Rheological behavior of concentrated emulsions containing carotenoids with different polarity

Abstract

The rheological behavior of concentrated oil-in-water emulsions containing carotenoids (2% (w/w) with different polarity (polarity order: lycopene LY < beta-carotene BC < apocarotenal AC ≪ lutein LU) and its relationship with the microstructural changes caused by three-month storage at 4 °C and 30 °C was studied. The smallest particle size and the highest span were obtained for LY emulsions, followed by BC and AC and then by LU. The most emulsions presented a shear-thinning behavior. The freshly prepared emulsions showed a similar viscoelastic behavior with a weak gel-like structure. Storage of emulsions containing apolar carotenes LY, BC and AC caused the formation of less viscous systems, but still with the shear-thinning character. Storage of emulsion containing polar LU induced its flocculation, especially at 30 °C, which resulted in its increased viscosity and a higher degree of thixotropy. In the case of AC, BC, and LU emulsions, the viscous properties prevailed in these emulsions after their storage at both temperatures. Emulsion system with apolar LY presented a more structured system resistant to changes in the viscoelastic properties induced by storage.