Today we’re once again cracking open the Field Guide to Flavour, introducing you to another of the flavours and aromas you may experience with each brew you taste. On deck today: trans-2-nonenal.
A wet cardboard flavour indicates the presence of trans-2-nonenal.
Trans-2-nonenal happens as a result of oxidation. Oxidation can happen at any point during the brewing process, and it is also an unavoidable side-effect of aging.
Type: trans-2-nonenal is part of a large group of compounds called unsaturated aldehydes.
Tastes like: wet cardboard
How it’s used: this off flavor is always undesirable.
How it happens: this off flavor is generated through the oxidation of unsaturated aldehydes. When something is oxidized, it is stripped of its electrons. Scientists haven’t yet explored the actual formation of trans-2-nonenal – so how it is actually made is a bit of a mystery.
Brewers must strictly control the amount of oxygen introduced into the brewing process, in order to minimize the oxygen present in the finished brew – keeping a lid on the amount of trans-2-nonenal that can be formed. At Moosehead, our system keeps that pesky oxygen under tight controls, but we are nevertheless particularly vigilant during the aeration of hot wort, and we watch for unnecessary splashing during product transfer.
Fun facts: cask and bottled conditioned beers can stave off this off-flavour longer than regularly conditioned beers, because of the presence of yeast – which helps to absorb oxygen.