Bread crust rich in antioxidants

The crust is a rich source of antioxidants providing a greater health benefit.— Photo by K.Pichumani

The crust is a rich source of antioxidants providing a greater health benefit.— Photo by K.Pichumani  

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. The findings appeared in the Journal of Agricultural and Food Chemistry. 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 fibre, 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, formerly with the German Research Center of Food Chemistry in Garching, Germany.

Using a conventional sourdough mixture containing rye and wheat flour, Hofmann and his associates analysed 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, 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 earlier to play a role in cancer prevention.

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 colour associated with the surface of baked breads. The same reaction also produces flavour compounds and other types of antioxidants. Pronyl-lysine 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.

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