Ultrasound-Assisted Formulation of a High-DHA Omega-3 Concentrate: Physical and Oxidative Stability of Oil-in-Water Emulsions.

Omega-3 (n-3) polyunsaturated fatty acids (PUFA) are associated with several health benefits, but their high susceptibility to lipid oxidation and low water dispersibility limit their incorporation into food products. In this study, an oil-in-water emulsion was developed from a commercial fish-oil concentrate containing 92% w/w total n-3 PUFA and 73% w/w docosahexaenoic acid (DHA), using octenyl succinic anhydride (OSA)-modified starch as the sole emulsifying carrier. Response surface methodology was used to evaluate the effects of oil content, ultrasound emulsification time and ultrasound amplitude on the volume-weighted mean droplet diameter, D[4,3]. The selected formulation, prepared with an oil content of 20% w/w relative to the total solids, an emulsification time of 180 s, and an ultrasound amplitude of 100%, exhibited a D[4,3] of 121 ± 1 nm. During storage at ambient temperature in darkness, the emulsion maintained low peroxide values, ranging from 1.2 to 1.4 meq O2/kg oil, and thiobarbituric acid reactive substances (TBARS) values between 1.3 and 2.1 mmol/kg oil during the first 5 days, indicating that the formulation delayed lipid oxidation of the n-3 PUFA concentrate. The addition of α-tocopherol did not improve oxidative stability compared with the control emulsion. In contrast, ascorbic acid maintained low peroxide values and reduced TBARS accumulation during storage, with values lower than those of the control emulsion and close to the initial TBARS value of the n-3 PUFA concentrate. These results indicate that, under the conditions evaluated, ascorbic acid was more effective than α-tocopherol in delaying the formation of secondary lipid oxidation products.