Whey Protein Concentrate and Egg White Powder as Structuring Agents of Double Emulsions for Food Applications

This work aims at studying the effects of whey protein concentrate (WP) and egg white powder (EW) as structuring agents in double emulsions (W1/O/W2). A D-optimal design was developed considering the following factors: type (WP, EW) and concentration (0, 5, 10 g/100 mL) of protein used to gel the inner water phase (W1), W1 volume percentage (20%, 30%, and 40%) in primary emulsion (W1/O), and W1/O volume percentage (40, 50, 60%) in W1/O/W2. The 21 samples were investigated by FT-IR spectroscopy, which revealed different protein conformations depending on W1 and W1/O fractions, and a better interaction with oil of WP rather than EW. Highly significant (p < 0.001) multivariate models were computed for yield, rheological properties, and creaming stability of W1/O/W2, being W1 and W1/O the most influent factors. Protein type significantly affected W1/O/W2 rheology, revealing a better structuring ability of EW with respect to WP, resulting in higher apparent viscosity and consistency coefficient values. A W1/O/W2 optimized for maximum values of apparent viscosity, yield, and creaming stability was developed, composed of 10 g/100 mL EW in W1, 29% W1, and 60% W1/O, with an oil content of 42.6 mL/100 mL. The optimized emulsion gave results in good agreement with the predicted values, thus confirming the validity of the developed multivariate models for the design of double emulsions with desired features.