Microwave Modulation of β-Amylase Kinetics and Structure to Suppress Starch Retrogradation in Mashed Potatoes

Starch retrogradation critically limits the quality and shelf life of potato starch-based foods. This study investigated the mechanism of microwave (MW) irradiation on β-amylase and further verified the synergistic anti-retrogradation effect of MW-modified β-amylase on mashed potato starch, revealing that enzymatic activity initially increased with short-term exposure but sharply declined under prolonged MW treatment. Compared to conventional water bath (WB) heating, MW irradiation induced conformational changes in β-amylase, reducing its α-helix content from 29.41% to 19.50% and driving conversion of α-helices to β-sheets and random coils to expose catalytic sites and free sulfhydryl groups. Enzymatic kinetic parameters indicated that MW energy reduced the Km while increasing the catalytic rate of β-amylase. Experimental verification demonstrated that MW-pretreated enzyme application alone similarly reduced the storage modulus, short-range molecular order, and relative crystallinity of starch systems. These findings demonstrate that the combined MW-enzymatic approach synergistically improves the anti-retrogradation properties of mashed potatoes through structural and molecular-level interactions between starch substrates and enzymes.