Adding lactose sugar to keg

A while ago I brewed a stout with the intention of adding lactose once it was in the keg. I was originally planning to dissolve the lactose sugar in about a pint of water, boiling it for 15, then adding it to the keg. I just had the idea of pulling a pint or so of the stout from the keg and boiling that with the sugar instead of regular water. Obviously I'd boil off the alcohol from it, but then I wouldn't be diluting the whole batch with the water.

Has anyone ever done this before? Would there be any downside to doing it this way?

Haven't done it but it is sound. No need to boil, just get it above 160F for a few minutes. No need to let it cool before dumping back in the keg.

I've kinda been pondering the same thing. I had a scale totally screw up on me for 2 batches in a row before I caught it, my Munich Porter had a way higher gravity than intended and is double roasty, was thinking maybe some lactose would help it out, but I've never added it to fermented beer.

Oh and the other victim batch of the bad scale...well you don't wanna even know how many hops went into that IPA......

helibrewer said:

Haven't done it but it is sound. No need to boil, just get it above 160F for a few minutes. No need to let it cool before dumping back in the keg.

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Really? 160º for a few minutes is enough to kill anything that might be in the sugar? Back when I used to bottle, I always thought I had to do the standard 15 minute boil to sterilize the priming sugar.

turkeyjerky214 said:

160º for a few minutes is enough to kill anything that might be in the sugar?

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No. To kill anything that might be in the sugar, you'd need to heat it to 253° F for at least 15 minutes (i.e., a pressure canner or autoclave). But there are two caveats to consider. 1) 160° for a few minutes will kill the vast majority of bad things that might be hiding in the sugar, and 2) very few organisms can survive in such a dry environment anyway, so there are likely very few potential contaminants in the sugar to begin with.

turkeyjerky214 said:

Back when I used to bottle, I always thought I had to do the standard 15 minute boil to sterilize the priming sugar.

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Nope, that's overkill. I heat my water up, but it's just to make the sugar dissolve more easily. Total sanitation is not really a dominant concern at that stage. You're about to dump it into a low-pH, high-alcohol environment in which most nutrients have already been depleted.

turkeyjerky214 said:

Really? 160º for a few minutes is enough to kill anything that might be in the sugar? Back when I used to bottle, I always thought I had to do the standard 15 minute boil to sterilize the priming sugar.

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Yes, that's the flash pasteurization protocol.

Awesome, thanks for the help guys! I figure I'll add the lactose tonight and have it on my new nitro tap in time for Thanksgiving.