Partial characterization of banana starches oxidized by different levels of sodium hypochlorite

Chemical, physical, physicochemical and functional properties of oxidized banana starch by different levels of sodium hypochlorite (0.25-2.0% active chlorine) were studied. The content of carboxyl and carbonyl groups in the oxidized starches increased when chlorine concentration increased, however the level of carboxyl groups was higher than carbonyl groups because carbonyl groups were formed during the reaction were transformed to carboxyl groups. The L* factor was used to characterize the whiteness of the oxidized starches. When chlorine concentration increased the whitness increased too, but at the highest chlorine concentration the L* values were not different (α=0.05). The oxidation carried out with a chlorine concentration between 0.25 and 1.0% produced starches with a viscosity peak higher than its native counterpart, however when the active chlorine concentration increased (1.25-2.0%) an inverse pattern was obtained; high chlorine concentration cleaved the starch chains and the peak viscosity decreased. The gelatinization temperature (T_p) of oxidized starches was higher than its native counterpart, but at the highest active chlorine concentration a decreased in the T_p value was obtained. The enthalpy values of the oxidized starches were lower than the native starch and in general those values decreased when active chlorine concentration increased. These results agree with those obtained from viscoamylography since starch degradation is carried out with high chlorine concentration. The swelling power of the oxidized starches measured at low temperatures was lower than its native counterpart and the water solubility index increased when temperature and chlorine concentration increased.