WINETECH Technical Yearbook 2019

YU GAO, MELANÉ VIVIER & JOHN MOORE: Institute for Wine Biotechnology, Department of Viticulture and Oenology, Stellenbosch University, Stellenbosch KEYWORDS: Enzymes, Cabernet Sauvignon, pectinases, pectin-lyase. AUGUST 2019 PECTIN-LYASE – THE KEY WINE ENZYME?

Exploring the secret ingredients in wine enzyme mixes and cocktails. INTRODUCTION Wi ne g r ape s ne ed t o be macerated to extract juice and the key ingredients, such as pigments and tannins, in order to craft wines effectively. This is particularly important in red winemaking where pigmented polyphenols and tannins need to be extracted to produce the backbone ‘body ’ and colour intensity of various wines. Not all winemakers use enzymes, but those that do, need up-to-date information on how they work on grape berry tissues.

Pectin, the jelly-like substances present in grapes and musts, a r e b r o ke n d own d u r i n g winemaking maceration (skin- contact) phases. Pectin is a polymer made from a chain of sugar acids (galacturonic acid units). The enzymes responsible for breaking down pectin are collectively called pectinases. Pectinase-rich enzyme mixtures help in this breaking down process as grape pectin can be quite resistant to deconstruction. Extending the skin contact phase as during cold maceration can be quite risky for the winemaker, since it raises the chances of spoilage to occur. Commercial