LAUSR

Abstract Freeze-drying treatment results in a marked disordering of starch structures because of the freezing of water and the sublimation of ice crystals. The objective of this work is to evaluate how the freeze-drying affects short-range ordered and crystalline structure, the structural compactness, size of reassemblied aggregates, and mesh size of starch gel network, by use of fourier transform infrared spectroscopy, small angle X-ray scattering and X-ray diffraction. Gels prepared from normal (NMS gel) and high-amylose maize starch (G50 gel) were selected as the model materials. After freeze-drying treatment, the short-range ordered and crystalline structures, the structural compactness, and the mesh size of starch gel network reduced for both starch gels. Long-range periodicity of reassemblied aggregates decreased via thinned amorphous region but unchanged ordered region. Impressively, G50 gel which had more ordered structures and a stronger gel network exhibited a higher resistant ability to the destruction of freeze-drying, and then showed little changes in microstructures after being freeze-dried in comparison with NMS gel. The ordered structures, compact reassemblied aggregates, and high-density mesh size-containing gel network may show a higher resistance to the destruction effect of freeze-drying treatment. This work systematically reveals the structural changes of starch gels subjected to freeze-drying treatment, which provides an in-depth understanding of gels structural changes during processing.