13 Chocolate and cocoa
The manufacture of chocolate involves roasting of cocoa beans
followed by grinding to form cocoa mass. Some of this cocoa mass is
pressed to release the fat, cocoa butter, and the remaining solids
when milled are known as cocoa powder.
13.1 Types of chocolate
Plain or dark chocolate is a blend of cocoa mass, sugar and cocoa
butter with traces of emulsifier and vanilla (or other flavours). It has
a strong slightly bitter flavour.
Milk chocolate is a blend similar to dark chocolate but in addition
it includes milk crumb which is made from dried milk. It contains
less cocoa mass than dark chocolate so it is paler in colour and the
presence of butter fats reduces the chocolate melting point.
In all cases the chocolate is the result of fine grinding (refining)
followed by conching (a prolonged mixing process) which modifies
the flavours, reduces the moisture content to very low levels and
ensures a good dispersion of the fat over the solid particulates.
13.2 Supply and storage of chocolate
Most biscuit factories do not manufacture their own chocolate so it is
necessary to consider only delivery and storage.
For large users it may be convenient and more economic to bulk
handle chocolate in warm liquid form. Road tankers are used to carry
and discharge the chocolate in a similar way to fats. The silos must be
jacketed, kept at 49"C, and the chocolate must be constantly agitated
in a gentle manner. The minimum temperature for bulk chocolate
storage is 45°C. This ensures that all the fat is liquid. Great care
should be taken to avoid contact with water or damp surfaces as even
traces of moisture will cause a great increase in the chocolate
consistency. As for fats, no valves or other fittings should contain
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copper or brass which will promote rancidity. In general, chocolate is
much more resistant to rancidity than pure fats, so that the liquid
form can safely be stored for several weeks.
Many users take delivery of chocolate in solid form. This may be
in large blocks or in small pieces. The large blocks will have been
moulded at the supplier’s factory and wrapped in plastic or waxed
paper to protect against atmospheric humidity. In the case of small
pieces, these may have been moulded, deposited or cooled as strips
which are subsequently broken in a random way before bulk packing
in moistureproof sacks for shipment.
Solid chocolate should be stored in rooms at about 15°C with a
relative humidity of 50% or less and well away from strong smelling
ingredients such as spices, cheese and chemicals. The value of
chocolate combined with its appeal to most people usually requires
that it is kept under lock and key!
Prior to use in an enrober or moulding plant the chocolate has to
be melted. Melting kettles are normally heated with hot water and it
is important that surface temperatures are maintained below 60°C
otherwise there is a risk of flavour change (and damage to the
lecithin) - a metallic flavour may be detectable if chocolate has been
overheated. The advantage of small pieces of chocolate compared
with larger blocks is that they are easier to handle and they melt more
rapidly.
Handling melted chocolate requires special equipment to ‘temper’
it before application onto biscuits. The techniques of tempering,
enrobing and moulding of chocolate is covered in Manual 5,
Secondary processing in biscuit manufacturing.
13.3 Chocolate drops, chips and chunks
Small pieces ‘drops’ of chocolate are sometimes used as an ingredient
in wire cut cookies. These ‘drops’ are typically about 5mm in
diameter and are formed either by depositing small drops of
tempered chocolate or by forming with a special moulding plant.
Chocolate ‘chips’ and ‘chunks’ may be formed by dribbling streams
of chocolate onto a cooling band and cutting to the desired length.
Although the chocolate melts when the cookies are being baked
there is no appreciable movement of the chocolate within the dough
so it sets again when the biscuit cools. This, therefore, offers a means
of including recognisable chocolate into cookies where the climate
may preclude the satisfactory use of a surface coating.
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13.4 Chocolate flavoured coatings
Real chocolate is made from roasted and ground coma beans with the
addition of sugar and extra cocoa butter. As cocoa butter is expensive
there are a number of chocolate look-alike products made from cocoa
powder, sugar and a vegetable fat not derived from the coma bean.
Some of these are simple fats like hardened palm kernel oil and
others are very sophisticated fats made and blended to resemble
closely cocoa butter in their physical characteristics. Chocolate
products made with these vegetable fats must be referred to as
chocolate flavoured coatings. They are usually cheaper than real
chocolate but their flavour is less attractive because their mouthfeel
is more waxy. They do, however have a value in some biscuit
products because handling the melted material is easier and by using
higher melting fats the coatings are less inclined to melt in warm
conditions.
13.5 Cocoa
Cocoa is a flavoursome powder produced from the cake formed when
cocoa butter is expressed from coma mass. There are two basic
types, dutched and natural, and each is available with fat contents
within a range of about 8-32%.
Dutched cocoa is made from roasted and shelled beans which have
been chopped, soaked in warm alkali solution, dried and ground to a
mass prior to the expression of the excess cocoa butter. This process
results in powder with darker and redder colours. The powder is
more easily dispersible in water, has a less astringent flavour and, of
course, has a greater alkalinity.
It is possible to achieve some very dark or even black cocoas by
the alkali treatment. Such cocoas are valuable for colouring biscuit
doughs and sandwich creams.
The higher the fat content the more rounded is the flavour of a
cocoa but also the higher the price. General purpose manufacturing
cocoa, as used in doughs, biscuit creams or as the basis for coatings,
has a fat content of between 9% and 12%, or a little higher, but
cocoa for use in beverages is richer in fat, usually not less than 22%.
Cocoa powder should be a fine, free flowing powder. It is
normally sold with a maximum moisture content of 5%. Higher
values may lead to mould growth during storage. Cocoa powder is
naturally hygroscopic so should be kept in moistureproof containers.
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Should the powder become too warm in storage the cocoa butter
will melt and lumping may occur. The apparent colour of cocoa
powder is dependent on temperature due to the condition of the fat
and warmer cocoa looks darker in colour.
Thus, the storage conditions for cocoa powder should be:
1 Humidity, less than 50% RH (relative humidity).
2 Temperatures, even and between 15-18"C, not exceeding 20°C.
3 Away from strong odours such as species, cheese, ammonia.
Under these conditions cocoa will keep for very long periods
(years).