Effect of Cooking Time on Biochemical and Functional Properties of Flours from Yam “kponan” (Dioscorea cayenensis-rotundata) Tubers

Aims: To determine the effects of cooking time on nutritional value of flours from yam “kponan” (Dioscorea cayenensis-rotundata) tubers.
Study Design: Analysis of Variance (ANOVA) was employed in this work.
Place and Duration of Study: Unité de Formation et de Recherche des Sciences et Technologies des Aliments (UFR-STA), Université Nangui Abrogoua, Abidjan, Côte d’Ivoire, during the period from June 2012 to July 2013.
Methodology: Yam tubers were randomly harvested at maturity (6 months after planting) from three different farms. Yam tubers were washed, peeled, cut into pieces and cooked in boiling water at 100ºC, for periods of 0 min (FNT), 5 min (F5), 10 min (F10) and 15 min (F15). After cooling, the samples were cut, oven dried at 45ºC for 48 h, milled, sieved, packaged and stored at 4ºC. Standardized methods were adopted for proximate and functional properties evaluation of yam “kponan” flours.
Results: Excepted the crude fat contents of flours, all the biochemical properties measured (dry matter, total ash, organic matters, total and reducing sugars, crude protein, carbohydrate) decreased significantly with the change in cooking time (p≤0.05). However, among functional properties studied, water absorption capacity, water solubility index and absorption capacity of some oils (palm oil, soybean oil, sunflower oil, red oil and olive oil) showed a significant (p≤0.05) increase with cooking time, whereas the foam capacity and stability of flours decreased significantly (p≤0.05). The flours exhibited different properties as showed by the Principal Component Analysis (PCA) that discriminated raw yam flour (FNT) from cooked yam flours after 5, 10 and 15 min (F5, F10 and F15, respectively).
Conclusion: The use of cooking method in yam “kponan” flours processing appeared beneficial to improve their nutritional potentialities.