Influence of elongational flow on phase separated inclusions within gelling biopolymer drops

Abstract

Drops of an immiscible biopolymer mixture containing maltodextrin/gelatine were shaped and set in an elongational flow in a flow cell called 4-RM. The kinetics of phase separation as well as the kinetics of gel formation were governed by the temperature differences which appear as the 60 °C maltodextrin/gelatine mixture reaches the 10 °C silicon oil in the 4-RM. The shape and inner structure of the drops were visualized with the help of a confocal laser scanning microscope (CLSM). The result showed that the solution phase separated into gelatine-rich and a maltodextrin-rich phase during the short time it takes to gel the particle, i.e. in approximately 2 s. It was found that the shape of the phase separated inclusions was affected by the elongational flow. Mixtures of a 10% constant gelatine concentration and a 2–15% maltodextrin concentration were evaluated. The size of the inclusions within the phase separated drops increases as the maltodextrin concentration increases. At a maltodextrin concentration of 12%, the phase inversion has occurred. Shape transfer between the drop and its inclusions was investigated. The length to width ratios of the drops and its inclusions were compared and it was found that for the gelatine-continuous drop created at a flow rate of 10 rpm the ratio responds well. A comparison of the Taylor parameter calculated from viscosity data before gel formation and image analysis of experimental results showed that deformation takes place within the critical stage of gel formation.