Lifting the lid – a class on wine fermentation and microbiology

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,

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2 thoughts on “Lifting the lid – a class on wine fermentation and microbiology

    1. Some good information was presented about indigenous (wild yeast) fermentation, but as a non-technical person, I felt for my snippet this angle was a bit far outside my knowledge, and all-too-easily tangled into the “natural” wine sidetrack….maybe another time

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