Release and perception of γ-nonalactone and massoia lactone in the red wine matrix: impact of ethanol and acidity

Abstract

Climate change (CC) is altering grape/wine composition, leading to challenges in maintaining wine sensory quality. Rising temperatures increase grape sugar levels, with higher wine ethanol (EtOH) contents, reduce total acidity (TA) converging with increased pH, modify the phenolic pattern, and lead to the accumulation of CC odorous markers such as gamma-nonalactone (C9) and massoia lactone (ML). These alterations often require interventive acidification to preserve microbial and chemical stability, and taste balance of wines. Previous studies addressed the effects of CC on wine proposing preventive and management strategies. The main objective of this study is to give a contribution by investigating for the first time the sensory impact of matrix-aromas interactions in wines representative of the main CC compositional effects in their whole.Model wine matrices (9) were reconstituted from a deodorized red wine, using a full factorial design based on 3 ethanol levels (12, 14, 16%), 3 pH/TA ratios (3.2/8=0.4, 3.6/6.5=0.55, 4/5=0.8) and spiked with C9 (155 ppb) and ML (26.8 ppb). The combinations simulated progressive CC impact from proper (12%, pH/TA=0.4, no CC effects), to alarm (14%, pH/TA=0.4, CC influencing EtOH levels with TA corrected by acidification) till dangerous (14%, pH/TA=0.8, CC affecting TA without correction; 16%, pH/TA=0.8, extreme CC effects) scenarios of wine quality. Discriminating (triangle test: TT) and descriptive (RATA) sensory tests and SPME/GC-MS quantitative analyses, were carried out to test the impact of compositional changes applied to the matrix on the perception and release of the two odorous CC markers and to explore perceptual interactions. TT showed significant differences in the perception of C9 and ML in wine considered dangerous for its alcohol content (16%) and corrected by acidification (pH/TA=0.4), indicating in this condition a combined effect of EtOH and acidic profile on their perception likely driven by physical-chemical phenomena. GC-MS analysis of wine headspace confirmed that this condition exhibited the highest release of C9 and ML. Moreover, RATA results showed that in the sample representative of extreme CC conditions (16% EtOH, pH/TA=0.8), the addition of C9 and ML led to a shift in aroma profile: red fruit notes, characteristic of the whole wine, were no longer perceived, while sweet notes became dominant, suggesting a significant matrix effect on the olfactory impact of these compounds. These findings highlight that CC and the corrective actions by winemakers can have a significant combined impact on the sensory quality of wine. Our study points out that adjusting the acidic profile of wine—an often-necessary step to improve stability and taste balance—may favor C9 and ML perception linked to CC and premature aroma aging. These results suggest that in a complex matrix such as red wine, adjusting a single parameter could be not enough and a holistic approach should be adopted.