Incomplete fermentation- Cream Stout

[No Outlet Brewing]

So I'm not exactly new to home brewing as the batch in question is #15 and #5 all grain. The recipe is question is a cream stout AG kit from Midwest Supplies. Brew day seemed to go well and hit OG spot on at 1.044. Fermentation started as expected and within 24 hours and a beautiful krausen had formed. Krausen fell after about 3 days as usual and then left it to condition for about 18 more days. Fast forward three weeks and on bottling day the FG reading is only 1.020 (target 1.010) giving me a approx abv of only 2.63 when it should have been around 4.3. I have missed OG before by small amounts but FG usually came out near where it should. Does the addition of lactose in a cream stout effect these numbers? Sorry for the newbie like questions but I've never really understood the science behind brewing as much as I should. Any info on where I may have gone wrong would be greatly appreciated.

 

[philjohnwilliams]

If the lactose was part of the original recipe then the OG and FG numbers should account for it. Lactose, as I am sure you are aware, is generally unfermentable by brewing yeast, so an excess of lactose will result in a higher FG, but like I said, if this was part of the original recipe then that should have been taken into account. Are you using a liquid or a dry yeast? When I started using liquid I was not oxygenating my wort enough and I had a few beers that finished high (1.020ish) so I might lean towards lack of oxygen as a.possible cause, but more details regarding your recipe and process would help.

 

[No Outlet Brewing]

Yes, lactose was added as part of the boil so should have been accounted for in the OG. Like I said, the OG was spot on based on the recipe. Yeast used was dry yeast Safale S-04. I do the old "shake the snot out of it" oxygenation method and has always worked in the past and initial fermentation started and looked great so I assumed everything would come out as usual.

 

[BOB357]

If you're using a refractometer to measure FG you need to use a calculator to adjust the reading to the correct FG. Once alcohol is present refractometers don't measure accurately. Also, it is possible that the kit instructions are off. Try entering the recipe in the recipe builder and see what it comes up with for FG.

 

[White Haus Brews]

My suspicions:
1) if you use a refractometer, make sure you use the appropriate calculator for FG as Bob mentioned.
2) lactose will bump up your OG & FG as it's unfermentable. (Not sure how that impact is handled by BF but you could experiment by taking it out of your recipe and it should lower your OG but not change your FG) How much did you add?
3) What was your mash temp? Higher than 150 and definitely if you're close to 160 you'll extract more unfermentable sugars and give you a higher FG.

Most importantly though, how is the taste? If you are getting what you like out of it no need to worry!

 

[No Outlet Brewing]

8 oz lactose added for full 60 min boil. Tried taking it out of the recipe with no changes to numbers. Mash temp of 152 for 60 min. Most importantly, initial samples seem to taste as desired. I would just like to figure out what caused this to avoid it in the future and become a more consistent brewer. Thank for all of the feedback so far.

 

[Nosybear]

So I'm not exactly new to home brewing as the batch in question is #15 and #5 all grain. The recipe is question is a cream stout AG kit from Midwest Supplies. Brew day seemed to go well and hit OG spot on at 1.044. Fermentation started as expected and within 24 hours and a beautiful krausen had formed. Krausen fell after about 3 days as usual and then left it to condition for about 18 more days. Fast forward three weeks and on bottling day the FG reading is only 1.020 (target 1.010) giving me a approx abv of only 2.63 when it should have been around 4.3. I have missed OG before by small amounts but FG usually came out near where it should. Does the addition of lactose in a cream stout effect these numbers? Sorry for the newbie like questions but I've never really understood the science behind brewing as much as I should. Any info on where I may have gone wrong would be greatly appreciated.

Lactose, unfermentable, will affect the final gravity. I don't know if it was part of the original prediction of finished gravity but it seems that for an OG of 1.044, 1.010 is a reasonable finish for an all-malt beer. How much lactose are we talking about and when was it added? Okay, the numbers I needed came in as I was writing. Assuming a 5-gallon batch, the 8 ounces of Lactose would have added about 5 points of gravity (46 PPG * 0.5 pounds / 5 gallons, or 5 points, within measurement error of an average brewing hydrometer). It would have added the 5 points on both sides, provided it was in the wort before you took your OG. If not, your FG was really 1.005. Before packaging, though, I'd let it stand a few days taking gravity readings to make sure it was through.

 

[White Haus Brews]

8 oz lactose added for full 60 min boil. Tried taking it out of the recipe with no changes to numbers. Mash temp of 152 for 60 min. Most importantly, initial samples seem to taste as desired. I would just like to figure out what caused this to avoid it in the future and become a more consistent brewer. Thank for all of the feedback so far.

Hmm that is weird. I'm guessing just a perfect storm of lactose, less fermentable sugars (if I found the right recipe kit it also had some crystal and black), and perhaps a less aggressive yeast although I'm not sure what you used. Did you confirm your FG with a hydrometer?

 

[No Outlet Brewing]

I did notice in recipe builder if I enter lactose under fermentables it does change the OG and FG numbers, and in that case I came up short on OG and FG is a lot closer. Under those conditions it would appear my mash efficiency was less than desired versus a problem with fermentation. Being an unfermentable sugar, should lactose be entered under fermentables or other ingredients? FG was taken with a hydrometer and temp corrected. Yeast used was Safale S-04 dry yeast.

 

[Nosybear]

I did notice in recipe builder if I enter lactose under fermentables it does change the OG and FG numbers, and in that case I came up short on OG and FG is a lot closer. Under those conditions it would appear my mash efficiency was less than desired versus a problem with fermentation. Being an unfermentable sugar, should lactose be entered under fermentables or other ingredients? FG was taken with a hydrometer and temp corrected. Yeast used was Safale S-04 dry yeast.

I'd enter it under "Fermentables" even though it isn't fermentable, just to track the additions to OG and FG. Kind of like Rice Hulls are listed in Fermentables to help out with strike water temperature calculations.

 

[Hawkbox]

I've never honestly used lactose so I'd just do what Nosy said.

 

[Craigerrr]

I'd enter it under "Fermentables" even though it isn't fermentable, just to track the additions to OG and FG. Kind of like Rice Hulls are listed in Fermentables to help out with strike water temperature calculations.

 

[terrytormonet]

thanks7