3.5.3. Emulsifying Activity Index (EAI) and Emulsion Stability Index (ESI)

The EAI and ESI were evaluated by following the method of [45]. The protein solution (15 mL) was mixed with 5 mL of sunflower oil. The pH values of the mixtures ranged from 2.0 to 12.0. The mixtures were homogenized at 7500× g for 1 min, using a homogenizer (Homelab, Shanghai, China). Then, 50 µL aliquots were taken from the emulsions at 0 and 10 min from the bottom of the tube and mixed with 10 mL of 0.1% sodium dodecyl sulphate (SDS) (1:200 dilution). The absorbance of the diluted solutions was noted at 500 nm immediately after emulsion formation (A₀) and at 10 min (A₁₀). The EAI and ESI were calculated using the following equations:

where EAI: emulsion ability index; ESI: emulsion stability index; T = 2.303; F: dilution factor (200); A₀: absorbance measured at 500 nm immediately after emulsion formation; A₁₀: absorbance measured at 500 nm after 10 min of emulsion formation c: protein concentration (0.01 g/mL) and θ: dispersed phase (oil) volume fraction [15].