At a brief educational class (sponsored by Lallemand’s Jason Amos) where presenters included Eveline Bartowsky and Sam Harrop MW, I was able to try several “trial” wines; these are unfinished wines , but demonstrated complex differences when using several different yeasts, malo etc.
Where I started
- Various yeasts exist on grapes (and in the winery) at harvest time, generally these are not very efficient, and in low numbers
- Cultured yeast basically drives the fermentation – (temperature and other factors play a part too). The key yeasts are strains of saccharomyces cerevisiae
- Winemakers look for efficiency of the yeasts converting the sugars -fructose and glucose- into alcohol, and “cleanness” (no VA, H2S etc)
- Fermentation may not be steady, but can proceed sulkily – and a fear of stuck/incomplete ferments exists
- Winemakers may use different yeast strains to ferment different varieties
- For red wines, nice to get malo to happen at end of fermentation – or near the end; converting malic acid to lactic acid – there are more stresses and complications if this doesn’t occur (although some wineries are happy to wait until malo occurs months later).
Where I ended up
- Different cultured yeasts make much more of an impact than I thought, both aromatically and structurally,
- Malo in conjunction with ferment (co-inoculation) made an attractive sensory and structural difference- making the wine seems more polished, less raw, and apparently this difference persists)
- Different malo bacteria also make a sensory difference (oenococcus oeni vs lactobacillus plantarum)
- Co-inoculation may have some practical difficulties in a larger winery with many fermentation vessels and batches coming in several times per day.
- So, altogether much more complex than I had assumed, with more winemaker control than previously imagined.
Further questions, and some homework
- use of (some) whole bunch; is co-inoculation effective to the same degree?
- use of slow fermenting yeast strains – pros and cons
- effect of using combinations of yeast strains
All up, the session was enough to disturb my benign neglect of fermentation and its intricacies, and propel me towards seeking further information,