The effect of temperatures and pH on the viscosity of syrups containing gums

The objectives of this study were to determine the effect of adding xanthan and CMC P-7SM gums at different concentrations on the viscosity of sucrose, com and Karo syrups at different temperatures and pH values and to ascertain the effect of the gums at three concentrations on the color of the syrups. In this experiment, three kinds of syrup were treated with the xanthan gum (0.1, 0.2 and 0.3 percent) and CMC P-75M gum (0.5, 1.0 and 1.25 percent). As a result 18 treatments were obtained for the experiment. Each treatment was replicated three times and three readings were taken for each replication. The apparent viscosity and color of each treatment were measured at different temperatures (26.7°, 37.8°, 48.9°, 60°, 71.1°C) and pH levels (the treatment pH and 0.5 pH unit below the treatment pH, and 0.5 unit above the treatment pH) with a Brookfield Synchro-Lectric Viscometer (Model LVF) at four different rates of shear (6, 12, 30 and 60 r.p.m.). The apparent viscosities between the syrups were significantly different. The apparent viscosities of the syrups decreased as the temperature was increased, but increased as the gum concentration was increased. There were no significant differences on the apparent viscosities at the different pH levels used in this experiment. The Newtonian behavior of the syrups was changed to pseudoplastic by adding the gums, in particular syrups to which xanthan gum had been added exhibited a more pseudoplastic behavior than syrups to which CMC P-75M gum had been added. Xanthan gum added syrups had a higher heat stability than the CMC P-75M gum added syrups. Chromaticity coordinates x and y of the gum added syrup were significantly different