I do a lot of this. Specialty grains only, Base malts require a warm mash. Boil the liquid for 5min to sterilise and add directly to fermenter. Apparently it can cause the finished product to be a little hazy but I don't care about that.
The Guten gives me ~21lt and with the cold mash it fills my fermenter. Works for me.
I do this with spec malts and add liquid to the cube, using the heat of the wort to sterilise. Haven't had any issues after doing on around 20 batches.
I currently get 3-4 cubes out of a batch, so with my last brew as an example, I used 100% munich as the base wort, one cube was left as is, one cube had cold-steeped caramunich, and another with cold-steeped RB.
Add different cube hops and use different yeasts and you can get yourself completely different beers from a single brew day.
Are we talking about "Cold Mashing" or "Cold Steeping"?
Mashing is where enzymes act on starch converting it to sugars (well mostly). All the enzymes in malt are there for the sprouting barley corn to use as an energy store. Naturally all the enzymes we use hot so they will work faster are present at low temperatures, and they will all work, just very very slowly!
I have seen estimates that it would take around 2 weeks for the enzymes to convert all the starch, naturally in that time the brew would be hopelessly infected.
Cold steeping to extract some of the flavour components of specialty malts is hardly new. CWE (Cold Water Extract) was a standard part of the information supplied by maltsters for generations and it still persists on some UK COA's (Certificate Of Analysis).
I have done a bit of digging into typical Yields (% of malt that is made soluble during the congress mash) expressed on a FGDB (Fine Grind Dry Basis), so the theoretically available extract (if there was no moisture in the malt) just the way its done...)) Deduct the typical moisture content if you like.
Second column is the % Extract from a cold steep
Third column is the % extract cold over hot (or normal mash if you prefer). Interesting to note that the best results are from very dark roasted malt/grain (>1000EBC), and the hump in the Crystal Malt extraction best results from light-medium Crystal. Worth noting that at best you are likely to get less than half of the goods from a cold steeped malt than from the same malt mashed.
All the Base Malts had CWE's <5%
Personally I cant see the point, unless you think it favorably affects the flavour. You will clearly get less out of your malt, there is also a recognised possibility of getting more starch and proteins into solution. When you consider the amount of work maltsters and brewers go to to minimise excess of both getting into the beer, I have to wonder how good an idea it is.
there is some food for thought - thank chaps.
the podcast was using extreme hot and cold mash temps for low abv brewing. i may have to re-listen, and then give it a try. ill update on success (or failure)