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Figueira, A., J. Janick, and J.N. BeMiller. 1993. New products from Theobroma cacao: Seed pulp and pod gum. p. 475-478. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

New Products from Theobroma cacao: Seed Pulp and Pod Gum

Antonio Figueira, Jules Janick, and James N. BeMiller


  1. COCOA PULP
  2. CACAO POD HUSK
    1. Potassium Salts for Soap
    2. Cacao Pigment
    3. Pod Gums
  3. SUMMARY
  4. REFERENCES
  5. Table 1
  6. 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


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 2.8 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.

Last update September 15, 1997 aw