New grape varieties with multiple resistance loci against powdery and downy mildew allow for a significant reduction in fungicide use. These fungus-resistant grape varieties (PIWI, from the German Pilzwiderstandsfähig) play a crucial role in achieving the goal of reducing pesticide use by 50% by 2030, as set by the European Green Deal. However, wine growers are reluctant to plant these new varieties due to a lack of experience in vinification and uncertainty about how consumers perceive and purchase wines made from these completely unknown varieties.

To gain a deeper understanding and develop oenological strategies for the new varieties, we vinified different wine styles from grapes of four white and three red PIWIs. The grapes were harvested from an experimental research vineyard at the Institute for Viticulture and Oenology in Neustadt, which contains the new varieties as well as four classic reference varieties. We analyzed data obtained from descriptive sensory analysis and correlated it with hedonic ratings from German, French, Italian, Danish, and Dutch consumers. Several consumer segments emerged, each with different drivers of preference. However, all consumers disliked wines that were sour, astringent, or green, as well as those with less fruit and color. Wine professionals also evaluated the same wines and provided similar judgments to the consumers: 9% of PIWI wines were rated significantly better, 9% significantly worse, and for 82% of the wines, no significant difference was observed.

To unravel the molecular basis, we analyzed aroma compounds such as monoterpenes and C13-norisoprenoids. The analysis of phenolic compounds included indirect measurements such as the Folin-C assay or the Harbertson-Adams assay, as well as targeted analysis using LC-MS or LC-DAD. In the comparison between Muscaris (PIWI) and Muskateller, Muscaris wines were richer in cis-rose oxide, while linalool and α-terpineol were more abundant in Muskateller wines. However, a sensory napping analysis could not distinguish wines from the two varieties. So far, no specific off-flavors have been detected in the new PIWIs, unlike those reported for older hybrid varieties. Although fungal resistance may be associated with increased polyphenol levels in grape skins, red wines made from PIWI varieties did not generally show higher concentrations across different winemaking styles.

Overall, when making wines from grapes grown in the same or very similar vineyards, PIWIs produced wines that were equivalent or even superior from both a sensory and hedonic perspective. Using different winemaking styles allows for the fulfilment of specific and varying sensory preferences of European consumers. Combining these findings with the widely reported improvements in sustainability associated with growing PIWIs should encourage a growing number of conventional and organic vintners to plant more PIWIs in the near future.