Characterization of the effect of food emulsifiers on contact angle and dispersibility of lipid coated neutrally buoyant particles

To investigate the dispersibility of lipid coated particles in food suspensions, contact angle of lipid surface at different pH, salt concentration, protein concentration, surfactant type and concentration was measured. Contact angle decreased with an increase in the emulsifier conecentration when the concentration was low, and reached a fairly constant value at higher concentrations. Whey protein was more efficient compared to other emulsifiers and decreased the contact angle from 100° to 40° at a concentration of 0.5 g/L or higher in water. Tween 20 was more efficient than other tween emulsifiers and it decreased the contact angle from 100° to 67° at a concentration of 1 g/L. Surface pressure area isotherm of 150-80SV soybean oil coated particles at an air–water interface was obtained using Langmuir trough. Contact angle of the particles at the air–liquid interface, inferred from the critical surface pressure in the isotherm, agreed well with the contact angle of planar surface obtained using goniometer. Dispersibility of 150-80SV soybean oil coated particles in aqueous solution was characterized by measuring the bulk particle concentration upon suspension. At pH 2.5, 5 g/L whey protein in the presence of 0.5 mol/L NaCl in 50 g/L citrate buffer showed highest dispersibility.