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‘Perfect head of beer’ in sight thanks to foamy findings

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University of Manchester researchers have taken a major step towards creating the “perfect head of beer” by investigating what makes foam more or less stable.

Dr Richard Campbell, an expert in physical pharmacy at the University of Manchester, said that his findings solve a stubborn mystery about the lifetime of foams by explaining how foams made using multiple additives – like those used in commercial products – behave.

Campbell made use of one of the world’s most powerful neutron sources, located at the Institut Laue-Langevin, to study mixtures containing both surfactant (a compound which lowers surface tension) and a polymer (used in shampoos and other products).

He fired beams of neutrons at the liquids used to make foams, then analysed the neutrons reflected from the samples.

“Just like when we see light reflecting off a shiny object and our brains help us identify it from its appearance, when neutrons reflect up off a liquid they are fired at, we can use a computer to reveal crucial information about its surface,” said Campbell. “The difference is that the information is on a molecular level that we cannot see with our eyes.”

This allowed Campbell and his colleagues to determine a correlation relating the stability of foam films (the building blocks of the foam bubbles) to how the additive molecules arrange themselves on the bubble surface.

An optimal arrangement of these additives renders the bubbles less likely to burst, resulting in a longer-lasting foam.

“Foams are used in many products – and product developers have long tried to improve them so they are better equipped for the task they are designed to tackle,” Campbell said. “But researchers have simply been on a different track, thinking of general surface properties and not about the structures created when different molecules assemble at the surface of bubbles.”

“We think this work represents a clear first indication that our new approach could be applied to a range of systems to aid the development of products that can make an impact in materials science and on the environment.”

The applications of this research could include beer with a head that lasts all the way down to the bottom of the pint glass, as well as better household products, including laundry detergents which minimise irritating foaming. It could also be used to develop more effective fire-fighting foam.

This new knowledge could even be applied to certain environmental problems, such as by improving the performance of oil-slick cleaning products (oil absorbent foam).

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