Analysis of the formation of starch — hydrocolloid binary gels and their structure based
on the relaxation times of the water molecules (in English)
Polimery 2011, No 6, 478
The formation of gels in the blending of cassava, corn, oat and potato starches with k-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 T1 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 T1 with an increase in temperature. The two latter hydrocolloids decreased gelatinization onset temperature by approximately 5 °C and made gelatinization more diffuse in time. The presence of hydrocolloids influenced also spin-spin T2 relaxation times. Initially, up to the onset gelatinization temperature, T2 was most effectively suppressed by xanthan gum. On cooling, T2 varied inconsistently. As a rule, T2 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.
Key words: cassava starch, cornstarch, guar gum, k-carrageenan, oat starch, potato starch, xanthan gum