Effects of oenological practices and site factors on benzenemethanethiol and rotundone concentrations in Blaufränkisch

Abstract

While several important Austrian red grape varieties, most notably Zweigelt, are increasingly affected by the consequences of climate change – such as berry shrivel, which leads to substantial qualitative and quantitative yield losses and remains largely uncontrollable – the variety Blaufränkisch has so far proven comparatively resilient to these developments. Against this background, Blaufränkisch was re-evaluated in recent investigations, with particular emphasis on two highly potent aroma compounds: benzenemethanethiol (BMT; odour detection threshold 0.3 ng/L; sensory descriptors “gunpowder”, “flint”) and rotundone (odour detection threshold 16 ng/L; “spicy”, “peppery”). Both compounds were quantified using specific GC–TQMS analytical methods. In a controlled maceration experiment, a homogeneous Blaufränkisch must was subjected to different treatment regimes involving the alternating addition of reduced glutathione (GSH-IDY), oak wood chips and oxygen. The results demonstrated that the application of oak chips led to a significant reduction in benzenemethanethiol concentrations (−18 %), whereas GSH-IDY and oxygen had no significant effect on BMT levels under moderate yeast-assimilable nitrogen (YAN) conditions. In addition, a field study investigated the effects of yield regulation and leaf removal on rotundone concentrations in Blaufränkisch. Site-related factors emerged as the dominant drivers of rotundone expression. Although a significant increase in rotundone concentration (+56 %) was observed at one site in the non-defoliated and non-yield-reduced (control) treatment, this effect could not be reproduced consistently across other locations. Furthermore, at one site, a mild infection with powdery mildew resulted in more than a tenfold increase in rotundone concentration across all treatments. Overall, the findings highlight a continued need for further research, particularly with regard to the formation pathways and modulation mechanisms of benzenemethanethiol. A deeper understanding of these processes may enable winegrowers to purposefully manage distinctive aroma profiles, thereby enhancing both sensory differentiation and market positioning in an international context.

References

Schlögl, N., Rauhut, D., Beisert, B., Sari, S., Eder, P., & Philipp, C. (2025). Influence of oak chips, glutathione-rich inactivated yeast, and oxygen during fermentation on the analytical profile of volatile compounds in Blaufränkisch wines. OENO One, 59(3).