Settling before red wine fermentation

by | Mar 17, 2023 | Relevant Resources, Blogs

Results from a study presented by Encarna Gómez-Plaza at Enoforum Web Scientists Conference 2023 revealed that settling red juice and adding the grape skins/marc back to conduct the fermentation can increase the colour and tannin content of the final wine significantly. In fact, the anthocyanin and tannin concentrations were not only much higher than the control but also considerably higher when compared to using a traditional red wine macerating enzyme. But this is not all. The experimental layout also included macerating with a conventional settling enzyme, characterised by its high pectin lyase content, to promote clarification and settling of white juice. The settling enzyme also performed better than the macerating enzyme, and the study researchers gave various reasons why this could be the case.

Red grape phenolics, after extraction, can bind to suspended grape cell wall material deriving mainly from the pulp of the grape berries. This can lead to the loss of these phenolic compounds when the wine is removed from its lees after fermentation. The anthocyanins and tannins can be better preserved by eliminating a large percentage of grape cell wall material through settling before fermentation and colour and tannin extraction. Voila! This, however, is not always practical in cellars. So, the second prize is using an enzyme high in pectin lyase activity. Prof Gómez-Plaza ended her talk with the question: “Should the pectin lyase content be prioritised in the composition of macerating enzymes?” Fascinating stuff, indeed.

A note on enzymes…
Commercial enzymes, produced mainly (but not exclusively) by Aspergillus niger fungal strains, are usually a blend of polysaccharide degrading enzymes and some other minor enzymatic side activities. Settling enzymes usually contain mostly the three main pectinolytic activities of pectin lyase, pectin methyl esterase and polygalacturonase. Macerating enzymes can also contain cellulase and hemicellulase as main activities. There are distinct differences between the enzyme offerings from different suppliers, not only in the specific cocktail of enzymatic activities within a particular product but also in the concentrations of the activities. Winemakers are advised to do trials to determine which products best suit their needs. Fortunately, red wine phenolics can easily be measured either the traditional way or nowadays also spectrophotometrically.

Osete-Alcaraz, A., Gómez-Plaza, E., Pérez-Porras, P., & Bautista-Ortín, A. B. (2022). Revisiting the use of pectinases in enology: A role beyond facilitating phenolic grape extraction. Food Chemistry, 372, 131282.

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