Thermo-reversible gel synthesized by 4-α-glucanotransferase with sol-gel transition tuned by subtle amylose manipulation

Thermo-reversible gels have garnered significant interest in food, pharmaceutical, cosmetic, and therapeutic delivery sectors. The increasing demand for plant-based ingredients has further propelled research into plant-derived gels. This study investigates the application of 4-α-glucanotransferase from Thermus thermophilus STB20 (Tt4αGT) to synthesize thermo-reversible gels from seven starches. Detailed rheological analyses and fine structural characterizations were conducted to elucidate the mechanisms underpinning gel formation. The results indicate that amylose content and amylopectin chain length distribution are pivotal factors; specifically, an amylose content exceeding 5% is essential for gel formation was proposed for the first time. Modified starches exhibited a higher proportion of both short (DP 6–8) and long chains (DP > 26) compared to their native counterparts. Rheological assessments demonstrated that these gels maintained thermal stability through repeated heating and cooling cycles between 90 °C and 4 °C. Notably, Tt4αGT treatment significantly enhanced gel strength, particularly in tapioca starch (TS), and improved the thickening performance and reversibility of starch. The gel network structure was primarily stabilized by hydrogen bonds, supplemented by electrostatic interactions. These findings highlight the potential of Tt4αGT-treated starches as versatile materials for various industrial applications.