Rheological Properties of Banana Puree at High Temperatures

Abstract

The rheological behavior of banana puree was determined using a dynamic stress rheometer with a pressure couette fixture, which allowed experiments to be conducted at high temperature. The pressure couette was pressurized with compressed air to 206.8 kPa (gage pressure) and experiments were carried out at temperatures ranging from 30 to 120 C. The shear stress values ranged from 10 to 170 Pa and the shear rate values from 10 À5 to 10 3 s À1. The model that best fitted the experimental data at all temperatures was the Herschel-Bulkley model. There was a usual tendency for the apparent viscosity to decrease with increasing temperature but an increase in apparent viscosity with increasing from 50 to 60 C and from 110 to 120 C was found. This could be due to interaction of polysaccharides present in banana puree. There was a slight difference between the apparent viscosity values for increasing shear stress sweeps and those for the decreasing shear stress sweeps suggesting time dependency of the rheological

Rheological modeling of non-depectinized beetroot juice concentrates

“…The selection of the rheological model that best describes the flow properties of the BJC of different concentration (25,35, 45 and 55°Brix) was selected on the basis of the data obtained experimentally. From the linear and nonlinear regression analysis, the BJC was observed to flow non-linearly which shows that the rheogram must have followed the non-Newtonian models which can be estimated either by the Power law or the Herschel-Bulkley fluid flow models.…”

“…The advantage of using parallel plates was the usage of less amount of volume of sample for testing. The viscosity of the beetroot juice concentrate (BJC) samples with different soluble solids content (25,35, 45 and 55°Brix) was measured at a temperature range of 30 to 80°C. This range was chosen because of the varying temperature of different processing conditions under which the juice experienced certain viscosity changes.…”

Rheological Properties of Green and Gold Kiwifruit Purees at Different Temperatures

“…A number of studies have shown that many of fruit purees behave either as a power law fluid or as a Herschel-Bulkley fluid [6][7][8][9][18][19][20]. The data fell on an approximately straight line but not passing through the origin which means that the sample was not a power law fluid.…”

“…Again the rest of the data were processed in the same way and revealed that the gold kiwifruit puree behaved as a Herschel-Bulkley fluid at the different temperatures. A number of other fruit purees had been fitted as well with the Herschel-Bulkley model including banana puree [7], blackberry pulp [8], raspberry, strawberry, prune and peach purees [19], mango pulp [21], blueberry puree [22], acai pulp [23] and siriguela pulp [24].…”

“…These kinds of fluids are generally described by empirical rheological models that give the best curve fitting rheograms [5]. The most widely used models for fruit purees are the Power Law and Herschel-Bulkley models [5][6][7][8][9][10]. At present, there have been limited studies on the rheological properties of kiwifruit puree and none for the gold kiwifruit.…”