Fructooligosaccharides Impact on the Hydration and Retro-Gradation of Wheat Starch and Gel

Abstract

In the present work, the hydration and retro-gradation of mixtures of wheat starch and fructooligosaccharides in diluted hydrated matrixes were discussed. Rapid Visco-Analyzer, differential scanning calorimeter, Fourier transform-infrared spectroscopy, scanning electron microscopy, and x-ray diffraction were used to determine the properties of the mixture of wheat starch and fructooligosaccharides. Swelling of the wheat starch showed significant changes when the addition of fructooligosaccharides surpassed 0.1 g/g starch. Water absorption index showed obvious change but there was no regular variation. The water solubility index of starch increased after adding the fructooligosaccharides and the highest value was up to 19.85 as compared with the control (3.61). There was no significantly change for the pasting parameters of the mixture. Fructooligosaccharides significantly affected the enthalpy of wheat starch from the result of differential scanning calorimeter analysis, and enlarged the freezing scope of the mixture gel (from –23.09 ± 0.25ºC to –38.85 ± 0.32ºC). The melting enthalpy of sample with fructooligosaccharides decreased by 9.9 J/g as compared with the control. Fourier transform-infrared spectroscopy results showed that there were no obvious differences between the samples with or without fructooligosaccharides except that the O–H stretching vibration of hydrogen bond of the mixture gel strengthened after storage for 2 or 4 days. Scanning electron microscopy results indicated fructooligosaccharides should be conductive for starch to form fine gel structures and could inhibit the retrogradation of wheat starch. X-ray diffraction spectrum further illustrated the fructooligosaccharides could interfere with the retrogradation of wheat starch during storage.