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Chocolate Production Technology – Part 1

Optimal Flavor Development

Depending on the specific context, the consumption of chocolate is characterized in "emotional",
"sensory" or "physiological" terms. Various authors have published scientific reports on the factors
determining flavor development during chocolate production. In earlier works, Heiss et al and – later
on – Ziegleder investigated how preliminary flavor development stages and AMADORI compounds in
the cocoa as well as the conching process contribute to flavor development. But beside flavor
development, it is also necessary to give consideration to the structural changes taking place from
the basic materials (liquid, powdered) to the flowable chocolate mass. Early on, Finke, Niediek, Roth
and Sommer pointed to the wide variety of influencing factors involved. Their findings and additional
research results [1, 2, 3] contributed significantly to broadening our knowledge of the factors
influencing the structural development of chocolate during conching.
A number of examples will show how such scientific findings can help optimize the development of
the chocolate flavor and structure in industrial chocolate production by the application of adequate
processes and production equipment.

Exploiting the entire

flavor potential of the cocoa
From a number of works we know that cocoa can be subjected to treatments – for example using glucose solutions – to
improve flavor development by better utilization of the existing amino acids [4, 5].
One of the most important points to be observed in such a treatment is to ensure intensive contact between the educts.
The crucial factor determining whether this can be achieved is the accessibility of the reacting components. Cocoa mass
appears to be better suited for this purpose than nibs. This becomes apparent when we look at the microstructure of the
cocoa particles present in the cocoa mass (see Fig. 1).

Fig. 1: Microstructure of ground cocoa nibs (defatted sample)

The microstructure of the cocoa particles present in the cocoa mass favors the reaction process. Therefore, contact be-
tween the cocoa particles and the glucose solution should preferably take place during or just after grinding. One possi-
ble process flow is shown in Fig. 2.
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Geröstete Kakao Nibs

Beigabe von
Glucoselösung

Prall- und Kugelmühle Lagertanks

Schermühle Nova 2000
SCBA
Fig. 2: Process diagram for glucose injection during cocoa mass production

The glucose solution is injected as early as during the pregrinding stage.

Investigations of cocoa masses of different origin have shown how glucose treatment influences the cocoa flavor. Among
other factors, the development of the cocoa flavor depends on the reaction degree of the existing amino acids. The fu-
rosin content serves as a measure for this. It is also a reaction indicator for the early Maillard reaction stage.

The following discussion reports the results of production-scale tests. The tests were performed according to the process
shown in Fig. 2. The cocoa beans used were from two different production regions (Ivory Coast, Ghana).

Fig. 3 shows the furosin contents as a function of the glucose solution concentration and the treatment time for the differ-
ent cocoa varieties (Ivory, Ghana). It is evident that the glucose treatment enables the furosin contents to rise apprecia-
bly. The striking fact here is that different furosin contents are already found in the untreated cocoa mass, depending on
the origin of the cocoa. But selective glucose treatment allows the furosin content to be increased to the point where it
reaches the value of untreated cocoa mass of different origin. This becomes evident when we compare treated Ivory mix
with untreated Ghana.
80 84.3 3.0%

70 2.4% 2.6%
2.4% 2.5% 2.5%
Fu rosin [mg/100g]

Feuchteg ehalt [%]

60 2.1%
2.0%
50

40 1.5%

30
33.3 1.0%
31.3 27.9
20
0.5%
10 23.8

8 7.8
0 0.0%
20
2O

20

2O
se

se

se
H
H
co

co

co
H

H
1%
7%
7%

7%
lu

lu

lu
G

G
0.
0.

0.
+
e

e
c.
+
+

+
n

hn

hn
c.

lu
oh

c.

c.
o

o
lu

G
lu

lu
G
G

5%

G
1%
0%

1%
1.
1.

Fig. 3: Influence of glucose injection on the furosin contents of different cocoa varieties

The kinetiks of the reaction are of special interest. The contact time in the grinding chamber is less than 60 seconds. But
despite this fact, the furosin content is multiplied as a result of the intensive contact inside the grinding chamber. On the
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other hand, subsequent treatment in the form of tank storage at 80°C will not increase the furosin content significantly
(see Fig. 4). Therefore, treatment during the grinding stage is a very favorable process variant.

2.9%
40 2.8% 3.0 %

35
2.3%
2.5 %

Feuchtegehalt [%]
Furosin [mg/100g]

30
34.6 33.3 2.0 %
25 1.7%

20 1.5 %
1.2%

15
17.6 17.2 1.0 %
10
0.5 %
5
6

0 0.0 %
e

2O

oC

2O

oC
os

80
H

60
c
lu

3%

7%
@

@
G

1.

2.
h
e

h
12
hn

12
+

+
c.

c.
o

ch

ch
lu

lu
na
G

na
7%

3%
0.

1.

Fig. 4: Influence of the contact time on the furosin content

Additional comparisons were made between milk and dark chocolates on a pilot scale (200 kg) as well as with a milk
chocolate (produced in industrial quantities). They confirm that it is easy to distinguish between the flavors of dark choco-
lates made from treated and untreated cocoa mass. Even with full-milk chocolate, appreciable differences were still
found to exist in a triangle test (significance in the triangle test p = 5%).

These results indicate that glucose treatment of the cocoa in the intensive processing zone of an impact and shear mill is
a promising process option, and that it can be integrated economically in the cocoa grinding process.

Particle size reduction —

preliminary stage to conching
Apart from the roasting of cocoa, conching of the chocolate is generally considered to be the pivotal process determining
flavor development. But when we consume chocolate, our sensation is determined not only by the analytical flavor con-
tent, but mainly by the availability of the flavor substances. This means that also the structure of the particles and their
wetting with cocoa butter determine the sensory quality. The nature and the characteristics of these particles are already
significantly influenced by the method of size reduction applied in chocolate production. Fig. 5 shows the structure of
particles contained in milk chocolate. The sample was prepared by sieving and defatting.
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Fig. 5: Structure of particles contained in milk chocolate

During size reduction in the grinding gap, enormous pressures, shear forces and „energy shocks“ act upon the solids (in
contrast, for example, to dry grinding or bead mill grinding). This not only reduces the particles, but also significantly pre-
pares their surface structures for the further development of flavor availability.

Chocolate Production Technology – Part 2

Optimal Flavor Development

In Part 1, we saw how glucose addition influences the development of the cocoa flavor. But during chocolate production,
other factors also play a crucial role. These include the types of raw materials used, the production process, the amor-
phization of the sugar, and control of the conching process.
We will now continue by looking at the production process.

We know that the cocoa and milk solids are the main flavor carriers of chocolate. But because the sugar particles ac-
count for about two thirds of the solids in standard milk chocolate, the flavoring of the sugar is extremely relevant to the
production process. This has already been pointed out by Niediek.
DSC analyses of the sugar crystals contained in refined milk chocolate clearly show that the condition of the sugar sur-
O O
faces changes in the two-stage refining process. Onset reductions of 42 - 45 C and Peak reductions of about 25 C are
caused by faults in the crystal lattice structure, or by amorphous structures and possibly the creation of mixed crystals of
the sugars (saccharose, lactose). But it is likely that the flavor substances form only part of all the substances adsorbed
by the sugar.
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DSC Vergleich mit ungewalztem Zucker

Kristallzucker:
Onset = 188.4 oC
Peak = 190.4 oC
Delta = 2.0 oC
Enth. = 134 J/g
Nach Vorwalzwerk:
Onset = 148.9 oC
Peak = 169.6 oC
Delta = 20.7 oC
Enth = 88 J/g

Nach Feinwalzwerk:
Onset = 143.7 oC Gemahlener Zucker:
Peak = 164.7 oC Onset = 187.3 oC
Delta = 21.0 oC Peak = 189.3 oC
Enth. = 92 J/g Delta = 2.0 oC
Enth. = 133 J/g

Fig. 6: DSC measurements of saccharose, ground saccharose, prerefined and refined chocolate

Size reduction creates highly hygroscopic, amorphous sugar surfaces. They adsorb water from their direct environment
and may then recrystallize by releasing water, thanks to the increased mobility of the molecules [6]. On the basis of the
prerefining and refining quality, i.e. the size reduction method and parameters, it is then possible to determine whether
water absorption and release takes place internally (with simultaneous adsorption of flavor substances, for example from
the milk powder or cocoa) or externally in the environment.
Proper prerefining and refining as a flavor-enhancing preliminary stage to conching limits the common moisture increase
from the environment to 0 - 0.1 % H2O. Improper size reduction or refining, combined with a humid ambient climate,
makes water increase rates of 0.3 - 0.5 % (in extreme cases up to 1 %) likely. Such high values significantly impair the
basic conditions for the conching process.
To date, alternative size reduction methods in milk chocolate production have not allowed the same sensory, structural
and rheological characteristics to be achieved with a given fat content as those obtained by the two-stage refining proc-
ess.

Conching —
synergy with the grinding gap
In his investigations, Dr. G. Ziegleder has made a number of interesting observations on the wide variety of chemical
reactions taking place in the conche and influencing the flavor as well as the taste [7].
When re-examining the individual particles, interesting synergies are found to exist in the conche – in addition to the pro-
cess functions of the reactor – with the above-mentioned functions of the roll gap.
The scanning-electron micrographs of cocoa particles after conching as well as multi-phase system models show that
the applied shear forces have a major impact on the development of the rheological characteristics and flavor availability.
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vor dem Conchieren nach dem Conchieren

Kakao-
Kakao- Kakao-
Kakao-
partikel partikel

Aroma x Kakaobutter Aroma x Kakaobutter

Fig. 7: Model explaining release of immobilized flavor during conching

According to the model, the flavor-bearing components entrapped in the cocoa are released under the action of the
shear forces and transferred to the surrounding phase.
As a result of the different structures and their wetting, chemically identical chocolates may have different flow character-
istics and induce different taste sensations. Shear forces are doubtlessly more efficient in disagglomerating the particles
than compressive forces, and therefore also in releasing the surfaces necessary for reactions. To obtain a good flavor
development, however, the gas balance is just as important. Care must be taken to ensure an adequate inner product
surface in conjunction with aeration and deaeration. Today, this process knowledge is already being successfully applied
on an industrial scale. For different chocolates, comparisons between conventional process technology (Frisse DÜC) and
systems using higher shear forces (Frisse DÜC-G) show clear rheological differences for a given recipe (Fig. 8).

90 18

80 16
Fliessgrenze (Pa) Viskosität (Pas)
70 -x- Kneten (DÜC) 14 -x- Kneten (DÜC)
-o- Scheren (DÜC-G) -o- Scheren (DÜC-G)
60 12

50 10

40 8

30 6

20 4

10 2

0 0
Dunkel Dunkel Dunkel Dunkel Dunkel Dunkel Milch Dunkel Dunkel Dunkel Dunkel Dunkel Dunkel Milch
22.4% 23% 23% 22.1% 35% 48% 35% 22.4% 23% 23% 22.1% 35% 48% 35%
Fett Fett Fett Fett Fett Fett Fett Fett Fett Fett Fett Fett Fett Fett
1) 1) 2) 3) 2) 3) 1) 1) 2) 3) 2) 3)

1) 5% Molke, 2) 0.1% PGPR, 3) Kristalline Laktose. Gleiche Walzmassen und gleiche Conchierzeiten.
Fig. 8: Influence of higher shear during conching on the flow characteristics

Simple modifications allow existing conventional machines of type DÜC to be converted to the DÜC type G with in-
creased shear.
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According to our model, these parameters have a positive effect on the finished chocolate, which is borne out by the
associated analysis results. The interesting point here is that the flavoring effects are intensified as the continuous phase
decreases, i.e. with lower fat contents. With high fat contents, the interactions between the particles tend to be mitigated
as a result of the larger distances involved.

Abstract
A number of authors have published scientific reports on the factors determining flavor development in chocolate produc-
tion. Buhler has given consideration to such suggestions in its process technology and production equipment. It has
thereby generated new knowledge and results for industrial chocolate production:
It is a well-known fact that cocoa can be treated with glucose solution to better utilize the existing amino acids. The as-
sessment of the furosin contents as indicators of the early Maillard reaction stage and the sensory appraisal of corre-
sponding chocolates show that these goals can be achieved with the least effort by very intensive contact between the
educts and brief temperature peaks during cocoa grinding in the grinding gap of impact and shear mills.
Microscopic observations allow size reduction processes to be assessed. Measurements of porosity, DSC, moisture and
rheology have shown it to be possible to decisively further develop the established two-stage refining process and
conching by applying optimally adjusted process parameters enhancing economy and end product quality.

Literature:
[1] Tscheuschner, H.D.: Neue Erkenntnisse über physikalische Vorgänge beim Conchieren, Zucker and Süsswaren-
wirtschaft, 2 (1995)
[2] Ziegler, G.: Changes during conching, Congress on chocolate technology, ZDS, Cologne (1998)
[3] Braun, P.: Water sorption and its effect on flowing of chocolate, ZDS, Cologne (2000)
[4] Ziegleder, G.: Aromaentwicklung in Kakao, Süsswaren 9 + 10 (1996), 22 – 24 + 60 – 62.
[5] Cros, Emile: Torréfaction, Cacao et Chocolat Production Utilisation Caractéristiques, 254,
1998, ISBN: 2-7430-0174-7
[6] Hartel, R.W., Shastry, A.V.: Sugar Crystallization in Food Products, Critical review, Food Science and Nutrition,
1991, 20(1)
[7] Ziegleder, G.: Aromaentwicklung beim Conchieren, Süsswaren 11 + 12 (1997), 44 - 46 + 20 - 22.

Authors:
Dipl.-Ing. Edi Boller,
Head of Chocolate / Cocoa business unit of Bühler AG, CH-9240 Uzwil
Dr. Peter Braun
Head of Technology of the Chocolate / Cocoa business unit of Bühler AG, CH-9240 Uzwil