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 are scheduled to appear 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.
Funding for this study was provided by the German research associations FEI and the AiF and Germany's Ministry of Economics and Technology.
The online version of the research paper cited above was initially published Oct. 16 on the journal's Web site. Journalists can arrange access to this site by sending an e-mail to email@example.com or calling the contact person for this release.
NOTE TO EDITOR: Attached are two bread recipes, courtesy of the historic Belmont Conference Center, which is owned and operated by the American Chemical Society.
The following recipes are courtesy of the Belmont Conference Center, an historic manor built in 1738. Belmont is located on 85 acres of exquisite rolling hills and fields, surrounded by Patapsco State Park, in Maryland. Owned by the American Chemical Society, Belmont is open year round, seven days a week for meetings, retreats, training seminars, weddings, company picnics and holiday receptions.
Black Olive Brioche
Yields 2 freeform loaves
6 oz. Water
1 oz dry active yeast
2 T milk powder (like Carnation dry instant milk)
1-cup bread flour
- Mix all the above ingredients in a large bowl and set aside one hour
Above sponge recipe after raising one hour
3-1/2 cup bread flour
8 egg yolks
1 whole egg
4 oz melted butter ( 1 stick)
4 oz cold butter (1 stick) precut into 1/2 inch cubes
1 T salt
1/2 cup sugar
1/4 cup chopped calamata or other black olive
- Put all dry ingredients into a large bowl and make a well in the center
- Mix together all wet ingredients including melted butter and olives then pour into flour well
- Mix with wooden spoon until completely wet
- Turn onto floured surface and knead in cold butter
- Dough will be sticky and keeping hands well floured will help
- Set aside covered in warm place until double in size
- Punch dough down and divide dough in two. Form into round balls
- Place on 2 greased cookie sheets and let rise again until double
- Bake in oven preheated to 350 F for 25-35 minutes or until top and bottom of the bread is golden brown. Since ovens vary, it is more important to pay attention to the doneness of the bottom of the bread than to the time.
- Allow to cool completely before cutting to allow the moisture to redistribute.
Carrot Quick bread
Yields 2 loaves
1/2 cup light brown sugar
2 cups sugar
1 2/3 cups mayonnaise
1 tsp vanilla extract
1 lb grated carrots
2T ground cinnamon
1 tsp ground nutmeg
Pinch ground cloves
1 tsp ground ginger
2-1/2 tsp baking powder
2-1/2 tsp baking soda
1 tsp salt
2-1/2 cups all-purpose flour
1/4 cups raisins
- Put all dry ingredients into mixing bowl
- Pour in all wet ingredients and mix with electric mixer until well blended
- Mix in carrots and raisins until distributed evenly
- Pour into 2 greased floured loaf pans
- Bake 40 minutes at 350 F or until toothpick comes out clean when inserted in the center. You may want to begin checking after 30 minutes of baking.
- Cool on wire rack before turning out of the pan.
Journal of Agricultural and Food Chemistry