Experimental methods for measuring coalescence during emulsification – A critical review

•Fundamental understanding requires direct measurement of coalescence.•A critical review of experimental methods to quantify coalescence is given.•Methods are classified and compared. Limitations are discussed.•Two state-of-the-art methods are identified, based on different principles.•An outline for application of these methods is given.

Emulsification is a common process in the production in many non-solid foods. These food-emulsions often have high disperse phase volume fractions and slow emulsifier dynamics, giving rise to substantial coalescence during emulsification. Optimal design and operation of food-emulsification requires experimental methods to study how emulsification in general and coalescence in particular progresses under different conditions. Methods for coalescence quantification during emulsification has been suggested in literature but they are rarely used in food-emulsification research. This contribution offers a critical review of the different methods that have been suggested with special emphasis on their applicability to technical food-emulsification. The methods are critically compared in terms of design limitations, degree of quantification and applicability. A state-of-the-art in the form of two methods is identified and guidelines for their application are suggested.