engleski

Determination of indole-3-acetic acid in Malvasia from Istria grape and wine

The phenomenon of untypical aging off-flavor, which is associated with higher concentrations of 2-aminoacetophenone (2-AAP) in white wines, can stem from some technological treatments applied in grape and wine production. In order to find out if a wine is liable to untypical aging off-flavor, it is necessary to determine the concentrations of indole-3-acetic acid and L-tryptophan, which are the precursors of 2- aminoacetophenone. The purpose of this investigation was to determine the influence of soil type and different yeast strains on the levels of L-tryptophan and indole-3-acetic acid in the grapes and wines of Malvasia from Istria. Grapes were harvested from two different soil type locations in Istria wine growing region and separately vinified according to the technology customary for white wines. Young wine samples were taken for analysis immediately after completed alcoholic fermentation. The investigation included the development and validation of the method for determining the levels of indole-3-acetic acid and L-tryptophan in must and wine by means of the liquid chromatography with fluorescence detection and a prior purification of samples by means of Solid Phase Extraction (SPE) on polystyrene- divinylbenzen columns. Luna C18 (250 x 4, 6 mm, 5 µm) was used column for component separation on HPLC. The efficiency and selectivity of two types of SPE columns (PS-DVB and MAX) were compared. Chemical analyses of compared musts and wines showed differences in L-tryptophan and indole-3-acetic acid concentrations that depend more upon the soil type than yeast strain used in this investigation.

indol-3-acetic acid; Malvasia; Istria; untypical aging off-flavor

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