Abstract
The influences of saccharides on hardening and water mobility of wheat starch gels stored at 2°C have been investigated. Hardening process of saccharides-supplemented gels could be separated into the four regions similarly to the control gel. In the region I, the creep compliance of the gels decreased exponentially with increasing storage period from the beginning of storage to several hours. In the following several hours, the compliance showed approximately a flat or slow increasing or decreasing change (region II). In the region III, the value decreased exponentially on the trend which was assumed the initial value extended. Finally, the compliance continued with decreasing more slowly (region IV). Except for D-ribose-added gel, no great differences were recognized among the initial creep compliance (J01) of saccharides-supplemented gels in the region I, and the compliances were smaller than the value of the control gel. However, D-ribose-added gel showed the same strain with the stress of which was about 60% in the other gels. Hardening rate constants (kI for the region I, kIII for the region III) of gels added with D-ribose, maltose, trehalose, sucrose, maltose, and malto-oligosaccharides (major components were maltose and maltotriose, or maltotriose) were smaller than the control gel. On the other hand, 13-fructose, D-galactose, melibiose increased the hardening rate compared to the control gel. Gel-stabilizing effect of disaccharides and oligosaccharides would be dependent on both constituent monosaccharides and glucosidic linkages in these molecules. The mobility of water in starch gels was inferred from measurements of apparent transverse relaxation time T2 using 17O-NMR techniques. The decreasing ratio of T2 to the initial T2 with storage was larger in order of maltose-added gel≤trehalose-added gel < sucrose-added gel <control gel < melibiose-added gel. The saccharides which reduced the hardening rate, resulted in adecrease in water mobility in the non-stored gel, and in a inhibition of progressive decrease in watermobility with the elapse of storage period.
