The Effect of Xanthan, Guar and Transglutaminase on the Physicochemical and Textural Properties of Gluten-free Doughnut

The main objective of the current study was to optimize gluten free doughnuts formula for which the effect of xanthan, guar and Transglutaminase (TGase) enzyme were investigated. Xanthan, Guar and TGase were added from 0 to 2% of flour basis to the basic formula. Treatments were designed based on the mixture design of the Minitab software. The optimum conditions were selected based on the oil absorption, hardness, color, porosity and specific volume. The results showed that the high oil absorption occurred at the high level of TGase in absence of gums and the minimum oil absorption happened at the triple point. TGase caused cross linkage between rice flour protein, potato flour protein, and soy protein concentrate, which led to making protein network, xanthan gum,creating viscoelastic properties and guar gum,generating inter-surface properties, finally resulting in the increase of porosity and specific volume of doughnuts respectively. The interaction between the components showed that increasing the amount of guar gum improved the lightness of doughnuts. Texture parameters showed that samples with just gums without TGase showed the highest hardness. The synergistic effects of these gums increased viscosity. Hardness was decreased by protein network induced by TGase. The results of this study showed that the formula containing all three components could simulate the protein network in the gluten-free doughnut. The optimum point was 0.98% of xanthan, 0.44% of guar and 0.58% TGase which showed the best responds.