FAC U LTY O F SC IE NC E
UN IVE RS ITY OF CO PENHAGE N
ANALYSIS OF AROMA COMPOUNDS OF ROSELLE BY
DYNAMIC HEADSPACE SAMPLING USING DIFFERENT
METHODS OF SAMPLE PREPARATION
NURUL HANISAH JUHARI, Camilla Varming and Mikael Agerlin Petersen
University of Copenhagen, Department of Food Science,
Dairy, Meat and Plant Product Technology Section, Rolighedsvej 30,
DK-1958, Frederiksberg C., Denmark. [email protected]
INTRODUCTION
Figure 4: Chromatogram of Roselle prepared as GD (left) and GMW (right) determined by
100
GC-MS.
90
CONCLUSION
 The ground and then mixed with
water (GMW) sample is chosen to
be the type of sample preparation
for further analysis of aroma of
Roselle.
 Reasons:
it
gives
efficient
extraction, ease of handling, and
ability to use internal standard.
Total number of compounds for each class
 Roselle (Hibiscus sabdariffa L.), is one of several underexploited
food crops with nutritional and food processing potential.
Utilization of Roselle flower as a food product is still meagre but
has economic potential (Figure 1).
 Sample preparation is often overlooked and is frequently
considered as ‘a means to an end’. Nowadays, there has been
impressive advancement in spectrometry and chromatographics
instruments for analysis of aroma and flavour (Luthria &
Mukhopadhyay, 2006).
 Different sample preparation methods may lead to differences in
the profile thus care must be taken to avoid sampling procedures
which may alter the substances being studied.
Figure 1: Photo  Objective: to determine the influence of different methods of
of plants and
sample preparation on the aroma profiles of dried Roselle flower.
Roselle flowers.
80
70
terpenes
others
60
lactones
ketones
50
furans
40
esters
aldehhydes
30
alcohols
20
acids
10
0
WD
GD
BTW
GMW
GMWKB
Different Methods of Sample Preparation
Figure 6: Total numbers of volatile
compounds for each class in Roselle
determined by GC-MS.
Figure 2: Different methods of sample
preparation.
Figure 3: Dynamic headspace sampling setup.
MATERIALS AND METHODS
 Samples were prepared by five different procedures: whole dry (WD), ground
dry (GD), blended together with water (BTW), ground and then mixed with water
(GMW), and ground and then mixed with water and kept in water bath
(40°C/2hr) (GMWKB) (Figure 2).
 Oven dried Roselle of the UMKL cultivar obtained from Malaysia was chosen to
study aroma profiles by using dynamic headspace sampling (Figure 3), and GCMS analysis (Figure 4). All samples were analysed in duplicate.
 Multivariate analysis (principal component analysis) was applied to GC-MS data
to evaluate the variation between the different sampling techniques (Figure 5).
RESULTS AND DISCUSSION
 A total of 125 compounds were identified using GC-MS.
 Compounds identified included terpenes (32), aldehydes (20), esters (16),
ketones (14), alcohols and furans (13), acids (9), sulphurs (3), lactones (2) and
others (3) (Figure 6).
 Different sample preparation of Roselle affected the amounts of aroma recovered
(Figure 5). Least amounts of aroma compounds were recovered in WD followed
by GD, BTW and GMW (Figure 6). The highest number of aroma compounds
was found in Roselle treated as GMWKB, probably partly due to release of
glycosidically bound volatiles.
 This may be because the GMWKB treatment facilitates the swelling and hydration
of plant materials, which improves the rate of mass transfer and breaks the cell
walls, resulting in increased extraction efficiency (Vinatoru, 2001) but also the
prerequisites for the enzymatic or chemically facilitated release of terpenes.
 Furans (2-pentylfuran, 2-acetylfuran, furfural) may be produced from the drying
process mainly the thermal processing.
 GMW was chosen as the preparation method because it was shown to be an
efficient extraction method without the possibility of excessive chemical changes
of the sample.
Figure 5: Principal component analysis (PCA) scores and loadings plot of Roselle
volatiles.
ACKNOWLEDGEMENT
This study was financially supported by the Ministry of
Education Malaysia and University Putra Malaysia.