3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P107 COMPARISON OF AROMA PROFILES OF
SEVERAL TyPES OF DARK ChOCOLATE
eVA VíTOVá a , BLAnKA LOUPAnCOVá a , HAnA
ŠTOUDKOVá a , JAnA ZEMAnOVá a , LIBOR BABáK a
and IVAnA MACKů b
a Faculty of Chemistry, Brno University of Technology
Purkyňova 118, 612 00 Brno, Czech Republic,
b Faculty of Technology, University of Tomas Baťa, T.G.
Masaryk square 588, 760 01 Zlín, Czech Republic,
evavitova@post.cz
Introduction
Chocolate (CHC) aroma has been the subject of extensive
research. Most of the research work deals with cocoa
beans, powder, liquor and CHC. CHC aroma is very complex
and is determined by the cocoa plant variety and the fermentation
and roasting process. Unfermented cocoa beans are
nearly without odour and have a bitter and astringent flavour.
Cocoa specific aroma precursors are formed during fermentation
by acid induced proteolytic processes 1 . Correct fermentation
is essential to produce a good flavour in the final CHC.
The different ways of fermenting will give rise to different
flavour, unfermented beans do not develop any CHC flavour
and are excessively astringent and bitter 2 .
The following roasting decreases water content and a
full CHC flavour is developed. The high temperatures remove
many of the volatile acids and other aroma compounds are
formed, in particular as a result of caramelization of sugars,
Maillard reaction, protein degradation and sulphur compounds
synthesis. The sources of hundreds of volatiles found
in roasted beans are the reducing sugars, free amino acids
and oligopeptides 3,4 . Several hundreds compounds have been
found in roasted cocoa, the most significant are n- and Ocontaining
heterocyclic compounds – alkylpyrazines, furans
and pyrroles. Roasting is the most important step for flavour
development, it is possible that cocoa subjected to an improper
roasting generates undesirable aroma 5 .
Finally, conching ends flavour development. The conching
is the mixing and shear of the CHC and results in the
removal of some undesirable volatiles 2 .
Current European legislation allows the addition of vegetable
fats to CHC up to a level of 5 % of the product weight,
provided that the addition is indicated on the label 6 . However,
this addition can influence flavour of CHC. The aim of this
work was to compare aroma profiles of three types of dark
CHC, produced with or without addition of vegetable fat.
Experimental
S a m p l e s
Three types of plain CHC: Figaro plain CHC (min. 48 %
cocoa), Figaro for cooking (min. 37 % cocoa) and Kaumy
CHC glaze (min. 35 % cocoa) were tested in this work.
s817
M e t h o d s
Aroma compounds were determined by the SPME-GC.
The SPME fibre CAR/PDMS 85 μm, extraction 20 min
35 °C. GC conditions: gas chromatograph TRACE GC
(ThermoQuest Italia) equipped with FID and split/splitless
injection port, DB-WAX capillary column (30 m × 0.32 mm
× 0.5 μm). The injector 250 °C, splitless mode, the desorption
time 5 min, linear purge closed for 5 min. The detector
220 °C. The carrier gas (n 2 ) 0.9 ml min –1 . The oven temperature
program: 40 °C, 1 min, 5 °C min –1 to 200 °C, 7 min.
Results
SPME-GC was used for the analysis of volatile aroma
compounds in three types of dark CHC with different content
of vegetable fat. This method is simple, rapid and very
mild, so it is suitable for the characterization of the food
aroma. The reproducibility, linearity and detection limits of
the method were determined in previous work 7 . Aroma active
compounds were identified and quantified using standards, in
total 56 compounds were found in CHC samples: 14 acids,
9 aldehydes, 8 ketones, 17 alcohols, 7 esters and 1 nitrogen
compound. According to the literature, the main cocoa flavour
components are alcohols, ethers, hydrocarbons, furans,
thiazoles, pyridines, acids, esters, aldehydes, imines, amines,
oxazoles, pyrazines and pyrroles 5,8 .
The total contents of aroma compounds of CHC tested
were compared. This comparison is presented in Fig. 1. The
comparison of single groups of compounds is in Fig. 2.
Figaro plain CHC is classic CHC, produced without
addition of vegetable fat. In total 50 aroma compounds were
identified in this type of CHC, the most abundant were ethanol,
propan-1-ol, butan-2,3-diol and phenylacetaldehyde.
These compounds arise during fermentation of cocoa beans
by the activity of present microflora 3 .
Figaro for cooking is plain CHC, intended for making of
various CHC sweets, glazes etc. It contains certain amount of
vegetable fat up to 5 %. In total 47 compounds were identified
here, the most abundant were methanol, ethanol, propan-1-ol,
butan-2,3-diol, acetic acid, acetone and phenylacetaldehyde.
Kaumy is CHC imitation, in which cocoa butter is completely
replaced by vegetable fat. Although its appearance is
very similar to CHC, different fat influences taste, it is not so
delicious thus is not suitable for direct consumption. Kaumy
is best for making of CHC sweets, where its unpleasant off
flavour is not so obvious. In total 46 aroma compounds were
found here, the most abundant were methanol, ethanol, propan-1-ol,
butan-2,3-diol and acetic acid.
All types of CHC contained the significantly high concentrations
of alcohols and fatty acids (Fig. 2.). The highest
content of alcohols and also quite high content of fatty acids
was in Kaumy glaze, so several these compounds probably
contribute to its unpleasant off flavour. Kaumy surprisingly
had also the highest total content of aroma compounds
(Fig. 1.), plain CHC, which is supposed to have the best
cocoa flavour, the lowest.