How is the dilution caused by a large starter reflected in OG and FG?

[iconoclast125]

I've seen a few questions here about starters and "include starter in bottling volume". My question is a little different.

I'm trying to figure whether (or how) the starter volume influences gravity in the fermenter. Suppose I'm brewing a high gravity beer, say, a tripel. To achieve 1.088 OG in the fermenter after adding a 3L starter which has a 1.005 FG, I expect my tripel's gravity after boil needs to be higher than my target OG, maybe 1.100. I don't see this anywhere. Changing starter volume in the recipe doesn't result in changes to the estimated OF or FG.

Am I thinking about this wrong?

Cheers!

 

[BeerSmith]

There is a box on the "Starter" tab at the very bottom which is "Add starter to bottling volume" which will factor the starter into the bottling volume.

Most people measure OG in the fermenter before adding the starter I believe - at least that's what I do.

To be fair I don't think this is included in the OG/FG calcs, but I will make a note to add it. However it should not change the ABV much since if you had a moderate starter in a moderate beer the ABV will be similar for the blend.

 

[McMullan]

Ideally, decant spent starter wort and pitch mainly yeast slurry. Unless made with kettle wort, it won't necessarily taste great and contains growth inhibitors secreted by yeast cells when resources get low. Otherwise, as already hinted at, measure OG after pitching.

 

[iconoclast125]

Thanks for the responses.

> Most people measure OG in the fermenter before adding the starter ... it should not change the ABV much.

Measuring OG before pitching is an option. If the OG of the starter is close to that of the full batch it shouldn't influence the calcs a lot. But for big beers, 3L of a 1.035 starter in 22L of 1.090 beer, that's 1.083.

>Ideally, decant spent starter wort and pitch mainly yeast slurry

I've been timing to pitch my starter at high krausen, but I guess I can make my starter a day or two earlier and decant some of the wort off the top to get a slurry.

Thanks again

 

[McMullan]

I've seen a few questions here about starters and "include starter in bottling volume". My question is a little different.

I'm trying to figure whether (or how) the starter volume influences gravity in the fermenter. Suppose I'm brewing a high gravity beer, say, a tripel. To achieve 1.088 OG in the fermenter after adding a 3L starter which has a 1.005 FG, I expect my tripel's gravity after boil needs to be higher than my target OG, maybe 1.100. I don't see this anywhere. Changing starter volume in the recipe doesn't result in changes to the estimated OF or FG.

Am I thinking about this wrong?

Cheers!

Pitching at high krausen is good practice, imo. I often repitch freshly harvested top-cropped yeast directly from batch to batch. The main benefit is that fermentation kicks off sooner, because the yeast cells are active and metabolically programmed to ferment. But it isn't necessarily good practice with a starter, because yeast/culture growth hasn't finished. There's a risk of underpitching, especially a big beer. Another option, if you want to pitch metabolically active yeast, is to decant the spent wort on brew morning or night before then resuspend the yeast slurry in wort that has a gravity comparable to the day's kettle wort. Then just add the volume. Otherwise just pitch yeast slurry within a few days of it being prepped, while it's fresh. As long as the yeast are fresh/in good shape fermentation starts within several hours, the normal time for a lag phase.

Another strategy for a big beer is to make a session beer then harvest and repitch the yeast, which is an easier way to get sufficient viable yeast cells acclimatised to wort.