The whisky congener group "mash" contains four sub congeners which all generally describe what is happening in the mash tun and what comes out of it.
Oddly enough "Malted Barley" is a congener the flavour wheel, "Porridge" is on there, but the product in between, the process step of milling the "malted barley" being "grist"/"flour" is not. Probably because there is nothing happening chemically, in the milling process that really alters a smell sensation. Probably! < indicates I am in doubt.
My interpretation of what's going on.
When the "grist" is added to the mash tun and water is mixed you can call this a "porridge" because from a enzyme point of view nothing has really happened yet.
Ones all the waters have been added and the enzymes did their thing to the "grist" or to be more precise the "starch" the "Wort" is drained and moved on to fermentation and the semi-dry stuff that is left over is removed which you can call "cattle feed" or "draff".
Bruichladdich describe their process on this page and it mentions the following.
After the fourth water has been drained off, we are left with a high-protein, low-carbohydrate porridge called 'draff', which is fed to Islay's cattle, part of what we like to call "the virtuous circle".
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So what you are left with is the non-soluble husks and other solid parts of the milled malted barley kernel and some "wort" that wasn't drained off. Oh and possibly some sweat and elbow grease from the person cleaning the mash tun.
I will probably not go into much more detail on this blog about the chemistry that results in "porridge" or "draff" since these are half products or waste products of the whisky making process and the only way you could smell them would be being a farmer getting the draff for your life stock or if you happen to be the lucky person having to clean the mash tun. "Porridge", in my interpretation only is around during a short period of the mashing process. So stick your nose in a mash tun if your do a tour!
I will do a blog about the congener of "wort" since that will go on to the next steps in the process.