Rheological Characterization of Yam and Potato Paste (<i>Dioscorea rotundata</i>) and (<i>Ipomea batata</i>) for Adhesive Purpose

Abstract

An experimental study has been carried out to determine the flow behavoir (rheological characterization) of potential adhesive of starch derived from sweet potato ( Ipoemoa batatas ) and yam ( Dioscorea rotundata ) at varying temperatures ranging from 40°C to 85°C with borax blend of 0.83%. The results obtained showed decreasing viscosity with an increasing temperature; potatoes had higher viscosity and density (27 × 10 3 cP), (0.813 g/m 3 ) than yam (23 × 10 3 cP), (0.415 g/m 3 ). The rheological data were evaluated by the power law and Casson models to describe the rheological behavoir. The Casson model gave a relatively poor fit to the experimental data with R values ranging from 0.899 to 0.967 from yam while a better fit was obtained for potato with r values ranging from 0.957 to 0.976. The predicted k and n values fit into experimental data ( K = 26.36 and 0.388) and ( K = 34.75 and 0.649) for yam and potato respectively; n < 1 showing Non-Newtonian behavoir. The relation between the temperature and K was described by an Arrhenius equation. Activation energies of 2.69 KJ/mol and 5.87 KJ/mol for yam and potato blends were obtained, indicating more sensitivity of yam blend to temperature compared to potato blend. With the experimental values obtained, a mathematical expression to relate shear stress and shear rate were proposed as: τ =26.36γ 0.388 and τ =34.75γ 0.649 , for both the yam and potato blends respectively.