Winetech Technical Yearbook 2022

MARCH

SHUTTERSTOCK

Smokin’ hot Western Cape terroir (PART 1)

THIS ARTICLE CONTAINS SCIENTIFIC FACTS, AS WELL AS THE RESEARCHER’S OWN PERSONAL OPINION, ABOUT INTERNAL AND EXTERNAL FACTORS IN TERROIR EXPRESSION.

BY MARIANNE MCKAY E evoked Australian vineyards baking in the afternoon sun, with kookaburras (very original, I know) calling in the hot gum trees nearby. Australian red wine is known for a minty green attribute that may present anywhere on the spectrum from full-on crushed gum-leaf to subtle garden spearmint. 1 The compound responsible for the minty/eucalyptus flavour in the Jacob’s Creek is 1,8-cineole, (commonly known as eucalyptol). Higher concentrations in wine are related to the presence of eucalyptus trees growing near the grapevines. For me, this is a powerful expression of terroir. METHOXYPYRAZINES AND TERPENES The terroir concept is complex and encompasses a huge number of factors including the grapevine’s own responses to climate, water, canopy management practices and soil composition. The methoxypyrazine concentrations found

in grape berries are a good example of an endogenous (internal) grapevine response to environmental conditions around it. Australian researchers have been able to differentiate international terroir/origin of wines based on their 3-isobutyl-2 methoxypyrazine (IBMP: ‘green pepper’ aroma) concentrations. Bordeaux wines were shown to have significantly lower levels of IBMP than their Australian counterparts. Climate, grape maturity, light exposure, various viticultural management practices and crop yield can all affect IBMP concentration, so it makes sense that the terroir will have a huge influence on these compounds. Another set of compounds that reflect grapevine’s endogenous responses are terpenes (spicy, floral smelling compounds in Muscat and Riesling grapes). It is well known that terpene concentrations increase in these cultivars in response to sunlight exposure and higher temperatures.

EUCALYPTUS AND TERROIR I tasted a Jacob’s Creek 2006 Cabernet Sauvignon the other day, definitely a rare occurrence for me. Despite the wine being 15 years old, the eucalyptus note leapt enthusiastically out of the glass and

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WINETECH TECHNICAL YEARBOOK 2022