Irradiation knocks wind out of beans

Food scientists have found a way to eat bean-filled food like curries and salads with far fewer episodes of flatulence. Indian researchers have discovered that blasting some beans with gamma rays can help oust most of the chemicals that make people 'uncomfortable'​, the New Scientist reports this week.

Bacteria in the large intestine produce the accumulation of gas that causes flatulence. When these bugs consume certain types of carbohydrates, called oligosaccharides, they produce a mix of gases that includes methane and certain sulphur-containing gases. On average, adults produce four to five litres of gas a day, and beans are the vegetables most commonly associated with excess wind. That is because up to 60 per cent of their carbohydrates are oligosaccharides.

Jammala Machaiah and Mrinal Pednekar in the food-science lab at the Bhabha Atomic Research Centre in Trombay, India, investigated the effect of radiation on the levels of these carbohydrates in various pulses common in the Indian diet, including mung beans, chickpeas, black-eyed beans and red kidney beans.

Using standard food irradiation technology, they irradiated some samples of each with a low-intensity gamma-ray beam, and other samples with a beam three times as strong. They then gave the beans the typical two-day soaking in cold water that people use before cooking the beans.

The researchers report in a paper to be published in the journal Food Chemistry​ that the initial irradiation slightly reduced levels of oligosaccharides. But the further reduction that occurs naturally with soaking was dramatically accelerated in the irradiated beans, especially black-eyed beans.

After two days' soaking, the low dosage of radiation reduced oligosaccharides in mung beans by 70 per cent, and the high dose by 80 per cent, compared with a drop of only 35 per cent in soaked beans that had not been irradiated.

Current legislation in Europe means that food can only be irradiated under licence, and the treated food has to be marked. Irradiation extends the shelf life of herbs and spices by killing the bacteria that make them rot.