Stability of fusarin C: effects of the normal cooking procedure used in China and pH.

Fusarin C (FC) is a naturally occurring mutagen found on Fusarium moniliforme-contaminated corn. In Linxian, China, an area of exceptionally high incidence of esophageal cancer, the milled corn is made into small cakes called wotou, which are steamed. It has been suggested that FC may play a role in the etiology of esophageal cancer, but this has been questioned, in part, because of the thermal instability of FC. We therefore measured the effects of temperature on FC stability, mimicking the cooking process. FC was extracted from the wotou and quantitated by both reverse-phase high-performance liquid chromatography and the Ames assay. After wotou were steamed for 30 minutes, 11% and 3% of the initial FC remained, as detected by the two assays, respectively. The milled corn, when moistened with water, had a pH of 6.1, which was lowered to 5.3 when it was inoculated with F. moniliforme and cultured for three weeks. Pickled vegetables are sometimes added to the wotou, which further reduces the pH. To determine the effects of pH on FC, it was heated in solution, with the pH varied between 4 and 8. Its stability was very pH dependent, decomposing more rapidly as the pH increased. Because ingested FC would also be subjected to the low pH of the stomach, it was treated for 30 minutes at 37 degrees C and pH values ranging from 1.0 to 7.0. FC was stable (less than 15% decomposition) under these conditions. If FC is a significant health threat, it could most easily be destroyed by cooking at slightly basic pH values.