3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P43 RAPID AuThENTIFICATION OF NATuRAL
juICES by GC-MS
AnDREEA IORDACHE, MOnICA CULEA and OnUC
COZAR
Babes-Bolyai University, Str. Kogalniceanu, nr.1, 3400 Cluj-
Napoca, Romania
mculea@phys.ubbcluj.ro
Introduction
A simple and rapid GC-MS method for the detection of
adulteration of natural fruit juices is presented. The method
consists of the analysis of sterol patterns and it is a useful
rapid approach for the fruit juices control by GC-MS 1 .
A GC-MS analytical method is described for some
natural juices analysis. The fingerprint of sterols was used to
characterize the natural juice.
Experimental
A rapid liquid-liquid extraction method was used. The
fruit juices were extracted by using petrol ether as a solvent.
The fruit juice extracts were separated on a capillary column,
and identified with a mass spectrometer.
A p p a r a t u s
The sterols were separated on a Rtx-5MS capillary
column, 15 m × 0.25 mm, 0.25 µm film thickness, in a temperature
program from 50 °C for 1 min, then ramped at
15 °C min –1 to 300 °C and held for 15 min. Identification of
sterols and their patterns were used for juice characterization.
A Trace DSQ ThermoFinnigan quadrupol mass spectrometer
in the EI mode coupled with a Trace GC was used.
The following conditions were used: ion source temperature
250 °C, injector temperature 200 °C, transfer line temperature
250 °C, splitter 10 : 1, electron energy 70 eV and emission
current 100 µA.
E x t r a c t i o n P r o c e d u r e
Ethanol, fruit juice and petrol ether 2 : 2.5 : 0.4, v/v/v,
were mixed in a cap vial for 2 minutes. Then the mixture was
centrifugated 2 minutes. 1μl was injected twice into the GC.
Ethanol was used for pectine and emultion agents precipitation.
Results
Different compounds such as volatile aroma compounds,
fatty acids and sterols have been identified into the cromatograms
of the extracts of orange (Fig. 1.), grapefruit and
pineapple juices. A nIST library was used for compounds
identification from the mass spectra obtained after gas chromatographic
separation. The sterols identified from the fruits
juices were the following: cholesterol, campesterol, ergostanol,
stigmasterol, beta-sitosterol, the main sterol, isofusterol
and citrostadienol. Limonen was the main volatile compound
extracted from citrus fruits.
s665
Fig. 1. Compounds separation from orange extract
Fig. 2. presents the separation of sterols from the fruit
juice extract (orange). The fingerprint chromatograms of
different fruits differ in the concentration of this sterols, but
there are also few variation of the sterols identified in orange,
grapefruit and pineapple juices In pineapple was identified
stigmastenone at the retention time of citrostadienol
(alpha 1 sitosterol).
Fig. 2. Separation of sterols from orange extract
Table I
Sterols identified in orange juice extract
Tr [min] Compound M m/z
11.3 Valencene 204 161
14.6 nooklactone 218 147
25.3 Campesterol 400 400
25.4 Ergostanol 402 233
25.5 beta-stigmasterol 412 412
25.9 beta-sitosterol 414 414
25.97 isofucosterol 412 314
26.8 citrostadienol 426 285
Table I presents the compounds identified into the chromatogram
of the orange juice extract.
Table II presents the important ions of the compounds
identified in juices. The ratio of different peaks area from