Rheological behavior of high methoxyl pectin from the pulp of tamarillo fruit (Solanum betaceum).

Rheological behavior of a high methyl-esterified pectic fraction (STW-A) from tamarillo was evaluated at different concentrations in water and with sucrose (50% w/w, pH 3). STW-A dispersions at 3, 5, and 8% (w/w) showed low apparent viscosities, shear-thinning and liquid-like behaviors. They were well fitted using the Ostwald-de Waele model and obey the Cox-Merz rule. The viscosity and the viscoelastic behavior were greatly modified by the presence of sucrose. STW-A at 1% (+ sucrose) showed shear-thinning and concentrated solution behavior. Pronounced shear-thinning and gel-like behaviors were obtained with STW-A at 2 and 3% (+ sucrose). Their flow curves profiles were better fitted using the Hershel-Bulkley model and not followed the Cox and Merz rule. Temperature sweeps (5-80°C) showed that STW-A formed thermostable gels. Altogether, our results suggested tamarillo can be a new source of pectin with potential applications as thickeners/gelling agents depending on solvent or applied processes.