Final gravity seems high

[thechasm442]

Hey there. Just a quick question. I have a extract stout recipe that I came up with and the first 2 times I brewed it I had an OG of 1.070 and a FG of 1.015

This time around the only difference in recipe is that I added 1/2 lb of lactose sugar in the last 5 minutes of brewing. It is now 2 weeks later and the krausen is gone so I have moved it to the secondary to age with vanilla bean and my gravity is different. The OG this time was 1.076, however the current gravity is 1.025. The only real difference I can deduce is that the first 2 batches fermented @ 71-72 degrees and this batch fermented @ 68 degrees. I will of course take another reading in 2 weeks when I am done with the aging and ready to bottle but my question is does this seem normal? The beer tastes good at this point, although it does not have the sweetness I expect from a milk stout, however I will not add a simple syrup solution until I taste it after vanilla aging, if at all.

Thanks.

 

[unionrdr]

I think the .5lb of lactose added to the OG/FG a little. Seems not enough for the milk stout qualities. Check it after aging just the same. It might still drop a couple of points.

 

[TopherM]

Fermentation temp wouldn't affect attenuation unless you fermented too low, and neither of your batches was fermented too low. There's a set amount of fermentables in extract, and the yeast will always eat around 75% on average of those fermentables if they are active.

The attenuation of the first batch was 78%, the 2nd one was about 67%. Lactose is unfermentable, but it still adds to the sugar density (i.e., gravity points) of the wort, so it does factor into your OG and FG readings, but won't ferment. That's why your numbers are off, the unfermentable sugar. If you could magically take the lactose out, I think you'd find that the numbers are practically identical in both batches.

Don't worry too much about the numbers. Just finish the beer out.

 

[WoodlandBrew]

Like the others have said, the latose will not ferment. To put some numbers on it, the 1/2 pound of lactose will add about 20 GU, in five gallons that will be 8 of the gravity points.

Did you aerate the exact same way, and how much yeast did you pitch?

 

[Cordane]

Did you aerate the exact same way, and how much yeast did you pitch?

This. Apart from the lactose addition, I'll guarantee you the discrepancy is here. Not that it's a real problem or anything - beer tastes good, right? But yeah, the yeast will do it.


Shake the bejeezis out of that carboy before pitching!

 

[thechasm442]

Thanks to everyone for the input

I did the same aeration as the last 2 batches, which was basically vigorous shaking of the carboy for 10 minutes, giver or take some time to rest my arms. I pitched the same yeast in every batch, which was 2 smack packs of wyeast 1056. I understand that lactose is not fermentable, I just thought my current gravity would be lower considering that it was significantly lower in previous batches and lactose was the only added ingredient that does not ferment.

 

[WoodlandBrew]

It only takes 40 seconds of vigorous shaking to fully saturate, but if you do 10 minutes I guess you can skip the gym. (see WYeast site on pitch rates for that number)

The first batch FG was 15 plus the 8 points of the lactose brings you to 23. That's only two points short of where you ended up.