Juice turbidity and fermentation method: key drivers of aroma complexity in Italian Riesling grape spirit production

Juice turbidity and fermentation mode are key factors affecting aroma formation in grape spirit production, but their combined effects remain unclear. In this study, Italian Riesling juice under two turbidity conditions (clear and turbid) was fermented either spontaneously or with commercial yeast, generating four treatments. Physicochemical properties, volatile compounds, odor activity values, and sensory characteristics of base wines and grape spirits were compared. Both factors significantly influenced base-wine composition and these differences were reflected in the distillates. Spontaneous fermentation increased aroma diversity and complexity, whereas inoculated fermentation produced a more uniform volatile profile. Clear juice favored floral and fruity esters, while turbid juice promoted fermentation-derived aroma precursors. Distillation further amplified treatment-dependent volatile differences, resulting in distinct aromatic styles. These results show that juice turbidity and fermentation mode jointly shape aroma development from fermentation to distillation and provide guidance for targeted aroma modulation in Italian Riesling grape spirit production. • Juice turbidity and fermentation mode jointly shaped the aroma profile of grape spirits. • Spontaneous fermentation increased aroma diversity and overall compositional complexity. • Clear juice favored the formation of floral and fruity aroma-active esters. • Turbid juice promoted fermentation-derived precursors associated with aroma richness. • Distillation amplified treatment-dependent differences in volatile composition.