Figure 3.

Transition temperatures determined by dynamic oscillatory rheology. a) Ca²⁺/gelatin/polyphosphate rheology. The elastic modulus (G’, black symbol) increased sigmoidally as the temperature was raised from 0 to 40 °C at Ca²⁺ ratios greater than 0.15. b) Expanded scale to demonstrate the crossover temperature of the elastic (G’) and viscous (G”, grey symbol) moduli. The solidification or gellation temperature decreased with increasing Ca²⁺ ratio. The 0.25 Ca²⁺ ratio was excluded for clarity. (Symbols: ◆ 0.3/0.6, ■ 0.25/0.6, ▲ 0.2/0.6, ●0.15/0.6 Ca²⁺ ratios). c) Mg²⁺/gelatin/polyphosphate rheology. (Symbols: ◆ 0.8/01.0, ■ 0.9/1.0, ▲ 1.0/01.0 Mg²⁺ ratios). d) Expanded scale to demonstrate the crossover temperature of the elastic (G’) and viscous (G”, grey symbol) moduli. The comparative measurements were made with constant strain of 0.1% and frequency of 1.0 Hz.