Jumal of Chromatography, 391 ( 1987) 457-460
Elsevier Science Publishers B.V., Amslerdam - Prinlcd in The Netherlands
CHROM. 19 352
NoteRapid analysis of coffee flavour by gas Chromatography using a pyrolyzer
K. HARADA. O. NISHIMURA and S. MIHARA*Ogawa & Co., Ltd., 6-32-9 Akabanenishi. Kita-ku, Tokyo 115 (Japan)(Received December l6th. I986)
Gianturco1 discussed the Formation and rate or production or volatile compounds during the roasting coffee beans. As the roasting time was increased. boththe number and size or the chromatographic peaks increased. This phenomenon indicates that most components or coffee aroma arise from the roasting process1-2.
Baltes3 has recently described phenol formation during coffee rusting.
The Curie-point principle has been widely used as a method for analyzing
non-volatile materials4j. First a sample is rapidly heated to a temperature that issufficient to decompose it to volatile substances. These are then analyzed by gas
chromatography (GC). Colenutt and Thorburn6 adopted a conventional pyrolysis
GC system for the analysis or volatile compounds. In their system, desorption isachieved in the pyrolysis unit, but no pyrolysis occurs.
This paper presents a simple and rapid method for analyzing the flavour orcoffee grounds using a gas chromatograph equipped with a pyrolyzer. The results
obtained with this method were compared with those from conventional methods.
i.e., headspace analysis and simultaneous distillation-extraction (SDE).
EXPERIMENTAL
Gas chromatography
A 50-m fused-silica capillary column (0.22 mm Lb.) corted with Carbowaib
20M was used to separate volatiles transferred lo the column through the splitter
injection port. The splitting ratio was adjusted to 1:50 with carrier gas -(nitrogen) at
22 p.s.i.The linear flow-rate was 42 cm/s and the column fow-ratle was 2.0 ml/min.
The injection port tempera4l.fe was 200'C. The column temperature was increased
from 80 to 200℃ at 2℃/min.The gas chromatograph used was an Hitachi Modell63 equipped with a flame ionization detector heated to 250℃.
Gas dhromatography-mass spectrometry ( GC-MS)
An. Hitachi Model M-80B mass spectrometer-gas chromatograph (HitachiModel 663) equipped with an Hitachi Model.0101data System was used under thefllowing conditions: ionization voltage, 70 eV ; emission current,80μA; ion accel-eration voltage, 3100 V; ion-source temperature.200℃.

Curie-point pyrolyzer
volatiles w-ere removed from a ca. 10-mg sample of Colombian Arabic coffee
grounds by heating at 235℃ in a ferromagnetic sample support in the pyrolyzer. The
total heating time was 3 s. The pyrolyzer can easily be connected to the original
injection port or the gas chromatograph or the gas chromatograph-mass spectrometer unit.
Headspace sampling
A 150-g amount or coffee grounds was placed in a 500-ml headspace vessel
equipped with an Allihn condenser. The trapping column (l70 mm × 6.4 mm LD.)
containing ca. 2 g or Porapak Q (60-80 mesh) was fixed to the top end of the Allihn
condenser. A 400-ml volume of water at 70℃ was poured into the vessel. The extraction or the coffee grounds and the trapping or headspace volatiles were carriedout in a water-bath at 70℃ stirred at a constant rate. The headspace vessel waspurged for 2.5 h by the passage of nitrogen at a flow-rate of 240 ml/min. The entrapment column was reversed 7 and heated at l80℃ for 0.5 h. The volatiles collectedin the trapping were then backflushed to a glass trap chilled with solid carbon dioxide 7. The trap was rinsed with 30 μl of diethyl ether. This permitted efficient transferof the trapped volatiles into a vial for storage until analysis.

Simultaneous distillation-extraction (SDE)
A Nickerson-Likens extractor as modified by Schultz el al.8 was used. A 400-g
amount of coffee grounds in 11 of water was added to a 2-1 flask, and 150 ml ofdichloromethane were added to a 300-ml flask. The distillation head was attachedand then both masks were heated to boiling. The distillation was carried out for 6 hat atmospheric pressure. The extract was dried over anhydrous sodium sulphate forl2 h and then evaporated to ca. 0.5 ml for instrumental analysis.

RESULTS AND DISCUSSION
Fig. I shows a gas chromatogram of the volatiles from coffee grounds obtainedin the Curie-point pyrolyzer at 235℃. When the pyrolyzer was used at different
heating temperatures ranging from l70 to 235℃ (total heating time per sample: 3 s).
the qualitative composition of the volatiles from the coffee grounds did not change.
The effuent gas From the outlet or the pyrolyzer had a coffee -like odour. Since theabove heating conditions arc much milder than the roasting. conditions used forcoffee beans (I80-215℃ for I5-17 min or 260℃ for 5 min)2, the influence or thepyrolysis or the coffee grounds may be neglected in the analysis or the volatiles. The
mixture or compounds in Fig. 1 was analyzed by GC-MS and ideIIti6ed by comparing MS and retention time data with those or individual compounds.
The headspace analysis (adsorbent trap) (Fig. 2) and SDE methods (Fig. 3)

were chosen in order to compare the results for the qualitative analysis or volatilecompounds from coffee grounds. The dependence or the headspace method on compound volatility is obvious. The peak area % drops off quite quickly as the vapour
pressure or the compound decreases.
The SDE method gave very good recoveries 9. Its disadvantages include theproblems or the solvent front overlapping with low boiling compounds and artifact
formation due to thermally induced change. Changing to SDE had a very negative
effect on the recovery or polar substances. e.g., acetic acid (peak l3).
The. pyrolyzer method amount a very simple and efficient means of isolating
flavours from a very small amount of coffee grounds. It is possible to analyze both
low boiling compounds, e.g., acetaldehyde (peak 1) and acetone (2) and high boilingcompounds, e.g., guaiacol (22) and phenol (23) using the pyrolyzer method, as shownin Fig. 1. Consequently. this method is very simple and useful for the analysis offlavour compounds in food.