In spite of the extensive polymeric degradation observed, in all cases some lineal and branched polymeric molecules remain, as reflected by the iodine complexes formed. This demonstrates that the structure of starch is conserved.
The increasing reducing sugar content is shown as a drop in the TS.RS−1 ratio, revealing that the effect reached at a 50 kGy dose is much more marked in the case of cassava starch, where the polymeric content is reduced about 57%, than in the case of bean starch, where the corresponding reduction reaches 19.5%. This indicates that amylopectin, predominant in cassava starch, experiences more damage in its average chain length.
It had been shown by Sokhey and Hanna (1993) and Sokhey and Chinnaswamy (1993) that in corn starch irradiation, even though both the branched amylopectin and the lineal amylose molecules resulted fragmented, the effect was greater in the amylopectin with respect to the amylose. In addition, in studies on irradiated cassava, waxy maize and wheat starch, the reducing sugar content increased with the irradiation dose (Raffi et al., 1981; Ananthaswamy et al., 1970).