Effects of Fructose-Oligosaccharides on Retrogradation Characteristics of Rice Starch

To identify the effects of fructo-oligosaccharides on retrogradation characteristics of rice starch, we determined the setback viscosity, syneresis rate, firmness, amylose leaching, and dynamic rheology of rice starch paste blended with fructo-oligosaccharides in contrast to the widely reported anti-retrogradation additive β-cyclodextrin. The retrogradation characteristics of rice starch were analyzed by Fourier transform infrared (FTIR) spectroscopy, low field nuclear magnetic resonance (LF-NMR), scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and confocal laser scanning microscopy (CLSM). The results showed that fructo-oligosaccharide treatment significantly decreased the peak viscosity, final viscosity and setback value of gelatinized rice starch paste. In addition, after short-time refrigeration, fructo-oligosaccharide-treated rice starch exhibited lower syneresis rate (21.82%), hardness (16.26%) and amylose leaching (17.25%), indicating that fructo-oligosaccharides could improve the water retention and stability of rice starch. Also, fructose-oligosaccharides decreased the storage modulus, water mobility, relative crystallinity, and ratio between transmittance at wavenumbers of 1047 and 1022 cm^-1 of rice starch paste, and made the network structure become more compact, showing better anti-retrogradation efficiency. Therefore, fructo-oligosaccharides have excellent potential in delaying the retrogradation of rice starch-based foods.