Saturday 19 December 2009

Flavour Compound of the Week

Welcome to flavour compound of the week. In this ‘feature’ of my blog I will introduce you to (bore you to death with) a different flavour compound each week, describing its sensation, origins and some of its chemistry.

Flavour in the most important part of beer. That goes without saying. Rather irritatingly for brewers it is also the most complicated. This is why global brands are low in flavour. It is easier to control flavour when there is very little there in the first place. There are thousands of known flavours in beer and probably more unknown ones. All have thresholds and act additively, synergistically and or antagonistically to each other. That is some can promote the detection of other flavours and some can mask them.

In truth, with regard to a lot of flavour compounds we don’t know exactly where they come from.

I am starting with a compound that I know more about than most because I studied it for my thesis at university. It is the wonderfully-named 2,5-dimethyl-4-hydroxy-3(2H)-furanone or DMHF for short.

DMHF smells like candyfloss and strawberry jam. As with most flavour compounds it smells differently at different concentrations and in different contexts. At high concentrations it has been described as having a rotten note. Interestingly (or not) DMHF is not only formed by non enzymic browning of malt sugars during malting and wort boiling but is also produced by yeast during fermentation. It is likely that the yeast transforms a precursor molecule which has been formed during a stage of the brewing process involving heat.

Stronger beers with more dark malts will have higher levels of DHMF than pale weaker beers, although a beer with less back ground flavours (hops, fruit, roast) may exhibit more than beers 'with a lot going on'. Look out for it in less hoppy barley wines, dubbels and strong German lagers.
Next time you're in the company of a beer nerd and they are reeling off a list of abscure chemicals that s/he has picked up in the beer, just mention that a whiff of 2,5-dimethy-4-hydroxy-3(2H)-furanone has just danced like a zephyr across your olfactory epithelium and that should keep them quite for a few seconds.


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