Influence of Blanching on Some Nutrient and Anti-nutrient Compositions of Bitter Yam (Dioscorea dumetorum)

Bitter yam (Dioscorea dumetorum) is essentially underutilized probably due to its characteristic bitter
taste. The bitter taste may be related to its nutrient and anti-nutrient mix which could be improved by
simple processing methods. The study evaluated the influence of blanching on some nutritient and
anti-nutrient compositions of bitter yam (Dioscorea dumetorum) flour obtained after blanching (at
100°C) for varied time. The study was conducted at the Department of Food Technology, School of
Industrial and Applied Sciences, Federal Polytechnic Nekede, Nigeria. The nutrients and anti-nutrients
in the blanched and unblanched samples were determined by standard methods. The content in the
sample blanched for 18 minutes increased respectively by 1.88% and 1.13% for moisture and
carbohydrate, but decreased, by 60.00%, 19.61%, 5.80% and 13.65% for fat, crude fibre, ash and
protein relative to control (0 minute). Blanching caused a decrease by 67.43% and 62.26% for alkaloid
and tannin in the sample blanched for 18 minutes relative to control. The results were time dependent
and significant (p<0.05). Thus, although the significant reduction in tannin and alkaloid may improve
taste, the process reduced many important nutrients and may diminish the keeping quality of the
resultant flour. Thus, we recommend the processing method when bitter yam flour is required for
immediate use and as a low fat-energy source. Since many nutrients and anti-nutrients (medicinal
components) could leach into the blanch water, further study on the utilization of the waste water and
other processing methods is warranted.