Some people can't eat a lot of beans because of the flatulence problem

Jammala Machaiah, researcher

The average adult produces four to five litres of gas a day.

Scientists at the food-science lab at the Bhabha Atomic Research Centre in Trombay, India used standard food irradiation technology.

In Europe, food can only be irradiated under licence, and must be marked. The process extends the shelf life of herbs and spices by killing the bacteria that make them rot.

Deterrant

The Indian researchers examined mung beans, chickpeas, black-eyed beans and red kidney beans.

Some samples with a low-intensity gamma-ray beam, with others treated with a beam three times as strong.

All the beans were then soaked in cold-water for two days before being tested.

Oligosaccharide levels are reduced naturally by soaking.

Soaking, plus a low dose of radiation reduced levels in mung beans by 70%.

Levels in beans treated with a high dose were cut by 80%.

In beans which had not been treated, there was a drop of only 35%.

Black-eyed beans and chickpeas also showed a marked improvement.

Kidney beans were unaffected by the treatment, but the scientists say they only low levels of oligosaccharides.

Jammala Machaiah, who carried out the research with colleague Mrinal Pednekar, said: "In India, beans are a very popular and important part of the national diet, but some people can't eat a lot of beans because of the flatulence problem.

"This is unfortunate, as it is a very good source of essential nutrients. Irradiation would make beans less of a problem."

'Good for the gut'

Stephen Cole is technical director of Enzyme Services and Consultancy in Blackwood, Wales which is looking at enzymes which break down oligosaccharides in animal feed to prevent pigs or chickens becoming bloated.

He said oligosaccharides were "anti-nutritional factors", and added "If irradiation helps reduce them that's good."

But Catherine Collins, spokeswoman for the British Dietetic Association, told BBC News Online oligosaccharides were good for the gut because when the bacteria react to them, they help keep the immune system working effectively.

She said: "The immune system is in a state of readiness. When it meets something like salmonella, it very quickly leaps into action and gets rid of it."

Without the oligosaccharides, the gut's immune system would deal with serious infections less well

Oligosaccharides also help control cholesterol levels.

Ms Collins said she also had concerns about irradiating food.

"If you're irradiating it sufficiently to reduce oligosaccharide levels, what effect will it have on anything else."

Glenn Gibson, a food microbiologist at Reading University, added: "Flatulence is an important indicator of a healthy gut system.

"It's only a social problem. You need to expel gas to ensure your gut is functioning properly."

He said we should all just learn to live with flatulence.

Details of the research have been published in New Scientist, and in the journal Food Chemistry.