Development of eco-friendly submicron emulsions stabilized by a bio-derived gum

• Submicron droplet size was obtained by single-step rotor/stator homogenizer.
• Rosin gum inhibits Ostwald ripening growth.
• High surfactant concentration triggers destabilization by depletion flocculation.
• Highly stable d-limonene submicron emulsions were obtained.

Many traditional organic solvents are being gradually replaced by ecofriendly alternatives. d-Limonene is a terpenic (bio)-solvent that fulfils the requirements to be considered a green solvent. d-Limonene sub-micron emulsions suffer from Ostwald ripening destabilization. In this study, we examined the influence of the addition of a natural gum (rosin gum) to d-limonene in order to prevent Ostwald ripening.This contribution deals with the study of emulsions formulated with a mixture of d-limonene and rosin gum as dispersed phase and Pluronic PE9400 as emulsifier. The procedure followed for the development of these formulations was based on the application of product design principles. This led to the optimum ratio rosin gum/d-limonene and subsequently to the optimum surfactant concentration. The combination of different techniques (rheology, laser diffraction and multiple light scattering) was demonstrated to be a powerful tool to assist in the prediction of the emulsions destabilization process.Not only did the addition of rosin gum highly increase the stability of these emulsions by inhibiting the Ostwald ripening, but it also reduced the emulsions droplet size. Thus, we found that stable sub-micron d-limonene-in-water emulsions have been obtained in the range 3–6 wt% Pluronic PE-9400 by means of a single-step rotor/stator homogenizing process.

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