Being given a pint with a head is a common cause of infuriation for pub-goers.
But a new study suggests the more foam there is on a beer, the more aroma the drink packs.
In lab tests, scientists in Japan found that a prominent layer of froth makes beer up to twice as aromatic, serving as a ‘tantalizing entrée’ of the beer’s overall flavour.
Flavour compounds are concentrated in the millions of individual bubbles in the beer’s whippy foam layer.
When each one collapses, aroma components are released into the atmosphere along with carbon dioxide, leading to an increased perception of flavour.
Beer drinkers often get aggrieved if they think their pint has too much head – but the new study suggests it adds to the flavour
The study was led by researchers at Kyushu Sangyo University in Fukuoka and Asahi, the Japanese brewing company.
‘Beer foam plays a novel role as a carrier of aroma, specifically promoting the release of some characteristic aroma compounds,’ they say.
‘Beer foam can promote the release of specific and attractive aromas to encourage beer drinking,’ they say in their paper.
‘Foam acts as an efficient gas exchange surface directing aroma toward the drinker’s olfactory sensors.
‘It provides the drinker with the first tantalizing entrée regarding the quality of the beer’s flavours, freshness, refreshingness, and wholesomeness.’
Whether fruity, malty or earthy, we’re able to perceive the nuanced flavours of beer due to olfactory receptors in the nose.
Meanwhile, the taste buds on our tongue detect the ‘taste’ of the beer – so whether it’s sweet, sour or bitter.
There are typically hundreds of flavour compounds in a beer, which are released by the fermentation during the brewing process.
The scientists captured aromas from the beer both before and had been frothed up using ultrasonic waves (pictured)
Punters may want to get their money’s worth of liquid by insisting on very little head – but this may come at the cost of reduced flavour (file photo)
The science of beer foam
Beer is produced through a fermentation process that converts sugars in malted grains to alcohol and carbon dioxide (CO2), which is the gas in beer bubbles.
Beer bubbles are important sensory elements of beer tasting because they transport flavour and scent compounds.
When you open a bottle of beer, the sudden drop in pressure encourages dissolved CO2 to escape from the beer.
Most of this CO2 escapes in bubbles that form at the sides and bottom of a glass, where microscopic cracks and imperfections serve as starting points for the gas to gather.
When the CO2 at a nucleation site reaches critical volume, a bubble detaches from the glass and launches itself toward the beer’s head.
Examples include isoamyl acetate, a compound that smells like banana or pear, and ethyl decanoate, described as having lactic and fruit aromas.
For the study, the team used Japanese beer ‘purchased from the local Japanese market’.
Even though three of the study authors were from Asahi, the brand of beer – and whether they used ale or lager – was undisclosed.
The beer was placed into a sealed glass cylinder so that aromas could only escape through a glass straw at the top, assisted by an inward flow of nitrogen.
Aromas were monitored with a special type of mass spectrometer, an instrument that measures compounds in real-time in an air sample.
The scientists captured aromas from the beer both before and had been frothed up using ultrasonic waves.
This ultrasonic treatment mimicked the physical process a beer might experience when being poured into a glass in a pub.
This allowed them to monitor aroma compounds that would be inhaled through a drinker’s nose for both a foamed beer and a flat beer.
Overall, the team found ‘concentrated rates of aroma components’ were between 1.3 to 1.9 times higher from the frothed-up beer, compared with the beer without any head.
They also found evidence that the more ‘hydrophobic’ or water-repellent a flavour is, the more likely they are to be concentrated in the foam.
Aromas were monitored with a special type of mass spectrometer, an instrument that measures compounds in real-time in an air sample
Researchers also say beer foam acts as a ‘lid’ to prevent the escape of gaseous carbon dioxide, keeping the drink fizzy
But they admit the absence of foam accentuates hydrophilic flavors in the actual liquid, such as malt and caramel.
‘[We] clarified a novel role of beer foam as a carrier of aroma,’ they say in their paper, published in Journal of the American Society of Brewing Chemists.
‘Beer foam can promote the release of specific and attractive aromas to encourage beer drinking.’
The researchers list a number of other benefits of beer foam, including acting as a ‘lid’ to prevent the escape of gaseous carbon dioxide, keeping the drink fizzy.
‘Creamy foam provides a unique mouthfeel on the upper lip when we drink it, and so it is thought to play a role in making beer delicious,’ they add.
They also say the contrast between the foam and the colour of the liquid ‘is a symbol of beer’s beauty’.
Ireland is the real home of BEER! Scientists discover the elusive ancestor of yeast used for lager in a forest in Dublin
Scientists have discovered the ancestor of the yeast species necessary for the production of lager beer – in Ireland.
Saccharomyces eubayanus is a little-known species of yeast that gave birth to the yeast used today to brew lager, Saccharomyces pastorianus.
S. eubayanus was first found in the Patagonian Andes back in 2011, but experts have found it for the first time in the European wild, in Dublin woodland.
They now want to create a new beer using the rare ‘mother’ yeast S. eubayanus, which could create new flavour profiles never before tasted.
Along with water, grain and hops, yeast is one of the four primary ingredients used to make beer.