[denny]

Myth, really? I’ve not seen anything (admittedly I’ve not gone looking) that questions it’s effectiveness. This is new to me.

That is because most amateur brewers are drinking the stir plate Kool-Aid without knowing anything about yeast propagation.  The spinning bar places shear stress on the cells.  However, the real crime is allowing the starter to ferment out, so that the supernatant (the liquid above the yeast sediment) can be discarded.  The reason the supernatant has to be discarded in a stirred culture is because it is foul.  That odor and taste is the result of shear stress.  Allowing a culture to ferment out wastes ergosterol and unsaturated fatty acid reserves, resulting in less healthy cell walls, which, in turn, lengthens lag time and increases O2 requirements.

I am in the process of writing a new blog entry on the stir plate myth.  Stir plates were not designed for cell culture.  They became the gold standard in amatuer brewing out of ignorance, not knowledge, just like secondary fermentation.  This information is not new to people who been following this forum for the last six or so years.  I presented my "Shaken, not Stirred" method about that long ago. My method greatly reduces cost and simplifies making a starter.

I have only just joined the forum but this is interesting news. I probably fall into your bracket of most amateur brewers also, I spin 24 hours, rest 24 hours and the chill in fridge overnight to decant. As you say, I think the supernatant can taste cidery, certainly not pleasant so I get rid of it. I have got blowoff tube activity in hours following this approach however so up to this point haven’t seen a reason to change.

I did it that way for many years.  Then I tried Mark's method.  Now I don't even know where my stir plate is, it's been so long since I've used it.

I will have search on this technique and give it a test, many thanks.

Search this forum.  That's where it was first introduced