CHARACTERIZATION OF VISCOELASTIC PROPERTIES OF POTATO (Solanum Tuberosum) AND COCOYAM (Colocasia spp) TUBERS UNDER COMPRESSION LOADING

Abstract

Production and processing of many root and tuber crops especially cocoyam are still manually done. Adequate knowledge of their mechanical properties is a prerequisite for the development of machinery for harvesting and processing of cocoyam and potato This research examines the mechanical behaviour of three (3) varieties of cocoyam: Colocassia esculentum (Taro/Red), Xanthosoma sagittifolium (Tannia/ White), and Mpotompoto (Ghana cocoyam); and three varieties of potato: white sweet potato (ipomoea batatas), red sweet potato (Satsuma-imo) and Irish potato (solanum tuberosum) under compression loading. The evaluation parameters investigated include compressive extension at break, the compressive load at break, the maximum compressive extension, energy at break, load at yield, modulus of elasticity as well as the compressive strain and stress at yield. Stress relaxation test were also carried out on all the samples. Cylindrical shaped samples were obtained from these materials for easy handling and examination. From the study, the Ghana cocoyam variety had the highest values in all the mechanical properties measured among the three varieties of cocoyam while the white cocoyam was the least. Also, the white sweet potato variety has the highest values of the mechanical properties measured among the three varieties of Potato while the red sweet potato had the least. From the Analysis of Variance (ANOVA), of all the tubers tested, all the varieties of cocoyam were not significantly different from one another but all the varieties of potato show a clear significant difference from one another. Also, the red sweet potato and the white sweet potato were not significantly different from one another. For the stress relaxation tests, white cocoyam has the highest relaxation time of 245 seconds and hence more mechanically stiff that red and Ghana cocoyam. The Irish potato had the highest stress relaxation time of 170 seconds and hence more mechanically stiff that white and red sweet potato. It also implies that more force is required to work on the Irish potato variety that the other two varieties considered. This study has provided data required for processing and better postharvest handling of the tubers and further help to provide global solution to the challenge of tuber handling