Effects of Konjac Glucomannan on the Crystal Structure of High Acyl Gellan Gum
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Abstract:
In order to explore the interaction between natural polymers, the effects of konjac glucomannan on the crystal structure and physicochemical properties of high acyl gellan gum, under heating and microwave treatments, were studied in this work. Changes in crystal structure were analyzed by synchrotron radiation X-ray fiber diffraction, the frequency dependences at 45 and 25 ℃ as well as the temperature sweep in the range of 5~80 ℃ were measured using a rheometer, and the change in thermal stability was measured using the modulated differential scanning calorimetric technique. The results showed that konjac glucomannan led to a diminished crystal lattice but its orthorhombic structure was unchanged. The lattice parameters a, b, and c were changed from 14.6 × 10-10 m, 16.8 × 10-10 m, and 21.2 × 10-10 m to 13.2 × 10-10 m, 13.7 × 10-10 m, and 17.5 × 10-10 m, respectively. Konjac glucomannan caused a decrease in the storage modulus G' and an increase in the loss angle tan (δ) of high acyl gellan gum; the sensitivities of G’ and δ to frequency and temperature were enhanced. No significant differences were found in the impacts of heating and microwave treatments on the physiochemical properties. The results suggested that the helical molecular interaction in high acyl gellan gum was hindered by konjac glucomannan, and konjac glucomannan did not facilitate the formation of high acyl gellan gum gel network and crystalline structure.
