Effects of Tuber Age and Variety on Physical Properties of Cassava [Manihot Esculenta (Crantz)] Roots

Abstract

Poor postharvest storability of cassava roots has led farmers into leaving the tuber in-ground for a long time even after maturity thereby leading to lignifications. Besides, this practice has been reported to result in changes in the physiological structure of the roots, hence the need to investigate the influence of this on the engineering properties of the root. Two improved cassava varieties, TME 419 and TMS 30572 and a local variety, Oko-iyawo were investigated in this study. Selected physical properties which include diameter and peel thickness at the head, middle and tail (D_H, D_M, D_T, P_H, P_M and P_T), mass, length, Peel Proportion by Weight (PPW) and density for tubers aged 12, 15 and 18 Months After Planting (MAP) were measured  using standard methods. The data were analyzed using the two way ANOVA in SPSS 15. The mean D_H, D_M, D_T, P_H, P_M, P_T, mass and length ranged respectively from 36.67 (8.76) – 43.32 (11.53) mm, 35.26 (15.77) – 45.58 (7.68) mm, 26.06 (12.94) – 33.87 (10.30) mm, and 1.30 (0.25) – 4.60 (1.13) mm, 1.23 (0.23) – 4.52 (1.08) mm, 1.19 (0.16) – 4.06 (1.05) mm, 229.78 (146.98) – 489.11 (274.28) g, and 232.98 (85.43) – 344.18 (90.37) mm. They were significantly influenced by age except D_M and D_T while oval shape was established from the dimensions indicating suitability for mechanical peeling. Mean PPW ranged from 17.36 (2.73) – 24.09 (7.32) % which showed that younger tubers have more flesh for human consumption and older tubers thick peels more useful in animal feed. Analysis of variance showed that the tuber age had a very strong influence on all the physical properties except D_M and density. Varietal influence on tuber mass, D_H, D_M and density was not statistically significant. The study established the importance of tuber age and variety as factors to be considered in the design and development of cassava processing and handling equipment for effective and efficient performance of the machines.

Keywords: Cassava, postharvest, tuber age, cassava variety, physical properties