Effects of Controlled Partial Fermentation on the Composition and Sensory Profile of Pedro Ximénez Wines

Pedro Ximénez sweet wines are traditionally produced from raisined grapes and are characterised by very high sugar and ethanol contents. However, there is growing interest in wines with lower sweetness and improved sensory balance. The aim of this study was to evaluate the effect of controlled partial fermentation of Pedro Ximénez raisined grape must prior to fortification on the chemical and sensory properties of the resulting wines. Fermentations were conducted until ethanol concentrations of 3.0, 5.0, 6.5, and 7.7% (v/v) were reached, after which fermentation was arrested, and all wines were standardized to a final ethanol concentration of 9% (v/v). Fermentation progression resulted in a reduction of residual sugar content from 445 to 313 g/L and significant increases in titratable acidity, volatile acidity, glycerol, higher alcohols, ethyl acetate, and 2-phenylethanol. Hierarchical cluster analysis confirmed that fermentation degree was the main factor driving wine differentiation. Sensory evaluation showed that partial fermentation reduced the intensity of characteristic descriptors such as honey, raisin, and fig while simultaneously decreasing sweetness perception and increasing freshness and overall balance. Wines fermented to 6.5 and 7.7% (v/v) ethanol received the highest preference scores from the expert sensory panel. These results indicate that controlled partial fermentation is a feasible technological strategy for modifying the composition and sensory profile of Pedro Ximénez wines and provide a basis for further optimization of alternative, less sweet Pedro Ximénez-style wines.