I also stop the stirring after 6 hours to let krausen form. Mark Van Ditta proposed using a media flask and shaking until the entire starter is foamed, maximizing yeast to O2 available surface area, and pitching at high krausen - roughly within 8-10 hours. I adapted my process to mimic his "Shaken, not Stirred" methodology.
I cannot claim lab quality results. Using a hemocytometer, do basic counts, noting all budding cells at 90 minute intervals over 4-6 hours. Then using higher optical power, look at both mother and daughter cells to determine scars and new buds. This is done in a normal starter, with 100x dilution and m/b staining (added during dilution). With what I have seen, yeast subjected to sheer forces yield a substantial larger number of very small daughter cells, many that cannot metabolize the meth blue dye. I have not done GC or MS analysis to determine off-flavors empirically. I tend to favor viability over cell mass - as a replication cycle is only 90 minutes. Viability (in my method) is to count and compare mothers with 2+ buds at least 50% of the mother size. With some zinc and magnesium in the starter, along with a shot of pure O2, you should exit the lag phase within an hour (assuming tempering the yeast to room temps). Then it is a simple matter of setting timers, using a hemocytometer, meth blue staining, and a decent scope, and a lot of free time. (all done in a 1.040 starter wort with extra pale DME + yeast nutrient). I need to look this up in the Boulton/Quain Yeast and Fermentation book to confirm.
If I let the yeast go dormant (like a missed brew-day, so crashing the starter), then decanting and adding a 1.030 starter wort on it - and timing to pitch at high krausen yields impressively short lags, especially at 1 M/P or higher cell counts.
I have not done the plating over sequential starters (96 samples over the log/exponential phase from iterative starters is the golden standard proposed by Luria & Delbrück). So take it as anecdotal at best. (qualification, I clearly muffed my first LODO experiment). YMMV.
A simple experiment to confirm is to run a "shaken" or mildly stirred starter side by side with a "stirred" starter, and simply smelling and tasting the supernatant - it is striking. Let it run till expected FG, cold crash - taste the resulting clear beer. A partial hop pellet included in the starter wort seems to eliminate or suppress any unwanted LAB growth.Statistics: Posted by mchrispen — Fri May 06, 2016 12:42 am
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