Winetech Technical Yearbook 2022

DECEMBER

SHUTTERSTOCK

Lipids in white winemaking – THE TOO OFT-IGNORED ESSENTIAL NUTRIENTS

IT IS IMPORTANT FOR WINEMAKERS TO UNDERSTAND THE FACTORS CONTRIBUTING TO LIPID DEFICIENCY IN GRAPE JUICE AND SOLUTIONS TO CIRCUMVENT THIS.

BY LETHIWE MBUYANE, JAMES DUNCAN & BENOIT DIVOL

LIPIDS ARE HYDROPHOBIC MOLECULES , such as fats and oils. In grapes, they are found in the outer waxy layer of the berry, in the skin, flesh and seeds at differing concentrations. These compounds – which are integral components of cell membranes – are used for energy storage, serve as precursors to varietal aroma production, and are involved in the ripening of grape berries. During the winemaking process, they serve as a key nutrient for the growth of yeasts. While not typically quantified in grape must,

a shortage of lipids may cause sluggish fermentations and the production of off-flavours. PRE-FERMENTATIVE CLARIFICATION IN WHITE WINEMAKING AND THE LINK WITH LIPID CONTENT Lipids form part of the insoluble fraction of grape must. This fraction also contains polyphenol oxidases and esterases. These two enzymes can be detrimental as they can result in the browning

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WINETECH TECHNICAL YEARBOOK 2022