THE MANKETTE: MONGONGO NUT TREE (Schinziophyton rautanenii)

OVERALL OBJECTIVE

To review the characteristics, growth requirements, distribution and importance of mungongo tree (Schinziophyton rautanenii)

SPECIFIC OBJECTIVES

• To establish the importance of mongongo in oil production.
• To establish the potential of mungongo in production of other products besides oil.

INTRODUCTION

The mungongo tree (Schinziophyton rautanenii) occurs naturally in Southern Africa and is a staple food in the Kalahari among the hunter gatherers (Graz 2007).Archaeological evidence has shown that they have been consumed amongst San communities for over 7000 years and their popularity stems in part from their flavour and in part from the fact that they store well and remain edible for much of the year (Wikipedia 2009).In its core distribution areas where its abundant, nutritional value and reliability equals many cultivated staple crops. Outside its core area it is eaten but not as a staple (Agro forestry tree database 2009).The mungongo tree is most important in that the nuts have edible oil which is extracted and is locally used in food preparation and personal care products and can also be used in manufacturing industries for production of various products (Julian et al 2009).

LITERATURE REVIEW

SCIENTIFIC CLASSIFICATION

Kingdom  : Plantae

Division   :Magnoliophyta

Class        : Magnoliopsida

Order       :Malpighiales

Subfamily: Crotonoideae

Tribe       : Ricinodendreae

Genus      :Schinziophyton

Species    : Rautanenii Authority: (schinz) Radcl- sm

Synonyms: Ricinodendron rautanenii Schinz (Wikepedia 2009).

COMMON NAMES

English- mankett tree, wild akkernut, featherweight tree.

Tswana- mongongo

Bemba – mukusu (Agroforestry tree database 2009).

! Kung Bushmen - //Xa, mongongo

Lozi – mungongo

Herero – mangetti, mongongo

Kwangwali – ugongo, ngongo

Shona – mungomangoma

Afrikaans – wilde okkerneut (Natural hub 2009).

ORIGIN AND GEOGERAPHICAL DISTRIBUTION

Distribution of S.rautanenii in Africa

The tree is distributed widely throughout Southern Africa. There are several distinct belts of distribution, the largest of which stretches from northern Namibia into northern Botswana, South- western Zambia and Western Zimbabwe. Another belt is found in Eastern Malawi and another in Eastern Mozambique (Wikipedia2009). It is sometimes planted in southern DR Congo and Zambia. It has been planted on a trial basis in Israel, but productivity there seems to be very low (Graz 2007).

ECOLOGY

Schinziophyton rautanenii occurs as scattered trees or small localized stands. It grows on wooded hills, in bush veld, on sandy ridge tops, sometimes on alluvial margins of major rivers and limestone outcrops (Ronne and Joker 2006). In the area where it occurs the mean annual temperatures are about 20°C, and the maximum daily temperatures often exceed 30°C; the plant tolerates light frost, but temperatures below 7°C kill seedlings (Graz 2007).The tree is found between 5˚S and 23˚S and occurs at 200–1500 m altitude and grows well when the annual rainfall is 200–1000 mm (Ronne and Joker 2006). This shows that the tree does well in hot dry climates with poor rainfall (Beau 2003).It is always found on deep sands with a 94–99% fine sand component (Graz 2007) and it is most frequent and occasionally dominant in Kalahari sand woodlands but is also found in munga woodland, scrub mopane and lake basin chipya.In core distribution areas it occurs in large grooves of open woodland  as a dominant or co-dominant tree species with other species like A.quanzensis and B.africana.The largest grooves can be 450 hactres and occur on sand crests, smaller ones are found where sand banks are against bedrock. It is also common on hummocks along alluvial margins of important water courses for example the Zambezi marshy. The tree does well on well drained deep sandy, sandy alluvium or rocky soils. It is rare on calcareous soils and does not do well on waterlogged, poorly drained or on soils subject to flooding (Agro forestry tree database).Its habitat is also subject to frequent fires (Graz 2007).

DESCRIPTION

The Schinziophyton Rautanenii tree is a dioecious shrub or small to medium-sized

tree up to 20 m tall (Graz 2207) and has a large straight trunk 1 metre in diameter

 with stubby and contorted branches and a large spreading crown (Beau 2003).The

 bark is up to 5 cm thick and is pale grey to light golden-brown , smooth first later

 becoming reticulate and flaky. Young branchlets, leaf buds and stalks have reddish brown furry hairs and both the branches and stems exude a white gum (Ronne and Joker 2006). The tap root goes down until it reaches water but the lateral root is very small (Beau 2003).

The Schinziophyton Rautanenii  tree (Ronne and Joker 2006)

  

The leaves are alternate, digitally compound, consisting of 5-7 leathery segments usually hairless below and with grey woolly hairs above. the leaves are also dark green on the upper side and creamy white on the underside (Agro forestry tree database 2009).The leaflet is also a wide lance to an egg shape. The leaflets are carried on hairy stalks that are up to 15cm in length and the leaves are also about 15cm long and there are usually 1 or 2 black glands on the upper side of each leaf-stalk (Beau 2003).

1, flowering twig; 2, part of male inflorescence; 3, female flower; 4, fruit, showing part of stone (Graz 2007)

The flowers are whitish yellow, dioecious, in loose rusty sprays. Inflorescence a terminal panicle and male flowers are in long rusty sprays while female flowers are shorter in length (Agro forestry tree database). Male inflorescence is 10–22 cm × 4–8 cm and female inflorescence is 5–6 cm × 2–3 cm. Male flowers have a pedicel 2–5 mm long, calyx lobes, 5 mm × 2–3 mm, and petals 6–7 mm × 2–3 mm. Female flowers have a pedicel 7–10 mm long, calyx lobes 8–9 mm × 5–6 mm, petals are 9 mm × 4 mm (Graz 2007).

The mongongo nuts (Ronne and Joker 2006)

Fruit is ovoid up to 3-5 cm × 2-3.5cm in diameter when dry and up to 7 × 5cm when fresh and consists of 5 layers; a light green fruit skin, a layer of fruit flesh, a thick and hard nut shell, a thinner woody inner shell and an edible nut (Leger 2003) weighing 7-10g with leathery skin and fleshy, dry, spongy pulp 2-5mm thick, shell tough 3-7mm thick. The stone contains 1 and occasionally 2 kernels. (Agro forestry tree database 2009).

The mongongo nut (Wikipedia 2009)

The fruit soft spongy pulp layer is about 20% of the fresh fruit (by volume), pleasantly aromatic and sweet at maturity. The skin takes up to 10% of the fruit by volume and the remaining 70% is the nut like seed, including the wide hard shell around it (Natural hub 2009).

GROWTH AND DEVELOPMENT

When the seed has germinated, the radicle grows slowly. When it is 5–10 cm long, 5–12 secondary roots emerge in a ring from immediately above the root-tip. When these roots are 20–50 mm long the plumule starts to emerge. The growth from seedling to sapling stage depends very much on the fire regime prevailing in the area. Fires reduce young saplings back to ground level as long as their bark is too thin to protect them (Graz 2007). The tree is deciduous and fruits after 15-25 years of growth but with irrigation they may start as early as after 4 years (Ronne and Joker 2006) and may live up to 100 years. From March to October the tree is leafless and it flowers from September to December (early summer) just before the beginning of the rains. Fruits develop from December to March and most fall off the tree from April to May and thereafter ripening continues on the ground (Agro forestry tree database 2009).   

USES

The fruit have been described as a “staple diet” in some areas especially among the San bushmen of Northern Botswana and Namibia (Wikipedia 2009).It is available the whole year and can be stored for a long time and even in those years when trees only bear fruits they still provide enough to keep people going. The fruit can be eaten fresh can be dried and is soaked in water and cooked, then mashed and eaten as a porridge. Alternatively it is fermented to give a refreshing potent beer or distilled for alcohol.      The nut is eaten together with the woody inner shell because it is difficult to remove the shell without wasting parts of the nut.

The nut consists of a white, very tasty and highly nutritious flesh. As the woody inner shell is uncomfortable to chew, the nut is mainly pounded in a mortar thereby reducing the shell to small piecies.This is then cooked together with meat and vegetables and eaten (Leger 2003).Fruit pulp and the seed meal which is rich in protein is fed to cattle, however the feed is suspected to cause a discolouration of beef.Widlife like elephants and Kudu feed on fruits (Agro forestry tree database 2009).

The kernel is rich in oil. The oil is used locally for cooking and for commercially for making soaps, varnishes, cosmetics, linoleum and oil cloth industry (Ronne and Joker 2006).Margarine has been made from the oil in Germany and England. The highly unsaturated oil may also serve well as paint medium for vanishing purposes. The oil from nuts has also been traditionally used as a body rub in the dry winter months to clean and moistern the skin (Agro forestry tree base 2009) and in cosmetics the oil is used for its hydrating and restructuring properties and ultra violet radiation protection for hair and skin (Graz 2007).

The wood being both strong  and light makes excellent fishing floats, insulating material, dart-boards, notice boards,masks,drums , temporary canoes and packing cases. The hollow trunks of the tree often form water reservoirs where rain water can be gathered. (Wikipedia 2009).Wood used as an insulating material and for constructing of crates and coffins. In Namibia the wood is also used for the construction of ox-drawn sledges that are used to transport goods in sandy areas. In Zambia the wood is used for carpentry and to make musical instruments, curios and toys, while the seeds are used in board games. The inner bark is used to make strings, for example for nets (Graz 2007).The branches are used as traditional fire sticks and truncheon cuttings are used for fencing. Roots control erosion as they protect sandy soils from wind and water erosion. The tree also provides shade and shelter in hot areas for example the Kalahari Desert and can be used for reclamation as it has potential use in desert encroachment prevention and sand dune stabilization (Agro forestry tree database 2009).The bark is used by women for straightening hair.

Medicinally the bark provides a cure for stomach and diarrhea.The middle red part of the bark is broken into pieces, put in cold water and cooked for up to 5-10minutes.The bark is removed after cooling down and the decortion is drunk. It is also a helpful drink for pregnant women who are feeling sick (Leger 2003).The roots are used as a remedy for stomach pains and the nuts are tied around ankles and are said to relieve leg pains (Agro forestry tree database 2009).

PROPERTIES

The nutritional composition of the fruit pulp per 100 g edible portion is: water 13.4 g, energy 1307 kJ (312 kcal), protein 6.6 g, fat 0.6 g, carbohydrate 70.2 g, fibre 3.5 g, Ca 89.6 mg, Mg 195 mg, P 46.0 mg, Fe 0.7 mg, Zn 1.4 mg, thiamine 0.28 mg, riboflavin 0.11 mg, niacin 0.12 mg, ascorbic acid 8.5 mg (Graz 2007). The kernel is 57g by weight fat. Of this about 43% are poly unsaturated fats (almost entirely linoleic acid), about 17% saturated fats (palmitic and stearic acid) and about 18% mono unsaturated fat (oleic) (Wikipedia 2009).The kernel also has per 100 g, water 4.8 g, energy 2685 kJ (641 kcal), protein 28.8 g, fat 57.3 g, carbohydrate 2.4 g, fibre 2.7 g, P 839 mg, niacin 0.42 mg(Graza 2007) and 193mg Ca, 527mg Mg, 3.7mg Fe, 2.8mg Cu, 4mg Zn, 0.3mg thiamine, 0.2mg riboflavin, o.3mg nicotinic acid, 565mg vitamin E ( almost entirely as y-tocopherol).Due to the very high y-tocopherol content, the oil is very stable and does not oxidise into “rancidity” for a very long time in spite of the high African heat (Natural hub 2009). Mungongo seeds oils from Zambian samples showed  a light yellow oil with refractive index of 1.4830, acid values 1.6%,  a peroxide value of 10 mg/kg and a solidification point of -7˚c, suggesting that this oil is rich in unsaturated fatty acids (Julian et al 2009).

SOWING AND GERMINATION

Propagation is mainly by seeds and seeds remain viable for up to 2 years when stored at 10˚c (Agro forestry tree database 2009).Germination is erratic and takes place over an extended period. Without pre-treatment a germination rate of 26% has been obtained. If the shell is removed prior to sowing the kernel is treated with ethylene the germination rate can reach 80% or more within 6 days. The rate of non surviving seedlings is high but once a seedling has been established it needs little attention. The seeds should be sown in sandy soil in half shade and the temperature kept above 7˚c.The seedlings very quickly develop deep roots ( Ronne and Joker 2006).

DORMANCY AND PRETREATMENT

A large number of the seeds remain dormant a year or more. The woody endocarp makes germination difficult and therefore needs to be removed or the end cut off to expose kernel before sowing. After shelling the seeds can be soaked in water for a week followed by storage under high temperature and humidity for 2 days in order to reach better germination. Alternately treatment of the kernels with either ethephon, ethylene or phosphonic acid can be done in order to speed up the germination process and rate (Ronne and Joker 2006).

DESEASES AND PESTS

Fallen fruits are attacked by moth and larvae which eventually eat all the fleshy parts. Timber is rapidly attacked by sap stain fungus, Ceratocystic maniliformis and elephants occasionally break branches of the tree reducing productivity (Agro forestry tree database 2009).The wood is not durable and susceptible to termite and lyctus attack (Graz 2007).

HARVESTING

The seeds are mature when the fruits have turned brown and soft and are shed while they are green (Ronne and Joker 2006).Since the fruit ripens on the ground they are simply picked up from under the trees. Harvesting starts at the end of the rainy season when fresh fruits have fallen. Gathering continues until the end of the dry season (September–November) when half of the fruits have already lost their pulp to insects. During the rainy season (November–March), when drinking water is found more easily, nuts are collected from more remote groves (Graz 2007).

YIELD

Fruit production is very closely linked to the amount of rain of the previous season, with crop yields higher in years following heavy rains. High rainfall after flowering has been found to damage the developing fruits, as do fires late in the dry season. Some estimates indicate yields of 200–1000 kg/ha in northern Namibia, and about 300 kg/ha in Angola (Graz 2007).Each female tree has around 950 fruit a year given sufficient rainy season. In a good year the seeds may be “knee deep” under the trees (Natural hub 2009). According to the extraction method and efficiency of unit of employed, yields of 28% of oil (traditional hand press) to 38% of oil (hydraulic press) can be achieved. In Zambia alone, the estimated production of about 3000 metric tonnes of seed would yield around 840 metric tonnes of oil. This represent a modest product supply for a niche oil product and simultaneously have a high impact for local and regional communities (Julian et al 2009).  

STORAGE AND VIABILITY

Seed is orthodox and should be stored at low moisture content in airtight containers. The seeds remain viable for up to 2 years if stored at 10˚c.In the seed bank at RBG kew, seed has been stored for 6 years at -20˚c maintaining a viability of 80% ( Ronne and Joker 2006)

MANAGEMENT

Once established the tree requires very little attention as it can withstand years of drought and has a few pests and disease incidence. Seed should be sown in sandy soil (Agro forestry tree database 2009).

GENETIC RESOURCES

The Tree Seed Centre of the Directorate of Forestry, Windhoek, Namibia has a comprehensive seed collection and as Schinziophyton rautanenii is widespread and is not damaged by the collection of fruits, it does not seem to be in danger of genetic erosion (Graz 2007).

PROSPECTS

Because of their local abundance, reliability of supply, ease of collection and good nutritional value, the kernels of Schinziophyton rautanenii remain an important traditional source of food in the Namib desert. The fruits are only collected from wild stands and it is unlikely that they will become important outside the area where they are used traditionally (Graz 2007).

DISCUSSION

The mongongo tree is distributed widely throughout southern Africa in the wild. The tree survives in low rainfall areas with poor soils where there is no crop production. As the tree grows in the wild it is not managed and so there are no production costs. The nuts are also available all year round and so provide a source of food and oil throughout the year. Both the fruit pulp and the kernel are highly nutritious and provide oil and are both used in food and industrial production of various products. The wood of the tree is also used to produce various wood products and various parts of the tree are used for medicinal purposes. The tree takes many years to bear fruit and its germination percentage is very low. It is also affected by a few pests and diseases.

CONCLUSION

The mongongo tree provides food in marginal areas where there is very little crop production. The oil is very nutritious and is used for cooking and in manufacturing of various products in industries. The oil however has a low keeping quality and so deteriorates rapidly. There is therefore potential for commercial production of oil from the mongongo nut.

RECCOMMENDATIONS

As the land where the mungongo trees are indigenous is not suitable for agricultural exploitation and all nuts are collected from the wild, the development of additional uses and external markets for this under recognized oilseed can benefit the rural communities and provide a new export product from Africa and a new ingredient for global cosmetic industry. However the keeping quality of oil should be improved and research should also be focussed on reducing the number of years for the tree to produce fruit which can enable it to be produced commercially.

REFERENCES

1.      Agro forestry Tree Database. A Tree Species Reference and Selection Guide.17 February 2009. http//www.worldagroforestrycentre.org.

2.      Beu M.2003 .The Mungongo: Manketti Nut. Natural food nuts uncommon.

3.      Graz F.P.2007.Schinziophyton rautanenii (schinz) Radd-sm.Prota 14: Vegetable oils.

4.      Julian H.R, Korach A.R, Simon J.E, and Wamulwange C. 18 February 2009.Mungongo Cold Pressed Oil (Schiniziophyton Rautanenni): A new Natural product with Potential cosmetic applications.ISHS Acta Horticulture 756. http://www.actahort.org.

5.      Leger S.2003. The Hidden Gifts of Nature.

6.      Natural hub.com. 17 February 2009. http://www.naturalhub.com.

7.      Ronne C and Joker D. April 2006.Seed Leaflet Number 114.Forest and Landscape Denmark.

Wikipedia.The free Encyclopedia.18 February 2009.http://en.wikipedia.org