THE IMPACT OF MALOLACTIC FERMENTATION ON THE VOLATILE COMPOSITION OF THE TRINCADEIRA WINE VARIETY

Abstract

Use of commercial starters for malolactic fermentation (MLF) is a common practice, and outcomes of this procedure are very relevant for wine producers because aroma attributes might change according to the strain used. MLF was carried out in the Trincadeira wine variety in three batches: spontaneously and with inoculation of two different commercial starters. Wine extracts before and after MLF were obtained through liquid–liquid extraction. Gas chromatography/ion trap mass spectrometry analysis allowed the detection of 21 compounds, some of them tentatively identified through electron impact spectra comparison with a database, through interpretation of multistage mass spectrometry and chemical ionization mass spectrometry spectra and confirmation by comprehensive multidimensional gas chromatography/time of flight-mass spectrometry (GC × GC/ToF-MS). After MLF, an increase in ethyl lactate, γ-butyrolactone and diethyl succinate and a drop in isoamyl acetate, ethyl octanoate, ethyl decanoate, 2,3-dimethyl-hexan-3-ol, propanol, isobutanol and 2,3-butanediol was observed. The concentrations of the 10 compounds are statistically different in wines before and after MLF, and wines after MLF show significant differences for the nine compounds. PRACTICAL APPLICATIONS The Trincadeira variety is broadly used in the production of red wine in the south region of Portugal. Nevertheless, little was published concerning this red wine variety in international literature, where most frequently, the analysis of the volatile constituents of Trincadeira is not the goal. Moreover, the evaluation of the malolactic fermentation (MLF) impact produced by indigenous or selected starter bacteria on the aroma composition of the wines produced with their grapes was never studied before. The interesting behavior of this variety during MLF described in this work might possibly explain the unique characteristics of the overall bouquet produced with it. The main volatile compounds obtained after all three MLF processes were identified and quantified using gas chromatography/ion trap mass spectrometry, gas chromatography/chemical ionization mass spectrometry (GC/CI/MS) and gas chromatography/multistage mass spectrometry (GC/MS/MS) and standard coinjection. Comprehensive multidimensional gas chromatography (GC × GC) was used for confirmation purposes in all cases where standards were not available in order to also validate the results obtained by GC/CI/MS and GC/MS/MS.