Fermentation Arrest Density Modulates Congener Composition and Sensory Profile in Aromatic Grape Distillates

Stopping fermentation is a critical, yet insufficiently standardised, step in the production of aromatic grape distillates, as it influences residual sugar, yeast metabolism and the availability of volatile precursors. This study evaluated the must density at the time of fermentation arrest as a process control parameter for Torontel grape distillates. Five treatments were established by halting fermentation at densities ranging from 1.050 to 1.010 g/mL, followed by batch distillation. The distillates were evaluated using physicochemical analyses, including alcohol strength and the concentration of key volatile congeners such as methanol, acetaldehyde and higher alcohols. Furthermore, these analyses were complemented by gas chromatography with flame ionisation detection (GC-FID) and sensory evaluation by experts. Increased must density was associated with higher concentrations of methanol, acetaldehyde and higher alcohols, whereas ethanol content decreased. Although clear differences in chemical composition were observed among the evaluated process conditions, overall sensory acceptability exhibited only limited variation across the fermentation arrest densities. However, distillates obtained from intermediate density levels showed better aromatic balance and sensory harmony. Multivariate analysis suggested that fermentation arrest density was associated with the main patterns of chemical variability observed among the evaluated distillates, whereas its association with overall sensory perception appeared to be more limited. These findings provide a useful framework for optimising fermentation arrest strategies in the production of aromatic partially fermented grape distillates.