Decoded: Why does beer taste so good?

London: The love for beer is trapped inside the yeast that creates its captivating taste, a new study suggests.

Beer yeasts produce chemicals that mimic the aroma of fruits in order to attract flies that can transport the yeast cells to new niches, Belgian researchers have found.

Interestingly, these volatile compounds are also essential for the flavour of beverages such as beer and wine.

“The importance of yeast in beer brewing has long been underestimated. But recent research shows that the choice of a particular yeast strain or variety explains differences in taste between different beers and wines,” said Kevin Verstrepen from the University of Leuven.

“In fact, yeasts may even be responsible for much of the “terroir,” the connection between a particular growing area and wine flavour, which previously often was attributed to differences in the soil,” said Verstrepen.

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Yeast is essential in production of bread, beer and wine.

Humans have been using yeast for thousands of years to produce bread, beer and wine.The microbes eat sugars and convert them into carbon dioxide gas and alcohol. In bread, the gas causes leavening of the dough while the alcohol evaporates during baking.

In beer and sparkling wines, both the alcohol and carbon dioxide gas are retained; whereas in wine the gas is allowed to escape.

However, the role of yeast cells is more complex than the conversion of sugars into alcohol and carbon dioxide. Yeast cells also produce several aroma compounds that are key for the taste, flavour and overall quality of beer and wine.

In fact, different yeasts are producing different amounts of these aroma compounds. Whereas the importance of yeast aroma production is now fully appreciated, the reason whyyeast cells would make these special, volatile chemicals remains mysterious, researchers said.

A new collaborative study shows that the fruity volatiles produced by yeast cells are highly appealing to fruit flies.

This attraction allows some yeast cells to hitch a ride with the insects, who carry the otherwise immobile microbes to new food sources.

Moreover,the key yeast gene driving aroma synthesis, all but abolishes the attraction of flies to the mutants.

The brain activity in flies that are exposed to such aroma-mutants is very different from that in flies exposed to normal, fruity yeasts, researchers said.

“Flies are strongly attracted to normal yeast cells, when compared to mutant yeasts that don’t produce esters. Knowing that esters make beer taste good, it seems that the sameflavours that allow us to enjoy our beer, probably evolved to attract flies and to help yeast disperse into broader ecosystems,” said Emre Yaksi, the neuroscientist who led theexperiments on flies.

The research was published in the journal Cell Reports.

PTI