Analysis of free and bound aroma compounds in grape berries using headspace solid-phase microextraction with GC-MS and a preliminary study of solid-phase extraction with LC-MS

An extraction procedure for the aroma compounds from musts and wines has been developed, using solid-phase microextraction (DVB/CAR/PDMS fibre) from the headspace of heated samples (50 degrees C). Analysis was performed with gas chromatography - mass spectrometry. The method was applicable to the analysis of different aroma compounds ( aliphatic, aromatic aldehydes, terpenes) in a broad concentration range (1-5000 mu g L-1). A stir-bar sorptive extraction procedure was also tested, but was not effective enough due to the lack of a suitable desorption device. Free aroma compounds in must samples of different grape varieties were analysed, and their release was evaluated after enzymatic or acidic hydrolysis. Different hydrolytic approaches were tested and the most successful was the enzymatic hydrolysis ( with two different enzymes) and acidic hydrolysis at pH 3. Acidic hydrolysis at pH 1 resulted in substantial decomposition and re-arrangement reactions of terpenes. Non-hydrolysed terpene glycosides were extracted from the musts using solid-phase extraction and the extract was analysed with liquid chromatography - mass spectrometry (electrospray interface). Some compounds were tentatively identified as terpene glycosides.