Protein stabilized oil-in-water emulsions modified by uniformity of size by premix membrane extrusion and their colloidal stability

The pattern of drop size distribution for oil-in-water emulsions stabilized by bovine serum albumin (BSA) and β-lactoglobulin (β-lg) was modified using a membrane extrusion (ME) technique. Initially, premixed emulsions were prepared employing conventional apparatus, a sonicator or rotor–stator type homogenizer, before permeating through a polycarbonate membrane to modify the size and uniformity of oil drops. Due to the shear stress by flow induced by the ME, the coarse oil drops in the premixed emulsions were disrupted resulting in a diminished droplet size and improved uniformity of size. The ME operated at a too high flux, however, led to the coalescence of dispersed particles indicated by the increased diameter and size polydispersity of the oil droplets. Greater ability of β-lg than BSA to be employed for the ME process was reported; this was suggested by the wider flux range providing the required emulsions of β-lg than did BSA. After establishing the adequate permeating flux condition, the stability of the ME emulsions was compared to the control sample without ME. A lower creaming rate as well as better long-term maintaining of the drop size was shown by the ME emulsions compared with the control samples. This actually confirmed the greater colloidal stability of the emulsions containing uniform sized dispersed drops.