Water‐Oil Absorption Index (WOAI): A Simple Method for Predicting the Emulsifying Capacity of Food Proteins

An index for describing the relative hydrophilic‐lipophilic character of proteins was proposed based on the measurement of the “spontanoeous water and oil uptake”. The water‐oil absorption index (WOAI) showed a defined correlation with emulsifying capacity (EC) for most proteins making it possible to predict EC in a simple way. Maximum emulsion capacity was achieved when the WOAI was nearly two, that is when the protein absorbed twofold more water than oil. Proteins with WAOI greater than two had increasingly hydrophilic characteristics and concomitantly increasingly low EC. Proteins with WOAI lower than two showed increasingly lipophilic characteristics and concomitantly increasing low emulsifying capacity. The finding of this study supports the concept that emulsifying capacity of proteins depends on the suitable balance between the hydrophilic and lipophilic characteristics, rather than merely high values for each one.