Flour is a powder made of cereal grains or roots. It is the main ingredient of bread, which is a staple food for many civilizations, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history. Wheat flour is one of the most important foods in European and North American culture, and is the defining ingredient in most European styles of breads and pastries. Maize flour has been important in Mesoamerican cuisine since ancient times, and remains a staple in much of Latin American cuisine. Flour contains a high proportion of starches, which are complex carbohydrates also known as polysaccharides. Leavening agents are used with some flours, especially those with significant gluten content, to produce lighter and softer baked products by embedding small gas bubbles. The production of flour has also historically driven technological development, as attempts to make gristmills more productive and less labor-intensive led to the watermill and windmill, terms now applied more broadly to uses of water and wind power for purposes other than milling. Potassium bromate (KBrO3), is a bromate of potassium and takes the form of white crystals or powder. It is typically used as a flour improver (E number E924), strengthening the dough and allowing higher rising. It is an oxidizing agent, and under the right conditions, will be completely used up in the baking bread. However, if too much is added, or if the bread is not cooked long enough or not at a high enough temperature, then a residual amount will remain, which may be harmful if consumed. Potassium bromate might also be used in the production of malt barley where the U.S. Food and Drug Administration (FDA) has prescribed certain conditions where it may be used safely, which includes labeling standards for the finished malt barley product. It is a very powerful oxidizer (EÂ° = 1.5 volts comparable to potassium permanganate). Bromate is considered a category 2B (possibly carcinogenic to humans) carcinogen by the International Agency for Research on Cancer (IARC). Potassium bromate has been banned from use in food products in Europe, as well as the United Kingdom in 1990, and Canada in 1994, and most other countries. It was banned in Sri Lanka in 2001 and China in 2005. It is also banned in Nigeria, Brazil and Peru. In the United States, it has not been banned. The FDA sanctioned the use of bromate before the Delaney clause of the Food, Drug, and Cosmetic Act went into effect in 1958 â€” which bans carcinogenic substances â€” so that it is more difficult for it to now be banned. Instead, since 1991 the FDA has urged bakers to voluntarily stop using it. In California a warning label is required when bromated flour is used.