Stir Plate Usage

Hank Speaks… So Listen by Hank Bienert

By now those who want a stirplate (July’s subject) have made one or bought one or decided they don’t want one. I address the first 2 groups:
My dog Rocky never chases cars since, being uber introspective; he knows he does not WANT a car which is a way of addressing the pivotal question in life concerning objects of desire, said question being – “What do you do with it now that you’ve got it?” For the brewer who now commands a stirplate, GROW LOTSA YEAST !!

Studies have shown up to a FOUR fold increase in cell count in first (and most important) 24 hours versus shaking the fermenter whenever one has the time and, although not four fold, an increase in colony count much better than direct oxygen bubbling which means with a stirplate one can:
1) re-use harvested yeast or
2) use past “best date” LIQUID yeast or
3) build a large cell count for a big beer or, as some say, with fermenting most lagers a position I take since I built my stirplate. Although I like doing different things and enjoy seeing if I can bring a moribund colony back to life against the odds, the first reason noted about the ability to re-use yeast is really the best reason and it is NOT, as some assume, to save money (unless you make less than $2.50/hour) since new yeast can cost about 3-4 times $2.50 and it will take 3-4 hrs. total time to rebuild a colony.

SECOND to FOURTH generation yeast is more robust than what comes from the brew shop! Ok how do we use the stirplate? First we need a starter. A cup of DME in a quart of water will give an SG of 1.044 which some say is too strong so they will dilute it a bit to about 1.030. I do NOT do this preferring to use my wortcicles – When I am drawing off the cooled wort from the pot I avoid the novice’s mistake of taking less than pristine product. I do take the questionable remainder and put it overnight in a covered container on the fridge and (PRAISE BE St. ARNOLD of METZ, patron saint of brewing!!) sedimentation occurs which will give me additional clear wort. If my original wort from yesterday’s brewing has started fermenting, I add this new found wort to the fermenter since the first 24 hours is a window in which enough cell multiplication is occurring to allow the introduction of less sanitary wort and we can still add oxygen.

If the fermenter is not rolling along or if my wortcicle supply is low then I put the new goods in a freezer quart size Ziploc bag and there’s your wortcicle. When it’s time to use it, give it a 10 minute boil.

Back to stirplate technique. We have cooled starter material and I add the stir bar which I used to swipe with vodka but now have a different approach, based on Travis Combel’s suggestion at a discussion* we had at a recent CCH meeting. Now I will now just boil the stir bar with the wortcicle.

*Discussion?..yes.. I go to CCH functions as The Roving Reporter, not just a slack-jawed “gimme free beer” guy..which is why the CCH board pays me the big bucks.

Add the yeast and start the spin at a moderate rate just enough to dimple the surface of the liquid with the vessel loosely covered – NO bubbler since we want O2 to come into solution. Some preach a 24 hr. spin then cold crash to drop the new colony down but I am more conservative and want to be absolutely sure, especially if this is a resurrection of a stored, harvested colony that I am not just moving dead cells around so I spin x 12 hours and then add another 4 ounces of wort and place a bubbler on it to prove viability. It would be risky to throw bad yeast onto fresh wort and from time to time the yeast did NOT pass the second stage so I discard it.

I do not give a second dose challenge when using dry yeast since the modern 11.5 gram packets if refrigerated are amazingly durable.

As always,. constructive comments are welcome via the Hopline … for those uncomfortable with readin’ n’ writin’ big words, please continue to mumble during meetings from the back row which is where I like to sit/sip/mumble . . . and where the often and previously mentioned (yet sadly still unseen) free beer should be delivered.