Depending on your viewpoint, the flurry of attention being paid to azodicarbonamide (ADA) is either recognition of a serious health concern or just another Internet kerfuffle. There’s no doubt among bakers that this flour maturing agent — or dough conditioner, as most describe it — is highly useful. But does it have a future in baking?

In early February, Subway announced that it was moving away from ADA, which is used in formulating the frozen doughs it bakes off at its nationwide chain of sandwich shops. “The complete conversion to have the product out of the bread will be done soon,” the company said in a Feb. 7 media statement.

ADA is Generally Recognized as Safe (GRAS) by the Food and Drug Administration (FDA) for use in cereal flour and breadmaking only. But what prompted Subway’s decision were petitions to the company started by a food blogger, Vani Hari, a.k.a. “Food Babe” and founder of She stated that this chemical, also used in producing yoga mats and shoe rubber, has been linked to asthma and cancer. More than 67,000 consumers signed her petition.

This was quickly followed by a petition filed with FDA by the Center for Science in the Public Interest (CSPI) to bar ADA as a food additive or to at least reduce the amount permitted. CSPI called on McDonald’s to also discontinue this ingredient in its buns. Two days later, Sen. Charles Schumer (D-NY) launched a campaign to ban ADA, noting that when heated, it forms trace amounts of semicarbazide, a known carcinogen in humans.

The American Bakers Association responded with a Feb. 7 statement to its members. “Past FDA sampling results have indicated appropriate low-level use in products,” it said. “As a dough conditioner, it has a volume/texture effect on the finished loaf. It is a functional ingredient that improves the quality of bread, and any substitutes are likely not to work as well as ADA.”

The association cautioned members that usage rates are limited by FDA to 0.0045%, flour weight basis (45 ppm), and that if used, its presence is required to be disclosed on product labeling. It recommended the information resources provided by the Center for Food Integrity (CFI) and asked that members contact ABA for additional follow up.

Why use ADA?

The Standards of Identity for bread and rolls (21 CFR 136) list approved oxidizers to be potassium bromate, calcium bromate, potassium iodate, calcium iodate and calcium peroxide — all at maximum use levels of 75 ppm based on flour. Also permitted are dehydro-­L-ascorbic acid, added in the form of ascorbic acid at an unrestricted level, and azodicarbonamide at a maximum level of 45 ppm.

Why do bakers need flour maturing agents, or oxidizers, at all?

A bit of history throws light on the problem. Early on, bakers learned that wheat flour, when left to sit for a while after milling and before baking, produced finished baked foods with substantially improved overall quality. Bakers received their flour in wooden barrels or fabric bags, containers that were not airtight. In the time it took for flour to reach the bakery, it was exposed to oxygen in the atmosphere, and that oxygen acted on the flour’s proteins to adjust their performance.

When safer, more sanitary and more secure means of shipping flour came along — multiwall paper sacks, sealed tote bins, bulk tank trucks and railroad tanker cars — flour got to the bakery not only more quickly but also with far less exposure to atmospheric oxygen. Long periods of onsite storage can compensate for natural oxidation; however, the required time and storage space to allow freshly milled, “green” flour to age naturally made it economically unattractive to modern bakers.

That’s when chemical oxidizers entered the picture. They could do the job at relatively low cost and in very small amounts.

Much speculation, theorizing and research still revolves around how oxidizers work to improve the breadmaking quality of wheat flour. Some scientists say these compounds inhibit native proteases, an activity termed “the bromate effect” during the late 1930s. Others said they oxidize the thiols that would otherwise soften the dough or by aiding the interchange between thiols and disulfide bonds in proteins. Still others claimed they affect protein aggregation or foster enzyme catalysis of ascorbic acid to act as a reducing agent.

A simpler explanation is that use of flour maturing agents, or oxidizers, shortens the required fermentation time and produces bread with a finer cell structure, which makes the crumb appear whiter.

Past and future options

In the 1980s, potassium bromate came under scrutiny like that now directed at ADA, but minus the multiplying effect of the Internet and blogosphere. Cereal science researchers and bakers alike always believed that bromate was entirely converted to harmless bromide during the baking process. As the science of measurement improved, however, miniscule amounts of bromate were found in the parts-per-billion range. Eventually, studies reconfirmed bromate could be used safely but at much reduced levels. FDA recommended it be kept to 20 ppm or less, a considerable cut in the previous top level of 75 ppm.

Although FDA did not ban potassium bromate, many bakers moved away from it. Another factor influencing these decisions was that it was named on California’s Proposition 65 list. Bakers serving that market faced complying with the state’s law that required a posted warning at point of sale.

Bakers turned to other oxidizers, with ADA becoming a popular choice because of its relatively low cost and good ­efficacy. In Europe, however, bakers were prohibited from using bromates and ADA. Long ago, they accepted ascorbic acid, which also enjoys recognition for its vitamin C value, as their oxidizer of choice.

Bread made with ADA has “a higher volume, finer grain, thinner cell walls and softer texture, and the dough has better handling characteristics,” said Julie M. Jones, PhD, distinguished scholar and professor emerita, foods and nutrition, St. Catherine University, St. Paul, MN, speaking to, a website sponsored by CFI.

“Fermentation is faster, and bread rises better,” she said. “Every minute a dough is out on the floor has a cost, so longer fermentations may mean greater cost.”

As for human health risks, Carl Winter, PhD, director of the FoodSafe Program and extension food toxicologist at University of California, Davis, observed in a CFI report, “The toxicological concerns seem to stem from the potential exposures of workers to much higher levels of the chemical through inhalation, which is a very different scenario than is faced by consumers.” People are much more likely to encounter semicarbazide from glass jars with plastic lids, he noted.

If ADA is withdrawn from bakery use, what remains? Of those listed by the Standard of Identity, ascorbic acid has the highest potential. Recently, enzymes have been explored for their protein modification properties. Both are also considered clean-label ingredients.