Food nanostructuring of paprika capsules obtained by coacervation for improving carotenoid storage stability

In this study, paprika carotenoids were encapsulated by coacervation with a nanostructured material (NE) prepared with alginate/zeolite and another non-nanostructured (AA) made only with alginate to study the effect of nanocavities in the microstructure on the energy interactions of adsorbed water and the chemical stability of carotenoids. Capsules were characterized through fractal analysis of image, water sorption isotherms, water melting point, thermodynamic properties, and chemical stability during storage. Surface fractal dimensions were between 2.75 and 2.8 for NE and were larger than those obtained for AA, which were between 2.57 and 2.7. NE capsules showed the endothermic fusion peak at −4.42 °C, while AA capsules around 0.97 °C. Adsorbed water enthalpies calculated from adsorption isotherms of the capsules showed the maximum stability of total carotenoids at the crossing of the integral and differential enthalpy intercross ₍$a_w$ = 0.121 for AA and 0.443 for NE) and at the water adsorption at Langmuir-type primary sites. NE capsules improved carotenoid retention two-fold compared to AA after 63 days of storage. These results confirmed that controlling the nanoporous at the food microstructure improved the chemical stability of carotenoids during storage.