Physicochemical properties of food grade acetylated cocoyam (Xanthosoma sagittifolium) starches

Starch was isolated from cocoyam (Xanthosoma sagittifolium). It was further modified by acetylation using NaOH and NaHCO3 at room temperature (28±3 oC). The pasting and physicochemical properties of the native and modified starches were then studied. Pasting properties of the alkaline modified cocoyam starches showed higher peak viscosities (245.92-256.96 RVU) compared to low peak viscosity (215.5 RVU) of the native starch. The modified starches were characterized by higher setback viscosities (112.79-110.17 RVU) in relation to native starch (105.88 RVU). Similarly, the alkaline modified starches had lower gelatinization time (4.47-4.50 min) compared to the native starch (4.60 min). Other functional properties, notably solubility and swelling power of the modified starches, showed higher swelling power (4.0-6.9%) and solubility indices (4.0-4.8%) compared to the native starch with lower swelling power (2.7%) and solubility index (0.9%). The degree of acetylation and substitution for cocoyam starches was 2.1-2.4 and 0.08-0.09 respectively. The study shows that starch acetylated with NaOH and NaHCO3 has better properties than native cocoyam starch and therefore it can be concluded that acetylated cocoyam starch produced under these conditions may be used as an alternative food grade starch additive for industrial purposes thereby encouraging import substitution.