Theobroma cacao L.
Analysis of Biomass Fuels
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.
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
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).
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
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
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)
Native to South America, probably on the equatorial slopes of the
Andes; now cultivated pantropically, especially in West Africa.
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).
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.
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
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)
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:
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.
Buchanan, R.L. 1979. Toxicity of spices containing
methylenedioxybenzene derivatives: A review. J. Food Safety 1:275.
C.S.I.R. (Council of Scientific and Industrial Research).
1948–1976. The wealth of India. 11 vols. New Delhi.
Duke, J.A. 1978. The quest for tolerant germplasm. p. 1–61.
In: ASA Special Symposium 32, Crop tolerance to suboptimal land
conditions. Am. Soc. Agron. Madison, WI.
Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer
index with more than 85,000 entries. 3 vols.
Jenkins, B.M. and Ebeling, J.M. 1985. Thermochemical properties of
biomass fuels. Calif. Agric. 39(5/6):14–16.
Leung, A.Y. 1980. Encyclopedia of common natural ingredients used in
food, drugs, and cosmetics. John Wiley & Sons. New York.
Palotti, G. 1977. The 'time for a Coca Cola' may not be right.
Industrie Alimentairi 16(12):146–148.
Perdue, R.E., Jr. and Hartwell, J.L. (eds.). 1976. Plants and cancer.
Proc. 16th Annual Meeting Soc. Econ. Bot. Cancer Treatment Reports
Purseglove, J.W. 1968–1972. Tropical crops. 4 vols. Longman
Group Ltd., London.
Reed, C.F. 1976. Information summaries on 1000 economic plants.
Typescripts submitted to the USDA.
Sutton, R.H. 1981. Cocoa poisoning in a dog. Veterinary Record
Tyler, V.E. 1982. The honest herbal. George F. Stickley Co.,
Last update Friday, January 9, 1998 by aw