Before you read this lactose is milk sugar and lactase is an enzyme that breaks down lactose so people with lactose intolerance can eat dairy products. It can be easy to confuse the two.
In the past before I was lactose intolerant I used to brew a chocolate cake stout that had lactose in it. I want a way to brew the same beer but add lactase to it. The issue is that once I add the lactase it will break down the lactose and the yeast will ferment it. So I want to ferment the beer (I add the lactose during the boil) normally, add something that will kill/arrest the yeast and then add the lactase.
What would be the best thing to kill/arrest the yeast?
Why on earth would you want to add both lactose and lactase? This makes no sense. Lactose isn’t THAT flavorful where it is an essential ingredient. Instead, I would consider the use of maltodextrin and/or Windsor yeast which only attenuates about 60%. That will give you a similar result if you start from the same OG.
Take a look at potassium sorbate and potassium metabisulfite or sodium metabisulfite. I was recently looking into how to backsweeten cider without restarting fermentation and found that these are commonly used in wine and cider to do exactly what you want.
After reading a few different articles and watching a few different videos, I ended up adding 2 crushed Campden tablets (sodium metabisulfite) to 2.5 gallons of fermented cider. Let that sit for a day then added 3.5g of Sorbistat K (potassium sorbate). Let that sit for 2 more days and the yeast should no longer be active.
i thought I was lactose intolerant for a few years, but ive sort of just dipped into it and found its not an issue. uh anyway though.
i thought about this a fair bit when i thought i was lactose intolerant - large amounts of flaked barley, more crystal malts? im thinking the best solution for what you want is to make a delicious stout with a high FG and elements that point towards what you like in the milk stout just like others said above. i mean do these first, and then if that isn’t enough it probably would be science experiment time or simply keep a supply of lactaids beside the keg.
I feel your concern though, I still try to avoid lactose beers.
Because the lactase has more time to break down the lactose. While taking a lactase pill (lactaid) when drinking also works, it works more efficiently the longer it is in contact with the lactose.
Just use a different non-fermentable sugar like maltodextrin.
I suspect breaking down the lactose will change the flavor — lactose + lactase → glucose and galactose which are both significantly sweeter than lactose.
Maltodextrin will add body while being much closer to the sweetness of lactose.
My wife is the one who does the meads, but I thought she mentioned that the potassium metabisulfite & potassium sorbate don’t actually kill the yeast, but rather suppress the yeast. I could be wrong.
Not trying to be pedantic, and I’m not sure if there’s a practical difference in this case.
Basically the sulfite stuns things, the sorbate prevents reproduction. So you really can’t stop an inflight fermentation, but you can prevent one from re-starting. Ish.
Use of sorbate and sulfite is not a perfect technique. Results can vary. It works better only if the yeast is very old, very tired, there’s hardly any sugar, and you don’t then show them a bunch more sugar and expect them not to eat it. Bait & switch kind of thing with young healthy yeast? Yeah… good luck with that.
Lactose is not necessary in a sweet stout. It’s just typically used as ONE of the ways to add unfermentable body to the beer. You can use a combination of high mash temperature (more dextrines in the wort) and malto-dextrine powder. I’d start with a high mash temp and augment with malto dextrine prior to packaging if you don’t land the body you were after.
I’m not trying to add more body to the beer, I want to add sweentness. The beer I brewed in the past was a chocolate cake stout. A 6-7% stout with 1 lb of lactose and 8oz cocoa powder.
If all you are trying to do is add sweetness, the lactose/lactase thing is needlessly complicated.
One solution is to reduce the BUs to make the residual sweetness more detectable. Another is to simply back-sweeten the fermented, cold-crashed beer with a glucose solution. If it’s cold crashed, the cold, dormant yeast won’t ferment the glucose. You could also add the glucose solution on a per-glass basis so people can sweeten it to taste.
I don’t understand why we’re not all talking about maltodextrin. It definitely works. It’s not very sweet, but that’s fine, then just use a lot of it. Perhaps 1 to 1.5 lb per 5 gallons. Yes it will add body. But it will add some sweetness as well. Almost the same as lactose, but it’s not lactose. If you want to offset the body portion of it, then mash really low for a long time and/or use a highly attenuative yeast to balance the body out. Plenty of knobs to turn here besides messing around with enzymes which is almost certain to ruin a beer.
I’m adding my +1 (again) to your maltodextrin suggestion. It would have roughly the same sweetness & body contribution as lactose — without messing with any other additions to try to arrest fermentation.