EFFECT OF PRETREATMENTS ON COLOR, FUNCTIONAL AND PASTING PROPERTIES OF WHITE (DIOSCOREA ROTUNDATA) AND YELLOW YAM (DIOSCOREA CAYENENSIS) VARIETIES

The effects of blanching, sulfiting and cooking pretreatments on color, functional and pasting characteristics of flours of Dioscorea rotundata (Abuja, Amula, Gbangi) and Dioscorea cayenensis (Alo) cultivars were investigated. The L* (71.4579.98), a* (2.36-4.72), b* (19.96-25.71), Delta E (0-6.68), Delta C (0-5.75) and hue angle (78.99-84.77) varied significantly with pretreatment and yam variety. Also, loose (0.44-0.77 g/cm(3)) and packed (0.79-0.97 g/cm(3)) bulk densities, water (13.522.0%) and oil (10.0-19.0%) absorption capacities, and solubility (13.40-59.10%) and paste transparency (44.50-61.90%) varied with pretreatment and variety. Average peak viscosity of cooked and sulfited yams of Abuja, Amula, Gbangi and Alo was 19.58 and 16.96, 35.33 and 131.84, 92.18 and 79.00, and 61.88 and 163.92 rapid visco analyser, respectively. Peak, trough, breakdown and setback viscosities of pretreated yams were significantly lower than the untreated control. Flours of pretreated Alo and Gbangi varieties showed higher values of peak, trough, breakdown and setback viscosities than Amula and Abuja varieties.