| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 91 === Abstract
The effects of sucrose, trehalose and maltose on the rheological properties of locust bean gum (LBG) and guar gum (GG) solutions at dilute and semi-dilute states were investigated, using a capillary viscometer and a rheometer with flow or small-amplitude oscillation mode. Basically, the intrinsic viscosity of the GG examined in aqueous solution was higher than that of the LBG. The intrinsic viscosities of both galactomannans decreased insignificantly in the above disaccharides at 5-20% (w/w), but significantly at 40%(w/w). Similar effects were also observed on the initial coil-overlap concentration (C*) of the galactomannas. The decreasing effects were more notable for trehalose than for the other two sugars. By using the Cox-Merz superposition rule in understanding the potential association of the galactomannas at semi-dilute concentrations, the rheological behaviors of the 1%(w/v) GG solutions at 20 and 60oC in the frequency range between 0.1~100 Hz agreed with the Cox-Merz rule. However, the Cox-Merz rule did not describe well the rheological behaviors of the 1%(w/v) 80oC-ectracted LBG (LBG80) in the frequency range between 0.1~100 Hz, in which the observed complex viscosity was greater than the apparent viscosity. This phenomenon could be related to the association of galactomannan molecules. By time-temperature superposition-Arrhenius approaches, the obtained activation energies of anti-deformation during rheological measurements were higher for the 1%(w/v) LBG80 in 40%(w/w) trehalose aqueous solutions (38.3 kJ/mol) than those in the sucrose and maltose (35 kJ/mol). All above results suggest than trehalose had more notable influences on the rheological properties of the galactomannan solutions than did sucrose and maltose.
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