Modulation of chemical stability and in vitro bioaccessibility of beta-carotene loaded in kappa-carrageenan oil-in-gel emulsions

In the present paper, ionotropically structured κ-carrageenan based oil-in-gel (o/g) emulsions were tested as potential carrier systems for the delivery of β-carotene. In situ ionic gelation was induced by Na⁺, K⁺ or Ca²⁺ added at the level of 0.2-0.6% (w/w). All o/g emulsions exerted a true gel like behaviour with storage modulus (G') being reduced according to the order: K⁺>Ca²⁺>Na⁺. Ionic gelation induced a moderate increase in the microscopically assessed lipid droplets radii. O/g emulsions containing monovalent ions exerted the highest β-carotene retention throughout isothermal storage particularly at high (37 and 55°C) temperatures. Notwithstanding, increasing ionic strength resulted in acceleration of β-carotene degradation rates for all cation species. β-Carotene bioaccessibility was significantly lower in Ca²⁺o/g emulsions due to the formation of complexes between the biopolymer matrix containing β-carotene and bile salts. A good correlation between β-carotene bioaccessibility, physical and colloidal aspects of the micellar digesta fractions was observed.