A Comparative Quality Evaluation of White Yam (Dioscorea Rotundata) and Water Yam (Dioscorea Alata) Chips as African Fries

Abstract

This study was conducted to evaluate the quality characteristics of Dioscorea rotundata and Dioscorea alata as alternative to potato in French fries production and effect of frying time on the quality index and acceptability of resultant yam chips. The yam chips were pretreated by blanching for 10minutes at 90 o C, and soaking in 5% citric and sodium metabisulphite acid solution for a period of 30minutes. The treated blanched yam chips were deep fried at 170 o C for 21 minutes, but the chips were withdrawn at intervals of 3minutes to determine the moisture content, textural properties and sensory attributes of the chips.The proximate composition of the fried chips was evaluated using established procedures of the Association of Official Analytical Chemists (AOAC). The textural properties such as Peak force and deformation at break of the deep fried chips were determined using a Universal Instron testing machine.The fried yam chips were subjected to sensory analyses (colour, crispiness, mouthfeel, taste, overall acceptability) using a 9-point Hedonic scale. Data obtained were subjected to Analysis of Variance ANOVA and means separated by Duncan Multiple Range test.The result of the proximate analysis on the two varieties of raw yam tubers showed that wateryam (D.alata ) had a significant (p>0.05) higher moisture content (69.49%) and protein values (7.60%) than white yam (D. rotundata) having 64.84% and 4.55% respectively).D alata had a significant (p>0.05) high fibre content of 2.34 % compared to D rotundata which had 1.42%. On the other hand, D. rotundata, has greater amount of carbohydrate (26.70%) than D. alata with (20.18%).A significant (p< 0.05) lower moisture content existed for the fried chips samples from 3 minutes to 18 minutes for both white yam (54.32-32.76%) and water yam (61.32-31.03%).Frying time had a significant lowering effect on the moisture content of fried chips. White yam (D. rotundata) showed significantly (p>0.05) high force at peak than wateryam (D. alata), with values of 26.30N, and 7.30N respectively. Results showed that frying time had significant (p>0 05) effects on the peak force and deformation at peak of the fried yam chips for the two varieties. The pre-treatments given to the yam chips produced from the two yam varieties, gave some desirable sensory characteristics. The sensory scores showed that fried white yam chips had a significant (p>0.05) highest score (7.14) compared to wateryam fried chips (6.39) at 21st minute frying time even in terms of colour, taste, mouthfeel and overall acceptability.The use of yam as a substitute for potato in French fries production would make fries to be more affordable and promote its utilization in French fries production.