Flow behaviour of yams grown in Papua New Guinea

P. A. Sopade

Abstract

Dioscorea rotundata Poir. is a recently introduced yam in Papua New Guinea (PNG). Its rheological behaviour was studied as well as that of D. alata and D. esculenta. A rotational viscometer at speeds 0.5–100 rev/min was used and 4% slurries of the yam flours at temperatures 25–75 °C were studied. Results were presented as shear stress-shear rate data, which were modelled with the power-law equation. The equation adequately described (r = 0.9898–0.9998) the rheological behaviour and the power-law indices were: D. alata, 0.67 ・} 0.057; D. esculenta, 0.42 ・} 0.093; D. rotundata, 0.34 ・} 0.045 indicating pseudoplastic behaviour as the viscosity was essentially (CV = 3–11%) timeindependent. The temperature dependence of the consistency index (viscous nature) was analysed using the Arrhenius equation and the correlation coefficients were between 0.9722 and 0.9946. The D. rotundata  slurry was the least sensitive to temperature changes. The significance of the rheological information for the success of the introduced yam in the PNG food chain is highlighted.

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