Photodegradation of cassava and corn starches

The baking expansion properties of sour cassava starch (Polvilho azedo) are attributable to photochemical starch degradation induced by heterolactic f ermentation after sun-drying. This study investigated the effects of UV irr adiation on the different structural levels of cassava starch as compared t o those of corn starch and dextrins. Photosensitive compounds excited at 36 0 and 290 nm in cassava starch were photodegraded when starch was exposed t o sunlight or 360 nm irradiation. UV irradiation depolymerized cassava and corn starches, inducing modifications due, at least in part, to a mechanism involving free radicals. Lactic acid was also photodegraded. Photodegradat ion induced by UV absorption could have been due to fluorescent chromophore s found in starches and nonfluorescent chromophores present in glucosidic u nits.