Starches of two water yam (Dioscorea alata) varieties used as congeals in yogurt production.

The physicochemical properties of water yam (Dioscorea alata var. Akaba and Matches) starches were determined prior to their use as congeals for yogurt production. The moisture content ranged from 9.34% to 15.8% for A100 (100% Akaba) and M100 (100% Matches), respectively, indicating lower moisture content in the Akaba variety compared to Matches variety. Similar trend was observed for their water activity. The pH ranged from 5.88 to 6.93 indicating low acidity of the water yam starches. The water absorption capacity (WAC) ranged from 4.10 to 4.89 g/g, seemingly restricted reflecting protein-moisture interaction of the starches. Although the swelling power did not differ significantly (p > 0.05) ranging from 10% to 14%, they were quite restrictive as the WAC. The L* values of the starches were predominantly lightness in color, highest for A100 sample. The pasting temperatures of Akaba (A100), Matches (M100), and A50:M50 were not significantly different (p > 0.05). Peak viscosity of the water yam starches was in a range of 509-528 BU. The highest attributes were for taste (6.4), mouthfeel (5.4), flavor (5.4) sourness (4.6) and consistency (5.9), which were obtained from 1.5 % Matches, 0.5 % Akaba + 0.5 % Matches, 1.0 % Akaba + 1.0 % Matches samples. The overall acceptability (5.8) was higher than the control yogurt (4.7), indicating sample 0.5% Akaba + 0.5% Matches as the best-bet yogurt.