Adding sugar after main fermentation

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trn

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I'm making a few modifications to a batch of an IPA that came out quite good last time. I'm increasing OG to around 1.077 to get it into honest to goodness imperial IPA range. Using WLP001, I can get around 76% AA tops, which would leave me at FG=1.018. I want it to be a bit dryer, so I'm considering adding some dextrose after the main fermentation slows. After looking through the archives, this seems to be the most useful:

For my IPA's, I always get 75% attenuation with WLP001. If I want more, I add sugar once fermentation has slowed/stopped. Boiled with water at a ratio of 1lb corn sugar per 1 cup water. I've found that if you take the percentage of the grain bill that the corn sugar will be and multiply it by .8, add that number to your attenuation (usually 75% for me) and you get your new expected attenuation. I like to target 1.012 depending on the grain bill and expected ABV. Don't want to add too high a % of corn sugar depending on the grain bill. Simple grain bills get a lower % of corn sugar.

So, if 5% of the grain bill will be corn sugar then 5% * .8 = 4% an I expect the final attenuation to be 75% (typical) + 4% = 79%. Works every time.

Since this is an extract batch, I'm thinking more in terms of gravity points. So if I were to keep aiming for 77 points, I can use about 73 points worth of extract and 4 of dextrose (5%) and I might expect AA more like the 79% in the example above.

Is this thinking right? I'm not really worrying too much about exact numbers, but I just want to have at least a rough idea of how much to add and if it really makes sense for me to be doing it.
 
When I get 75% attenuation, the fermenter is at 68F, the last 4 IPAs with WLP001 have shown this. I just did a test and fermented at 72 and got 77.6% attenuation. I haven't duplicated or triplicated this yet but I'm pretty sure the temp directly affects attenuation so keep that in mind.
Also, when fermenting at 72, the .8 rule I was using turned into the .85 rule.
It looks like with the 76% attenuation you've been getting, if you start at 1.077, you'll finish at 1.017-1.018 (depending on a heavy or light 1.077). Take a gravity reading when activity stops and figure out how much more you want to dry it out. I use beersmith and change the corn sugar percentage, then multiply by .8 (depending on fermentation temp now), add that to the avg attenuation for the yeast input and check the final expected gravity it spits out. If you use .5 lb corn sugar (~5.66% of the total bill) and ferment at 68F, I would expect your beer to finish around 1.014. I just quick threw in DME and corn sugar into beersmith and that's what it spit out. I'm brewing all-grain so YMMV.
 
Excellent. This will get me well on my way. I don't think my level of experience even merits this much detail, so I'll just get some rough numbers from your approach and see what happens.
 
Actually, I'm abandoning that approach and moving on to step mashing with separate beta and alpha amylase rests to control fermentability. I'll still use the corn sugar approach as a back up if the FG is too high on the first tests.
 
Would adding simple sugar to a beer really give you a lower FG than it was going to go to without it? If you let the beer hit FG, say 1.018 and then add dextrose, the yeast is going to chomp that dextrose down pretty quick and up your attenuation, but you pretty much just increased your OG. I would think you would just ferment back down to 1.018 but not any further.
 
Would adding simple sugar to a beer really give you a lower FG than it was going to go to without it? If you let the beer hit FG, say 1.018 and then add dextrose, the yeast is going to chomp that dextrose down pretty quick and up your attenuation, but you pretty much just increased your OG. I would think you would just ferment back down to 1.018 but not any further.

This was my thinking also.

I would like to hear if other have experienced this also.
 
Alcohol is lighter than water, so if you're adding alcohol without adding anything else, then it'll lower your SG after it ferments. Right after you add the sugar, it'll raise it up, but then it'll drop lower than it was before the addition.
 
I brewed a 1.116 (32 lbs grain) barleywine that I pitched on a 001 yeast cake( high octane amber 6.6%). After primary fementation slowed, I added 1lb dme, 1lb organic cane sugar, 1lb turbinado. A week later, I added 9 oz dme and another lb of organic cane sugar. The 001 knocked it down to 1.030. After two months total, I racked into a secondary. Two months later I checked again, it was down to 1.024. I made a starter, and kept both beers at 65-66* during fermentation. This particular batch of 001 sure worked well for me. All in all, if my calcs were correct +/- 17.5% abv and 120 IBUs! Truth be told, after only 6 months it is a bit hot yet.
 
Would adding simple sugar to a beer really give you a lower FG than it was going to go to without it? If you let the beer hit FG, say 1.018 and then add dextrose, the yeast is going to chomp that dextrose down pretty quick and up your attenuation, but you pretty much just increased your OG. I would think you would just ferment back down to 1.018 but not any further.

This was my thinking also.

I would like to hear if other have experienced this also.

I probably have the least experience here, so I'm not claiming any authority. But, what I've read is that a late addition of easily fermentable sugars gets the yeast going again and somehow tricks them into fermenting some what they didn't get the first time. Why this might be so, I don't know. From what I've read, people claim success with this and commercial breweries have been known to do it, so I figured I'd give it a try. If anybody has a more convincing story I'd love to hear it.
 
Actually, I'm abandoning that approach and moving on to step mashing with separate beta and alpha amylase rests to control fermentability. I'll still use the corn sugar approach as a back up if the FG is too high on the first tests.

One day, I may follow in your footsteps... may need to start AG first ;)
 
Alcohol is lighter than water, so if you're adding alcohol without adding anything else, then it'll lower your SG after it ferments. Right after you add the sugar, it'll raise it up, but then it'll drop lower than it was before the addition.

Very true! I guess what I was really thinking was that you will be left with the same amount of unfermented sugars in the beer. Meaning adding your simple sugar late is not to get the yeast active so they ferment more of the more complex sugars but so they don't "eat" the simple first and then get lazy (stressed) leaving too much maltose and more complex sugars at the end.
 
Does adding corn sugar after primary fermentaion add to the alcohol level? I read to make a 'hyper beer' you can add small amounts of sugar a little at a time to slowly boost the ABV. Is this correct? Are there any other concerns i should have when doing this?
 
Look up Invert Sugar here on HBT. Made from white table cane sugar and citric acid (lemon juice), yeast love it! You will too.
 
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