DEVELOPMENT OF LONG-TERM STABLE MIXED SODIUM CASEINATE AND PEA PROTEIN ISOLATE-STABILIZED NANOEMULSIONS FOR THE DELIVERY OF CURCUMIN

Nanoemulsions (NEs) with extremely small droplet size (radius <100 nm) were found to possess characteristics that have many advantages over conventional emulsion systems. These nano-sized droplets were found to contribute to higher stability of the NEs and also found to improve the bioavailability of poorly water-soluble bioactive components. The overall aim of this thesis is to develop oil-in-water (O/W) NEs stabilized by a mixture of sodium caseinate (a dairy protein) and pea protein isolates (a pulse protein). The mixed protein stabilized NEs were utilized to encapsulate a bioactive compound, curcumin, where the goal is to investigate its stability, delivery and bioavailability through in vitro digestion studies. Various concentrations (2.5 – 10 wt%) of sodium caseinate (SC) were used as the sole emulsifier in the development of 5 wt% O/W NEs and their long-term storage stability for 6 months was investigated. The sodium caseinate stabilized NEs (SCEs) developed in this work displayed an average droplet diameter less than 200 nm, which remained unchanged for an experimental time fame of 6 months. However, all of them displayed rapid creaming, which increased with an increase in protein concentration, in accordance with previous studies. It was postulated that excess unabsorbed protein caused depletion flocculation leading to creaming of oil droplets, which was confirmed using confocal laser scanning microscopy. Calculation of depletion interaction energy showed an increase in attraction with protein concentration and decrease with a reduction in droplet size, making NEs more resistant to flocculation than conventional emulsions. Next, pea protein isolate (PPI), was utilized to partially replace SC and thereby PPIs efficacy in the formation and long-term stabilization of mixed protein NEs (MPEs) was investigated. Total aqueous phase-protein concentration of 5, 7.5 and 10 wt%, with SC and PPI in a 1:1 ratio, was used. As a control individual PPI-stabilized NEs (PPIE) were also prepared. PPI failed to produce stable flowable NEs displaying excessive droplet and protein aggregation. At higher concentrations of PPI (7.5 and 10 wt%), the emulsion transformed into viscoelastic gels. Interestingly, the mixed SC and PPI-stabilized NE did not display any creaming or aggregation and remained stable throughout the experimental timeframe of 6 months with average droplet diameter