On this page it is claimed that wine yeast needs some tannins to work, and that this can be a cause of stuck ferments in, say, flower wines. I have never heard of this, and cannot seem to find a good reference that corroborates this claim. Is it true?
I have never head this before, and after looking around quite a bit I couldn't find any evidence to support (or even suggest) the link.
Only thing I can think of is either: this refers to a non S. cerevisiae yeast (maybe Brett or some other wild yeast), though I couldn't find any evidence of that either; or, some other substance beneficial to yeast happens to correlate to the amount of tannins in the grapes or be extracted by the same factors that favor tannin extraction.
In beer production, polyphenol content (tannins are a kind of polyphenol) tends to decrease during fermentation, which is actually due in part to its adhering to the outside of the yeast cells (similar to what bitter hop resins do), so I'd really think tannins would have exactly the opposite effect (that is, an inhibitory effect) as what this page suggests.
In the last two 5 gallons batches of 14 % apple wine that I made , I left the tannin out to cut down on the bitter taste . Both got stuck at about SG 1.020 . I have been making wine for 12 years with tannin and never had a stuck fermentation . Starting SG 1.106 <> Starting acid 3.45 <>yeast , Lalvin Ec 1118 <> Dick Benham .
This article suggests certain polyphenols may negatively affect yeast life span: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3503821/
I have fermented many flower wines/meads with and without Tannin and never really had any stuck fermentations, I find oxygenation to be a far bigger factor leading to stuck fermentations.
But, always happy to be proved wrong.