From New Crops, Proceedings of the Second National Symposium NEW CROPS: Exploration, Research, Commercialization
by Antonio Figueira, Jules Janick, and James N. BeMiller
New Products from Theobroma cacao: Seed Pulp and Pod Gum
COCOA PULP
CACAO POD HUSK
Potassium Salts for Soap
Cacao Pigment
Pod Gums
SUMMARY
REFERENCES
Table 1
Fig. 1
Theobroma cacao L.
(Sterculiaceae), an important tropical rain forest species, is grown
for its oil-rich seed, to produce cocoa and cocoa butter. Cocoa seeds
are a major cash crop of the tropical world, but prices fluctuate
widely and economic hardships occur when prices are low. Despite this,
only about 10% by fresh weight of the fruit is commercialized, although
several promising commercial products could be obtained from the fruit
(Greenwood-Barton 1965).
One strategy to increase income for
cocoa growers is to identify and commercialize new products that will
not interfere with the main seed crop. In this paper, we review a
number of new products that have potential for increasing returns to
cocoa growers. These include seed pulp and products from pod husk
waste; byproducts from the chocolate processing industry, such as cocoa
shell, cocoa cake, and cocoa dust (Abiola and Tewe 1991) are not
included.
COCOA PULP
Cocoa
seeds are surrounded by an aromatic pulp which arises from the seed
teguments (technically an aril). The mucilaginous pulp is composed of
spongy parenchymatous cells containing cell sap rich in sugars (10 to
13%), pentosans (2 to 3%), citric acid (1 to 2%), and salts (8 to 10%)
(Lopez 1986).
During on-farm processing of cocoa seed (the
exportable products), the pulp is removed by fermentation and is
hydrolyzed by microorganisms. Hydrolyzed pulp is known in the industry
as "sweatings." During fermentation, the pulp provides the substrate
for various microorganisms which are essential to the development of
chocolate flavor precursors, which are fully expressed later, during
the roasting process. Fermentation was once thought to be simply an
easy way to remove the pulp to facilitate drying, but its importance to
cocoa quality has been well established (Lopez 1986).
The
schedules for fermentation vary according to location and season,
chamber size, depth of seed layer, and physical turning of the seed.
Although pulp is necessary for fermentation, often more pulp occurs
than is needed. Excess pulp, which has a delightful tropical flavor has
been used to produce the following products: cocoa jelly, alcohol and
vinegar, nata, and processed pulp.
Approximately 40 liters of
pulp can be obtained from 800 kg of wet seeds. Cocoa jelly is produced
by cooking fresh pulp mixed with sugar at the rate of 300 to 600 g to
one liter pulp. The pulp contains about 1% pectin (Wood and Lass 1985).
The jelly has a fruit-acid flavor and is a popular delicacy in Bahia,
Brazil.
By controlled fermentation and distillation, sweatings
can be made into an alcoholic spirit with 43% ethanol. Alcohol produced
can be further fermented by Acetobacter sp. to produce acetic acid, but
vinegar is not yet a commercial product (Samsiah et al. 1991).
Cocoa
sweatings have been shown to be a suitable substrate for fermentation
to produce nata (Samsiah et al. 1991), a product usually obtained from
fermentation of coconut water by Acetobacter aceti subspecies xylinum.
Nata is processed to an agar-like product, packed in syrup, and is
consumed as a dessert in Asia.
Recently, a small industry
utilizing fresh pulp has been established in Bahia for a number of
tasty products. The pulp can be consumed fresh in the form of juices
and "shakes." In small stalls, seeds with pulp are extracted from
individual pods and placed, as ordered, in a modified food blender in
which a metal disc with holes instead of blades. Milk or water is
added, and after a few seconds of blending, the contents are poured
through a strainer, producing a frothy, delicious, refreshing beverage.
Enough pulp is usually left on the seed for normal fermentation, but
pulpless seeds can also be added to intact seed to complete
fermentation. Pulp can be preserved by freezing and used for ice-cream,
yogurt flavoring, and juice concentrates. Because of the expense of the
freezing process, cocoa pulp has not been marketed outside Bahia. It is
our belief that this product could have large scale accep-tance, and we
recommend market studies in temperate countries.
Extraction of
pulp does not interfere with subsequent seed fermentation, and
reduction of pulp before fermentation may be beneficial to cocoa
quality (Schwan and Lopez 1988). In Brazil, seed quality is improved by
the removal of pulp in order to reduce acidity. Commercial depulping
machines of various sizes have been developed based on a revolving
cylinder, which removes about 60% of the pulp and does not injure the
seeds. Bahia alone produces about 300,000 tonnes of dry cocoa seeds.
Each ton of dry seeds represents 300,000 t of pulp, of which 60% will
be needed for fermentation, leaving an excess of 120,000 t. If only 10%
of this quantity would be utilized in Bahia alone, there would be
sufficient raw product available to produce 12,000 tons of pulp.
CACAO POD HUSK
Each
ton of dry seeds represent about 10 tons of husk (fresh weight). At the
present time, pod husks are a waste product of the cocoa industry, and
present a serious disposal problem. They become a significant source of
disease inoculum when used as a mulch inside the plantation. Fresh or
dried husks may be used as livestock feed, but theobromine content (ca.
0.4%) restricts the proportion that can be consumed, and its use has
been limited. Although acceptability by animals is satisfactory,
digestibility is considered poor and dependent on processing cocoa pod
husk (Adomako and Tuah 1988). Reports indicate that pod meal can
constitute 20% of ration for poultry, 30 to 50% for pigs, and 50% for
sheep, goats, and dairy cattle, but these values may be too high (Wood
and Lass 1985). The toxic dose of theobromine for rats (LD50) is 1254
mg.kg-1 (Abiola and Tewe 1991).
Low digestibility of polysaccharides restrict the use of pod husks for methane production in biodigestor (Lopez et al. 1985).
Potassium Salts for Soap
Cocoa
pod husks contain 3 to 4% potassium on a dry basis (Wood and Lass
1985). Pod husk ash has been used to make soap in Ghana and Nigeria
(Oduwole and Arueya 1990; Arueya 1991).
Cacao Pigment
A
cocoa husk extract called cacao pigment, which is a mixture of
condensed or polymerized flavonoids (such as anthocyanidins, catechins,
leukoanthycyanidin), sometimes linked with glucose, has been utilized
in Japanese food industries (Kimura et al. 1979). Recently this extract
has been shown to inhibit cytopathic effects of HIV in cell culture
(Unten et al. 1991). The anti-HIV activity was attributable to
interference with the virus adsorption, rather than inhibition of the
virus replication after adsorption.
Pod Gums
In
cacao, lysigenous cavities filled with mucilaginous substances occur in
roots, stems, flowers, and leaves (Brook and Guard 1952) as well as
fruit husks (Figueira et al. 1992). Krishna Moorthy and Subba Rhao
(1976, 1978, 1980) also isolated gums from the seed pulp.
Polysaccharides of cacao were first characterized by Whistler et al.
(1956), who found differences in hot-water-soluble polysaccharides
between seed and pod husks. Blakemore et al. (1966) examined the
hot-water-soluble fraction of husk polysaccharide and concluded that
the major part of this fraction was a pectic material. Cocoa pod husks
were examined as a source of pectin by mild acid extraction by Adomako
(1972) and Berbert (1972), but yields were low and the pectin was
inferior to apple or citrus pectin in gel-forming ability. Krishna
Moorthy and Subba Rhao (1978, 1980) found that gums from seed pulp were
effective in low concentrations as a binder for pharmaceutical pills,
and reported that suspending properties were superior to tragacanth,
sodium alginate, sodium carboxy-methyl cellulose, and methyl cellulose.
Gum karaya produced from various Sterculia species, Sterculiaceae, mainly S. urens
Roxb., has been used in the food and medical industry (Glickman 1982),
but its use has diminished because its supply is variable and
unreliable. We have recently characterized cocoa gums from pod husks
and stems to evaluate their potential as a replacement for gum karaya
or as a new commercial product (Figueira et al. 1992).
Yield
averaged 1.5% of fresh weight and 8.4% dry weight for stem gum, and
0.7% of fresh weight and 8.7% dry weight for pod gum. Cacao pod gum was
closer in composition to gum karaya than was stem gum (Table 1). Both
cocoa gums contained the same monosaccharides as gum karaya but with
the addition of arabinose and with higher proportions of rhamnose. The
major component of stem gum was glucose, not found in the other two
gums and also contained more glucuronic acid. Cacao stem gum has a
higher viscosity at concentrations below 1% than gum karaya (Fig. 1).
SUMMARY
Unutilized
portions of cocoa pods contain many potential new products that could
provide extra income for cocoa growers. The most promising products
appear to be cocoa pulp and the gums from pod husks. Although cocoa
pulp is now essentially a waste product, exploitation will require a
considerable investment in freezer processing equipment. Potential uses
for pod gums include binders for such products as pet food,
emulsifiers, and fixatives. More research is needed to discover
economic uses of this product. For maximum efficiency, we foresee a
combination of seed fermentation, pulp and gum extraction in a single
operation. This may be carried out by medium to large growers in an
on-farm operation, or by a cooperative facility that will service small
growers.
REFERENCES
Adomako, D. 1972. Cocoa pod husk. Phytochemistry 11:1145-1148.
Arueya,
G.L. 1991. Utilisation of cocoa pod husk in the production of washing
powders. In: Abst. Int. Cocoa Conf.: Challenges in the 90s, Kuala
Lumpur, Malaysia, 25-28 Sept. 1991.
Abiola, S.S. and O.O. Tewe. 1991. Chemical evaluation of cocoa by-products. Trop. Agr. 68:335-336.
Berbert, P.R. 1972. Estudo da pectina do mel e da casca do fruto do cacau. Rev. Theobroma 2(2):49-51.
Blakemore, W.S., E.T. Dewar, and R.A. Hodge. 1966. Polysaccharides of the cocoa pod husk. J. Sci. Food Agr. 17:558-560.
Brooks, E.R. and A.T. Guard. 1952. Vegetative anatomy of Theobroma cacao. Bot. Gaz. 13:444-454.
Figueira,
A., J. Janick, M. Yadav, and J.N. BeMiller. 1992. Cacao gum: a
potential new economic product. In: Proc. Int. Cocoa Conf. Challenges
in the 90s (in press).
Greenwood-Barton, L.H. 1965. Utilisation of cocoa by-products. Food Manufacture 40(5):52-56.
Kimura, K. 1979. Manufacturing procedure of natural pigment from cacao bean. Japanese Patent no. Showa 54-10567.
Krishna Moorthy, N. and B. Subba Rhao. 1976. Study of the gum from cocoa (Theobroma cacao) seed husk. Eastern Pharmacist XIX, 224:121-123.
Krishna Moorthy, N. and B. Subba Rhao. 1978. Binding properties of the mucilage of cocoa gum (Theobroma cacao) for tablets. Indian J. Pharm. Sci. 40:175-177.
Krishna Moorthy, N. and B. Subba Rhao. 1980. Suspending properties of the mucilage of cocoa gum. Indian J. Pharm. Sci. 42:46-48.
Lopez,
A.S. 1986. Chemical changes occurring during the processing of cacao.
In: P.S. Dimick (ed.). Proc. Symp. Cacao Biotechnology. The
Pennsylvania State Univ., University Park.
Lopez, A.S., H.I.S.
Ferreira, A. Llamosas, and A.P. Romeu. 1985. Situaçao atual da
utilizaçao de subprodutos de cacau no Brasil. Boletim Tecnico 133.
CEPLAC, Bahai, Brazil.
Odwole, O.O. and G.L. Aruyea. 1990. An economic analysis of soap production from cocoa pod husk. Café, Cacao, Thé 34:231-234.
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S., Y.Q. Lan, and C.E. Chong. 1991. Development of food products from
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the 90s, Kuala Lumpur, Malaysia, 25-28 Sept. 1991.
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A.S. Lopez. 1988. Mudanca no perfil da fermentacao de cacau ocasionada
pela retirada parcial da polpa da semente. Rev. Theobroma 18:247-257.
Unten,
S., H. Ushijima, H. Shimizu, H. Tsuchie, T. Kitamura, N. Moritome, and
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Table 1. Sugar comparison of cacao gum and gum karaya.
| | Sugar composition (molar ratio)z | | Gum source | Rhamnose | Arabinose | Galactose | Glucose | Xylose | Mannose | Galacturonic acid | Glucuronic acid | | Gum karaya | 1.6 | 0.0 | 1.0 | 0.1 | 0.0 | 0.0 | 1.3 | 0.6 | | Cacao stem gum | 2.0 | 1.7 | 1.0 | 0.0 | 0.0 | 0.0 | 1.1 | 1.4 | | Cacao pod gumy | 2.4 | 2.1 | 1.0 | 0.1 | 0.1 | 0.0 | 1.1 | 0.6 | | Cacao pod gumx | 1.0 | 0.3 | 1.0 | 0.0 | 0.0 | 0.3 | 0.0 | 0.0 | | Cacao pod gumw | 0.4 | 0.2 | 1.0 | 0.4 | trace | 0.3 | 1.3 | 0.0 | | Cacao pod gumv | 0.6 | 0.4 | 1.0 | trace | 0.3 | 0.0 | 13.4 | 0.0 |
zAll monosaccharides were standardized for galactose molar concentration.
yFigueira et al. (1992)
xWhistler et al. (1956)
wBlakemore et al. (1966)
vAdomako (1972)
Fig. 1. Viscosity changes with concentration of cacao pod gum and gum karaya at different spindle speeds.
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