Questions about priming a keg with sugar

[Gtrman13]

I recently made a 2.5 gallon batch of a cream ale and put it in a 5 gallon keg. I normally force carb with my kegerator's CO2 tank, but I decided it would be better for the style to prime the keg with lactose. I didn't/still don't know quite what I'm doing here, but I just went for it anyway. I racked the beer to the keg, added 2 oz of lactose, used my tank to purge the O2 and seal the lid, and now it's been sitting for five days at room temp.

I've been told to use less sugar in a keg than a bottle, but I'm not sure how things work out if there is only 2.5 gals of beer in a 5 gal keg. I'm sure I won't have the exact right level of carbonation but I don't know if I'll be low or high! Also, how much time does it need to sit before I can hook it up to my tank and bring down to serving temp? Will there be any kind of yeast cake on the bottom of the keg?

It's frustration not being able to observe anything or take any measurements when that keg is all sealed up!

 

[Golddiggie]

You do realize that lactose is a non-fermenting sugar, right?? You might as well have thrown sand into the brew.

For a half batch (2.5 gallons) of cream ale, in a keg, you need about 1.08oz of PRIMING sugar to get it to a CO2 volume of 2.6...

Sugar takes 3 weeks at 70F... The corny just means you need to use less sugar, not that it will take any less time to carbonate.

 

[Gtrman13]

Non fermenting sugar, eh? Of course I knew that...

Well, thanks for the reply. It's off to chill now!

This may not be the place to ask, but why do some sugars not ferment? I've never heard of anything like that.

 

[Waunabeer]

Lactose is derived from milk and I guess the yeasties are lactose intolerance because they don't consume these sugars vs. nearly 100% of the others. Lactose is good for adding slight sweetness and body to a beer (usually stouts or other dark beers), without adding higher alcohol levels.

I put some in my chocolate oatmeal stout for those very reasons; offset some of the chocolate bitterness and give it more body.

You'll probably need to carefully open the keg and add some dissolved corn sugar for carbing, otherwise you'll just have sweet, flat beer in a few weeks. Good luck.

 

[Golddiggie]

From wikipedia...

"Because lactose is unfermentable by beer yeast, it adds sweetness, body, and calories to the finished beer."

I've never purchased lactose, so I don't know if there's anything on the label to let you know it's not going to ferment. I would imagine that if you added any to a recipe in any of the brewing software's it would increase the OG and FG by the same amount...

 

[a10t2]

This may not be the place to ask, but why do some sugars not ferment? I've never heard of anything like that.

Lactose is a disaccharide, but the enzyme needed to cleave it (lactase) isn't produced by brewers' yeast.

1.1 oz of priming sugar sounds really low, BTW. That would give you about 1.7 vol of CO2, assuming the primary was at 68°F. For 2.4 vol of CO2 you'd need to use about 2.0 oz.

 

[Golddiggie]

1.1 oz of priming sugar sounds really low, BTW. That would give you about 1.7 vol of CO2, assuming the primary was at 68°F. For 2.4 vol of CO2 you'd need to use about 2.0 oz.

Actually, no... Remember, this is a half batch (2.5 gallons, not 5)... So 1/2 the sugar needs to be used...

 

[a10t2]

Right, I took that into account. 1.1 oz in 2.5 gal gives 0.8 vol CO2, plus whatever's in the beer to begin with.

Actually, I was wrong too. You need to pressurize the 2.5 gal of headspace. So to carbonate 2.5 gal of beer, with 2.5 gal of headspace, to 2.4 vol, you'd still need ~4 oz of sugar.

 

[Bohica]

I just kegged 5g of 80 shilling scotch ale with 5 oz corn sugar that came with the kit for priming when botteling.
I called my LHBS first and they said that it would be fine but i would have to use CO2 to dispense later.
Was this too much sugar?

 

[Golddiggie]

I just kegged 5g of 80 shilling scotch ale with 5 oz corn sugar that came with the kit for priming when botteling.
I called my LHBS first and they said that it would be fine but i would have to use CO2 to dispense later.
Was this too much sugar?

Depending on what your CO2 volume target was, and what temp the beer is at... But, unless you vent during the carbonation process, chances are this is going to be extremely over-carbonated.

To get as close as possible to using 5oz of sugar in a keg, I have to put the temperature at 70F, and even then, the CO2 volume is about 4.5 (off the charts)... Considering the style range is 1.5-2.3 volumes. If you're storing this in a keezer, kegorator, or any place cool, it's going to be carbonated higher than 4.5 (closer to 5 volumes)... I'm not sure what soda is carbonated to, but I don't think it's even that high.

Next time, use one of the calculation tools, telling it you're kegging, so that you get the correct amount of priming sugar... 1 ounce of sugar, at 45F (keeping the keg in the keezer/kegorator) would have given you a CO2 volume of 2.0-2.1... Going to the top end of the style range (2.3 volumes) would have only needed 1.31 ounces of sugar at 45F...

 

[a10t2]

Next time, use one of the calculation tools, telling it you're kegging, so that you get the correct amount of priming sugar... 1 ounce of sugar, at 45F (keeping the keg in the keezer/kegorator) would have given you a CO2 volume of 2.0-2.1... Going to the top end of the style range (2.3 volumes) would have only needed 1.31 ounces of sugar at 45F...

When using a priming sugar calculator, the temperature input is the warmest the beer has gotten after fermentation, not the storage temperature. Chilling a beer doesn't generate any additional CO2, but cold fermentation allows more to remain in solution.

Bohica: 5 oz of corn sugar in 5 gal (assuming it fermented around 68°F) will give you about 2.7 vol of CO2. That's high, but not extreme - domestic light lagers are usually 2.7-2.9.

 

[Golddiggie]

When using a priming sugar calculator, the temperature input is the warmest the beer has gotten after fermentation, not the storage temperature. Chilling a beer doesn't generate any additional CO2, but cold fermentation allows more to remain in solution.

Bohica: 5 oz of corn sugar in 5 gal (assuming it fermented around 68°F) will give you about 2.7 vol of CO2. That's high, but not extreme - domestic light lagers are usually 2.7-2.9.

Since my brews typically are fermenting in the 62-68F range, I usually calculate around 65F since it's closer to that for more time.

Are you 100% sure you spec'd out that the brew was in a KEG??? Makes a big difference in the tools I use for how much sugar you add. Typically you need about 1/2 the amount of sugar for kegs than you would need if you put the brew into bottles...

 

[a10t2]

Are you 100% sure you spec'd out that the brew was in a KEG??? Makes a big difference in the tools I use for how much sugar you add. Typically you need about 1/2 the amount of sugar for kegs than you would need if you put the brew into bottles...

What calculator are you using? I'd be really surprised if being in a keg or a bottle made any difference. The amount of CO2 needed is the same either way.

 

[Golddiggie]

What calculator are you using? I'd be really surprised if being in a keg or a bottle made any difference. The amount of CO2 needed is the same either way.

The one built into Beer Smith... I've also talked with the brewers from the LHBS and they confirm that in kegs, you use less sugar than in bottles. You also want to make sure the keg seals, or it may never carbonate (hit it with gas to get the seals to seat fully)... With the high amount of sugar used, chances are, you'll need to bleed off some of the excess CO2... Pick up one of the pressure gauges that go onto the gas post of the keg to make sure you're not getting too much pressure inside, for the desired carbonation level.

 

[a10t2]

That's interesting. I can't think of a reason why they would carbonate to different levels, but then again I've never tried it. Searching the forum, it seems like opinions are divided. Which is strange, because it isn't like the difference between 2.7 and 4.5 vol would be subtle.