What is open-top fermentation? And what are the benefits?
Open-top fermentation – ask Decanter?
Ben Carpenter, Edinburgh asks: What are the benefits of using an open-top fermenter in the winemaking process?
Alistair Cooper MW replies: During the early stages of fermentation, open-top fermenters allow for increased oxygen contact which can help the yeast build a strong population.
This can help prevent what is known as ‘stuck ferments’ – when the yeasts become dormant before fermentation has finished.
Open-top fermenters also allow easy access to the cap (the grape skins that rise to the top) and allows them to be punched down into the fermenting must easily.
The heat generated during fermentation can easily escape the vessel, and an open-top can help better manage the fermentation temperatures.
Likewise, ethanol can also escape in the absence of a lid, which may be desirable or not, depending on the winemaker.
Open-top fermentations are only practical for relatively small volumes of wine, and are mainly used for red wines (or orange wines), as white wines tend to be fermented in the absence of grape skins.
Great care is also needed with open-top vessels as too much oxygen exposure may allow bacterial spoilage to enter the fermenting must.
Alistair Cooper MW is a broadcaster and writer and regular Decanter contributor.
This question first appeared in the June 2018 issue of Decanter magazine, subscribe to Decanter here.