Prediction profiles of the emulsion stability for pH 4, 6, and 8
are shown on Fig. 3. At pH 4 (Fig. 3a), the emulsified volume
increased very slightly with tannin concentration and ionic
strength. It is thus likely that the emulsion stability is governed
by the steric repulsion between droplets, due to the multilayer tannin
adsorption. However, at pH values ranging from 6 to 8 (Fig. 3a
and b), tannin concentration effect is limited and the emulsified
volume decreases when the ionic strength increases. Maximum
of emulsified volumes would be obtained for values of pH superior
to 8 and ionic strengths lower than 50 mM. In this pH range, tannins
are more and more negatively charged: catechin and epicatechin
pKas are 8.2 and 9.2, respectively (Slabbert, 1977). Droplets
are mainly stabilized by electrostatic repulsions. Increasing ionic
strength at these pHs induce the screening of the charges and thus
a lowering of the repulsions. At lower pH (4 for instance), tannins
Prediction profiles of the emulsion stability for pH 4, 6, and 8are shown on Fig. 3. At pH 4 (Fig. 3a), the emulsified volumeincreased very slightly with tannin concentration and ionicstrength. It is thus likely that the emulsion stability is governedby the steric repulsion between droplets, due to the multilayer tanninadsorption. However, at pH values ranging from 6 to 8 (Fig. 3aand b), tannin concentration effect is limited and the emulsifiedvolume decreases when the ionic strength increases. Maximumof emulsified volumes would be obtained for values of pH superiorto 8 and ionic strengths lower than 50 mM. In this pH range, tanninsare more and more negatively charged: catechin and epicatechinpKas are 8.2 and 9.2, respectively (Slabbert, 1977). Dropletsare mainly stabilized by electrostatic repulsions. Increasing ionicstrength at these pHs induce the screening of the charges and thusa lowering of the repulsions. At lower pH (4 for instance), tannins
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