Module 12. Cocoa and chocolate products
Lesson 41
COCOA BEAN PROCESSING
41.1 Introduction
The Swedish botanist Linnaeus named cocoa bean Theobroma cacao, meaning ‘food of the Gods’ to reflect its spiritual and social importance to the Mayans and Aztecs.
41.2 Varieties of Cocoa
There are three types of cocoa:
41.2.1 Criollo
It has white cotyledons. The chocolate made out of it is of light brown colour quite like milk chocolate. It has pleasant flavour, nutty type with only a mild typical chocolate flavour. Criollo is rare in production. Criollo (regarded as flavour cocoa) is mostly grown in Central and South America.
41.2.2 Forastero
Most of the world’s cocoa is derived from Forastero trees (i.e. 95% of world cocoa crop). It is made up of small, flattish and purple beans.
41.2.3 Trinitario
It is a hybrid between Forastero and Criollo trees. It is a disease resistant hybrid, regarded as a flavour bean. It has a strong chocolate flavour; in addition ancillary flavours such as fruity, raisin, caramel, molasses and spicy notes. It is the most fully-flavoured cocoas. It is ~ 3% of world production.
The Trinitario and Criollo varieties produce mainly the ‘fine’ and ‘flavour’ cocoas.
Cocoa tree was exclusive to the Americas around the Valleys of Amazon and Orinoco rivers. West Africa produces over 70% of world cocoa. Now, cocoa trees are cultivated in more than 40 countries around the world.
Certain cocoa trees become productive in 3-4 years, while in past 6-7 years was common. The pod contains some 40 seeds or beans. After fermentation and drying, one pod produces some 40 g of beans, 1 bean typically weighing around 1 g.
41.3 History of Cocoa beans
On his fourth voyage to America, Columbus reportedly discovered a canoe off the Yucatan Peninsula laden with fruit and cocoa beans. Years later (i.e. beginning of 16th Century), Cortez confirmed the remarkable value assigned to the cocoa beans.
Cocoa processing developed during the 18th Century in the Netherlands. In 1828, to reduce the fattiness of chocolate drink, Coenraad Johannes Van Houten developed a mechanical pressing process to fractionate the cocoa liquor into cocoa butter and cocoa cake. In 1947 discovery was made by John Fry in England that by adding cocoa butter to mixture of liquor and sugar, chocolate was created.
41.4 Cocoa Bean Processing
41.4.1 Fermentation of beans
Chocolate obtained from slaty, unfermented beans tastes extremely unpleasant, being very bitter and astringent without any apparent chocolate flavour.
Cocoa beans are subjected to microbial fermentation for 7-12 days in large bin; the colour, flavour and texture of bean are modified. Fermentation begins with yeasts converting the sugars in the pulp to ethanol. This produces the initial aerobic conditions, and then bacteria start to oxidize the ethanol to acetic acid and further to CO2 and water; producing heat, raising the temperature during the first 24 h to 40°C in a good active fermentation.
On the second day, the pulp starts to break down and drain away. Bacteria further increases, lactic acid is produced and an acetic acid bacterium, under slight more aerobic conditions, actively oxidizes alcohol to acetic acid; temperature reaches to ~ 45oC.
Total 5-6 days fermentation is necessary; bacterial activity continues under increasingly good aeration; high temperature is maintained by bacterial activity. Turning helps in securing an even degree of fermentation.
41.4.1.1 Chemical changes
The proteins and polyphenols are essential for development of chocolate flavour.
Anthocyanins and other polyphenolic compounds in the pigment cells can diffuse out into the adjacent main storage cells. The enzymes breakdown the coloured anthocyanins resulting in some bleaching of cotyledons. As more air reaches, oxidative or browning reactions start to predominate and the tissue darkens.
41.4.2 Cleaning
The adhering pulp and mucous is removed.
41.2.3 Drying
41.2.3.1 Sun-drying
It takes about a week of sunny weather to dry down to 7.0% moisture, needed to prevent mould growth during storage.
41.2.3.2 Forced-air driers
Artificial drying poses two problems
(a) Beans are dried too quickly resulting in beans becoming very acidic.
(b) Smoke may find its way onto the beans, producing unpleasant acrid, smoky or tarry taste.
41.2.4 Cleaning and grading
From the silo storage/burlap bags, cocoa beans pass through cleaning machines: screens, magnets and controlled air streams. The extraneous material removed includes sticks, stones, string and metal objects.
41.2.5 Blending
Substantial variation in flavour exists among cocoa beans, produced in different countries; difference is due to fermentation. Blending provides opportunity to obtain a certain flavour and cope up with inconsistency of cocoa beans in flavor and other quality aspects. This contributes to uniformity.
41.2.6 Thermal pre-treatment
Loosening of cocoa shells by means of a thermal shock; achieved with hot air, saturated steam or infra-red radiation.
41.2.7 Breaking and Fanning (winnowing)
The cocoa shell is polluted with sand, high bacterial count and pesticide residues. To remove shell, the beans are first broken between adjustable toothed rollers. The broken pieces are subsequently separated in fractions by sieving. Each fraction is treated with a stream of air which carries away the light shell pieces.