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Three improved cassava varieties-TME 419, TMS 98/0505 and TMS 30572 were monitored from planting and harvested at three months interval-10, 13 and 16months respectively. Selected chemical properties of the cassava varieties-hydrogen cyanide, amylose, moisture and starch contents were determined at each harvesting regime. These chemical properties were optimized and a faced central composite design (k=2) was employed to study the effect of experimental variables on the chemical properties. Moisture content ranged from 49.96% (TME 419-16months) to 70.21% (TMS 98/0505-13months). Hydrogen cyanide ranged from 40.92mg/kg (TME 419-13months) to 47.85mg/kg (TMS 98/0505-16months). Amylose content of the cassava varieties varied from 17.64% (TMS 30572-10months) to 23.11% (TMS 98/0505-16Months). Starch content ranged from 13.30% (TMS 98/0505-16months) to 32.39% (TME 419-13months). However, optimization showed that the following minimum and maximum values were obtainable from the chemical properties studied: minimum moisture content 55.94% (TME 419-16months), maximum moisture content 70.89% (TMS 98/0505-13months). Minimum hydrogen cyanide 41.03mg/kg (TME 419-13months), maximum hydrogen cyanide obtainable was 46.48mg/kg (TMS 30572-16 months). Minimum amylose obtainable was 18.31% (TMS 30572-13months) and the maximum amylose obtainable was 21.70% (TMS 98/0505-10 months). Minimum percentage of starch obtainable was 17.99 from the cassava variety TMS 98/0505 harvested at the 16 th month while the maximum obtainable was 32.32, from the cassava variety TME 419 harvested at the 13 th month.

Starches obtained from five selected improved cassava species (NR 93/0199, TMS 96/0304, TMS 98/0581, TMS 92/10326, TMS 98/12123) were chemically modified by oxidation, acetylation and acid-thinning. Baking potentials of these starches were investigated. Acetylated starches significantly (p<0.05) gave the highest values in specific volume (10.25 ml/g). Acid-thinned starches significantly (p<0.05) yielded the lowest values in specific volume (2.92 ml/g). Oxidized starches maintained the least positions in some sensory properties-aroma (6.60), and general acceptability (6.62). TMS 96/0304 significantly (p<0.05) had the lowest value in specific volume (5.54 ml/g). Highest values were obtained in specific volume (6.82 ml/g) for NR 93/0199 as well as for TMS 98/12123 among the cassava species. Although the different modification methods and cassava species showed no significant (p>0.05) effects on the sensory properties of the wheat/cassava starch bread samples, the native starches and TMS 98/0581 had the highest scores for general acceptability.

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