Analysis of the formation of starch - hydrocolloid binary gels and their structure based on the relaxation times of the water molecules

The formation of gels in the blending of cassava, corn, oat and potato starches with kappa-carrageenan, guar and xanthan gums and some of their selected properties have been studied. 0.2 % admixture of xanthan gum, significantly decreased the spin-lattice T(1) relaxation time, whereas similar admixtures of guar gum and K-carrageenan had a relatively weak influence upon starch gelatinization providing, however, a slight increase in T(1) with an increase in temperature. The two latter hydrocolloids decreased gelatinization onset temperature by approximately 5 degrees C and made gelatinization more diffuse in time. The presence of hydrocolloids influenced also spin-spin T(2) relaxation times. Initially, up to the onset gelatinization temperature, T(2) was most effectively suppressed by xanthan gum. On cooling, T(2) varied inconsistently. As a rule, T(2) in binary gels was higher than in those of plain starch. In all the studied blends both relaxation times monotonously declined with temperature. The activation energy of water molecules in binary gels on cooling was estimated.