WINETECH Technical Yearbook 2020

Manipulation of Shiraz flavour

INTRODUCTION The contribution of yeasts to wine com­ position and quality is well-known (Jolly et al ., 2014). Saccharomyces yeasts drive alcoholic fermentation by converting the grape sugar to alcohol, carbon dioxide and other compounds that affect wine aroma and taste. Another group of yeasts important to winemaking is the non- Saccharomyces yeasts, also known as “wild yeasts”. This group has different oenological characteristics from S. cerevisiae and can potentially improve wine quality through enhanced wine aroma and complexity. Non- Saccharomyces yeast species, such as Hanseniaspora uvarum (anamorph: Kloeckera apiculata ), are frequently found on grapes and in grape must, and are known to dominate the initial phases of spontaneous fermentations (Capozzi, et al ., 2015). Mixed culture fermentations of H. uvarum and S. cerevisiae have been shown to enhance wine aroma profile and improve the quality of Negroamaro wine (Tristezza et al ., 2016). Most non- Saccharomyces yeasts are poor fermenters and are therefore used in combination with S. cerevisiae to complete the fermentation. Malolactic fermentation (MLF) is an enzy­ matic reaction performed by lactic acid

MARCH 2020

This article is a shortened version of the scientific paper published in Fermentation (Du Plessis et al ., 2019) . The aim of this study was to determine the effect Hanseniaspora uvarum in combination with Saccharomyces cerevisiae , lactic acid bacteria and two malolactic fermentation strategies had on Shiraz composition and flavour. 3 ARC Biometry, Stellenbosch KEYWORDS: Yeasts, lactic acid bacteria, malolactic fermentation, chemical profile, sensory evaluation, wine style HEINRICH DU PLESSIS 1 , MARET DU TOIT 2 , HÉLÈNE NIEUWOUDT 2 , MARIETA VAN DER RIJST 3 , JUSTIN HOFF 1 & NEIL JOLLY 1 : 1 ARC Infruitec- Nietvoorbij, Stellenbosch, 2 Department of Viticulture and Oenology, Stellenbosch University, Stellenbosch,

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