page 1
page 2
page 3 page 4
page 5
< prev - next > Food processing Snack foods KnO 100199_Cocoa and chocolate (Printable PDF)
Cocoa and Chocolate
Practical Action
The crushed material is winnowed to remove the broken pieces of shell. This is achieved by
sieving and blowing air through the material.
Alkalisation is a treatment that is sometimes used before and sometimes after grinding to modify
the colour and flavour of the product. This was developed in the Netherlands in the last century
and is sometimes known as “Dutching”. This involves soaking the nib or the cocoa mass in
potassium or sodium carbonate. By varying the ratio of alkali to nib, a wide range of colours of
cocoa powder can be produced. Complete nib penetration may take an hour. After alkalization
the cocoa needs to be dried slowly.
The cocoa nib is ground into “cocoa liquor” (also known as “unsweetened chocolate” or “cocoa
mass”). The grinding process generates heat and the dry granular consistency of the nib is
turned into a liquid as the high amount of fat contained in the nib melts.
Production of cocoa butter
Cocoa butter can be extracted using extrusion, expeller, or screw presses. Cocoa butter can be
produced from whole beans, and mixtures of fine nib dusts, small nibs, and immature beans.
Sometimes, whole nibs are pressed when the expeller cake is needed for the manufacture of
coatings and therefore must be free from shell and as low as possible in cocoa butter content.
When pressing whole beans, very light roasting or even no roasting is needed, and this gives the
mild-flavoured cocoa butter that is desirable for milk chocolate.
Hydraulic presses
Hydraulic presses are used to produce cocoa powder and cocoa butter. Cocoa powder can be
prepared by the hydraulic pressing of finely ground cocoa liquor. This can be achieved by
compressing the liquor in heavy steel pots until a predetermined amount of cocoa butter is
squeezed through very fine mesh screens or filters situated at each side of the pot. The pots,
each with a capacity of about 18kg, are mounted in a horizontal frame and the cocoa liquor,
heated to 93-102oC, is pumped in at a pressure of up to 300lb per square inch. Cocoa butter
immediately starts to be forced out through the filter screens and when the pots are full the
pressure pump is turned off and a hydraulic ram set in motion. A pressure of up to 6000lb per
square inch is then applied. Cocoa butter runs from the pots to a trough and eventually to a
collecting pan situated on a balance. When the required amount of cocoa butter has been
extracted the ram is reversed to the starting position, the press pots open up and the cocoa
cakes from each pot are deposited on a conveyor and taken away for grinding. The extracted
cocoa butter will need to be cleaned to remove non-fat solids in suspension; this can be done by
filtration or centrifugally. Cocoa butter produced by this method is normally a very pale yellow
colour and it sets at a fairly hard fat showing crystal formation. Its melting point is 35oC
(Glossop, 1993).
Cocoa beans for expeller pressing are either very lightly roasted at low temperatures or not
roasted at all. They may be just warmed sufficiently to loosen the shell. The beans are steamed
before being fed to the press to soften them and help release the cocoa butter. Basically the
expeller press consists of a tapering tube perforated along its length in which is situated a
rotating screw. The cocoa beans are fed into the tube where they are subjected to shearing and
increasing pressure by the action of the rotating screw. Cocoa butter is forced out through the
perforations in the tube. The tube is terminated by an adjustable cone which gives a variable
gap between the tube and the cone. Thick flakes of expeller cake are extruded through this gap.
The extracted fat must be filtered or centrifugally separated to remove cocoa solids. Expeller
cake contains 8-9 percent fat and this can be extracted using organic solvents.