

Hazelnuts contain high levels of protein, 14.3 – 18.2 g/100g depending on the variety. The main amino acid is glutamic acid, followed by arginine. The amino acid composition of hazelnuts is given in table 1. The amino acid content is similar between cultivars and the essential amino acid pattern is representative of a high quality protein.
Hazelnuts have a high (arg) to (lys) ratio which helps balance the artherogenic effect of a diet with a high ratio of lys to arg (table 1). Arginine is used to make protein, can be degraded to nitric oxide (NO) - an endogenous vasodilator, which helps to relax smooth muscle in the arterial wall, and inhibit platelet aggregation and development of atherogenic plaques.

Table 1. Amino acid content of hazelnuts (g/100g) (blue denotes essential amino acids).
Amino acids (g)
Hazelnuts – amino acids in 100g of nuts
Tryptophan
0.19
Threonine
0.50
Isoleucine
0.55
Leucine
1.06
Lysine
0.42
Methionine
0.22
Cysteine
0.28
Phenylalanine
0.66
Tyrosine
0.36
Valine
0.7
Arginine
2.21
Histidine
0.43
Alanine
0.73
Aspartic Acid
1.68
Glutamic acid
3.71
Glycine
0.72
Proline
0.56
Serine
0.74

Antioxidants.
Hazelnuts contain high levels of a- tocopherols (table 2). The total and individual tocopherol contents were different between varieties, with tocopherol content ranging from 225.8 to 552.0 mg/g freshly extracted oil.

Table 2. Mean total and individual tocopherol contents (mg/g oil) of hazelnuts

Total tocopherol
a
b
g
d
hazelnuts
399
339.9
11.2
45.0
2.7

Tocopherols are antioxidant vitamins which may protect against oxidation, or damage to cells in the body. Vitamin E could play a role in preventing certain kinds of cancer and (CHD). However the interaction of antioxidants may make them more effective. Tocopherols have different efficiencies as antioxidants, with d>g~b>a. Other known antioxidants eg Selenium are present in hazelnuts.
Plant Sterols
Hazelnuts are high in sitosterol, although the levels of plant sterols vary between cultivars. Sitosterol ranged from 1416 to 1693 mg/g lipids, campesterol ranged from 78 to 114mg/g lipids and D5 – avenasterol ranged from 110 to 170mg/g lipids. Hazelnuts contain plant or phytosterols which act as antioxidants, and in the digestive tract appear to combine with cholesterol from other foods and prevent absorption of cholesterol. This may reduce serum total cholesterol and LDL cholesterol levels.

Table 3. Main composition of desmethylsterols (ug/g lipids) in oil extracted from hazelnuts

Total sterols
Campesterol
Sigmasterol
Sitosterol
D5-Avena sterol
D7-Avenasterol
D7-Sigmasterol
Hazelnuts
11813
91.2
17.3
1514.8
112.0
45.0
33.0

Vitamins and Minerals.
Hazelnuts are a good source of vitamins and minerals including copper which is thought to reduce blood cholesterol levels and slow the development of arteriosclerosis. Adequate magnesium is also implicated in reduction of CHD mortality.

Dietary Fiber.
Dietary fiber ranged from 9.8 – 13.2% of hazelnut kernels, although the standard reference value for dietary fiber is recorded in table 5.

Fat Content.
Hazelnuts have a high fat content, although the total oil content varies by cultivar from 54.6 – 63.2% . This fat is mainly monounsaturated fatty acids.The mono and polyunsaturated fatty acids oleic and linoleic acid represented over 90% of total fatty acids (table 4). The saturated fatty acid content of hazelnuts is very low (table 5).

Table 4. Mean total oil and fatty acid (FA) composition of nuts (% total)

Hazelnuts
Total oil %
58.4
16:0 palmitic
4.9
16:1 palmitoleic
-
18:0 stearic
1.9
18:1 D9 oleic
77.5
18:1 D11 oleic
1.0
18:2 linoleic
13.7
18:3 linolenic
0.1
20:1
0.1

Table 5. Composition of hazelnuts per 100g tree nuts.
Nutrient (units)
Hazelnuts – nutrients in 100g of tree nuts
Calories (kcal)
628
Protein (g)
15
Total fat (g)
61
Saturated fat (g)
4
Monounsaturated fat (g)
46
Polyunsaturated fat (g)
8
Carbohydrate (g)
17
Fiber (g)
10
Calcium (mg)
114
Iron (mg)
5
Magnesium (mg)
163
Phosphorus (mg)
290
Potassium (mg)
680
Sodium (mg)
0
Zinc (mg)
2
Copper (mg)
2
Manganese (mg)
6
Selenium (mcg)
4
Vitamin C (mg)
6
Thiamin (mg)
0.6
Riboflavin (mg)
0.1
Niacin (mg)
2
Pantothenic acid (mg)
1
Vitamin B6 (mg)
0.6
Folate (mcg)
113
Vitamin B12 (mcg)
0
Vitamin A IU
40
Vitamin A (mcg) RE
4
Vitamin E mg
15


Harvesting, handling and storage.
Hazlnut quality depends mainly on the composition of the lipid content which makes up 60 – 70% of the dry weight of the kernel. Storage of nuts will depend on the stability of the oil. Those with higher levels of tocopherols may be more stable, and able to be stored longer, as the major cause of reduction in palatability of stored hazelnuts is the oxidation of their oils. The high linoleic acid content of hazelnuts may be responsible for the auto – oxidation of hazelnut oils. The taste and flavour of hazelnuts are dependant on several compounds which also affect quality and nutritional value of the hazelnut. The levels of monosaccharides in nuts may give an indication of the storage conditions required. In previous studies the most important factors were storage temperature and humidity, wheras the composition had an effect on more adverse conditions.

Macadamia Nuts.

The macadamia is considered to be one of the world's finest gourmet nuts because of its unique, delicate flavour, its fine crunchy texture and rich, creamy colour. These features, together with relatively low volumes of production, have led to the successful promotion of macadamia as a luxury dessert nut. Macadamia nuts account for less than 0.5% of the world's total tree nut production, approximately 8,000 tonnes of kernel in 1989-1990.
The macadamia nut is the only commercial food crop indigenous to Australia, originating along the fringes of rainforests in southeast Queensland and northeast New South Wales, from 250S to 280S latitude and within 24 km of the Pacific coast. Of the three species of macadamia, only two are edible - the smooth-shelled Macadamia integrifolia and the rough-shelled M. tetraphylla. Only Macadamia integrifolia has been developed commercially. The rough-shelled macadamia, although producing a raw kernel of excellent eating quality, often contains a higher percentage of sugars which may caramelise on roasting, thus detracting from its appearance.

Botanical Features.
The evergreen macadamia tree is medium to large, attaining a height of up to 18 m and a spread of up to 15 m. It produces a number of vegetative growth flushes per year, with peaks of flushing in late summer and spring in Australia. The oblong to oblanceolate leaves are arranged in whorls of three and often have spiny, dentate margins, and short (5-15 mm) petioles. Three buds are arranged longitudinally in the axil of each leaf. Multiple branches and inflorescences may therefore be produced from each node. The pendulous racemes, 10-15 cm long and bearing up to 200 creamy white flowers, are borne on older wood. Although floral induction occurs in autumn, cool temperatures induce a period of dormancy. Racemes commence growing slowly in late winter and anthesis occurs in early spring. Less than 5% of flowers set fruit and many of these abscise 5-6 weeks after anthesis, coinciding with the stage of endosperm development and the commencement of rapid nut growth. Nuts take 6 months to mature.
Nut set is enhanced by cross-pollination. It is therefore recommended that at least two varieties be grown in orchards, often in alternate rows. Activity of pollinating insects, mainly native and domestic bees should be encouraged.
The fruit is a globose follicle in which only one of two ovules develops. In some varieties, however, a percentage of the nuts produced are twins, resulting from the development of both ovules. Twins are undesirable because of the difficulty, of extracting whole kernels. Mature fruits usually, but not always, abscise when the fibrous husk is still green. As the husk dries, it splits along a single suture to release the nut, consisting of a hard, thick, rough, stony, light-tan shell that encloses the kernel.
The rough-shelled macadamia is readily distinguished from the smooth-shelled species. The leaf margins are more serrated, with up to 40 spines on each side and while new leaf growth of M. integrifolia is pale green in colour, young M. tetraphilla leaves are an attractive pink to red colour. Racemes are longer (up to 30 cm) and bear up to 500 reddish-pink flowers.

Ecology.
The macadamia occurs naturally in the fringes of subtropical Australian rainforests. Temperature is the major climatic variable determining growth and productivity, the optimum being 25° C. Although the mature macadamia is capable of withstanding frosts as low as 6° C for short periods, longer periods or lower temperatures may severely damage or kill mature trees. Developing inflorescences are particularly susceptible to frost damage. However, there is a low temperature requirement for flowering, the critical minimum above which flowering is suppressed being 20° C. On the other hand, continuous and prolonged exposure to temperatures greater than 35° C often produces chlorotic and sometimes distorted growth.
The macadamia tree has several features suggesting adaptation to relatively harsh environments, including sclerophyllous leaves and dense clusters of fine, proteoid roots which develop to enhance nutrient uptake from poor soils, particularly those low in phosphorus. The conditions required for optimum production, however, are quite different from those for survival. Macadamia trees can be grown in a wide range of soils but not on heavy, impermeable clays and saline or calcareous soils. The trees are most suited to deep, well-drained soils with a high organic matter content (3-4% carbon), medium cation exchange capacity and a pH of 5.0-6.0.

Production.
The commercial development of macadamia occurred in Hawaii where most of the crop is sold locally to tourists or exported to mainland USA domestic market where macadamias comprise less than 3% of all tree nuts consumed. Hawaii dominates the world market with over 70% of the world's total production. Over the last decade, macadamia production has more than doubled and will continue to increase as plantings throughout the world come into production. The already intense competition from established nut crops has highlighted the need to develop new markets and promote more widespread consumption.

Composition.
The quality of the macadamia nut is related to its oil content and composition. Mature nuts contain at least 72% oil (specific gravity (SG) < 1.0) for optimum eating and processing quality. Kernels with SG of 1.00-1.025 are classed as second grade but can be used for lower grade products. Third grade kernels (SG > 1.025) are commercially unacceptable. Oil accumulation does not commence until the nuts are fully grown and the shell hardens. It accumulates rapidly in the kernel during late summer when the reducing sugar content decreases. The composition of mature, roasted and salted macadamia nuts is shown in Table 2. As with many oil seeds, the protein is low in methionine. Fresh kernels contain up to 4.6% sugar, mostly non-reducing sugar. The oil consists of mainly unsaturated fatty acids and is similar in both species, although the proportion of unsaturated to saturated fatty acids appears to be slightly higher in M. integrifolia (6.2:1 compared with 4.8:1). Detailed fatty acid composition is shown in Table 3. The fatty acid composition and the absence of cholesterol may lead to the promotion of macadamias as a high-energy health food. The major volatile components in roasted macadamia kernels are apparently similar to those found in other roasted nuts, although little detailed information is available.

Table 2. Nutritive value (g/100g) of macadamia nuts roasted in oil and salted.
||
Water (%)
2
Energy (KJ)
3064
Protein (g)
7.1
Fat (g)
78.6
Fatty acids Saturated (g)
11.4
Monounsaturated (g)
61.1
Polyunsaturated (g)
0.014
Carbohydrate (g)
14.3
Calcium (mg)
46.4
Phosphorus (mg)
203.6
Iron (mg)
1.8
Potassium (mg)
332.1
Sodium (mg)
Sodium – unsalted raw (mg)
264.3
7.1
Thiamin (mg)
0.21
Riboflavin (mg)
0.11
Nicotinic acid (mg)
2.14
Magnesium (mg)
0.12
Zinc (mg)
1.4
Manganese (mg)
0.38
Copper (mg)
0.33

Table 3. Fatty acid composition of macadamia nut oil (Cavalatto et al., 1966)

Fatty acid
Content (%)
18.1
67.1
16.1
19.1
16.0
6.2
17.0
1.7
16.0
1.6
20.4
1.6
18.2
1.3
14.0
0.8
12.0
0.6

Harvesting, Handling and Storage.
Macadamia nuts fall from the tree naturally when they are mature. Freshly fallen mature nuts may contain 25% moisture. The husk must therefore be removed as soon as possible to prevent overheating, mould development and deterioration in quality. The dehusked nuts are initially dried either artificially or air-dried to 10% moisture or less before they are delivered to processors. The nuts are then dried further in silos to 1.0-1.5% moisture for longer-term storage, for most efficient cracking of the shell and thus more complete recovery of the whole kernel. Drying is performed in two stages (at 52° C down to 4.5% moisture and then 77° C down to 1.5% moisture) to avoid adverse effects on kernel quality. After cracking and separation of the shell from the kernel the product can then be lightly roasted and salted or packaged raw in bulk in vacuum packed foil-laminate bags which help to prevent development of rancidity. Traditionally kernels have been roasted in coconut oil but dry roasting is becoming more popular. The packaged product is kept in cold storage to prolong shelf-life. Under these conditions the kernel can be safely stored for at least a year.