Effect of cassava starch substituion on the functional and sensory properties of trifoliate yam (<i>Dioscorea dumetorum</i>) flours

Abstract

This study was carried out to determine the effect of cassava (Manihot cranzt) starch substitution on the functional and sensory properties of trifoliate yam (Dioscorea dumetorum) flour. The trifoliate yam tubers were peeled, washed and boiled for 30 minutes and dried in hot air oven at 60oC for 48 hrs. The dried samples were milled, sieved (600 µm sieve size) and packaged. The cassava tubers were also peeled, washed and ground. The cassava paste was mixed with water, sieved (muslin cloth), and the cassava starch was allowed to settle and the water decanted. The starch cake was rinsed four times, dried in the oven at 40oC for 24 hrs, milled and sieved. The cassava starch was used to substitute 10, 20, 30, 40 and 50% of trifoliate yam flour. The control white yam (Dioscorea rotundata) tubers were peeled, washed and diced. The diced yam tubers were parboiled at temperature of 70oC and left for 12 hours in the cooking water. They were dried at 60oC for 48 hrs, milled, sieved and packaged. Functional and sensory properties of the flour samples were determined. Statistical analysis was carried out to test for significant difference (p ≤ 0.05) using one way analysis of variance (ANOVA). The control sample had the highest peak viscosity (201.22 RVU), holding strength (167.17 RVU), final viscosity (324.25 RVU) and set back viscosity (157.08 RVU).These were significantly different (p ≤ 0.05) from all the samples. Sample TF had the least peak viscosity value of 54.13 RVU while sample TC5 (50% cassava starch) had higher value (98.33 RVU) among the substituted samples. Breakdown viscosity follows the same trend with peak viscosity; it increased with increase in cassava starch substitution. Holding strength, final viscosity and setback values ranged from 24.39-39.01 RVU, 36.46-66.42 RVU and 12.08-27.42 RVU respectively. These three parameters decreased with increase in cassava starch substitution with higher values in sample TF (trifoliate yam flour). Pasting time and pasting temperature also ranged from 4.59-5.24 min and 73.88- 79.27oC, respectively. Swelling index and water absorption capacity ranged from 1.97-2.97 and 1.51-2.49 mlH2O/g, respectively. There were no significant differences (p > 0.05) in samples TC3, TC4 and TC5 (30, 40 and 50% cassava starch) in bulk density but the sensory evaluation showed that sample TC3 (30% cassava starch) was generally acceptable in colour, taste, odour and texture when reconstituted into a stiff dough.Key words: Functional, sensory, trifoliate yam, cassava