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Winnipeg Free Press - PRINT EDITION

We've found mustard flour kills off E. coli

By: Rick Holley / The Learning Curve

Posted: 10/11/2009 1:00 AM | Comments: 0 (including replies)

Medical research has taught us there is a strong link between eating healthy and being healthy.

However, we don't always know what food is healthy. There are no absolutes. We more easily accept advice from those we trust and technical experts are low on the list of those trusted, perhaps because they are often more interested in impressing than informing.

It was about 50 years ago that political wind in the U.S. blew up a storm about the over-consumption of fat, obesity and heart disease that was based on less-than-certain science. When the reduction in dietary fat intake occurred and people were still obese -- and heart disease remained a major problem -- re-examination of data and new studies showed it was not fat intake per se that was related to heart disease. The problem was the chemical composition of those fats (HDL and LDL, cholesterol and trans fat).

Now there is mounting evidence that consumption of easily absorbed, refined carbohydrates may significantly contribute to obesity, diabetes and heart disease.

That includes high-glycemic index food and those containing high-fructose corn syrup used since the 1970s to sweeten most soft drinks and many processed foods.

While these issues are important, there are other factors that can influence the healthfulness of foods. Our interest in consuming minimally processed foods (low fat, salt and preservatives) and fresh fruits and vegetables has mushroomed, and Mediterranean recipes have become a popular dietary approach to ward off heart disease.

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.

Dr. Rick Holley is a professor in the Department of Food Science at the University of Manitoba.

The Learning Curve is an occasional column written by local academics who are experts in their fields. It is open to any educator from Winnipeg's post-secondary institutions. Send 600-word submissions and a mini bio to thelearningcurve@freepress.mb.ca.

Republished from the Winnipeg Free Press print edition October 11, 2009 b3

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