Microencapsulation of betalains by foam fluidized drying

Betalains were microencapsulated by fluidized bed drying of a beetroot juice foam made with different concentrations of egg albumin and using the suspension of foam-covered balls during drying. The foams were prepared by whipping using a commercial mixer. The influence of whipping time, juice solids:egg albumen ratio, surface tension, and zeta potential on the foam's physical, chemical, antioxidant and microstructural properties during fluidized bed drying were studied. The kinetic data of betalains degradation were used for estimating the activation energy during the drying of beetroot foam from 60 to 80 degrees C. The albumin content affected the surface tension and zeta potential, which were critical for foam stability. The best physical stability of the foams at 1:3 and 1:4 juice solids:albumin ratio was achieved. During fluidized bed drying, moisture content decreased drastically in the first 4 min at 60 degrees C, whereas, at 70 and 80 degrees C, it was 2 min. The degradation kinetics of betalains during drying was of first-order reaction, with activation energies of 16.5 and 24.3 kJ/mol at 1:3 and 1:4 beetroot juice solids:albumin ratios. The antioxidant activity of the reconstituted foam powders had IC50 values ranging from 0.763 to 0.857 & mu;g/mL and 1.308-1.401 & mu;g/mL for DPPH and ABTS, respectively. The microstructure of the dried foam samples showed a distribution pore size of 167.1 & PLUSMN; 55 & mu;m, suggesting resistance to deformation during fluidized bed drying. These results provide useful information for designing foam powders to protect and stabilize bioactive molecules with a simple process and cost-effectiveness that provides highquality powders.