A comparison of functional properties of native Malawian cocoyam, sweetpotato and cassava starches

Cassava, cocoyam and sweetpotato constitute underexploited but yet important sources of starch for the Malawi industry. The functional properties of starches isolated from cassava, cocoyam and sweetpotato were studied and compared. Results revealed diverse functional properties among the starches from the different sources. With increasing temperature, water binding capacity, swelling power and solubility of the starches increased. Cocoyam and sweetpotato starches exhibited lower water binding capacity and swelling power, paste clarity and viscosity but higher degree of syneresis than cassava starches. Solubility was higher in cocoyam starches than sweetpotato and cassava starches. Cocoyam starches had higher gelatinization temperatures than sweet potato and cassava starches but similar transition enthalpies with cassava. Retrogradation studies by differential scanning calorimetry and turbidometry revealed higher levels of retrogradation for cocoyam and sweetpotato starches compared to cassava starches. Thus starches from sweetpotato, cocoyam and cassava would play different roles in various industrial applications.   Key words: Sweetpotato, cocoyam, cassava, starch, functional properties.