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Non-Newtonian Characteristics of Pomegranate Puree added with Xanthan and Guar Gums at Different Temperatures
A study was conducted to determine the rheological properties of pomegranate puree (PP) as affected by different gums (xanthan and guar gums) and temperatures (25, 35 and 45°C). The rheological properties of the samples were determined using a rotational rheometer at a shear range of 1 to 40 s-1. The PP added with xanthan and guar gums were found to be Non-Newtonian fluids following the Herschel-Bulkley model. The yield stress and consistency coefficient of the PP with xanthan gum at different temperatures were higher than those of the PP with guar gum but the opposite was observed for the flow behavior index. Moreover, all rheological properties of the PP regardless of type of gum addition decreased with increasing temperature. The consistency coefficient was related to temperature using an Arrhenius-type relationship. The PP with xanthan gum (16.11 kJ/mol) has higher activation energy than the PP with guar gum (11.44 kJ/mol). The yield stress values of the PP with xanthan gum and guar gum can be related to temperature by linear regression equations and the flow behavior index values by exponential regression equations.
