Temperature-Based Grapevine Ripeness Modeling for cv. Touriga Nacional and Encruzado in the Dão Wine Region, Portugal

In the present study, we calibrated and validated thermal models to predict DOY date at which grape maturity index, potential alcohol/total acidity (PA/TA), reaches 0.75 (MS0.75), 1.0 (MS1), 1.5 (MS1.5), 2.0 (MS2) for two grapevine Portuguese varieties, Touriga Nacional (TN) Encruzado (EN), growing in Dão wine region, Portugal. Daily rates of forcing calculated with Sigmoid (SM) function Degree Day (DD) were used. The outcomes show that best performance was obtained heat accumulation starting flowering (tx = EL23). analysis model sensitivity changes rate coefficients (T0, e, d) enabled selection same all stage each variety. selected revealed significant predictability, though dependent on variety (EFF > 0.81 TN EFF EN). non-linear regression analyses sugar concentration (SC) total (TA) accumulation, using select models, demonstrated a high fraction SC TA variance explained by variation these temperature-based indices. Comparatively TA, results highlight conditions accumulated from had lower influence pH juice variance.