Effects of altitude on the chemical composition of grapes and wine: a review

Of the geographical parameters in a winegrowing site, altitude is an important determinant of wine composition and quality. Grape polyphenols and volatiles comprise a large and varied group of compounds that contribute considerably to the sensory and health-promoting properties of wine. This review surveys the impacts of altitude and its related climatic characteristics on the phenolic and aroma compounds of grapes and wine through the examination of existing literature. Furthermore, this review highlights the challenge of distinguishing the effects of parameters, such as air temperature, variety, vine water status, soil and UV radiation, from the altitude effect. Overall, high-altitude growing sites can favour an increase - albeit at different intensities - in content of many chemical compounds found in grapes and wine, such as total polyphenols, total monomeric anthocyanins, catechins, quercetin derivatives and cyanidin-derived anthocyanins, trihydroxylated flavonols, carotenoids, isoamyl acetate and ethyl hexanoate. However, the altitude factor seems to be cultivar-dependent; in fact, it can exert a positive effect on the concentrations of acylated anthocyanins and of total aroma compounds in some cultivars (e.g., Ekşikara and Glera) and a negative effect on the same components in other cultivars (e.g., Merlot and Cabernet-Sauvignon). Its influence on the polyphenol content can also differ between different parts of the same cultivar; for instance, an increase in skin tannins and a decrease in seed tannins have been found to be concomitant with an increase in altitude in Syrah grapes. Moreover, at higher altitude, the effect of an increase in UV-B radiation can lead to an enhancement in colour intensity due to an increase in the synthesis of anthocyanins, flavonols and tannins. Due to their cool climate, high-elevated winegrowing regions represent favourite cultivation sites under current and future global warming