WINETECH Technical Yearbook 2021

VITICULTURE RESEARCH | JUNE 2021

Understanding the “terroir effect” (PART 2)

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

AIR TEMPERATURE Green and peppery flavours

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. Part 1 of this expanded three article series introduced the terroir effect on wine aroma and gave an overview of the main families of aromatic grape and wine compounds. Part 2 focuses on specifically how terroir shapes grape and wine aroma expression, and Part 3 gives insights on the prediction and management of aroma typicity relating to terroir. INTRODUCTION Much is known about the role of climate and soil on wine typicity and by measuring air temperature, radiation, rainfall, soil water holding capacity, and vine nitrogen

status, the link with each other becomes clearer. Comprehensive databases are available on all of the relevant parameters, and these can be spatialised and quantified at vineyard scale. The winemaker’s role in shaping a wine’s future by reacting to berry composition is of vital importance. Of equal importance is the viticulturist, who also has a major influence on the terroir effect by suitably reacting to the above-mentioned soil and climate conditions. THE EFFECT OF MAJOR TERROIR FACTORS AND GRAPE AND WINE AROMA Due to the large amount of information, the terroir effect on aroma cannot be fully discussed – the reader is encouraged to study the “Recent advancements in understanding the terroir effect on aromas in grapes and wines” ( OENO one 4, 985- 1006) article for more information.

Methoxypyrazines, IBMP in particular, decrease in grapes undergoing maturation wi th an increase in temperature . An increase in IBMP is seen in higher altitude vineyards, attributed to lower temperatures. Cooler vintages result in a marked increase in (-)-rotundone levels, a peppery flavour in Syrah. Volatile thiols and C 13 -norisoprenoids It seems that 4MMP decreases under high temperatures in wines from Sauvignon blanc and it has been shown that cool climate Riesling (Germany) contained less TDN than warm climate Riesling (South Africa). Dried fruit aromas There is a clear effect of higher temperature and the development of dried fruit

aromas in grapes. Must and wine samples marked by this aroma has higher levels of γ-nonalactone, massoia lactone, furaneol or MND (3-methyl-2,4-nonanedione – dried fruit aromas such as dried prune). Other aroma compounds Particularly high levels of DMS (dimethyl sulphide – enhances blackcurrant aromas

WINETECH TECHNICAL YEARBOOK 2021 | 19