Physiological Ripeness

physiological ripeness or sometimes physiological maturity, terms loosely used by some winemakers, especially in the New World, to contrast with ripeness measured by the normal analytical measures of must weight, acidity, and ph. The terminology is imprecise because all grapes undergo physiological ripening irrespective of how it is assessed.

The concept of physiological ripening arose when winemakers realized that in many, particularly warmer, wine regions, these chemical measures were not sufficient to predict the optimum harvest date for wine quality. In its simplest form, the concept includes aspects of the berry’s maturation which describe changes in a ripening grape berry important to eventual quality. These include skin colour, berry texture including skin and pulp texture, seed colour and ripening, flavour, and phenolic changes, often accompanied by lignification of the berry stem. It is increasingly common to measure anthocyanins and other phenolics. The aim is to pick at as near optimum values of as many of these parameters as possible. Wine quality is thought to suffer if only a few parameters are at optimal value when the fruit is harvested; factors such as weather conditions, site, and viticultural technique, especially a shaded canopy microclimate, can unbalance these relationships. A common example is the relatively faster rate of sugar increase in warm to hot climates compared with phenolic development, flavour increase, and acid decrease. The resulting wines tend to be high in alcohol without necessarily being accompanied by ripe fruit aromas and phenolics. On the other hand, varietal flavour appears to increase more quickly relative to sugar in cooler climates.