Berry Phenolics in Cabernet Sauvignon (Vitis vinifera L.) during Late-Stage Ripening

Abstract

The trends in changes to berry weight and phenolic concentrations of Cabernet Sauvignon berries during the later stages of berry ripening from different pruning and irrigation treatments were examined. Maturity was defined as total soluble solids (TSS). Berry phenolic concentration was examined using a 50% ethanol extract of grape homogenate, which is commonly used in the Australian wine industry to measure grape anthocyanins. Berry weight and berry composition were examined at three maturity stages over three vintages. Three pruning treatments were established with two irrigation treatments superimposed to provide a wide range of berry sizes and phenolic measures. Increasing maturity had consistent effects on berry weight across vintages and on berry phenolic composition within vintages. In a commercial context, peak total anthocyanin concentration and content might be a useful guide to harvest decisions, but in this study total phenolic and tannin measures did not assist in these decisions, as these measures were highest at higher than commercially acceptable TSS. In a research context, this information can be useful in determining the pattern of anthocyanin, total phenolic, and tannin accumulation and decline and would be useful in conjunction with wine measures of these parameters to determine relationships between berry and wine composition. Pruning treatments were associated with consistent effects on berry weight across vintages and maturity stages and consistent effects on total anthocyanin and total phenolic concentrations, but not on tannin concentrations. Irrigation effects were less consistent within or between vintages and the effects were highly dependent on vintage conditions.