Characterisation of ß-carotene partitioning in protein emulsions: Effects of pre-treatments, solid fat content and emulsifier type.

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 ß-carotene in emulsions with various formulations in-situ using confocal Raman microscopy (CRM). The partitioning of ß-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 ß-carotene partitioning into the aqueous phase. Increasing the solid fat content in the carrier oil favoured the migration of ß-carotene into the aqueous phase. The use of WPI as the emulsifier resulted in a greater partitioning of ß-carotene into the aqueous phase compared to when Tween 40 was the emulsifier. This study demonstrates that partitioning of ß-carotene between the aqueous and oil phase is dependent on the characteristics of the oil phase, emulsifier type and processing.

In situ quantification of ß-carotene partitioning in oil-in-water emulsions by confocal Raman microscopy.

Confocal Raman microscopy (CRM) was able to quantify the ß-carotene concentration in oil droplets and determine the partitioning characteristics of ß-carotene within the emulsion system in situ. The results were validated by a conventional method involving solvent extraction of ß-carotene separately from the total emulsion as well as the aqueous phase separated by centrifugation, and quantification by absorption spectrophotometry. CRM also enabled the localization of ß-carotene in an emulsion. From the Raman image, the ß-carotene partitioning between the aqueous and oil phases of palm olein-in-water emulsions stabilized by whey protein isolate (WPI) was observed. Increasing the concentration of ß-carotene in an emulsion (from 0.1 to 0.3g/kg emulsion) with a fixed gross composition (10% palm olein:2% WPI) decreased the concentration of ß-carotene in the oil droplet. CRM is a powerful tool for in situ analyses of components in heterogeneous systems such as emulsions.