Effect of ultrasound-pretreated starch on the formation, structure and digestibility of starch ternary complexes from lauric acid and β-lactoglobulin

Starch, lipids, and proteins are key macronutrients in starchy foods. Their interactions during processing can form starch-lipid-protein ternary complexes, significantly affecting food quality. Ultrasonic treatment, as a common processing method, is expected to regulate the quality of starchy foods by influencing the formation of ternary complexes. This study aimed to understand the effect of ultrasonic pretreatment on the formation of starch-lipid-protein ternary complexes using various types of starches. Wheat starch (WS), maize starch (MS), and potato starch (PS) were gelatinized and treated with ultrasound at various power densities (0-40 W/L) to form complexes with lauric acid (LA) and β-lactoglobulin (βLG), respectively. Ultrasound increased the amylose content of gelatinized WS, MS, and PS and shifted their chain length distribution towards the short chains. Results from Fourier transform infrared spectroscopy, laser confocal micro-Raman, X-ray diffraction, and differential scanning calorimetry showed that the largest amount of WS-LA-βLG complexes was formed at the ultrasonic power density of 10 W/L, and MS-LA-βLG and PS-LA-βLG complexes at 20 W/L. Additionally, ultrasound enhanced the content of resistant starch (RS) in the starch-LA-βLG complexes. The RS content increased from 14.12 % to 18.31 % for WS-LA-βLG, and from 19.18 % and 20.69 % to 27.60 % and 28.63 % for MS-LA-βLG and PS-LA-βLG complexes, respectively. This study presents an approach for facilitating the formation of ternary complexes, contributing to the development of low-GI functional foods.