In vitro gastric lipid digestion of emulsions with mixed emulsifiers: Correlation between lipolysis kinetics and interfacial characteristics

Emulsions stabilized by a mixture of emulsifiers may show a tailored functionality depending on the compatibility of the emulsifiers employed. This was proposed in a previous work dealing with distinct lipolysis kinetics of citrus pectin (CP) and Tween 80 (TW80) based emulsions. CP provided a fast a high extent of gastric lipid hydrolysis, TW80 presented negligible digestion and emulsions stabilized with mixtures presented intermediate lipolysis kinetics. The current research work aimed to investigate the interfacial mechanisms underlying gastric lipolysis to further understand the encountered behavior on a fundamental basis. This was achieved by monitoring the interfacial tension kinetics and measuring the interfacial rheology of interfacial layers during in vitro digestion using a modified pendant drop technique. This allowed the correlation of emulsions in vitro lipolysis kinetics and interfacial phenomena during digestion. Two extremely different interfacial tension kinetics were observed when single layers of CP versus TW80 and intermediate kinetics were observed for the binary interfacial layers, importantly correlating with results obtained with emulsions. These findings are discussed in detail and confirm that competitive adsorption between emulsifiers and lipase (e.g. orogenic displacement) is a key factor determining the lipolysis kinetics of emulsions stabilized by mixed emulsifiers.