Effects of emulsifiers on the physicochemical stability of Oil-in-water Nanoemulsions: A critical review

The thermodynamic instability of food nanoemulsions may occur during production and storage due to environmental stress or reaction with other constituents, appearing in the forms of sedimentation, creaming or oil oxidation. Such instabilities reduce the tendency to consumption and threaten consumers' health. The present study aimed to review the effects of emulsifiers on the physicochemical stability of oil-in-water nanoemulsions. Emulsifiers were selected considering several factors, including the preparation and processing methods, nature, concentration, hydrophilic-lipophilic balance, molecular weight, particle surface charge, ambient temperature, pro-oxidants and antioxidants, and type of the food matrix. Emulsifiers often include proteins, esters of polyoxyethylene (e.g., Tween), fatty acids, polysaccharides, and phospholipids, which play a key role in the formation and stability of food emulsions through adsorption at the oil–water interface. Determining the impact of emulsifiers on the control of instability at the interface contributes to the production of the healthiest, safest, and most stable nanoemulsion-based structures. Since emulsifiers have individual structures and different functional properties, they should be selected based on the desired product properties. Therefore further research is required to identify novel emulsifiers or a combination of emulsifiers with different properties for food applications.