EFFECT OF CHEMICAL MODIFICATION TYPE ON PHYSICOCHEMICAL AND RHEOLOGICAL CHARACTERISTICS OF BANANA STARCH

Isolation of non-conventional starches has increased in the last decade; chemical modification of these no conventional starches may produce starches with improved physicochemical and functional properties that are not available from commercial starches. Banana starch was acetylated and oxidized and the thermal, pasting and rheological characteristics were evaluated. The low carbonyl and carboxyl groups might be due to the starch source. The acetylated banana starch obtained had a low degree of substitution (0.04). The acetylated banana starch had lower temperature and enthalpy of gelatinization than oxidized and native banana starches, had higher peak viscosity in the viscoamylographic profile than its native counterpart. The oxidized starch produced the peak viscosity during the cooling step and the three starches had higher viscosity during the cooling step, showing a gel conformation. The native. acetylated and oxidized starches showed a non-Newtonian behavior of the shear-thinning type. The rotational test showed that oxidized banana starch had a firmer gel than acetylated starch, which agrees with the viscoamylographic results.