Glycerol production is normally only a consideration for wine yeasts.
High attenuation can apparently lead to increased glycerol formulation, so this would work well with French Saison, Belgian Triple and Belgian Ale – however, these would all impart very distinct, phenolic/Belgian flavour characteristics so, not exactly ideal for all applications.
Heat shocking the yeast to force increased glycerol production can be done with wine yeasts - but we’d tread with caution trying this with beer yeasts since generally, they’re much less robust than wine strains.
In winemaking, 6 hours after yeast pitching the must temperature may be raised to 34°C (93.2°F) and held for 4 hours, or perhaps 45°C (113°F) for 10 minutes, before being cooled back down to 20°C (68°F) or less. This brewer is welcome to experiment, but I’d start by favouring beer yeasts with higher temperature tolerances just to be safe.
It’s also worth noting that fermenting under present may also increase glycerol level as well. And finally, that the impact of glycerol on mouthfeel will be much less significant than the effects of high unfermentable sugars from the non enzymatic (cold) mashing they’re proposing to try.
The effects of heat shock and ethanol stress on the viability of a larger brewing yeast strain during fermentation of high gravity wort were studied. These stress effects resulted in reduced cell viability and inhibition of cell growth during fermentation. Cells were observed to be less tolerant to heat shock during the fermentation of 25°P (degree Plato) wort than cells fermenting 16°P wort. Degree Plato (°P) is the weight of extract (sugar) equivalent to the weight of sucrose in a 100 g solution at 20°C (68°F).
Further to this, we have a little further information regarding glycerol production of some of our beer yeasts:
- French Saison is a relatively high glycerol producer, just as I had anticipated – however, it is only good for Saison or Farmhouse style beers.
- Bavarian Wheat may be relatively high producer, but again this is only suitable for certain styles of beer (namely wheat or wit beers).
- New World Strong Ale, while not the highest producer of all, as we suspected is possible the best option of the neutral character strains in our range.
- US West Coast Ale is a relatively low glycerol producer compared to most strains.