Hydrocolloids with emulsifying capacity. Part 1 – Emulsifying properties and interfacial characteristics of conventional (Acacia senegal (L.) Willd. var. senegal) and matured (Acacia (sen) SUPER GUM™) Acacia senegal

The emulsifying properties and interfacial behaviour of conventional arabic gum (Acacia Senegal, control gum) and after thermal maturation (EM1 and EM2) were studied. All gums presented good oil in water emulsifying capacities. However, after 20–60 high-pressure homogenization passes, matured gums formed more homogenous emulsions with smaller mean oil droplets (0.4 μm) than the control gum (0.65 μm). Modification of pH from 4.5 to 7.0 did not affect sample characteristics. The film-forming capability of all samples at air–water interface was studied using adsorbed and spread techniques. The greater the amount and molecular mass of the arabinogalactan protein (AGP) component in the gum, the better the interfacial properties (tension drop kinetic and interfacial tension final values). Good dilatational elasticity was found for all three gums samples, corresponding to highly elastic interfacial films. The spread films of matured gum EM2 rearranged during compression, passing through liquid expanded, liquid condensed into solid states. Conversely, control and EM1 gums only formed liquid expanded films and smaller surface coverage than EM2. Analytical interfacial results confirm the improved emulsifying properties of matured gums. The properties of the AGP molecules in the gums could be responsible for these differences.

Conventional arabic gum (A. Senegal, control gum) was thermally matured. Two samples (EM1 and EM2) presenting the same protein content but enhanced molecular mass and AGP proportion were compared to the conventional gum. We have studied the emulsifying and interfacial properties of these samples by laser light diffraction, drop tensiometry, dilatational elasticity and Langmuir compression isotherms. Matured gums formed finer emulsions than the conventional gum. The greater the amount and molecular mass of AGP component in the gum, the better the interfacial properties.