Encapsulation of anthocyanin-rich extract from blackberry residues by spray-drying, freeze-drying and supercritical antisolvent

The extract obtained from blackberry (Rubus fruticosus) residues was encapsulated in polyvinylpyrrolidone (PVP) by three methods: the conventional spray-drying (SD) and freeze-drying (FD) techniques, and the new method of supercritical antisolvent (SAS), using CO2 as antisolvent and ethanol as solvent of the organic solution (extract + PVP). The methods and their produced particles were evaluated in terms of precipitation yield, residual ethanol and moisture contents, anthocyanin concentration, antioxidant capacity, morphology, crystallinity and thermal stability. SD,FD and SAS achieved particles with good anthocyanin yields (above 76%), high antioxidant capacity (above 1001.unol TE/g particle) and were effective to concentrate anthocyanins in PVP without great degradation. Using SAS, particles with 1.42 mg ECy3G1/g were achieved. Nevertheless, SAS particles presented high residual ethanol (8.17% w/w) and moisture (1130% w/w), whereas in SD and FD particles these contents remained below 2 and 5%, respectively. Scanning electron microscopy revealed a spherical shape in the particles obtained by SD, while those produced by SAS and FD presented irregular agglomerates. The encapsulation processes were equivalent in terms of thermal protection of the extracts and they did not modify the crystallinity and thermal behavior of PVP. The SAS process achieved preferential precipitation of anthocyanins when compared to SD and FD, since supercritical CO2 does not have any affinity to such compounds. (C) 2018 Elsevier B.V. All rights reserved.