Below is a general guide on how to brew a NEM (Non Enzymatic Mash) otherwise known as a cold mash. The reason we use this is to capture color, flavor and mouth feel from malts while limiting the extraction of complex carbohydrates. In other words, we drop out the starch and remove it before fermentation so that the yeast has less sugar to eat and convert into alcohol.
I use brewfather for all my brewing tools and to create my recipe’s but I’m sure most programs will be similar. I find that when I am doing a NEM batch if I drop my brew-house efficiency to 23% and reduce my hop additions to half. Low alcohol beers need to observe BU/GU ratio’s be reduce perceived bitterness. That gives me good results. I also hotcube and offset my hop editions by 20 minutes and / or whirlpool editions or I overshoot my IBU’s and end up with a beer thats too bitter.
Start by collecting water in a bucket of some sort, and be prepared to cool it to around 5 degrees Celsius (fridge temp). I pour my milled grains into a BIAB (Brew In A Bag). I dont adjust water chemistry at this point.
I give it a good stir to break up any dough balls.
I give it a good spray with sanitiser and put on the lid.
Put in the fridge at around 5 degrees Celsius for about 12 hours.
Pour off the top into a 25 Litre hotcube (or similar) which has a tap on the bottom. I don’t tilt the container and I ensure that I leave all of the starch sediment I can in the bottom of container 1.
I take the lid off and get it ready to lift the bag. Do not squeeze the bag. It will add a grainy, worty flavour.
Lift the BIAB with a pully. Do not squeeze or disrupt the grain. This will fill the Hotcube with clean, un-sedemented wort.
You dont have to sparge, its a personal preference and a useful way to make up water level.
If I sparge, I Leave the hotcube to sit in the fridge, or on the bench, for another 2 hours. The hotcube has around 2 Litres of dead space under the tap and this will fill with sediment again. You must remove this or it will scorch your kettle.
This step is not entirely necessary if you are careful enough the first time to not disrupt the wort.
Once all the sediment is removed I heat the wort to mash temp, put in my bag of grains, add my water chemistry and mash at 80ºc.
This can be done in a pot on the stove if you dont have a brew kettle.
I sometimes boil or sometimes I just do a 90ºc hopstand and add my bittering hops, whirlfloc, Yeast nutrient. It depends of the beer style.
After boil/hopstand I pour the hot wort into a HDPE hotcube and leave it overnight for future fermenting.
