Head Space Gas Chromatographic Method Using the Internal Standard for Determination of Aroma of Roast and Ground Coffee

Studies on aroma of coffee (Part 1)

Abstract

An internal standard method for the gas chromatographic head space analysis of the aroma of roast and ground coffee was developed as follows. Five grams of ground coffee was weighed into a 20 ml glass vessel. The vessel was sealed with the silicon rubber septum which hung a filter paper strip (1×2cm). Five μ1 of the internal standard solution (sec-butanol, 3% in benzylalcohol) was injected onto the paper strip with a microcyringe. After equilibration at 30°C for 60 min, 0.1 ml of the head space gas was applied to a gas chromatographic method. 1) The internal standard substance was in adsorption equilibrium when the vessel was incubated at 30°C for 60 min. 2) The relative amount of the aroma based on a relative peak height (sec-butanol=1.00) was little influenced by temperature. 3) A linear relationship existed between the amount of internal standard substance and its peak height. 4) The reproducibilities based on the coefficient of variation ranged from 3.2% (propionaldehyde) to 10.0% (n-hexane) for quantitative analysis of the aroma constituents in the head space gas. 5) The aroma characteristics and the changes of the flavour during storage of ground coffee were studied by comparison of the relative concentration of ten constituents in the headspace gas.