EFFECT OF TUBER SECTIONING ON THE FUNCTIONAL PROPERTIES OF FLOUR FROM WHITE YAM (DIOSCOREA ROTUNDATA) AND WATER YAM (DIOSCOREA ALATA) IN ORU EAST, IMO STATE, NIGERIA

Abstract

White yam (D. rotundata) and water yam (D. alata) were obtained from Mgbidi market, Oru East, Imo State, Nigeria, and the effect of sectioning on their functional properties was studied. Each of the yam tubers was sectioned as follows: head, middle, and tail of the yam tubers. They were manually peeled with a stainless-steel knife, washed, and sliced to a thickness of 2mm. The yam slices were treated for 20 min in 800 ppm sodium metabisulphate, drained of the solution, dried in a cabinet drier at 70 °C until a constant weight was obtained, and cooled to 25±2 °C. They were milled using an attrition mill, sieved through a 0.2mm aperture sieve, packaged in an airtight container, and labeled for subsequent analysis. The functional properties of the flour samples were determined according to the AOAC standard methods. Results were statistically analyzed at a 0.05 significance level using the General Linear Model to determine the mean, standard deviation, and analysis of variance. The results showed that, except for the swelling index, which decreased from 10.08 to 4.07 for heat-treated tail sections, the other functional properties examined were not significantly different (p > 0.05). On average, the flour from water yams had higher wettability (22.69s), oil absorption capacity (3.87g/ml), and gelatinization temperature (71.73 °C).  However, flour from white yams had a higher average bulk density (0.53g/ml), emulsion capacity (5.11%), water absorption capacity (4.9g/ml), and swelling index (4.09).  The results showed that there were significant (p≤ 0.05) differences in the functional properties of flour from the two varieties of yam tubers under examination. Based on the findings of this research, since no significant differences were observed among sections, flour from the whole tuber should be used instead of sectioning in food processing, such as for dough and pasta products, where swelling capacity is important. The high oil-absorption capacity of water yam flour suggests it could be used more effectively in baked products to enhance sensory attributes.