July 6, 2013Posted in: Notes, Pharmacognosy
Cocoa seeds are used to derive products like cocoa powder, chocolate and cocoa butter. It was used in the early days in Mexico and was first used to make cocoa butter as early as 1695. Cortez had described the preparation of a beverage obtained from cocoa seeds called ”chocalatl”. It is also known as theobroma and cacao. In latinized Greek the word theobroma is broken down as “theo” as in “god” and ”broma” meaning “nectar” or food. Cocoa contains alkaloids, the most important ingredients being theobromine, caffeine, and trigonelline. Chocolates containing cocoa are a rich source of procyanidins which are useful antioxidants. The characteristic bitter taste of cocoa is obtained during roasting due to the reaction of theobromine with the diketopiperazines.
||Dried seeds of Theobroma cacao
||Malvaceae (formerly Sterculiaceae)
||Cocoa is mainly produced in South America(main regions being Brazil, Colombia, Ecuador, Guiana and Venezuela), Central America, West Indies, Nigeria, Ghana, Ceylon, Java.
- Cocoa tree is usually 4-6 m high, with sometimes exceeding 8 m.
- Berry shaped cocoa fruits are attached to the trunk and branches varying in length from 15-25 cm enclosing the seeds( 40-50 in no.) in a sticky whitish pulp.
- The flattened ovoid seeds are 2-3 cm long with a width of 1.5 cm.
- A thin endosperm lining covers the embryo. The irregularly folded cotyledons form the greater part of the kernel.
- Both, the testa (easily removed from cocoa beans which have been fermented and roasted) and kernel are reddish brown in color with the intensity of the color depending on the variety and the processing method.
- Cocoa contains alkaloids mainly theobromine (3,7-dimethylxanthine), present about 0.9-3 % in kernels or nibs and 0.19-3% in the husks. Although lesser amounts of theobromine is found in the husks, commercially theobromine is obtained from the husks of the cocoa tree. Caffeine (0.05-0.35%), trigonelline and cocoa butter is also present.Water soluble polyphenols i.e epicatechol, anthocyanins and leucoanthocyanins are also present in 5-10% concentrations in the fresh seed. The plant is thus rich in anti-oxidants.
Structure of Theobromine
- Cocoa butter (also known as theobroma oil) is present in the kernel (nib) in around 55% which is formed by grinding the kernel into a liquid mass called chocolate liquor. From this molten mass cocoa butter is removed by hydraulic pressing. Cocoa butter comprises of triglycerides mainly of oleic, palmitic and stearic acids.75% of the fats present in cocoa butter are mono unsaturated.
- The remains left after removing cocoa butter from the kernel is dried and powdered to form cocoa powder. Alkali treated cocoa powder is better color and flavor compared to untreated cocoa powder.
- Theobromine shows positive results for the murexide test (Drug is mixed with small amounts of potassium chlorate and a drop of HCl. It is then evaporated to dryness and exposed to ammonia vapors. Purple color is produced.). Theobromine crystallises as white rhombic shaped needles.
- Theobromine can be distinguished from caffeine on the basis that it is precipitated from dilute HNO3 by silver nitrate. Also sublimation point for theobromine is at 220°C whereas caffeine sublimes at 178-180°C.
|Adulterants/Allied drugs/ Substitutes
- Coffee seeds: They consist of dried seeds of Coffee arabica. Its chemical composition is made up of caffeine(1-2%), tannin, chlorogenic acid, sugars, fats and pentosans.
- Kola seeds: They consist of dried cotyledons of the seeds of various species of Cola. They can also be called as bissy or gooroo nuts. The color of the seed varies according to the species (eg. white or crimson seeds of Cola acuminata, red seeds of Cola alba etc). They contain caffeine(1-2.5%), small amounts of theobromine(in free and combined form) and 5-10% of tannoids (catechol and epicatechol).
- Guarana: It is dried paste prepared from seeds of Paullinia cupana. It is also called as Pasta guarana or Brazilian cocoa. It consists of caffeine (2.5-7%), 12% of tannins(also called as guarana red) and other constituents resembling that of cocoa and kola.
- Tea: They consist of dried leaves of Camellia sinensis (Thea sinensis). The leaves consist of caffeine(1-5%), tannins(10-24%), small amounts of theobromine, theophylline and voltaile oils. It also contains an enzyme called thease which partly converts the phlobatannin into phlobaphene.
- Cocoa powder and butter have gained wide use in food industry in the preparation of chocolates.
- The presence of procyanidins in cocoa has been attributed to have antioxidant activity (scavenge free radicals) and also to inhibit lipid peroxidation thus in turn lowering cholesterol levels. Thus chocolates have useful antioxidant and anti-aging properties.
- Theobromine present has activity similar but less potential to that of caffeine and thereby acts as a stimulant (increase in energy levels, increase in alertness and motivation). It also acts as a diuretic with lesser action than its isomer theophylline.
- Cocoa butter is used in medicines mainly in suppositories and ointment base and in cosmetics to make lipsticks and other topical products.
- It has also been suggested that cocoa helps relieving mood disorders.
- It may help in preventing and correcting magnesium deficiency.
|Other Notes (life cycle, extraction etc.)
||Extraction of theobromine: Cocoa husks are boiled with water and then filtered. The solution is treated with lead acetate to precipitate tannins and filtered again to get rid of the excess lead. It is then evaporated to dryness. Alcohol is used to extract theobromine from the residue and then purified by recrystallization from water.
Preparation of Cocoa seeds: The fruits are cut open and the embedded seeds are separated from the pulp and allowed to ferment in boxes, tubs or earth cavities for around 3-9 days taking care of the temperature to not rise above 60°C. Liquid oozes out of the seeds which have a color change from white or red to purple. The seeds may or may not be washed after fermentation. After this stage, they are roasted to lose acetic acid and water at a temperature of 100-140°C, to achieve its characteristic odor and taste. This roasting process helps in removing the testa too. The seeds are rapidly cooled down and the testa and seeds are separated from each other by the “nibbling” process using a machine. At times, seeds are directly dried in the sun but that leaves an astringent and bitter taste disregarding the process.
||Cocoa may be a trigger factor for migraine headaches due to the presence of phenolic flavonoids.
- Trease and Evans’ Pharmacognosy, 16e (Evans, Trease and Evans Pharmacognosy)
Elsevier: New York, 2009.
- Ara DerMarderosian, et. al. The Review of Natural Products 4th Edition.
- Kokate, C. K.; Gokhale, S. B.; Purohit, A. P. A textbook of Pharmacognosy, 29th ed.; Nirali Prakashan: Pune, 2009.