Understanding the bioactive partitioning between the phases of an emulsion system underpins strategies for improving the efficiency of bioactive protection against degradation. We analysed partitioning of β-carotene in emulsions with various formulations in-situ using confocal Raman microscopy (CRM). The partitioning of β-carotene into the aqueous phase of emulsions increased when whey protein isolate (WPI) was heat or high pressure-treated prior to emulsion formation. However, increasing the concentration of high pressure-treated WPI reduced the β-carotene partitioning into the aqueous phase. Increasing the solid fat content in the carrier oil favoured the migration of β-carotene into the aqueous phase. The use of WPI as the emulsifier resulted in a greater partitioning of β-carotene into the aqueous phase compared to when Tween 40 was the emulsifier. This study demonstrates that partitioning of β-carotene between the aqueous and oil phase is dependent on the characteristics of the oil phase, emulsifier type and processing.
Varying the β-carotene (0.1-0.3 g kg(-1)) and whey protein isolate (WPI) (2-20 g kg(-1)) concentrations in an oil-in-water (O/W) emulsion influenced the partitioning and stability of β-carotene upon 30 d storage at 25 and 40 °C. The total β-carotene in the emulsion was extracted with a solvent and quantified using UV/visible spectroscopy. The β-carotene in oil phase was obtained using in situ Raman micro-spectroscopy. The β-carotene in the aqueous phase was obtained by difference. Increasing β-carotene concentration resulted in increased partitioning of β-carotene into the aqueous phase whereas increasing WPI concentration had the opposite effect. With all freshly made emulsions, there was a higher proportion of β-carotene found in the oil phase. At the end of the storage period, the higher proportion and concentration of β-carotene was in the aqueous phase. This suggested that oxidation of β-carotene occurred faster in the oil phase and that WPI in the aqueous phase protected β-carotene against oxidation. This work informs the formulation of protein-based emulsions for the delivery of β-carotene.