Effects of Reducing Agents and Baking Conditions on Potassium Bromate Residues in Bread

Potassium bromate is a well known dough conditioner that has been used for many years in breadmaking around the world. It is used to improve dough-handling properties, oven rise, texture, and loaf volume and to control bread properties affected by changes in wheat qualities between crop years. Potassium bromate is a slow-acting oxidizing agent. It reacts until the end of the make-up stage, moderately increasing dough viscoelasticity. The rate of the reaction then increases rapidly, following the rise in temperature during the final proofing and initial baking stage. Although L-ascorbic acid (AsA) exerts an effect on dough properties similar to that of potassium bromate, the mechanism of its oxidization properties in dough differs from that of potassium bromate. Unlike potassium bromate, AsA is a fast-acting agent that increases dough viscoelasticity during the mixing stage. Potassium bromate was first introduced as a bread improver in the United States during the 1910s. In Japan, potassium bromate has been registered as a food additive since 1953. In 1982 and 1983 Kurokawa and coworkers (11,12) published the results of animal tests that demonstrated that potassium bromate, when administered in drinking water, was associated with renal cancer in some rats. Furthermore, the development of analytical methods revealed the presence of potassium bromate residues in finished baked goods, which stimulated regulatory concerns in many countries (2,6). The UN Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) recommended in 1993 that potassium bromate should be removed from the list of approved flour treatment agents in the Codex Alimentarius. In Japan, following a request from the Ministry of Health and Welfare, the baking industry voluntarily stopped using potassium bromate. Recently, however, several new breads that use potassium bromate as a dough conditioner have been introduced to the Japanese market with the appropriate regulatory approval. The baking industry in the United States has investigated both the optimization of baking parameters and effective agents that can be used to reduce residual bromate (1, 5). When used properly, potassium bromate turns into bromide in the finished product. A recent risk assessment by the FDA estimated 20 ppb bromate as a one in 1 million upper-bound cancer risk level for consumers at the 90th percentile for intake of baked products, which often is used to indicate an insignificant risk level (4). Due to health concerns and regulations, analytical methods that provide accurate and precise data on potassium bromate residues have been developed. Initially, high-performance liquid chromatography (HPLC) with a post-column reaction was developed to determine the amount of bromate in water (14). More recently, an HPLC method (8) that combines the clean-up procedure with a series of solid-phase extraction columns was developed to detect bromate residue levels as low as 3 ng/g in bread and has received approval with peer-verified status from AOAC International (9). The current study was designed to measure the effects of bread type, ingredients, and processing conditions on potassium bromate residues in finished baked products as measured using the improved analytical method. This methodology, including the preconcentration procedure used in this study, has detection levels as low as 0.5 ppb potassium bromate in bread (10).