@peebee has a couple of threads on this subject, if you do a forum search.
Thanks
My low alcohol "project" has gotten a bit eclipsed by the "invert sugar" and "pyknometer" projects (the "brown malt" ramblings have gotten a bit neglected too). But I do continue my low alcohol "research" (i.e. I buy commercial offerings in for my "abstention days"!).
When I left off the low alcohol "project" I was exploring the "cold mash" ideas: No-one need go there, it's full of difficulties and very real hazards (burning out your boiler element out doesn't sound like fun). But the "cold mash" ideas do set you up to appreciate the (very) hot mash approach! Haven't tried mashing at 80C+ yet, but the method certainly has merits.
David Heath has a video on a low ABV IPA using a 80°c mash + Windsor. It is a smaller grist than usual but he adds body with lactose.
Yeap, David Heath's video is a good introduction to the technique. But, by his own admission, it is based on the work by Lallemand that
@Sadfield posted above. Mashing at 80+C sounds disastrous, but the beta-enzymes will run for a few minutes at that temperature and most sugar (for a low alcohol brew) is already in the malt (glucose, sucrose, etc) and only needs leaching out. The alpha-enzymes tolerate the temperature a bit longer and make sure the starch is converted (to long chain "dextrin").
Lactose is added for sweetness which may counter the high bitterness in low alcohol beers? Lactose isn't for body, the huge quantity of dextrin from the mash does that.
And that's also the importance of using yeast like Windsor. They won't ferment malt-triose (the commonest dextrin). Use something like US-05 and you can forget about "low alcohol"! I used S-33 (but was only mashing at 74C which often resulted in higher ABV than desired), but I am edging towards Windsor as a more reliable yeast flavour-wise. Dry yeast is fine (and "aerating" pointless), liquid yeasts
... probably wasted on these beers? But they
must be malt-triose intolerant.
Some commercial yeasts for low alcohol brewing (also obtainable for HB) will not ferment "maltose", but I think (I don't
know) they might be responsible for the unfermented wort flavour of some commercial beers. Mashing at 80+C sounds much smarter.
I don't think I got astringency from it. It was overly bitter though - possibly I'm confusing hop bitterness with astringency?
You are picking out two common problems there. Bitterness is often confused with astringency (even though astringency is a feeling, not a flavour), possibly because they often (but not exclusively) go hand-in-hand.
And the second, excessive bitterness, is a recurring problem with low alcohol beer. Most excessively bitter low alcohol beers also exhibit a "dank, corrugated cardboard" flavour: I'd include "Brewdog Nanny State" (along with my attempts to copy it!) and "Big Drop Paradiso" amongst this category, although "Big Drop" somehow get away with the "dankness" in their "Pine Trail" beer* (Big Drop was my favourite low alcohol beer, but they seem to have given up on their original pale ale). Trusting in the OG:IBU ratio principal seems the best way to avoid excessive bitterness in these beers even though it might indicate tiny hop additions.
[EDIT: *They list this beer with a face puckering 42IBUs! A pale ale I made only had 15g hops (Nelson Sauvin) in 18L, and they were all steep hops to keep the IBUs down ... 6IBUs calculated. Did have 25g as dry hops too.]