| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 92 === This study was to investigate the influence of the interaction between starches and barleyβ-glucans on the physical properties and water mobility of starch-barleyβ-glucan mixtures. Rice starch from three cultivars, Taichung Native 1 (TCN1; 29.5% amylose), Tainung 67 (TNu67; 12.7% amylose) and Taichung Sen Waxy 1 (TCSW1; 1.2% amylose) and barleyβ-glucans with four different molecular weights (Mw) (10×104∼58×104) were used as samples. The results of Rapid Visco Analyser (RVA) analysis showed that the addition of barleyβ-glucans with different Mw caused the decrement in the initial pasting temperature of nonwaxy rice starches (TCN1 and TNu67). The decrement increased with increasing the Mw of the β-glucans. For the viscosity parameters during heating of starch pastes, they increased significantly by adding barleyβ-glucans of a high Mw (58×104), but lowered by those of a low Mw (10×104∼22×104) to an extent more remarkable for a lower Mw and especially for the TCN1 with a high amylose content, followed by TNu67 and TCSW1. The existence of barleyβ-glucans hardly affected the thermal properties of 20% starch suspensions during gelatinization but decreased the storage moduli (G'') of hot pastes, the G'' increase during cooling and the G'' after cooling to 25℃of 5% starches. The decreasing effects were the most remarkable for TCN1 between the starches examined and more significant for a β-glucan with a lower Mw. The changes of G" were generally similar to the G'' mentioned above, except for the systems of the high-Mw β-glucan that showed the opposite effects. The addition of barleyβ-glucans elevated the tanδand the frequency dependencies of G'' and G" of the starch gels to an extent greatening with the increment of barley β-glucans molecular weights. Pulsed nuclear magnetic resonance (PNMR) analysis indicated that the addition of barleyβ-glucans caused a decline of liquid-like spin-spin relaxation time (T2b) more remarkably for barleyβ-glucan of a greater
molecular weight and especially for waxy starch TCSW1. Microscopy images displayed that adding barleyβ-glucans somewhat altered the morphology of starch granules after gelatinization. Generally speaking, the addition of low-Mw barleyβ-glucans resulted in the decreases in viscosity, elasticity and T2b of starch-barleyβ-glucan mixtures. The decreases in these parameters except T2b, rose with reducingβ-glucans molecular weights. Accordingly, the Mw of barley β-glucans and the amylose content of starches played a important role in their interactions and in turn the physical properties of their mixtures.
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