Role of the phases composition on the incorporation of gallic acid in O/W and W/O emulsions

This work aimed to study the incorporation and preservation of gallic acid (GA) in emulsions formulated using soybean oil as oil phase, polyoxyethylene sorbitan (Tween 20) and polyglycerol polyricinoleate (PGPR) as surfactants. The systems evaluated were oil-in-water (O/W) and water-in-oil (W/O) emulsions prepared using the same aqueous to oily phases weight ratio (3:1). The volume fraction of surfactant was 0.01, 0.02 or 0.04 and gallic acid concentration in the final emulsions was 0 or 0.5% w/w. Increasing GA concentration did not show any effect on the initial or equilibrium interfacial tension (22 mN/m) in GA solution/soybean oil systems but reduced the average diameter of the droplets in both emulsions. The W/O emulsions showed bimodal droplet size distribution, pseudoplastic behavior and the presence of GA decreased the phase separation. The O/W emulsions exhibited kinetic stability, monomodal droplet size distribution and Newtonian fluid behavior. Results showed that the emulsification process was an efficient method to protect the bioactive against oxidation. Fresh O/W emulsions showed higher GA retention but during the storage time, the W/O emulsions showed a better capacity to retain the gallic acid. However, both emulsions exhibited high retention of bioactive (>86.61%) after 7 days of storage showing that this strategy could be used in different emulsified food products.