常见问题

What causes the extraordinary thermal hysteresis of agar hydrocolloids?

Agar's remarkable thermal hysteresis—the wide temperature gap between its setting point (32–45°C) and its melting point (85°C+ override)—is driven by its unique multi-stage physical gelation mechanism. Upon cooling below the setting temperature, individual linear agarose chains undergo a coil-to-helix transition via intermolecular hydrogen bonding to form left-handed double helices. As cooling continues, thousands of these double helices undergo side-by-side lateral aggregation to form thick, rigid structural bundles known as junction zones. Melting the resulting three-dimensional macrogel requires significant thermal energy to break apart these dense crystalline-like aggregates, rather than just separating isolated single polymer chains.