Fabrication and stability of colloidal delivery systems for flavor oils: Effect of composition and storage conditions

Colloidal delivery systems are needed to encapsulate, protect, and release functional lipophilic components in the food and beverage industries. In this study, we examined the influence of lemon oil type (1-fold and 4-fold) and surfactant-to-oil ratio (SOR) on the formation and stability of colloidal dispersions containing lemon oil, non-ionic surfactant (Tween 80), and buffer (pH 2.6). Initially, an oil-in-water stock emulsion was formed and then different amounts of this stock emulsion were titrated into surfactant micelle solutions. The influence of SOR and oil type on the formation of colloidal dispersions was examined using dynamic light scattering and turbidity measurements, and then the stability of these systems was evaluated during storage at different temperatures (4, 20, 32 and 55 °C). SOR and oil type had a pronounced influence on the nature of the colloidal dispersions formed, as well as on their storage stability. At relatively high SORs all of the lemon oil was incorporated into surfactant micelles and a microemulsion was formed, but at relatively low SORs micelles became saturated with lemon oil and emulsion droplets remained. The saturation surfactant level depended on lemon oil type. The long-term stability of the emulsions showed complex behavior depending on SOR, oil type, and storage temperature. In some cases droplet size decreased which was attributed to solubilization, whereas in other cases droplet size increased which was attributed to Ostwald ripening and/or coalescence. This study provides useful information for the rational design of food grade colloidal delivery systems for encapsulating flavor oils and other functional lipids for application in foods and beverages.

► Lemon oil type and surfactant-to-oil ratio affect colloidal dispersion formation.
► Surfactant-to-oil ratio determines whether emulsions or microemulsions are formed.
► Lemon oil type and storage temperature influence emulsion stability.