Mixed pastes of starches with guar gum

Abstract

Gelation characteristics (Brabender viscograph) and flow curves (Haake rheometer) were taken for corn, oat, potato and tapioca starch - guar gum 3 wt. % aqueous, binary blends at following ratios: 10:0, 9:1, 8:2, 7:3, 6:4, 5:5,4:6, 3:7, 2:8, 1:9, and 0:10. It was concluded, that increasing amount of guar gum added to the starches increased the Brabender viscosity of the composites, and this phenomenon was more pronounced in tuber starches. An addition of guar gum also increased the set back viscosity, hysteresis loop areas and shear thinning (pseudoplasticity) of the composites. Blends of both tuber and cereal starches with guar gum provided negative synergistic effects at elevated temperatures, whereas the cooling of cereal starches - guar gum systems led to weak but noticeable positive synergistic effects. The water deficiency in the starch granule environment caused by guar gum perturbed the course of gelation. Thermodynamic incompatibility of guar gum and starches in blends complicated the pattern of the gelation characteristics.