Deacetylation Thresholds Trigger Dual Thermal Transitions and Two-stage Melting in KGM/κ-Carrageenan Composites

Konjac glucomannan (KGM) and κ-carrageenan (κ-Car) are widely used hydrocolloids with strong gel-forming properties. Our previous work demonstrated that KGM promotes κ-Car coil–helix transition via a chain conformation entropy mechanism, yet how deacetylation-induced changes in KGM structure regulate this effect remains unclear. Here, KGM with graded degrees of deacetylation was investigated in κ-Car composite gels using rheology, micro-DSC, variable-temperature NMR, AFM, and SAXS. Results show that  KGM&apos;s gelation-promotion effect is tightly regulated by chain flexibility versus aggregation propensity. Mildly deacetylated KGM (degree of deacetylation, DD < 48%) retains flexible chains that enhance κ-Car helix formation, yielding a single gelation transition. With increasing deacetylation (DD < 76%), local deacetylated KGM self-association weakens cooperativity, producing two distinct gelation and melting events. At high deacetylation (DD > 87%), aggregated KGM domains form, and their promotion effect is largely suppressed. These findings provide structural insight into tuning hydrogel behavior through controlled polysaccharide modification.