A hot solution to bean sprout safety

Bacterial infection of mung bean seeds can cause outbreaks of food poisoning when the sprouts are eaten. Now research by a microbiologist from Nottingham University, UK has shown ways of disinfecting the bean seeds using natural methods and which do not prevent the beans from sprouting. "Bean sprouts are regarded as a healthy food, but they are often eaten raw in salads", said Apinya Vanichpun, presenting her findings at the Society for General Microbiology meeting in Harrogate today (Thursday 2 April), "If the bean seeds are contaminated with pathogenic bacteria there can be disease outbreaks when the sprouts are eaten".

"The challenge is to find a means of disinfecting the seeds that kills bacteria but that still allows the seeds to germinate to produce sprouts," she continued. "Consumers who want organic, "natural" foods do not want chemicals used to disinfect them and so this must be taken into account too."

Her experiments used Listeria monocytogenes bacteria, which causes listeriosis, a serious food borne disease which can lead to meningitis in people with a reduced immune system and abortion in pregnancy. Applying hot and chilled water in turn to the mung bean seeds killed significant numbers of the bacteria. However it had the disadvantage that it reduced the germination level of the seeds so producing fewer sprouts.

An equal mix of lime juice and vinegar was as effective in reducing bacterial numbers as a mixture containing sodium hypochlorite, the sterilizing chemical used in babies' bottles, and lactic acid; however this was still not as good as the temperature treatments. The lime and vinegar mix also had the problem that it affected the germination rate of the seeds more than did the sodium hypochlorite solution (only 78% sprouted with lime and vinegar against 98% with sodium hypochlorite),.

Hot water treatment seems to be a good option to use for seed disinfection as it would be a suitable choice for production systems that required the use of only natural products for organic fresh produce.

Source: Society for General Microbiology