Research report

​Use of treatments to prevent the growth of pathogens on sprouted seeds

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This project was commissioned to investigate the effectiveness of soaking and washing treatments that could be used at home to decontaminate seeds for sprouting.

In 2011, an outbreak of E. coli O104 occurred in Europe, which was associated with the consumption of sprouts grown from contaminated seeds. As a consequence of this outbreak, European regulations were introduced in 2013 that enhanced controls during the production of sprouts by food businesses to provide greater protection to the consumer. The regulations only applied to food businesses and did not extend to providing advice for people who wish to sprout seeds in a home environment. Therefore this project aimed to find a suitable treatment that could be used by people at home.

Mung beans and alfalfa seeds were artificially contaminated with Salmonella and E. coli O157 (non-toxigenic) at levels of approximately 107 cfu/g. Four different treatments (citric acid, acetic acid, a standard chlorine wash and hot water (90°C)) were applied to both types of seeds and the reduction in microbiological contamination was measured. After the seeds were treated they were sprouted to determine if the treatment had any effect on germination and if any contamination could be detected.

The findings showed that for both mung beans and alfalfa seeds that hot water (90°C for 2 minutes) was the most effective treatment at reducing microbiological contamination at over 4 log cfu/g on the inoculated seeds. When the seeds were germinated the hot water treatment had no adverse effect on the mung beans but it did minimally reduce the germination of the alfalfa seeds. Low levels of contamination were detected once the seeds had been sprouted indicating there is a risk that re-growth could occur.

In a real life situation it is likely that the initial contamination will be lower than that used in this experiment therefore using hot water to reduce the contamination on sprouted seeds is good practice to prevent illness.

The results from this project will be used by Food Standards Scotland to inform future risk assessments and food safety advice in relation to fresh produce.