Microwave‐assisted extraction of bioactive compounds fromAraucaria angustifoliabracts followed by encapsulation

Abstract

The aqueous extract of Araucaria angustifolia bracts was obtained by microwave-assisted extraction and encapsulated by spray-drying and freeze-drying using pectin/hydrolyzed collagen (PEC-HC) and polydextrose/partially hydrolyzed guar gum (PD-PHGG) dispersions, added to the extract in the proportions of 0.25:0.75:9 and 0.5:0.5:9 (wt/wt/wt), respectively. The powders encapsulated with the PD-PHGG mixture by spray-drying and freeze-drying showed the highest retention rates for total phenolic compounds (80.57% and 89.94%) and solubility (98.00 and 97.69 g 100 g−1), respectively. The scanning electron microscopy (SEM) images presented spherical forms on the spray-dried powders, while the freeze-dried powders exhibited irregular forms. The results obtained by FTIR suggested that the encapsulation occurred in all samples by physical interactions, whereas the thermogravimetric analysis showed that the PEC-HC powders demonstrated greater thermal stability. Accelerated storage tests indicated that the PD-PHGG freeze-dried powders had lower decrease in the antioxidant capacity. Practical applications The industrial use of Araucaria angustifolia bracts (sterile seeds) is currently considered a type of waste. However, the bracts present bioactive compounds, including condensed tannins, considered among phenolic compounds, the most important natural antioxidants. The phenolic compounds of the bracts were extracted by microwave, using exclusively water as a solvent. The application of green technologies is an interesting alternative for the food industry since the use of organic solvents is completely replaced, as well shorter exposure times to high temperatures are obtained and, consequently, lower energy expenditure and lower antioxidant capacity loss. For the encapsulation of phenolic compounds, dietary fibers and protein were used as wall materials, which resulted in a powder containing natural antioxidants, fibers, and essential amino acids, which can be applied in several food formulations.