Aroma changes in Chardonnay and Riesling base wines caused by the second fermentation were investigated by a targeted component analysis: A stable isotope dilution approach using headspace solid phase microextraction coupled online to gas chromatography mass spectrometry (HS-SPME-GC-MS) was applied to quantify 37 compounds relevant for sparkling wine aroma. In an enrichment experiment, glycosylated precursors isolated from one Chardonnay and one Riesling base wine were used to double the original amount in these base wines. Along with increased concentrations of precursor-derived volatiles after the second fermentation, descriptive sensory evaluation revealed an enhancement of fruity aroma impressions reminiscent of, for example, peach or cantaloupe. Except for benzyl alcohol, linalool, and 3-methylpentanol, no quantitative 2-fold increase of volatiles was found with a 2-fold increase in precursor concentration, as other metabolic pathways seem to interfere with aroma formation from glycosides.