Beer Forum

Here are a few questions that have been on my mind....

Why if you under pitch does the yeast not fully ferment? Since after all it is a fungi that keeps reproducing...hypothetically it should just keep reproducing (most likely too much sugar for the yeast = way to much excess product and kills the yeast)....

And the concept of using a starter...for HG wort and larger batches...What about adding malt extract to the wort during the, log or exponential growth phase of the yeast (ya know while it is active and making your airlock burp every 5 seconds)....Would that hypothetically work?

Yeast only reproduce in the presence of oxygen. When you make a starter on a stir plate you don't wind up with a liter of beer, you wind up with a liter of sour water with virtually no alcohol. When you under-pitch, the yeast will use all available oxygen to reproduce and when the O2 is gone it will start fermentation. Not enough O2 or yeast and you wind up with an under-attenuated beer. Or so I have read...

and what about feeding the wort extract during fermentation?

Well, if you under pitch and / or under aerate your wort I'm not sure how adding more wort during fermentation will help, unless you introduce additional O2 at the same time (listen to CYBI "DogFishHead 120 miniute IPA" with Sean Paxton, he aerates every day for the first 5 days). I've added simple sugar to a beer several days into fermention, so the yeast will ferment the more complex maltodextrins first, and I've added Fermaid K to big beers when fermentation is about halfway done, just not sure if there's any benefit to adding additional wort. Give it a try and let us know how it turns out. If your beers are under-attenuating it might be easier and pose less chance of introducing an infection by just making a bigger starter.

Dmp wrote:And the concept of using a starter...for HG wort and larger batches...What about adding malt extract to the wort during the, log or exponential growth phase of the yeast (ya know while it is active and making your airlock burp every 5 seconds)....Would that hypothetically work?

Sheen put it pretty succinctly. Yeast do two forms of respiration - aerobic, and anerobic. They don't reproduce when they go anerobic. If you want them to reproduce, they will need nutrients, food, and oxygen. There is no benefit of periodic feeding during the growth phase. The benefit of secondary fermentation (of simple sugars) is like he said - so that they work on the difficult, complex sugars first - and then the easy shit when they are less attenuative.


Mylo

Hopefully this beer won't turn out too sweet. And I most definitely learned my lesson about Large worts and high gravity beers...