Unusual gelation behavior of low-acetyl gellan under microwave field: Changes in rheological and hydration properties

The aim of this study was to investigate the effect of microwave heating on gel properties of low-acetyl gellan and to explore the potential mechanism of gelation behavior under microwave irradiation. Microwave heating dramatically enhanced the gel strength, hardness of low-acetyl gellan. Microwave-heated gels still formed strong network structures with 30 mM Ca²⁺ addition, but water bath-induced gels exhibited distinct pseudoplastic fluid behavior. Rheological analysis demonstrated that microwave heating increased the storage modulus (G') and loss modulus (G″) values of gels compared to water bath-induced gels. Low-field nuclear magnetic resonance (Lf-NMR) analysis and magnetic resonance imaging (MRI) showed that microwave heating promoted the hydration behavior of gellan, which contributed to the continuous regions in the gel network and further restricted the water mobility. These findings significantly increase our understanding of the mechanism by which microwaves improve gellan gel properties, thus facilitating the development of gel-related foods with tailored properties.