An adequate regulated deficit irrigation strategy improves wine astringency perception by altering proanthocyanidin composition in Cabernet Sauvignon grapes

Abstract Regulated deficit irrigation (RDI) is an agricultural practice that can enhance grapevine berry and wine quality. However, the effects of water deficit on concentration and composition of proanthocyanidins (PAs) and wine astringency are often limited and contrasting. Therefore, the profiles of PAs were investigated in Cabernet Sauvignon grown at 60% (RDI-1), 70% (RDI-2), 80% (RDI-3), and 100% (conventional irrigation, CI) of estimated evapotranspiration in 2016 and 2017. The treatments, replicated three times, were laid out in a randomized block design where any border effects were avoided. Our results showed that compared with CI, grapes grown under RDI had greater total concentrations of phenolic compounds. Skin PAs content increased in response to the RDI, especially in RDI-1 and RDI-2, while the seed PAs content was relatively insensitive to RDI. Hierarchical cluster analysis indicated that higher percentage of galloylation, molecular mass, mean degree of polymerization and the special extension subunits, such as percentage of (–)-epicatechin-3-O-gallate (%ECG) and percentage of (–)-epicatechin (%EC), led to greater astringency intensity in the wine. However, RDI-1 decreased perceived astringency due to the decreased %ECG and %EC of PAs extension subunits, and increased %ECG of PAs terminal subunits. Our study suggests that the irrigation levels at RDI-2 and RDI-3 can significantly influence the PAs compositions and improve wine astringency perception.