Production of fine emulsions at pilot scale for oil compounds encapsulation
Résumé
Feasibility of producing, at pilot scale (5 kg), stable oil in water emulsions with size of 1-2 mu m and 100-200 nm was investigated in relation with the oil content of the emulsion (4%, 8% and 12% w/w) and with the composition of the aqueous phase.
Sunflower oil was used as a model for oil-based compounds. Acacia gum (AG) was used as emulsifier and protective support in association with maltodextrin (MD) with DE 12 or 21 (weight ratio MD/AG = 3/2). Emulsions, with 40% w/w dry matter (carriers and oil), were. produced using first a high shear disperser (30 min) leading to coarse emulsions (similar to 2 mu m) and then a high pressure homogeniser (4 min recirculation) leading to sub-micron emulsions (similar to 200 nm).
Viscosity, size and size distribution of emulsions were found to be mainly governed by the aqueous phase viscosity. Maltodextrin DE 12 leading to more viscous aqueous phases was found to be more efficient for the production of finer emulsions. Whatever the composition, no oil oxidation was observed after processing and after 2 weeks storage. After 3 weeks, coarse emulsions presented two phases whilst the submicron ones were stable after more than 2 months.