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Bread Crust And Stuffing Rich In Healthy Antioxidants
November 12, 2002
(American Chemical
Society) -- The best thing since sliced bread may be bread crust: Researchers in Germany
have discovered that the crust is a rich source of antioxidants and may provide a much
stronger health benefit than the rest of the bread.
This is good news
for those who like to complement their holiday meals with bread stuffing, which is rich in
crust, but bad news for those who prefer to remove crusts from their bread, as they may
be sacrificing healthful antioxidants. The research findings appeared in the Nov. 6
print issue of the Journal of Agricultural and Food Chemistry, a peer-reviewed
publication of the American Chemical Society, the world's largest scientific society.
Although previous
studies have suggested that bread contains compounds that have a cancer-fighting
potential, much focus has been placed on its abundance of dietary fiber, which is
believed by some to help prevent colon cancer. The current study is the first to
identify a cancer-fighting compound that is concentrated in the crust, says Thomas Hofmann, Ph.D.,
lead researcher for the study and formerly with the German Research Center of Food
Chemistry in Garching, Germany. He is currently a full professor at the University of
Munster, Germany.
Using a
conventional sourdough mixture containing rye and wheat flour, Hofmann and his associates
analyzed bread crust, bread crumbs (the pale softer part of the bread) and flour for
antioxidant content and activity. They found that the process of baking bread produced a
novel type of antioxidant, called pronyl-lysine, that was eight times more abundant
in the crust than in the crumb. The compound was not present in the original flour.
Using human
intestinal cells, Hofmann's collaborator Veronika Faist, Ph.D., a researcher at the
Institute of Human Nutrition and Food Science in Kiel, Germany, showed that this
crust-derived antioxidant is the most effective component in bread for boosting the level
of phase II enzymes, which have been shown in previous studies to play a role in cancer
prevention.
The researchers are
currently conducting animal tests to determine whether bread crust and pure pronyl-lysine
actually boost antioxidant levels in plasma, but results have not yet been published.
Pronyl-lysine
is formed by the reaction of the protein-bound amino acid L-lysine and starch as
well as reducing sugars in the presence of heat. Chemists have long known that this same
process, called a Maillard reaction, is responsible for producing the brown color
associated with the surface of baked breads. The same reaction also produces flavor
compounds and other types of antioxidants.
Pronyl-lysine
is formed during baking in both yeast-based and yeast-free bread, also known as "tea
bread." The antioxidant is likely to be more abundant when bread is broken down
into smaller pieces and baked, as with stuffing, because the smaller pieces contain
more surface area on which these reactions can occur in comparison to larger bread
products, like loaves and buns, the researcher says.
In general, dark-colored breads (such as pumpernickel and wheat)
contain higher amounts of these antioxidants than light-colored breads (such as white
bread). Strong over-browning of bread, however, reduces the level of these
antioxidants, says Hofmann.
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