1. on density of chocolate and cocoa butter :
Chocolate
Solid 1.3 g/cm3 80 lb/ft3
Liquid 40oC (104oF) 1.2 g/cm3 76 lb/ft3
Cocoa Butter
Solid 15 degrees C (59 degrees F) 0.96 - 0.99 g/cm3 60 lb/ft3
Liquid 0.88 - 0.90 g/cm3 55 lb/ft3
A publication by Meursing provides the following data on density of cocoa powder :
The density of cocoa powder can be measured in cm3 /g, whether the powder is
compacted or not. It can also be measured in g/cm3 and, if this is the case, it is called
bulk density .
The density of cocoa powder varies with the percentage of fat and the degree of
alkalisation. One study found that 12% fat cocoa powder had a density of between 2.5
and 2.9 cm3/g before compaction and a density of between 1.76 and 2 cm3/g after
compaction .
The same figures in g/cm3 for bulk density are as follows: 12% fat cocoa powder had
a bulk density of between 0.35 and 0.4 g/cm3 before compaction and a bulk density of
between 0.5 and 0.55 g/cm3 after compaction .
References :
S.T. Beckett. Industrial chocolate manufacture and use. 3rd edition. Blackwell
Science, 1999
E.H. Meursing Cocoa powders for industrial processing. 3rd revised edition. Cacao de
Zaan, 1983
A publication by S.T. Beckett provides the following information on density of
chocolate and cocoa butter :
Crystallisation of cocoa butter
it has the ability to crystallise in several different forms according to how the liquid
fat is solidified. The different crystalline forms are characterised by differences in the
distances between the chains of glycerides and their angle of tilt .
There are 6 main polymorphic crystalline forms: I (or gamma form) (melting point
17oC) is created by rapid cooling of the liquid fat but it is unstable and can rapidly
transform to II (or alpha form) (melting point 21-24oC) and this form can change
more slowly to forms III and IV (or beta prime form) (melting point 25-29oC). Form
IV would generally be produced if untempered or poorly tempered chocolate were
cooled. This form changes rapidly to Form V (or beta form) (melting point 34-35oC)
which is stable and is the state produced in a well tempered chocolate. Form V very
slowly transforms into form VI and it may be accompanied by fat bloom .
If crystallisation takes place in chocolate which has already set it can cause cracks to
appear in the chocolate which dulls the surface. If there are temperature changes
during the storage of chocolate it can cause the crystal structure to change which can
cause cracking and/or fat bloom .
In chocolate making stability is important, otherwise the quality is poor and fat bloom
develops, this is achieved through tempering or controlled crystallisation. Tempering
generally takes the following form: melting of the fat, cooling to the point of
crystallisation, crystallisation and melting out of unstable crystals .
References:
Minifie B.W. Chocolate, cocoa and confectionery science and technology. 3rd edition
Van Nostrand Reinhold, 1989
Beckett, S.T., Industrial chocolate manufacture and use. 2nd edition Blackie
Academic & Professional, 1994
Cook, L.R., Meursing E.H. Chocolate production and use. Revised edition. Harcourt
Brace Johanovich, 1982
December 99
The tropicalisation/heat resistance of chocolate
products?
The type of chocolate and its ingredients will have an effect on the
heat resistance of the finished product.
In chocolate the fat element forms the continuous phase in which all
other ingredients are embedded. Therefore, the melting
characteristics of the fat used are of importance to the stability of
the chocolate in a tropical climate. The supplier of the chocolate
should be able to provide information on its melting point and solid
fat contents over a range of temperatures.
Melting point
This should be at or just above 36 degrees C to ensure that the
product melts in the mouth. If the melting point is too high it will
result in a waxy mouthfeel and not melt entirely. If the melting
point is too low the product may not be stable during storage in
summer or in hot climates. Fats melt over a temperature range and
so at any temperature below the melting point a part of the fat is in
solid state and a part is liquid.
Crystallisation
Cocoa butter is polymorphic and has more than 6 crystal forms, of
which only form V or beta form has the necessary heat resistance
and melting properties. To ensure that only the stable beta crystals
are formed during confectionery production the chocolate mass
needs to be tempered prior to solidification. Correct tempering
ensures a stable shelf life.
Milk fat
The addition of milk fat to make milk chocolate can soften the
product and make it less heat resistant. Milk fat has a different
crystalline form to cocoa butter and the resulting incompatibility can
lead to a destabilisation of the product.
The fat element of the cocoa butter can be replaced wholly or in
part with vegetable fats in order to improve heat resistance.
Cocoa butter equivalents
The replacement of part of the cocoa butter content of chocolate
with cocoa butter equivalents (CBEs) improves the heat stability of
the chocolate. In countries with a warmer climate the addition of
CBEs may significantly improve the shelf life of a chocolate product.
CBEs are vegetable fats derived from palm and shea oils which are
chemically and physically very close to cocoa butter. CBEs can be
made with heat resistant properties superior to cocoa butter.
Cocoa butter replacers
The replacement of most of the cocoa butter with cocoa butter
replacers (CBRs) can improve heat resistance. CBRs are derived
from oils such as soybean, cottonseed or coconut oil. They have a
very dissimilar composition to cocoa butter. The melting point of
CBRs tends to be higher than that of cocoa butter thus providing
greater heat resistance. Products containing CBRs cannot always be
called chocolate.
The tempering and cooling process is also important in improving
the stability of cocoa butter and CBEs and hence improving heat
resistance.
Tempering and cooling
Tempering is required to ensure that the chocolate has the
necessary shelf life. Tempering is conducted in a continuous process
whereby the chocolate is cooled and the cocoa butter forms stable
and unstable seed crystals. To keep only the wanted beta crystals
the chocolate is warmed to a temperature intermediate between the
melting points of the two forms, 88-90 degrees F (31-32 degrees C
for milk chocolate and 90-92 degrees F (32-33 degrees C) for semisweet chocolate. The milk chocolate is tempered at lower
temperatures because the milk fat suppresses the formation of seed
crystals. The temperatures will vary depending on the ingredients
and the quality of the raw materials. At this point most of the
unstable crystals are melted out, but some seed crystals will
remain. Tempering time is also important as seed crystals need
time to grow in size and mature. The chocolate should have some
'residence' time before use in the enrobing or moulding plant. The
length of time will vary depending on the intended use of the
chocolate.
Tempered chocolate needs to be cooled under gentle conditions to
promote the preferential growth of stable crystals. The best
temperature for this process is 55-60 degrees F (13-15 degrees C).
Moderate wind speed is recommended in the cooling tunnel to
remove the heat of crystallisation. The temperature should be
raised gradually to room temperature towards the end of the
tunnel.
References:
J. Kristott Confectionery fats - physics matters. Confection, p27-31, July 1998
Leissner, R. Reducing Costs with Cocoa Butter Equivalents. Chocolate &
Confectionery International, 2 (6): 24-25, November 1998
Weyland, M. Shelf life of chocolate and compound coatings. The Manufacturing
Confectioner, 78 (9): 121-140, September 1998
Duurland, F. Attributes of speciality fats. Chocolate & Confectionery International,
1 (3): 22-25, July 1997
December 99