Effects of pre-gelatinization methods on structure and physicochemical properties of kudzu starch

Kudzu is a traditional medicinal and edible plant, and starch is one of its major constituents. However, the inherent limitations of native starch, such as low transparency (8.85 %), poor solubility (1.34 %), and high gelatinization temperature, restrict its high-value applications. In this study, the effects of four pre-gelatinization methods (drum drying, extrusion drying, spray drying, and freeze drying) on the structural and physicochemical properties of kudzu starch were systematically investigated. Pre-gelatinization markedly disrupted the crystalline structure of kudzu starch, increased amorphous regions, and significantly enhanced cold-water swelling capacity and light transmittance. The extent of starch molecular degradation varied among processing methods, resulting in distinct functional behaviors. Specifically, drum-dried pregelatinized kudzu starch (DPKS) exhibited the highest swelling capacity (31.69 g/g) and light transmittance (23.77 %) in cold water, while extrusion-dried pregelatinized kudzu starch (EPKS) showed the greatest solubility (73.64 %). In contrast, spray-dried (SPKS) and freeze-dried pregelatinized kudzu starch (FPKS) demonstrated enhanced viscoelasticity upon rehydration in boiling water. Overall, this study expands the potential applications of kudzu starch in the food industry and provides a scientific foundation for targeted structural modification and functionality enhancement through selective pre-gelatinization strategies.