Beer Forum

I just did a small batch, designed to test the effect of trub on fermentation. I'd like your criticism of my process / hypothesis. Maybe it's been done, but I was feeling spontaneous.

Process:

- 2.5 gallon batch: Great Western 2-row, 20 Magnum 13.1% pellets, 15 minute boil, 1.035 OG.
- All new small-scale equipment, just purchased and sanitized.
- Wort was immersion chilled to 60F, and then poured into two 1 gallon fermenters, using the same funnel.
- Funnel aeration was the only method of oxygenation for both samples. Both samples were filled outside, at the same location.
- Equally-weighed 1/2 pack of US-05 dry yeast into each fermenter.
- One fermenter got clear wort, and one got the rest, including some of the trub.
- Sample with more trub got a little extra wort.
- Fermenting at 64F.

Expected Result:

- Both samples begin fermentation at the same time.

Observed Result:

- Faster start in the fermenter with less trub.

Photos (Brewday + 1):

- Both samples, with roused sediment:



- Both samples, with mostly-settled sediment:

How much faster start? Was there a difference in fermentation rate? Did one finish sooner? And of course, sample size...

I don't doubt that there would be a difference, but I'd think gravity readings would be the most useful indicator rather than the presence of bubbles.

Some additional info from Weihenstphan. scroll to page 93 for the English version.

http://mediatum2.ub.tum.de/doc/619244/619244.pdf

Quin, that is perhaps the best homebrewing-related link that I've ever seen. This makes me want to take skibikejunkie's suggestion and actually perform a gravity check, since the Weihenstephan article says exactly the opposite of what I inferred from my observation.

If the article's thesis holds true, for my case, then the trub did have a positive impact on fermentation (or will have a positive impact), and either still caused fermentation to start later or simply suppressed the typical visual indications of fermentation start (foam).

UPDATE:

Brewday + 2

OG for both samples: 1.035

Trub-light sample: 1.018
Trub-heavy sample: 1.026

kswbeer wrote:UPDATE:

Brewday + 2

OG for both samples: 1.035

Trub-light sample: 1.018
Trub-heavy sample: 1.026

Flies in the face of the article. Very interesting indeed.

I could see a variation from that Weihenstphan experiment if the percentage of trub to beer was higher. I seem to remember some mead makers saying something about yeast getting lazy when they have a lot of nutrients, which is the basis for staging the nutrient additions (or sugar additions, in the case of things like Belgian beers). Maybe the trub provides an abundance of yeast nutrients, thus making them a little slow. If this proves correct, repeating the experiment multiple times and decreasing the trub content each time would eventually give you that boost that Weihenstphan has observed.