Effects of novel physical processing techniques on the multi-structures of starch

Native starches have been modified by employing various methods for desired industrial applications over the last few decades. There have been intense interests to develop novel methods with advantages of high-efficiency, environment-friendly and easy operation for starch modification. Although there is more attention to the functional properties of modified starch for practical applications in the industry, structural changes are the basis of functional changes, hence understanding the structural alteration induced by processing techniques is a fundamental issue towards better utilization of starch and starch modification techniques. The current review mainly presents the effects of several efficient physical processing techniques on the changes in the starch multi-scale structure including molecular structure, crystallinity, lamellae structure, and morphology characteristic. Among these techniques, the influences of high hydrostatic pressure, cold plasma, and microwave treatments are emphasized, and research gaps to better develop these techniques for starch modifications are suggested. Physical processing techniques by means of pressure, heat, radiation or free radicals can affect amylose, amylopectin, and degree of their interactions in the crystalline and amorphous region, as well as the packing mode of the crystal structure, thereby resulting in various functional properties and extensive applications in starch industries. However, the exact mechanisms behind these modification techniques are inconclusive because there are many affecting factors mainly including processing parameters, starch origin, and environment. Exploring new research methods or improving modified equipment to reduce the influence of these interference factors should be a good inspiration to study physical modification. •Novel physical techniques applied in starch modification are reviewed.•Changes in starch structure and gelatinization properties are compared and discussed.•Problems and challenges to apply these physical techniques are presented.