Formulation and stability assessment of ergocalciferol loaded oil-in-water nanoemulsions: insights of emulsifiers effect on stabilization mechanism

In the study, we investigated the effect of emulsifiers with different stabilizing mechanisms on the formulation and stability of ergocalciferol loaded oil-in-water (O/W) emulsions. O/W emulsion stabilized by modified lecithin (ML; electrostatic stabilization), sodium caseinate (SC; electrosteric stabilization) or decaglycerol monooleate (MO-7S; steric stabilization) were formulated using high-pressure homogenization. The Sauter mean diameter (d3,2) of emulsions produced by ML, SC and MO-7S were 126 ± 1, 127 ± 4 and 138 ± 3 nm, respectively. The stability of resulting emulsions was evaluated when they exposed to different environmental stresses and during 30 days of storage at 25 and 55 °C. Results showed that the emulsions prepared by MO-7S or ML were stable against a wide range of pH (2–8), while SC-stabilized emulsions showed instability with extensive droplet aggregation at pH 4 or and 5. Only ML-stabilized emulsions showed droplet growth due to coalescence when treated at high NaCl concentration (300–500 mM). In the absence of glucose, SC-stabilized O/W emulsions showed better freeze-thaw stability, in comparison to those formed with ML or MO-7S emulsifiers. The emulsion produced by ML was found to be stable to droplet aggregation at heating temperatures (80–120 °C) for 1 h. All the O/W emulsions stored at 25 °C showed good physical and chemical stability. However, the chemical stability of ergocalciferol in emulsion system decreased in order of ML > MO-7S ≫ SC during storage at 55 °C for a period of 30 days. These findings provide valuable information for the development of nanoemulsion-based delivery system applied in food and beverage products.