Why a crisp can make bitter better...

Would you like a packet of crisps with your pint of bitter?

The answer is probably "yes", suggest researchers: because the salt in the crisps masks the bitter flavour and brings out the sweet tastes in the beer.

Although people usually think of salt as a flavour enhancer, new research by a team of American scientists suggests that it actually functions as a flavour "filter" on food, selectively enhancing and suppressing various tastes.

The result could explain earlier, puzzling results from the Eighties, which seemed to find that adding salt had little effect on other flavours - despite the fact that various cultures have used it as a condiment for thousands of years.

It could also point towards the reason why "low-sodium" foods, which are increasingly popular in the United States, as dietary salt is thought to contribute to high blood pressure, do not sell well: the absence of the chemical makes them taste flat.

The tests on 21 volunteers by Paul Breslin and Gareth Beauchamp at the Monell Chemical Senses Center in Philadelphia, provided water-based mixtures of urea, a bitter-tasting chemical, sugar and sodium acetate, a mild-tasting salt chemical. The volunteers were asked to rate the drinks for their saltiness, sweetness and bitterness.

Writing today in the science journal Nature, the scientists say: "As predicted, there was a selective suppression of the taste components by sodium acetate. The bitterness of urea was suppressed much more by the salt than was the sweetness of sucrose."

When all three chemicals were put into the water, the mixture was judged sweeter than if the salt was not in there, they added.

"The desire for sodium chloride [common table salt] and other salts in foods as diverse as [often bitter] vegetables. Oily foods and meats may be due in part to their ability to suppress unpleasant flavours," the researchers wrote. Other studies published earlier this year in the US showed that about a quarter of the population has a genetic combination which makes them very sensitive to bitter tastes. The use of salt would help to suppress this, especially in dark green vegetables such as broccoli, which have very bitter tastes on their own.

The researchers also suggest that companies making low-sodium foods should try to focus on blocking bitter tastes, instead of concentrating on the reduction of salt content.