Abstract: This study investigated the regulatory mechanism of pectin modified by electron beam irradiation (EBI) at doses of 0, 5, 10, 15, and 20 kGy on the stability of malvidin-3-O-galactoside (M3G). The structural modification effects of EBI on pectin were elucidated by using infrared spectroscopy as well as measuring weight-average molecular mass, monosaccharide composition, and degree of methylesterification. The influence of EBI on the pectin binding capacity and stability of M3G was determined, and the impact on the structure of pectin-M3G complexes was analyzed by measuring the zeta potential, average particle size, polydispersity index, and morphological characteristics. The results showed that with increasing irradiation dose, the weight-average molecular mass of electron beam-irradiated pectin first increased and then decreased, with a similar trend observed for the proportion of the homogalacturonan (HG) region. In contrast, the degree of methylesterification decreased continuously. After irradiation, both the binding rate and stability of the complexes were significantly enhanced in a dose-dependent manner. Pectin irradiated by 15 kGy of electron beam exhibited the highest binding rate to M3G and the complex between pectin irradiated by 5 kGy of electron beam and M3G displayed the best stability. The colloidal stability and uniformity of the complexes were both improved after irradiation. This study confirmed that low-dose EBI induced cross-linking of pectin to form a three-dimensional network structure, providing more binding sites and increasing steric hindrance, whereas medium- and high-dose EBI led to molecular chain scission, increasing the number of binding sites between pectin and M3G. Both structural optimization approaches could enhance the binding capacity of pectin with M3G, thereby improving the stability of M3G. These findings provide theoretical and technical support for anthocyanin stabilization and the green modification of pectin carriers.

Key words: electron beam irradiation; pectin; anthocyanin; malvidin-3-O-galactoside; stability