Soaking Effects of Chips from Two Bitter Yam Species on Chemical and Functional Compositions of the Flour

Abstract

Physico-chemical properties of foods are greatly influenced by some processing methodologies which thus affects the utilization of these foods. This research studied the soaking effect of two species of bitter yam chips D. dumentorum and D. hispida in water for for 6, 12, 18 and 24 h before oven drying and size reduction to flour. The various flour samples and their respective controls were analyzed for functional properties, vitamin C, beta carotene, phosphorus, calcium, pH and anti-nutrient (alkaloid and tannin) using standard methods. The results depicts that in flour samples of D. hispida and D. dumetorum, respectively, there were significant increase (from fresh to 24 h soaked samples) in pH values from acidic to near neutrality (5.2 - 7.5; 4.8 - 7.9), decrease in anti-nutritional factors (tannin (0.48 - 4.02%; 1.37 -15.83%) and alkaloid (nil; 0.14 - 1.26%), vitamin C (1.02 - 1.95; 1.22 - 2.39 mg/100g) and beta carotene (1.81 - 3.56; 4.24 - 5.79 mg/100g) and minerals (phosphorus (1.40 - 3.44; 1.78 - 4.50 mg/100g) and calcium (16.4 - 24.80; 4.23 - 28.16 mg/100g) with increase in soaking periods (h) due to leaching out of these nutrients in soaking water. Water/oil absorption capacity, swelling index, least gelation capacity and viscosity of samples decreased with increase in soaking time (h), while gelatinization temperature of samples increased with increase in soaking time (h). This shows that there was modification in compositions of these flours depending on the soaking time applied which provided information on utilization of soaking in water processes in optimizing the properties of bitter yam chips in flour production.