Do you measure OG before or after adding a yeast starter?

[kierent]

Hi all
Ok so I've done a fair bit of searching and found a few threads on decanting the starter before pitching. It seemed that was mainly to not mess up the volumes but I'll definitely do that next time. But yesterday I pitched 2L of starter (two step) into my Belgian strong ale. I measured the OG before I pitched the yeast and it was 1.070 in a 20L wort. After I pitched it was down to 1.062 in a 22L wort. Which one should I use to do my ABV calcs?

The starter was a 2-step- 1L water and 100g DME for a day, then tipped that into another 1L water/100g DME. I assume that because I've made a mini beer, that would also drop the OG points because of the alcohol in there.

What do you all think?
Thanks
Kieren

 

[kadmium]

Hi all
Ok so I've done a fair bit of searching and found a few threads on decanting the starter before pitching. It seemed that was mainly to not mess up the volumes but I'll definitely do that next time. But yesterday I pitched 2L of starter (two step) into my Belgian strong ale. I measured the OG before I pitched the yeast and it was 1.070 in a 20L wort. After I pitched it was down to 1.062 in a 22L wort. Which one should I use to do my ABV calcs?

The starter was a 2-step- 1L water and 100g DME for a day, then tipped that into another 1L water/100g DME. I assume that because I've made a mini beer, that would also drop the OG points because of the alcohol in there.

What do you all think?
Thanks
Kieren

Hey mate. For efficiency purposes you would go with pre starter OG in terms of measuring BH eff etc.

To work out the ABV of the beer then you could assume that 100g DME in 1L of water if you added the DME then topped to 1L should be 1.037ish OG and would ferment down pretty low being a starter so maybe a ball park or 1.006? So probably like a 4% ABV beer and then you added that to 20L

4% alcohol of 2L is 80ml in 22L would be about 0.32% ABV so just add that to your 1.062 to FG calculation.

I think.

 

[Dozer71]

Your yeast starter has a specific gravity of around 1.037, so you slightly diluted the wort of 1.07. As such to calculate the ABV of your finished beer you need to use 1.062 as that is the sg of your total wort that is to be fermented.

 

[kadmium]

Your yeast starter has a specific gravity of around 1.037, so you slightly diluted the wort of 1.07. As such to calculate the ABV of your finished beer you need to use 1.062 as that is the sg of your total wort that is to be fermented.

The sg of the starter was probably closer to 1.006 or so as its fermented out so it's 1.062 plus a little ABV from the starter.

 

[kierent]

Thanks gents, that makes sense. Definitely crashing and decanting the starter next time

 

[MHB]

Most of the change in gravity in the starter shouldn't be Alcohol. Yeast reproduces using the nutrient in the wort and Oxygen making yeast and very little Alcohol.
In fact if the extract content of the starter can be kept very low the yeast wont make any alcohol, its called the Crabtree effect if you want to do any reading up.
I suspect your final alcohol content will be just the classic Change in gravity/7.5
If you started with 20L at 1.070 (70 Points) and added 2L of water your OG would be 20*70/22 = 1.0636363... (~1.064)
if you just used that and your FG to calculate your ABV you should be very close.
Mark

 

[kadmium]

Most of the change in gravity in the starter shouldn't be Alcohol. Yeast reproduces using the nutrient in the wort and Oxygen making yeast and very little Alcohol.
In fact if the extract content of the starter can be kept very low the yeast wont make any alcohol, its called the Crabtree effect if you want to do any reading up.
I suspect your final alcohol content will be just the classic Change in gravity/7.5
If you started with 20L at 1.070 (70 Points) and added 2L of water your OG would be 20*70/22 = 1.0636363... (~1.064)
if you just used that and your FG to calculate your ABV you should be very close.
Mark

Awesome I never knew that, thanks for the info that is way cool! I will look it up for sure!

Is that how they get low or no alcohol beer?

 

[MHB]

Snip
Is that how they get low or no alcohol beer?

No, mostly they take the alcohol out of full strength or it just doesn't taste right.
M

 

[kadmium]

No, mostly they take the alcohol out of full strength or it just doesn't taste right.
M

There you go, learned something else new!

Cheers