State of Dispersed Lipid Carrier and Interface Composition as Determinants of Beta-Carotene Stability in Oil-in-Water Emulsions

Liposoluble bioactive compounds are often included in foods in emulsified lipid carriers. In the present study, the impact of the physical state of the lipid carrier and the interfacial composition of oil-in-water emulsions on the stability of beta-carotene was studied. Emulsions with hydrogenated palm kernel oil (HPKO) concentration of 10% (w/w) dispersing 0.05% (w/w) beta-carotene, and a water phase at pH 7 containing 30% (w/w) sucrose, were stabilized by 1%, 1.5%, 2%, and 3% (w/w) whey protein isolate (WPI). Crystallization and melting behavior of emulsified and bulk HPKO were studied by differential scanning calorimetry. The hysteresis of emulsified HPKO crystallization (onset approximately 10 degrees C; endset approximately 6 degrees C) and melting (onset approximately 17 degrees C; endset approximately 45 degrees C) allowed us to operate at 15 degrees C on systems with identical compositions but different physical states of the same lipid phase. Surface protein coverage of emulsions was calculated and size of the dispersed particles was characterized by dynamic light scattering. beta-Carotene contents of the emulsions during storage at 15 degrees C was analyzed spectrophotometerically. Results highlighted an impact of the phase of the lipid carrier and of the concentration of WPI on beta-carotene degradation. beta-Carotene loss showed zero-order kinetics. A liquid dispersed phase resulted in a low degradation rate but a high concentration of protein on a solid lipid carrier was likewise effective for beta-carotene protection.