Benzoyl peroxide - does not pose a safety concern

Reactions and Fate in Foods

Benzoyl peroxide in foods might possibly result of three secondary deleterious effects which include:1) the formation of harmful degradation products of benzoyl peroxide; 2) the destruction of essential nutrients; and 3) the production of toxic substances from the food components (Life Science Research Office, LSRO, 1980).

Degradation products of benzoyl peroxide

Benzoyl peroxide in food is almost completely (> 91%) converted to benzoic acid during processing. The benzoic acid content of the treated food would increase roughly equal to the benzoyl peroxide employed. The direct addition of benzoic acid and sodium benzoate to food is approximately two to three times this amount (Subcommittee on Review of the GRAS List, Subcommittee on GRAS, 1972). Furthermore, benzoic acid is naturally found in fruits, spices, milk products, meats, and beverages (Van Straten, 1977).

Destruction of essential nutrients

Bleaching of cheese milk during summer months with benzoyl peroxide effectively destroys the high level carotenoid pigments of this milk and affords a means of controlling the colour of cheese. To make-up for the reduced vitamin A activity of the bleached milk, it requires in some countries that sufficient vitamin A should be added to the curd to compensate for the vitamin A or its precursors destroyed in the bleaching process. (U.S. FDA, 2003b). Vitamin A itself seems little affected by the normal bleaching process. Sharratt et al. (l964) observed an increased incidence of testicular atrophy among rats receiving flour treated with high levels of benzoyl peroxide. They attributed these changes to a destruction of α-tocopherol, although no chemical-specific analyses were performed. Thus, conventional bleaching of flour and milk may destroy some α-tocopherol. However, the α-tocopherol content of both foods is relatively small (Lampert, 1975; Ockerman, 1978), so that its destruction would seem to have little nutritional significance. 

The oxidation of essential fatty acids represents another possible deleterious effect of benzoyl peroxide. Witten and Holman (1952) speculated that a pro-oxidant (benzoyl peroxide) might interfere with the normal metabolic conversion of linoleic and linolenic acids. The amounts of unsaturated fatty acids in flour were not reduced by treatment with benzoyl peroxide and no difference from untreated flour of unsaturated fatty acids could be detected. (Fisher et al., 1958). No data are available on the fate of other essential nutrients, i.e. ascorbic acid, thiamin, riboflavin, and pyridoxine and methionine, in foods bleached with benzoyl peroxide.

Further research into benzoyl perxide through the food standards agency lead me to find this little gem... Now I need to just find out at what concentration benzoyl peroxide is used when bleaching the flour used in white bread.

Acceptable daily intake of benzoyl peroxide.