I was doing some research last week and I came across one published paper from last year that was quite interesting, and I thought I'd share with you all. ("Influence of malt browing degree on lipoxygenase activity" Sovrano, S. Buiatti, S. Anese, M. 2006. Food Chemistry 99 711-717).
To start, there are a few science-y things I should mention. Lipids that naturally occur in malted barley can be broken down by several conditions during the mash and brewing process to form 2-trans-nonenal, a compound that creates a very cardboardy flavour in beer. One of the major pathways for this lipid breakdown is provided by the enzyme lipoxygenase (also naturally found in malt). Lipoxygenase oxidizes (attacks) the lipids to form the precursors that eventually create the dreaded 2-trans-nonenal.
The paper found, however, that specialty malts (crystal, carapils, roasted/black malt, etc) which are heated/kilned to cook the insides of the barley lack lipoxygenase activity. In addition, they found that mashes created with specialty malts also had a lower lipoxygenase activity than would be expected. Indeed, the specialty malts were actually inhibiting the action of lipoxygenase! Why? Well its rather complicated, so I'll let you nerdy types read the article yourselves and save the rest of you the boredom.
What does this mean to you? Well, possibly not much, as many all-grain homebrewers already use a bit of specialty malt in the grist, so there probably isn't much new for you. But if you're brewing a light-coloured beer (lager), consider the addition of a small amount of carapils or light crystal malt to the grist, it shouldn't alter the colour much and may help your homebrew shelf life.
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