Formulation of a Food Grade Water-In-Oil Nanoemulsion: Factors Affecting on Stability

Water in oil (W/O) nanoemulsions can be advantageous for encapsulation of bioactive hydrophilic substance alone or as a structural unit of a double emulsion. The influence of sonication time, addition of CaCl2 or bovine serum albumin (BSA) to aqueous phase, oil phase (corn or miglyol), and polyglycerol polyricinoleate (PGPR) content on droplet size and physical stability of W/O emulsions at a 30:70 ratio was investigated. Interfacial tension measurement, rheological analysis, Z-average measurement, and visual observations were used to characterize W/O emulsion stability. The results showed a rapid decease in interfacial tension to 6 mN.m-1 and mean droplet size to 347 ± 35 nm in the water/miglyol emulsion, but it was not adequate to establish physical stability. The slight solubility of miglyol in water can be attributed to increased coalescence during storage and an increase in droplet size. The addition of CaCl2 and albumin appreciably reduced the mean droplet size to128 ± 37 nm and increased the physical stability of the corn oil-based W/O emulsion. Rheological assessment showed there is significant relation between the elastic modulus and stability of water in the corn oil emulsion. The good affinity of the formulation ingredients (PGPR-corn oil-BSA) led to formation of compact interfacial and physical stability of the emulsion.