Properties of the starches from cassava cultivars and cocoyam grown in Malawi in industrial utilization

Abstract

The physicochemical and functional properties of starch from cocoyam and ten varieties of cassava grown in
Malawi were studied to unravel their potential in industrial application. The properties of starch varied
significantly with crop and among varieties. Cocoyam starch granules exhibited polygonal truncated shapes
and small sizes (average of 7 µm) while the cassava starch granules were rounded, irregular with oval and
truncated ellipsoidal-granules with average size of 10.14 µm. The cocoyam starch gave lower values of
amylose values content and paste clarity but higher phosphorus content, maximum wavelength of iodine
complex absorption and blue value than cassava starches. Cassava starches gels were more stable to freeze
thawing releasing 28.40 – 46.92% of the water than cocoyam which released 54.06% of its water. Swelling and
solubility of both cocoyam and cassava starches increased with temperature (60 - 90C) . Cocoyam starch
exhibited lowered swelling power and solubility than cassava starches. The studies of gelatinization and
retrogradation characteristics indicated similar enthalpy values of gelatinization of cocoyam and cassava
starch; cocoyam starch displayed higher retrogradation tendencies than cassava starches.