Prof makes seed decontamination breakthrough
By Keith Warriner, Department of Food Science
Jul 4, 2006, 22:31
University of Guelph
Keith Warriner, Department of Food Science
A University of Guelph food scientist is part of a team that has made a breakthrough in finding a safe, effective way to decontaminate seeds used to produce bean sprouts, alfalfa sprouts and other types of sprouts – culprits in several major food-borne illness outbreaks around the world.
Prof. Keith Warriner and his four colleagues have developed a sanitizer made of the same chemical used in toothpaste and contact lens solutions that is harmless to the sprouting seed but lethal to pathogens such as Salmonella and E. coli O157:H7. Their research is published today in the Journal of Food Protection.
"We developed a sanitizer that you just add to the steep water when the seeds start to germinate," said Warriner. "No one has ever done this before because if you add most sanitizers to the steep water, not only would the pathogens be killed, but also the developing sprouts. The secret of our development is that it's phytocompatible – it doesn't affect plant tissue; it affects only pathogens."
A $4-million industry in Ontario and a $260-million industry in North America, sprouts are popular because they're a rich source of vitamins, minerals and phytochemicals that reduce the risk of cancer and help lower cholesterol levels. Yet even after 600 people in Ontario contracted Salmonella from bean sprouts in November 2005 and 6,000 people in Japan fell ill and 13 people died after contracting E. coli 0157 from radish sprouts in 1995, there are still no safety measures in place to ensure pathogen-free sprouts.
The way sprouted seeds are produced is the biggest reason they have caused at least one food-borne outbreak every year since 1980, said Warriner. Salmonella or E. coli bacteria can lodge in tiny seed cracks and are difficult to eliminate. The seeds are germinated in a warm, humid environment for three to seven days – ideal conditions for the exponential growth of bacteria. Also, because most sprouts such as alfalfa can be eaten only raw, they are not exposed to temperatures high enough to kill bacteria that may be present.
In 1999, the U.S. Food and Drug Administration and the Canadian Food Inspection Agency (CFIA) recommended that sprout producers treat seeds with calcium hydrochlorite (bleach), but a year later, scientists tested the bleach decontamination method and found it didn't work, said Warriner. "This is one reason the number of food-borne illness cases linked to sprouts keeps rising."
For years, scientists have tested several decontamination methods, but all have failed to successfully decontaminate seeds or have detrimentally affected sprout development. Sprout producers have been left to either continue using the bleach method or to do nothing at all, and the CFIA has advised consumers who belong to high-risk groups, such as young children, seniors or people with weak immune systems, to avoid eating sprouts of any kind.
"There's obviously an identified need for this technology," said Warriner, whose team received funding from the Ontario Ministry of Agriculture, Food and Rural Affairs.
Unlike bleach, which is extremely harmful to the environment and to workers, Warriner's stabilized oxycholoro-based sanitizer called Germin-8-or is completely safe, he said. "There's actually no residue at all," he said.
A global patent has been submitted, and the producers of Germin-8-or are seeking regulatory approval and distributors in North America. Now that a safe, effective decontamination method is available, the researchers hope sprout producers will adopt the technology and enable consumers to enjoy the nutritional benefits of sprouts without worrying about contracting food-borne illness.
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