University of Granada 1 article published in JoVE Biochemistry In vitro Digestion of Emulsions in a Single Droplet via Multi Subphase Exchange of Simulated Gastrointestinal Fluids Julia Maldonado-Valderrama1, Teresa del Castillo Santaella2, Juan Antonio Holgado-Terriza3, Miguel Ángel Cabrerizo-Vílchez1 1Department of Applied Physics, Faculty of Sciences, Campus de Fuentenueva, University of Granada, 2Department of Physical Chemistry, Faculty of Pharmacy, Campus de Cartuja, University of Granada, 3Department of Software Engineering, School of Computer and Telecommunication Engineering, Campus de Aynadamar, University of Granada A pendant drop surface film balance implemented with a multi-subphase exchange, nicknamed the OCTOPUS, allows for mimicking digestive conditions by the sequential subphase exchange of the original bulk solution with simulated gastrointestinal fluids. The simulated in vitro digestion is monitored by recording in situ the interfacial tension of the digested interfacial layer.