EFFECTS OF CONCENTRATION, PH AND SALT CONTENT ON FLOW CHARACTERISTICS OF XANTHAN GUM SOLUTIONS

Effects of gum concentration (C), pH and salt content and of their interactions on shear-thinning (n), consistency (K) and plasticity (sigma(o)) indices of xanthan gum solutions were analysed. The study was performed on 48 samples prepared following a factorial design with eight xanthan gum concentrations (0.05-0.40% w/v), two pH values (3.5 and 6.0) and three sail content levels (0, 0.25 and 0.50% NaCl, w/v). In general, the effects of sail and pH difference depended on hydrocolloid concentration. Salt increased pseudoplasticity with no significant difference between 0.25 and 0.50% NaCl samples (alpha = 0.05). Interaction between hydrocolloid concentration and salt was significant for both K and sigma(o) values. Only for C > 0.25%, samples with salt were more viscous and more plastic. C x pH interaction was significant only for K values. When C < 0.35%, samples at pH = 3.5 showed higher consistency indices. Lowering pH produced a similar but weaker effect than salt addition on K values. This effect was not shown when salt was present.