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Moisture caused problems in ice cream coating
- a problem of the past
Palsgaard Technical Paper, August 2012
way to succeed
- let us help
you do
so.
By Arne Pedersen,
Product & Application Manager,
Bakery & Confectionery, Palsgaard
A/S.
Creating a
coating chocolate
Chocolate is a valued product to
be used as coating on many different products and the functions
are many. A typical confectionery
coating will protect and keep the
filling inside the praline and protect it from drying out. It will enable
customers to hold it without getting greasy fingers but when eaten
the chocolate will melt nicely and
together with the filling provide an
excellent taste. This is due to the
very special properties of confectionery fats like cocoa butter which
is unique in the sense that it is hard
and brittle at temperatures below
30° C (room and hand temperature) and completely melted at 35°
C which is the temperature in the
mouth.
Traditional
coating challenges
Challenges arising from using
chocolate as a coating are also
many as the result depends on the
interaction between the filling and
the coating – mainly on long term
basis as the problems typically
shows after a storage period. Migration of fat from the filling to the
chocolate causing the grey layer
called bloom is one big problem
(see figure 1) – another is leaking
Figure 1: Chocolate bloom caused by
migration of fat.
This article describes how an optimal mixture of
Emulsifier YN and PGPR efficiently solves moisture
caused problems when coating ice cream with
chocolate- or compound coatings. By using the special
properties of both emulsifiers the negative effect of
water in an ice cream coating is neutralized and a
stable and uniform production day is secured.
liquid filling – or instability due to alcohol content in the filling. All problems and challenges described in
numerous articles.
Ice cream coating
One area which is not described
very much is ice cream coating.
This application differs from the
coatings which are to be eaten at
normal room temperature and very
special production problems rather
than subsequent quality issues are
related to this application.
Ice cream coating is eaten together with the ice cream and during
this process the mouth is typically
cooled down to a temperature below 30°C which is far below the
typical melting point for well tempered chocolate based on cocoa
butter. The trick is that the chocolate used for ice cream coating is
not tempered and it is cooled very
fast to a temperature around minus
18°C. This treatment forces cocoa
butter to crystallize in a number
of different unstable crystal forms
with a low melting point – typically 25°C – which makes the ice
cream coating melt nice and easily
together with the ice cream when
eaten. The typical storage temperature at minus 18°C will keep the
crystals from re-crystallizing and
therefore secure the desired melt
down when eaten through out the
shelf life of the product. Alternately
a non temper vegetable fat with a
melting point around 25°C – e.g.
coconut oil can be used, either on
its own or in mixtures with e.g. cocoa butter.
Palsgaard Technical Paper - August 2012
Moisture caused problems in ice cream coating - a problem of the past
Dipping process
The dipping/coating process is
also different due to the low process temperatures and the very
short time from liquid to solid. In
a traditional coating process the
crystallization takes several minutes. Equally, there is plenty of time
to regulate the layer thickness and
shape by blowing/vibrating. When
coating an ice cream it is a matter of seconds before the coating
is fixed into a non-moveable layer,
and the layer thickness is defined
by the rheology of the chocolate,
the crystallization speed of the fat
used and the temperature of the
ice cream and the chocolate.
It is therefore important to be in
control of the rheology of the coating in order to get the desired layer
thickness and shape, and to use
the optimal temperatures in the ice
cream and in the chocolate coating.
One could think that this would
solve the problem and secure a
production free of problems, but it
is unfortunately not so.
Identifying the cause of
moisture problems in ice
cream coatings
During a production run the ice
cream coating will change its rheological properties due to the fact
that it is impossible to avoid water
from getting into the chocolate.
The fact is that an almost water
free 35°C hot chocolate is exposed
to ice cream containing more than
60% water, preferable at minus
15°C. Melted ice cream mix will
therefore migrate to the hot choco-
2
late and the water content in the
chocolate will gradually increase
causing a viscosity increase where
especially the Yield Value (YV)
(see box) in the chocolate will increase.
This process is speeded up if the
process parameters are not optimal e.g. too hot chocolate, the ice
cream is not cold enough when
dipped, and even ice cream dripping into the chocolate.
A gradual increase in the Yield Value in the coating will result in gradually thicker layer, risk of pinholes,
longer crystallization time and in
extreme cases separation of the
coating on the ice cream.
An immediate and typical reaction
on an increasing layer thickness is
to increase the temperature in the
chocolate bath. This will result in a
thinner layer, but also increase the
water migration and the heat damage on the ice cream is increased.
Addition of more fat will also help,
but naturally such adjustments
are not optimal as the production
should run smooth and uniform
creating uniform products. Additionally, adding more vegetable fat
will mean higher costs of the final
ice cream, as well as difficulty setting a precise cost of the final product as the cost will fluctuate.
How to create a
stable ice cream coating
So the big desire is to create a
coating which will act the same
way during the entire production
run despite it is exposed to various
amounts of melted ice cream mix.
To meet this we need to work with
emulsifiers and to create the perfect buffer against variations in the
rheology a combination of emulsifiers is preferred. The following will
describe the importance of using
emulsifiers in ice cream coating.
By sharing some experimental results with you guidelines to make
the most efficient mix of emulsifiers will be given. All in all this will
help you in creating an ice cream
coating which is stable, uniform
and very robust toward viscosity
changes during a production run.
introducing Emulsifiers
Lecithin (E322) typically derived
from soya or sunflower has traditionally been used to regulate the
rheology of an ice cream coating. In chocolate, lecithin is typically dosed around 0.4% as this
is where the optimal functionality
is found and is this exceeded the
YV will increase. In ice cream coating typically 0.7 – 0.8% is used in
order to have a buffer against water migration during the production
process. This is working but it is
possible to achieve a far better result!
Graph 1: Rheology on ice cream coating - The effect of lecithin and Palsgaard® AMP 4448.
0.7% lecithin
0.7% Palsgaard® AMP 4448
3500
3000
2500
2000
mPa∙s
1500
1000
500
0
0% ice cream mix
1% ice cream mix
2% ice cream mix
Palsgaard Technical Paper - August 2012
Moisture caused problems in ice cream coating - a problem of the past
Yield Value (YV) is defining the force
needed to initiate flow in a non Newtonian fluid like chocolate. The YV is
typically important when working at
low shear like moulding/vibrating.
Plastic Viscosity (PV) is the force
needed to maintain a constant flow in
a chocolate mass. The PV is important
when working at medium to high shear
like in the enrobing process.
Ammonium phosphatide or Emulsifier YN (E442) also known as
Palsgaard® AMP 4448 is a product
typically made from rape seed oil
and possesses a stronger functionality than lecithin. Emulsifier
YN can be added in higher dosages without negative effect on the
YV - the thickening effect - and is
therefore very well suited for the
ice cream coating application. To
read more about the unique functionality of Emulsifier YN, please
look at the end of this article*.
Testing the effect of
emulsifiers in ice cream
coatings
The increase in water content over
a production day, depend on the
production parameters and this increase can be as high as 1.5%. In
order to make the trials as realistic
as possible, up to 2% ice cream
mix containing 63% water was
added to the coating. In practice
this means a max. addition of 1.3%
water to the ice cream coating.
Graph 1 shows the increase in viscosity at shear rate 2 [1/s] (speed
of the chocolate) when applying
various amounts of ice cream mix
to a coating with and without lecithin or Palsgaard® AMP 4448 added. Experimentally this has been
found to be the best measuring
method for describing the conditions in an ice cream dipping process. It is also a good illustration
of the changes which may happen
during a production day. It is clear
that compared to the emulsifier
free ice cream coating, both the
addition of lecithin and Palsgaard®
3
The added benefit of PGPR
Polyglycerol Polyricinoleate –
PGPR (E476) also known as
Palsgaard® PGPR 4150 is an excellent emulsifier to add when a
decreased YV is required or an increased YV to be avoided. PGPR
is mainly reducing the YV in the
chocolate and is therefore always
used in combination with either
lecithin or Palsgaard® AMP 4448 to
achieve a pumpable product with a
low YV. To read more about PGPR
and its functionality please look at
the end of this article**.
One could say that the functional
effect of PGPR on the YV in chocolate is the opposite of the effect of
adding water, and therefore PGPR
will be ideal for ice cream coatings.
Graph 2 shows the increase in viscosity at shear rate 2 [1/s] (speed
of the chocolate) when applying
various amounts of ice cream mix
to a coating containing 0.7% lecithin or Palsgaard® AMP 4448 and
0.3% PGPR (Palsgaard® PGPR
4150).
When adding the mixture of lecithin and PGPR, the thickening
effect of the added ice cream mix
is reduced very much compared
to the ice cream coating with no
emulsifier added. The thickening
effect at higher water content has
been reduced by adding both lecithin and PGPR.
Graph 2: Rheology on ice cream coating - The effect of added water.
3500
0.7% lecithin +
0.3% Palsgaard® PGPR 4150
0.7% Palsgaard® AMP 4448 +
0.3% Palsgaard® PGPR 4150
1% ice cream mix
2% ice cream mix
3000
2500
2000
mPa∙s
AMP 4448 is delaying the increase
in the measured value – or in other
words delaying the thickening effect caused by the increasing water content in the coating during a
production day. When lecithin or
Palsgaard® AMP 4448 is added to
chocolate it will reduce the plastic
viscosity more than the YV, and as
water especially increase the YV,
lecithin and Palsgaard® AMP 4448
on its own seem to be a feasible
but not an optimal solution.
1500
1000
500
0
0% ice cream mix
It is interesting to see that the mixture of Palsgaard® AMP 4448 and
Palsgaard® PGPR 4150 show no or
only a little thickening effect when
adding the ice cream mix to the
ice cream coating. When adding
this combination, the coating will
be very robust towards increases
in water content, and this clearly
shows that it will be stable and uniform during a production day.
In the conclusion examples of additional use of coating as a result
of the higher measured values are
shown.
actual Application tests:
The curves clearly show the differences in the rheology at various
water contents and emulsifier additions but it is difficult to imagine
what these differences mean in an
actual production.
To convert the differences shown
in the graphs, we have conducted
a series of realistic application
tests. The method and results are
described in the following:
Test setup: An ice cream coating
base is produced, emulsifiers and
the defined amount of ice cream
mix (1 and 2%) added. The temperature of the ice cream coating is
kept at a dipping temperature of 37°C.
Palsgaard Technical Paper - August 2012
Moisture caused problems in ice cream coating - a problem of the past
The ice creams are kept at minus
18°C. A series of ice creams are
taken out of the freezer, weighed
– dipped and weighed to establish
the average amount of coatingpickup. Typical ice cream coating
pickup on this type of ice cream lollies is approximately 6.5 grammes
- equivalent to approx. 25 w/w %.
The aim of the test is to imitate
the possible changes in ice cream
coating-pickup during a production
day.
The recipe shown below in table
1 containing approx. 60% fat is
designed to give a thin and crispy
layer on moulded ice cream and is
a good and realistic test recipe for
the following trials. Recipes based
on speciality fat or cocoa butter will
provide similar test results.
Results of dipping tests
Graph 3 shows the result of the
dipping tests and this enable us
to compare the viscosity analysis
with the actual results of the dipping operation.
Table 1: Recipe of ice cream coating base
Ingredient
%
Cocoa Powder – low fat
10
Skim milk powder
3
Sugar
28
Coconut oil
50
Rape seed oil
9
4
This will both confirm the importance of the rheological analysis
and confirm the importance of having a stable and robust ice cream
coating.
Graph 3: %Pick up of ice cream coating - dipping test
45
0.7% lecithin +
0.3% Palsgaard® PGPR 4150
0.7% Palsgaard® AMP 4448 +
0.3% Palsgaard® PGPR 4150
1% ice cream mix
2% ice cream mix
40
1. When adding emulsifiers to
the high fat ice cream coating the measured value will be
lower – especially when adding PGPR. This is not reflected
in the dipping trials where the
pick up of ice cream coating is
very similar when no ice cream
mix is added.
2. When adding moisture to an
ice cream coating containing
no emulsifier, both the measured value and the coatingpickup increase dramatically
(from 25.4% to 40%)
3. The addition of lecithin and
Palsgaard® PGPR 4150 makes
the ice cream coating more
resistant against increasing
moisture content and the resulting thickening effect has
been reduced. The coating
pickup gradually increase from
25.5% to 30% - which, calculated on the ice lollies used
in the trial, result in 15 - 30
kg additional expensive coating/1000 litres of ice cream
4. The addition of Palsgaard®
AMP 4448 and Palsgaard®
PGPR 4150 shows the most
efficient effect as the average increase when gradually
adding up to 2% ice cream
mix was only from 25.8% to
26.8%. This result in only 0 –
7 kg additional use of coating
per 1000 l ice cream ensuring
a good stable and economic
production run
% ice cream coating pickup
It is interesting to see that the results of the dipping tests follow the
results of the rheological results
very well and we can therefore list
following from the tests:
35
30
25
0
0% ice cream mix
Conclusion
Ensuring a smooth and uniform
production flow when producing
coated ice cream will always be
based on optimal process parameters such as speed, very cold
ice cream, correct coating fat and
temperature. As seen even small
changes in the water content of
the ice cream coating has a quite
dramatic effect and therefore the
correct use of emulsifiers can assist in minimizing this effect. An
addition of a mixture of Palsgaard®
AMP 4448 and Palsgaard® PGPR
4150 has proven to be the best
combination to make a very robust
and uniform ice cream coating.
This means that within the realistic
water content this mixture will secure a uniform ice cream coating
with no thickening effect during the
entire production day.
Palsgaard Technical Paper - August 2012
Moisture caused problems in ice cream coating - a problem of the past
Contact details
For more information on the abilities of Palsgaard® AMP 4448 and
Palsgaard® PGPR 4150 in ice
cream coatings please contact:
Product & Application Manager
Arne Pedersen at [email protected]
or tel +45 7682 7682
To order samples of the above
products please visit www.
palsgaard.com to find your local
sales representative.
Literature reference:
(Click on titles to access the articles
online) or visit www.palsgaard.com/
downloads
* Emulsifier YN – the unique ingredient
** The importance of rheology in
formation and emulsifier functionality in chocolate production.
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