Hops A-Z: R is for Resin

Word association time. If I say 'the defining taste of beer is...' you would say...?

'Hoppy'? (if so, are you Gazza in disguise?)
'Bleurgh'! (if so, why are you still reading?)
'Malty'? (if so, please leave now and don't forget to take your whippet with you)

Beer is bitter. Well, perhaps not all beer, but bitterness is usually there at some level whether it's a gentle tingle or an excoriating pucker. That bitterness is put there by the bittering fairy with a swoosh of her magic dipstick - sorry, I meant to say it's put there by a dash of biochemistry. Acids, to be exact. Which are found in the soft resins.

The beta-acids are often ignored in discussions of hop chemistry, so let's pay them their dues. Lupulone, colupulone and adlupulone all contribute to the bitterness of beer, but towards the end of the process. They oxidise during fermentation and/or storage, so adding bitterness into the beer as it ages. They also run the risk of adding a vegetal tinge.

Most of the bitterness results from the presence of alpha acids. Humulone offers a soft - for many drinkers, desirable - bitterness. Cohumulone adds a harsher bitter taste; US hops such as Cascade and Centennial have proportionally high levels. Adhumulone does... something. But it's rather under-understood.

But those alpha-acids are poorly soluble in water. To get them into the wort, their chemistry needs altering. That's what boiling does; changing the acid's structure to allow water molecules to attach in a process known as isomerisation. Thus, some of the acids dissolve in the water.

Getting that bitterness into beer takes some doing. Hops lose alpha-acids in storage; only a percentage are taken up by the wort (the utilisation rate). More resin, more alpha-acid, isn't the easy answer. Optimisation of the resin's qualities, developed through research in both biochemistry and agriculture, seems to be the way to ensure that beer has a pleasantly bitter future.