Resistant starch (RS) is defined as the fraction of starch that escapes digestion in the small intestine due to either difficult enzyme/starch contact or to the strength of the crystalline regions formed both in native starch and in those retrograded starch. RS occurs naturally in some foods, and some may be generated in others as the results of several processing conditions. Varieties of techniques have been employed to obtain structural characteristics of RS such as their crystallinity, structural order, chain-length distribution and conformation, helicity, and double-helical structures. These structures play an important role in determining the physiological properties of RS such as their prebiotic and hypoglycaemic properties. However, such topic on structural characterization of RS and their structure-physiological function relationship have not been reviewed in previous literatures. Therefore, this review focuses on the past and current achievements of research on structural characterizations of a range of RS prepared from different sources of native starches as a result of a variety of processing conditions. The potential relationships between the structure and the physiological properties of RS, which is of paramount importance for the furtherance understanding and application of RS, are also reviewed in this study.

Resistant starch (RS) plays a key role in providing metabolic and colonic health benefits. In particular, RS type III (RS₃) is of great interest because of its thermal stability and its preserved nutritional functionality. RS₃ can be prepared by physical treatment, including high hydrostatic pressure, ultrasound, extrusion, autoclaving, microwave cooking, and heat-moisture treatment. The acid and enzymatic hydrolysis can also be applied to facilitate the generation of small molecules, which increases the inherent crystallinity of RS₃ upon retrogradation. Depending on processing conditions, RS₃ with diversified structural characteristics can be formed. These structures play a key role in determining the physiological behavior of RS₃. Therefore, a deep understanding of the structural rearrangement pattern during different processing treatment is of great importance for regulating the molecular structure of RS₃ and thereby its corresponding physiological properties. This review thus focuses on the past and current status of research into the in-depth study of RS₃ formation mechanism and the changes to RS₃ structural characteristics under different processing conditions. The objective was to provide a theoretical guidance for the rational selection of preparation methods for RS₃ and for designing RS₃ structures with specific physiological functionalities for relevant industrial applications.