Microbiological hazards associated with sprouted seeds

We last discussed sprouts and foodborne disease in the November 2000 issue of Food Safety and Hygiene. We noted then that while there have been no confirmed outbreaks of foodborne illness from sprouts produced in Australia, seeds grown in Australia had been associated with outbreaks in other countries in the 1990s.

Australia continues to be without reported incidents but sprouts remain a high risk product based on the number and seriousness of outbreaks reported overseas. They are one of the plant products for which the NSW Food Authority is to introduce the requirement for food safety programs.

The Campden and Chorleywood Food Research Association Group has recently published a Review of the microbiological risks associated with sprouts as part of its continuing review series. This comprehensive review reiterates the key challenges associated with the safe production of sprouted seeds and some of these bear repeating here.

They include:

Seeds have not been regarded traditionally as food products but as a crop to be replanted with only a small proportion set aside for food. Therefore historically the seeds may not always have been handled according to good agricultural practice.
The majority of cases of foodborne disease recorded in the scientific literature were due to Salmonella or Escherichia coli.
Storage, processing and shipping of seeds have the potential to introduce contamination due to unhygienic practices and equipment.
Foodborne pathogens can increase rapidly during the sprouting of seeds. Absence of pathogens on seeds is therefore critical.
There is currently no decontamination method that totally eliminates pathogens.

The review notes 33 reported outbreaks of illness associated with sprouts up to the end of 2001 with the majority having occurred in the United States. The US Food and Drug Administration (FDA) has made a concerted effort to educate producers and consumers of both alfalfa and mung bean sprouts on procedures to minimise the risk associated with these products. While the number of incidents reported annually did decline, the FDA has noted that alfalfa sprouts appear to be re-emerging as a significant vehicle for foodborne illness. There were five reported outbreaks in 2003 and two outbreaks up to mid-2004.

Most sprouted seed producers rely on treatment with relatively high concentrations of chlorine to reduce microbial load including pathogens on seeds for sprouting. However the reviewer concludes that further investigation into the use of combined treatments and novel procedures is necessary if a method is to be found for totally eliminating pathogenic microorganisms from seed sprouts.

Latest news – Sprouts cleared from deadliest foodborne disease outbreak
In our November 2000 bulletin we also discussed the 1996 outbreak of E. coli 0157:H7 in Japan which was initially attributed to white radish sprouts. Latest reports are that there was insufficient evidence for the Japanese government to link the sprouts to this outbreak (www.sproutnet.com). The Japanese government has been ordered by two lower courts and now the Japanese Supreme Court to pay compensation to sprout growers for business damages suffered from the unwarranted announcement.