Preparation of oil and the continuous water phase Soybean oil was stripped with alumina powder (MP112 EcoChromet ALUMINA N, Activity: Super I, Biomedicals) to remove impurities and endogenous antioxidants such as tocopherols . For both emulsification methods (i.e., colloid mill and microfluidics, see below), the oil was filtered using a 0.22-µm filter (Minisart High-Flow, Sartorius Stedim Biotech GmbH, Goettingen, Germany) to remove any small particles that can cause clogging of the microfluidic channels. To prepare the continuous phase, either Tween 20 or WPI was dissolved in a 10 mM phosphate buffer (pH 3.0) with a concentration of 2.35 wt.%. Next, the mixture was stirred for 2 hrs (WPI) or 30 min (Tween 20). For the lipid oxidation experiments, BODIPY 665/676 was added to the stripped soybean oil (final concentration of 1 or 50 µM) before making emulsions.