Purposely underpitching

Question

So I am planning a roggenbier, partially because I want to try one, but largely to grow up a cake to make 15 gallons of weizenbock.

Hefe's are ok in my mind, but my palette basically just wants more malt character. Voila rye instead of wheat, voila roggenbier.

I am going to keep the roggenbier on the low end of the style guidelines, probably around 1.050. Mr. M. Malty indicates that one vial into 5 gallons is underpitching by about half (need either 2 vials or 1L starter).

I have heard that the hefe yeasts from any lab are the masochists of the beer world. Pitch warm: no problem. Underpitch: no problem either. I actually do want a good bit of banana and a little less clove to come through in this beer to balance the earth/grit of the rye, however I was planning on fermenting relatively low, around 62-63*.

aaaaand now my question: do I need to do a simple starter or would I be better off getting some good phenolics by stressing this yeast a little (a lot?)? The last thing I want in this beer is fusels, but some good esters and weizen phenols would be great...oh and one final requirement: I'm trying to grow enough yeast for the weizenbock, MM says about a liter of slurry with 80% viability.

Answer 1

Underpitching/stressing the yeast is not a way to get a controlled result.

At 1/2 the recommended pitching rate wouldn't be a concern if you were fermenting warmer (66-68°F), but at 62°F I'd say you should at least start with the right amount of yeast, or you risk not least under-attenuation.

If you want less clove then ferment warmer also, and this will shift the balance towards banana. At 62°F I doubt you'll get much banana at all, especially if you underpitch. Also be sure to keep mash temps above 55°C/130°F to avoid creation of ferulic acid, which is the precursor to the clove flavor. (The actual rest temp is usually 43°C, but some breweries use 50°C - I'm saying a few degrees higher than that to be certain of headroom.)

A liter of slurry from 5 gallons is on the top end of what you can expect and you'll need to basically use the entire cake. If you want it to be 80% viable then rack off primary and reuse the yeast cake when FG is hit or add to a jar with fresh wort for use a day or so later.

Answer 2

Adjusting pitching rate is a very iffy way to control a flavor profile. How much do you underpitch to get the effect you want? How do you know your underpitching enough, assuming it even works? Yeast selection and fermentation temp are much more controllable. Also, a number of yeast specialists, such as Dr. Clayton Cone of Lallemand (http://www.danstaryeast.com/articles/yeast-growth) and Neva Parker of White Labs (http://www.homebrewersassociation.org/pages/lets-brew/homebrewing-seminars/2012), have cited underpitching as producing fewer, rather than more, esters. That said, if it's a 1.050 beer you could probably get away without a starter, although if it was me I'd use one. In short, don't try to control esters with pitching rate...use more reliable methods.