US AND CANADA: We've found mustard flour kills off E. coli

11.oct.09
Winnipeg Free Press
Rick Holley

Dr. Rick Holley, a professor in the Department of Food Science at the
University of Manitoba, writes in this column that to satisfy the
increased year-round demand for healthful products, the food industry
became global, invented chopped-bagged produce and made seed sprouts
(radish, bean, onion, alfalfa) available nationally. Then large
outbreaks of food-borne illness occurred across the U.S. and Canada.
Even fruits, juices, tomatoes, peppers and melons have been found
responsible.
Depending on the area, foods of plant origin are now responsible for
almost as many cases of food-borne illness as foods of animal origin.
Most of the recent notorious food-borne illness outbreaks involving
produce have been caused by salmonella or E. coli O157:H7.
But a less well-known organism, campylobacter, causes more cases of
gastroenteritis in Canada with salmonella a close second. All three
organisms normally reside harmlessly in animals and are periodically
shed in the feces. Try as we might to rid poultry and livestock of these
zoonotic pathogens, they're still there and tomorrow may bring on
another mind-numbing outbreak.
So where does my research at the University of Manitoba fit in? Most
work is in three areas, all food safety related.
In the first, we're studying zoonotic pathogen transfer in animal
environments. We have found that when liquid hog manure naturally
contaminated by salmonella was used at provincially approved rates to
fertilize pasture grazed by cattle, the cattle did not become
contaminated with salmonella.
The second area involves studying factors influencing the survival of
these pathogens and listeria as well as spoilage bacteria in food.
Most of this work has concentrated on meats.
The third area examines the ability of natural antimicrobials, such as
essential oils from spices, to inhibit these pathogens in foods; we're
currently looking at traditional dry-cured, raw fermented sausages
(Genoa, Hungarian) and dry-cured ham (prosciutto, Westphalian). Our
interest in fermented sausages came from the observation the process
currently approved for their manufacture cannot prevent final product
contamination by E.coli O157:H7 if it's present in the raw material
(ground beef).
We found that if we use cold mustard flour (treated with heat so it is
no longer spicy), as an ingredient in the fermented sausage or ham, if
any E. coli O157:H7 are present they will digest the flour to obtain
glucose from it. Inadvertently, they create isothiocyanates, which are
toxic to the bacteria, and they essentially commit suicide during
product manufacture.
Work is being done to fine-tune the recipe and fully characterize the
biochemical reactions responsible. Industry has shown interest in the
results because the cold mustard may permit manufacture of these
uncooked products with significantly reduced risk from the presence of
E. coli O157:H7.