Rheological characteristics of reconstituted spray dried beetroot (Beta vulgaris L.) juice powder at different solid content, temperatures and carrier materials

Investigation was carried out to study the effect of different carrier materials namely, maltodextrin (MD) and gum Arabic (GA) with original juice (OJ) on viscosity of reconstituted beetroot (Beta vulgaris L.) juice powder at different solid contents (Xs) 10 to 50% and wide range of temperature 10 to 85°C. The rheological parameter shear stress was measured up to the shear rate of 1000 s-1 by controlled stress rheometer using concentric cylinders. The investigation showed that all the reconstituted beetroot juice behaved like a Newtonian fluid. The Newtonian viscosity (η) ranges from 4.47 to 86.99, 4.76 to 176.15 and 5.60 to 1561.77 mPa s for original, maltodextrin (MD) and gum Arabic (GA) based juices respectively, depending upon the solid content and temperature used. The investigation showed that the Newtonian viscosity increased significantly (p<0.05) with increase in solid content, whereas it decreased significantly (p<0.05) with increase in temperature. Of all the carrier materials gum Arabic showed maximum viscosity followed by maltodextrin and original juice at same solid content and temperature studied. The temperature dependency of Newtonian viscosity of beetroot juice was described by Arrhenius equation. The flow activation energy (Ea) was markedly affected by type of carrier material and is increased significantly (p<0.05) with increase in solid content. The Newtonian viscosity of reconstituted spray dried beetroot juice increased with solid content and a significant (p<0.05) change was observed with different temperatures used and also markedly affected by type carrier material. A combined single equation relating Newtonian viscosity (η) to solid content and temperature was established. The results indicated dependency of the Newtonian viscosity of reconstituted beetroot juice on solid content, temperature and type of carrier material.