Effect of Galactomannans on the Thermal and Rheological Properties of Sago Starch

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Abstract
The thermal and rheological properties of sago starch have been studied in the presence of various concentrations of locust bean gum and guar gum of various molecular masses. At the concentrations studied (G‘, of the mixtures remained constant or actually decreased, and tan δ remained very low (0.01−0.03 at 0.1 Hz), indicating strong elastic gels. For the higher molecular mass samples G‘ increased significantly; however, the loss modulus, G‘ ‘, increased proportionally to a greater extent, and at 1% galactomannan tan δ was ∼0.20 at 0.1 Hz, indicating a reduction in elastic character. The systems were shown to undergo phase separation, and the variations in rheological properties have been discussed in the context of their phase behavior and the relative rates of the phase separation and gelation processes. The presence of galactomannans significantly improved the freeze−thaw stability. Keywords: Biopolymer; galactomannans; guar gum; locust bean gum; rheological properties; sago palm; sago starch