WINETECH Technical Yearbook 2021

VITICULTURE RESEARCH | MAY 2021

Understanding the “terroir effect” (PART 1)

BERNARD MOCKE: Private consultant KEYWORDS: Terroir, aromatic grape and wine compounds.

THE TASTE OF ANY GIVEN WINE, regard- less of cultivar, is inextricably linked to its origin. Environmental factors, such as soil and climate, influence organoleptic charac - ters and by deconstructing measurable soil and climate parameters, this influence on a wine’s typicity can be better understood. In Part 1 of this two-article series, a brief introduction on the effect of terroir on wine aroma and an overview of the main families of aromatic grape and wine compounds are given. Part 2 of this series will focus on specifically how terroir shapes grape and wine aroma expression, and the prediction and management of aroma typicity relating to terroir. INTRODUCTION It has long been acknowledged that wine typicity, or style and quality in other words, depends heavily on where vines grow. Local soil and climate conditions are major

influences on wine sensory qualities. It is up to the winegrower to harness optimal plant material and vineyard management practices adapted to site, and the wine­ maker to use appropriate winemaking techniques according to berry composition, in order to fully shape the terroir effect. But to go further than merely a descriptive link between wine typicity, soil and climate, these need to be broken down into measurable parameters. Simply put, the effect of climate can be assessed through the measurement of air temperatures, radiation and rainfall. Similarly, the role of soil can be assessed through the measurement of soil water-holding capacity and nitrogen status. GRAPE AND WINE AROMAS Wine aromas can be classified as primary (produced during grape ripening) , secondary (produced during fermentation)

and tertiary (produced during wine ageing), and it follows that their expression is of key importance. Odorous primary aroma compounds are either free (volatile) or bound (conjugated) to other molecules present in grapes and can be liberated during fermentation or ageing. Ester compounds (secondary aroma compounds) are rather abundant depending on wine composition. The hundreds of aromatic compounds that have been identified in wine can be further grouped into specific families. GREEN AND PEPPERY FLAVOURS Major contributors to green aromas are methoxypyrazines, particularly 2-me- thoxy-3-isobutylpyrazine (IBMP), which is responsible for green (bell) pepper aroma. C6 compounds also contribute to green aromas and their abundance in wine is modulated by the winemaking protocol fol-

lowed, but there is not a lot of information available in literature about the impact of environmental factors on their presence in grapes and wines. 1,8-Cineole, a monoter- pene, imparts minty flavours to wine and (-)-rotundone, a sesquiterpene, notably contributes peppery aromas to Syrah and other cultivars.

WINETECH TECHNICAL YEARBOOK 2021 | 17