Highly efficient encapsulation of linseed oil into alginate/lupin protein beads: Optimization of the emulsion formulation

Abstract

Encapsulation of linseed oil into high oil content alginate beads has appeared as a potential solution to delay oxidation of this highly unsaturated oil. Additionally, the use of vegetable protein as emulsifier is used in order to enhance the stability of the emulsion and thus the encapsulation efficiency (EE). The aim of this work was to optimize the emulsion formulation in order to maximize EE in dried beads. The effect of alginate (X1: 10–45 g/L) and lupin protein concentrations (X2: 10–50 g/L) in the aqueous phase and oil/water ratio (X3: 15–60 mL/100 mL) on EE, as well as on the oil content, was evaluated by a central composite experimental design (23). The mathematical model showed a great dependence of the studied variables and EE, demonstrating that high alginate and protein concentrations were desirable. By using the optimal formulation, spherical beads of approximately 1.80 mm were obtained. Actual EE (98.30%) for optimal oven dried beads was found to be close to the predicted value (100.88%). Moreover, the optimal beads contained 66.37% of linseed oil, being the most successfully delivered in in vitro digestive conditions. The stability of encapsulated oil against heat treatments (50–75 °C, 24 h) was higher than free linseed oil, demonstrating the effectiveness of the encapsulating system. Based on the results obtained, the encapsulating system used in this study is suitable for unstable oils for food or nutraceutical purposes.