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Theobroma cacao L.

Sterculiaceae
Chocolate, Cacao, Cocoa

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.


  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Toxicity
  5. Description
  6. Germplasm
  7. Distribution
  8. Ecology
  9. Cultivation
  10. Harvesting
  11. Yields and Economics
  12. Energy
  13. Biotic Factors
  14. Chemical Analysis of Biomass Fuels
  15. References

Uses

Cacao seeds are the source of commercial cocoa, chocolate, and cocoa butter. Fermented seeds are roasted, cracked and ground to give a powdery mass from which fat is expressed. This is the cocoa from which a popular beverage is prepared. In the preparation of chocolate, this mass is mixed with sugar, flavoring, and extra cocoa fat. Milk chocolate incorporates milk as well. Cocoa butter is used in confections and in manufacture of tobacco, soap, and cosmetics. Cocoa butter has been described as the world's most expensive fat, used rather extensively in the emollient "bullets" used for hemorrhoids.

Folk Medicine

Reported to be antiseptic, diuretic, ecbolic, emmenagogue, and parasiticide, cacao is a folk remedy for alopecia, burns, cough, dry lips, eyes, fever, listlessness, malaria, nephrosis, parturition, pregnancy, rheumatism, snakebite, and wounds (Duke and Wain, 1981). Cocoa butter is applied to wrinkles in the hope of correcting them (Leung, 1980).

Chemistry

Per 100 g, the seed is reported to contain 456 calories, 3.6 g H2O, 12.0 g protein, 46.3 g fat, 34.7 g total carbohydrate, 8.6 g fiber, 3.4 g ash, 106 mg Ca, 537 mg P, 3.6 mg Fe, 30 mg b-carotene equivalent, 0.17 mg thiamine, 0.14 mg riboflavin, 1.7 mg niacin, and 3 mg ascorbic acid. According to the Wealth of India, the edible pulp of the fruit contains 79.7–88.5% water, 0.5–0.7% albuminoids, astringents, etc.; 8.3–13.1% glucose, 0.4–0.9% sucrose, a trace of starch, 0.2–0.4% non-volatile acids (as tartaric), 0.03% Fe2O3 and 0.4% mineral salts (K, Na, Ca, Mg). The shell contains 11.0% moisture, 3.0% fat, 13.5% protein, 16.5% crude fiber, 9.0% tannins, 6.0% pentosans, 6.5% ash, and 0.75 theobromine. Raw seeds contain 0.24 mg/100 g thiamine, 0.41 riboflavin, 0.09 pyridoxine, 2.1 nicotinamide, and 1.35 pantothenic acid. The component fatty acids of cocoa butter are 26.2% palmitic and lower acids, 34.4 stearic and higher acids, 37.3% oleic acid, 2.1% linoleic and traces of isoleic. In g/100g the individual amino acids in the water soluble fractions of unfermented and fermented beans are lysine 0.08, 0.56; histidine 0.08, 0.04; arginine 0.08, 0.03; threonine 0.14, 0.84; serine 0.88, 1.99; glutamic acid 1.02, 1.77; proline 0.72, 1.97; glycine 0.09, 0.35; alanine 1.04, 3.61; valine 0.57, 2.60; isoleucine 0.56, 1.68; leucine 0.45, 4.75; tyrosine 0.57, 1.27; and phenylalanine 0.56–3.36 g/100g. Unfermented and fermented beans contain p-hydroxybenzoic acid, vanillic acid, p-coumaric acid, ferulic acid, and syringic acid, while the fermented beans also contain protocatechuic, phenylacetic, phloretic acid and the lactone esculetin and o- and p-hydroxyphenyl acids. Caffeic acid occurs in the unfermented beans (C.S.I.R., 1948–1976). According to an article in the Chicago Sun Times, people who suffer extreme depression as victims of unrequited love have an irregular production of phenylethylamine. Such individuals often go on chocolate binge during periods of depression. Chocolate is particularly high in phenylethylamine, perhaps serving as medication. Theophylline is a potent CNS and cardiovascular stimulant with diuretic and bronchial smooth muscle relaxant properties. Recently this drug was proven effective in preventing and treating apnea in premature infancy. Cocoa contains over 300 volatile compounds, including esters, hydrocarbonslactones, monocarbonyls, pyrazines, pyrroles, and others. The important flavor components are said to be aliphatic esters, polyphenols, unsaturated aromatic carbonyls, pyrazines, diketopiperazines, and theobromine. Cocoa also contains about 18% proteins (ca 8% digestible); fats (cocoa butter); amines and alkaloids, including theobromine (0.5 to 2.7%), caffeine (ca 0.25% in cocoa; 0.7 to 1.70 in fat-free beans, with forasteros containing less than 0.1% and criollos containing 1.43 to 1.70%), tyramine, dopamine, salsolinol, trigonelline, nicotinic acid, and free amino acids; tannins; phospholipids; etc. Cocoa butter contains mainly triglycerides of fatty acids that consist primarily of oleic, stearic, and palmitic acids. Over 73% of the glycerides are present as monounsaturated forms (oleopalmitostearin and oleodistearin), the remaining being mostly diunsaturated glycerides (palmitodiolein and stearodiolein), with lesser amounts of fully saturated and triunsaturated (triolein glycerides). Linoleic acid levels have been reported to be up to 4.1%. Also present in cocoa butter are small amounts of sterols and methylsterols; sterols consist mainly of b-sitosterol, stigmasterol, and campesterol, with a small quantity of cholesterol. In addition to alkaloids (mainly theobromine), tannins, and other constituents, cocoa husk contains a pigment that is a polyflavone glucoside with a molecular weight of over 1500, this pigment is claimed to be heat and light resistant, highly stable at pH 3 to 11, and useful as a food colorant; it was isolated at a 7.9% yield (Leung, 1980).

Toxicity

Reviewing the work on safrole, Buchanan (J. Food Safety 1:275.1978) concluded that it is the most thoroughly investigated methylenedioxybenzene derivative. The major flavoring constituent in sassafras root bark, safrole also occurs in basil (Perdue and Hartwell, eds., 1976), black pepper, cinnamon leaf oil, cocoa, mace, nutmeg, parsley, and star anise oil. When safrole was identified as a "low grade hepatocarcinogen, it was banned in root beer, and the FDA in 1976 banned interstate marketing of sassafras for sassafras tea. The oral LD50 for safrole in rats is 1950 mg/kg body weight, with major symptoms including ataxia, depression, and diarrhea, death occurring in 4–5 days. Ingestion of relatively large amounts of sassafras oil produced psychoactive and hallucinogenic effects persisting several days in humans. With rats, dietary safrole at levels of 0.25%, 0.5% and 1% produced growth retardation, stomach and testicular atrophy, liver necrosis, and biliary proliferation and primary hepatomas. Sutton (1981) reports the collapse and death of a 3-year old bitch that had eaten a 250 g package of cocoa. Postmortem examination revealed congestion of lungs, liver, kidney, and pancreas, and petechial and ecchymotic hemorrhage of the thymus, all compatible with acute circulatory failure. The stomach contained high concentrations of theobromine and/or caffeine. Though used cosmetically, cocoa butter has been reported to have allergenic and comedogenic properties in animals. Tyler (1982) produces a chart comparing various caffeine sources to which I have added rounded figures from Palotti (1977).

Cup (6 oz.) expresso coffee: 310 mg
Cup (6 oz.) boiled coffee: 100 mg
Cup (6 oz.) instant coffee: 65mg
Cup (6 oz.) tea: 10–50 mg
Cup (6 oz.) cocoa: 13 mg
Can (6 oz.) cola: 25 mg
Can (6 oz.) coca cola: 20 mg
Cup (6 oz.) mate: 25–50 mg
Can (6 oz.) pepsi cola: 10 mg
Tablet Caffeine: 100–200 mg
Tablet (800 mg) Zoom (Paullinia cupana): 60 mg
In humans, caffeine, 1,3,7-trimethylxanthine, is demethylated into three primary metabolites: theophylline, theobromine, and paraxanthine. Since the early part of the 20th century, theophylline has been used in therapeutics for bronchodilation, for acute ventricular failure, and for long-term control of bronchial asthma. At 100 mg/kg theophylline is fetotoxic to rats, but no teratogenic abnormalities were noted. In therapeutics, theobromine has been used as diuretic, as a cardiac stimulant, and for dilation of arteries. But at 100 mg, theobromine is fetotoxic and teratogen (Collins, FDA By-lines No. 2, April 1981). Leung (1980) reports a fatal dose in man at 10,000 mg, with 1,000 mg or more capable of inducing headache, nausea, insomnia, restlessness, excitement, mild delirium, muscle tremor, tachycardia, and extrasystoles. Leung also adds "caffeine has been reported to have many other activities including mutagenic, teratogenic, and carcinogenic activities; ... to cause temporary increase in intraocular pressure, to have calming effects on hyperkinetic children...to cause chronic recurring headache..."

Description

Small tree usually 4–8 m tall, rarely up to 20 m; at 1–1.5 m the terminal bud breaks into 3–5 meristems to give several lateral upright shoots; primary branching by successive whorls of normally spreading branches; young branchlets terete, grayish green or brownish, densely or sparsely pubescent, with simple or furcate hairs 0.1–0.3 mm long, later glabrate, more or less striate; stipules subulate, very acute, 5–14 mm long, 0.5–1.5 mm broad at base, pubescent, deciduous; leaves large, coriaceous or chartaceous, alternate, distichous on normal branches, green; petiole pubescent or tomentose, with simple, rather dense, spreading hairs, thickened pulvinate at ends; blades 12–60 cm long, 4–20 cm broad, elliptic to obovate-oblong, entire, glabrous; inflorescence on trunk and branches, usually borne on small tubercles in short cymose branchlets, peduncles 1–3 mm long, stellate-pubescent; bracts ovate or ovate-oblong, pubescent; bracteoles ovate-oblong, acute or subacute, 0.5–1.2 mm long, pubescent, deciduous; pedicels capillary, rigid, pale green, whitish or reddish, 5–15 mm long, with stellate or furcate hairs and sparce many-celled, glandular, capitate trichomes; sepals lanceolate or oblong-lanceolate, acute, white, greenish-white, pale violaceous or reddish, faintly 3-veined, united at base, 5–8 mm long, 1.5–2 mm broad, with hairs and trichomes; petals contorted in aestivation, thick-membranous, hood 3–4 mm long, 0.5–2 mm wide, obovate, rounded at apex, white, 3-veined, lamina pale yellowish, 1.5–2.5 mm long, 1.5–2 mm broad, obovate, attenuate at apex; staminodes 4–6 mm long, narrowly subulate, red or purplish, minutely papillose-pilose, ciliate, with slender, simple hairs; stamens diantheriferous, with anthers about 0.4 mm long; ovary oblong-ovoid, superior, with 5 carpels; fruits usually considered drupes but referred to as pods, indehiscent, variable in size and shape, 10–32 cm long, spherical to cylindrical, pointed or blunt, smooth or warty, with or without 5 or 10 furrows; pods white, green or red, ripening to green, yellow, red or purple; seeds 20–60 per pod, arranged in 5 rows, variable in size, 2–4 cm long, 1.2–2 cm broad, ovoid or elliptic; cotyledons white to deep purple, convoluted, large. Seeds/kg 625–1125. Roots mostly a mass of surface-feeding roots, with taproot penetrating to 2 m in friable soil, less deeply where compacted (Reed, 1976).

Germplasm

Reported from the South and Middle American Centers of Diversity, cocoa, or cvs thereof, is reported to tolerate some diseases, heavy soils, laterite, low pH, photoperiod, shade, slope, and waterlogging (Duke, 1978). Several subspecies and forms of cacao have been recognized, from which a great number of cvs have been developed. Some cvs are named according to the place where they were found or developed. Others are classified as 'Criollo' types which have elongated, ridged, pointed fruits and white cotyledons and 'Forastero', with short, roundish, almost smooth fruits and purplish cotyledons. Hybrids have been obtained with other species, e.g. Th. grandiflora, mainly to incorporate disease-resistance. (2n = 20)

Distribution

Native to South America, probably on the equatorial slopes of the Andes; now cultivated pantropically, especially in West Africa.

Ecology

Ranging from Subtropical Dry to Wet through Tropical Very Dry to Wet Forest Life Zones, cacao is reported to tolerate annual precipitation of 4.8 to 42.9 dm (mean of 109 cases = 16.3), annual temperature of 18.0 to 28.5°C (mean of 108 cases = 25.3), and pH of 4.3 to 8.7 (mean of 43 cases = 6.4) (Duke, 1978). Grown from 20°N to 20°S with the bulk between 10°N and 10°S, usually below 300 m, but in sheltered valleys of Colombia at 900 m. Requires uniformly high temperatures with recommended mean of 26.6°C. Trees are wind-intolerant and therefore are often planted on hillsides for wind protection and good drainage. Being drought-intolerant, cacao thrives in climates with high humidity and rainfall. Plants are shade-tolerant, and thrive in rich, organic, well-drained, moist, deep soils. Shallow laterite soils are said not to be suitable. Maximum temperature of 33.5°C and minimum 13°C, with diurnal temperature variation between 33.5 and 18°C are suggested (Reed, 1976).

Cultivation

Propagation may be by cuttings, buddings or graftings, but seeding is cheaper. Seeds germinate at maturity, and are viable only a short time. They may be stored 10–13 weeks if moisture content is kept at 50%. Soon after picking, pulp is removed from seed which are planted in shaded nursery beds or baskets. Transplant in few months (when ca 0.6 m tall) into shaded fields at 2.4 m x 2.4 m or 3.6 m x 3.6 m. Spacing is closer if soils are poor and elevations above 300 m. Fields should remain shaded for 3 years. Remove floral buds until trees are 5 years old. Cacao is of ten intercropped with other trees of economic value, as bananas, rubber, oil palm, or coconut. Weeding is by hand or herbicides. Irrigation may be practiced, but drain ditches should always be provided to prevent excess water. Responds to fertilizers, mostly in the absence of shade; recommended is 5 cwt urea, 2.5 cwt triple superphosphate, 10 cwt potassium sulfate per hectare. Windbreaks are usually provided.

Harvesting

Although fruits mature throughout the year, usually only two harvests are made. In West Africa, the main harvest begins in September, extends to February, with a second smaller harvest in May–June. From fertilization to harvesting the fruit requires 5–6 months. Harvest season lasts about 5 months. Pods are cut from trees and allowed to mellow on the ground. Then pods are cracked and the beans removed, the husks are burned. Beans are fermented in leaf-lined kegs 2–8 days before drying in sun, at which time they change from purple to brown. Beans are then bagged and shipped. Further processing includes roasting, crushing, and separating out the kernel, grinding the nibs and extraction of about half of the fat.

Yields and Economics

The world low production yield is 29 kg/ha in American Samoa, an international production yield of 346 kg/ha, and a world high production yield of 2,000 kg/ha in Haiti. Yields of 3,375 kg/ha of dry beans are possible on good plantations. The oil content (35–50%) suggests potential oil yields of more than 1750 kg/ha. Average yields range from 0.5–10 kg/tree; 2.25 MT beans/ha. Over 3375 kg/ha of dry cacao beans have been produced on plantations well-manured, well-shaded, and with excellent control of weeds, pests and diseases. In 1980, the US is estimated to have consumed more than 75,000 MT of cocoa butter, in a business amounting to nearly $600 million. Chocolate manufacturers consumed nearly half. One ton went into suppositories, 10 to 20% of which are made with a cocoa butter base. In 1981, there was a world surplus of ca 700,000 tons, close to 6 months production, and price down to ca $1.30/kg. In July 1965, a record cocoa crop in Ghana sent cocoa bean prices to below $0.20/kg, an all-time low. A dozen years later, the beans spiralled to more than $5.00/kg. Normally cocoa butter runs 25 times as high as the bean (Anon., 1981b). Two-thirds of the world's production presently comes from Ghana, Nigeria, and Ivory Coast in West Africa, and one-third from Brazil and Dominican Republic. In 1971, the US imported from Africa about 200,908 MT of cocoa beans, valued at $120 millions, and from Latin America, 107,841 MT valued at $54 millions. World production of beans in 1971 was 1.59 million MT. Major consumers are United States, West Germany, Netherlands, and United Kingdom. New York prices on 'Accra' beans in 1971 was $0.68/kg. Cocoa is produced in tropical countries, but is processed and consumed in temperate countries.

Energy

For every kilogram of dry beans, there can be 2 kg of pod meal; indicating a 1:2 seed:pod ratio. To convert production figures into pod waste figures, this suggests we multiply by two. Pod meal contains ca 12.6% moisture, 7.6% ash, 8.1% protein, 34.8% crude fiber, 3.3% fat, and 33.6% N-free extract. One hundred kg cacao pod meal has the same feeding value as 96–97 kg chopped corn (including husks). Prunings could amount to 1–8 MT/ha/yr, depending on biological and environmental variables. During the third year, main branches may be reduced to 3 or 4, and thenceforth, excess limbs and diseases tissues should be removed. For each MT of production, it seems safe to conclude there will be 2 MT of pods and 2 MT of prunings as residue, perhaps more in unshaded cacao. Shade trees might best be selected on basis of (1) nitrogen fixed, (2) fuelwood produced, (3) nonantagonism or amelioration of cacao. Seedling cacao does best with only 25% full sunlight, saplings with closer to 50%. Species of energy-fixing species of Albizia, Erythrina, Gliricida, Inga, Leucaena, Musanga, Peltophorum, and Terminalia have been recommended as shade trees or "Madre de Cacao". (Purseglove, 1968)

Biotic Factors

Midges are thought to be the pollinators of cacao, but aphids, ants, thrips, wild bees, or a combination of these are also suspect. Cacao grows in areas with high humidity; several hundred fungi have been reported as attacking this tree. However, the most important fungi that cause diseases which must be controlled include the following: Armillaria mella (Collar crack), Botryodiplodia theobromae (Pod rot), Botryobasidium salmonicolor (Pink disease), Calonectria rigidiuscula (Green point cusion-gall), Cephaleuros virescens (Algal spot), Ceratobasidium stevensii (Thread blight), Ceratocystis fimbriata (Canker), Corticium incisum (Thread blight), Fomes lamaensis (Brown rot), F. lignosus (White rot), F. noxius (Brown crust), Marasmius byssicola (Brown thread), M. perniciosus (South American witches broom), M. scandens (White thread), M. trichorrhizus (Brown thread), Monilia roreri (Gray pod rot), Nectria cacaoicola (Pod rot), Phytophthora palmivora (Black pod), Rosellinia bunodes (Root rot), R. pepo (Root rot), Septobasidium tanakae (Felty fungus), Sphaerostilbe repens (Violet root rot), Taphrina bussei (Witches broom), Thielaviopsis paradoxa (pod rot), Trachysphaera fructigena (Mealy pod), Ustilina zonata (Collar rot), and Verticillium dahliae (Sudden death). Bacteria known to cause disease in cacao include: Agrobacterium tumefasciens, Bacillus megatherium, B. subtilis, B. undulatus, Bacterium accendens, B. aceti, B. orleanense, B. xylineum, B. xylmoides, and B. xylum. Golden (p.c. 1984) lists the following nematodes: Aphasmatylenchus nigeriensis, Criconemella goodeyi, Helcotylenchus cavenessi, H. concavus, H. microcephalus, H. multicinctus, Hoplolaimus seinhorst, Meloidogyne incognita, M. incognita acrita., M. javanica, M. sp., Paratylenchus arculatus, Pratylenchus brachyurus, P. coffeae, P. sp., Rotylenchulus reniformis, Scutellonema clathricaudatum, Tylenchorhynchus annulatus, T. nudus, Xiphinema ebriense, X. elongatum, X. ifacolum, X. nigeriense, and X. setariae. Viruses isolated from cacao include: Akaran, Apoplectic disease, Asalu, Ilesha, Konongo, Kpeve cacao, Mottle leaf, Necrosis, New Juaben (B.C.), New Juaben cacao, Offa Igbo (Nigeria) cacao, Offa Igbo 1 and 2, Olanla 1 and 2, Red mottle, Swollen-shoot, Trinidad cacao, Vein clearing, and Viruses 1A, 1B, 1C, and 1M. Cacao trees may be parasitized by Cuscuta campestris, C. cublinclusa, and Phthirusa theobromae.

Chemical Analysis of Biomass Fuels

Analysing 62 kinds of biomass for heating value, Jenkins and Ebeling (1985) reported a spread of 19.04 to 17.97 MJ/kg, compared to 13.76 for weathered rice straw to 23.28 MJ/kg for prune pits. On a % DM basis, the hulls contained 67.95% volatiles, 8.25% ash, 23.80% fixed carbon, 48.23% C, 5.23% H, 33.19% O, 2.98% N, 0.12% S, and undetermined residue.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Friday, January 9, 1998 by aw