Evaluation of physical stability of whey protein-stabilized red palm oil emulsion by monitoring the changes of droplets characteristics

Abstract

The physical stability of a whey protein (WP)-stabilized red palm oil (RPO) emulsion as affected by the type and concentration of WP used was evaluated by monitoring the changes in its droplet characteristics after storage and accelerated testing. Emulsions containing 30% (v/v) RPO were stabilized by WP isolate 90 (WPI), WP concentrate 80 (WPC80), or WP concentrate 76 (WPC76) at various concentrations (2.5–15% (w/v)) via emulsification employing a two-step rotor-stator homogenization combined with a phase inversion technique. Based on the results, changes in droplet characteristics did not always represent the visually observed stability of the emulsions. In this study, WPCs performed better than WPI in forming a stable RPO emulsion. Higher WP concentrations produced smaller emulsion droplet sizes with better emulsion stability when stored at varied temperatures (i.e., 30 °C, 45 °C, and 60 °C). However, when stored at 60 °C, all the emulsions produced were least stable. Based on the results, the 15% WPC76-stabilized emulsion showed the best stability. This study found that the droplet size characterization could not fully explain the stability of the emulsion, and the emulsion investigated destabilized through different dominant mechanisms when it was stored compared to when it was centrifuged. This study provides information needed for developing a stable WP-stabilized emulsion to be the RPO carrier system.