The encapsulation of purple cactus pear (Opuntia ficus-indica) pulp by using polysaccharide-proteins as encapsulating agents

Abstract

Cactus pear (Opuntia ficus-indica) pulp (CP) was encapsulated with a soybean protein isolate (SPI) and an SPI blend with maltodextrin (MD) or inulin (I). A 22 statistical factorial design for each system (CP-SPI, CP-(SPI þ MD) and CP-(SPI þ I)) was used. The independent variables were the CP/encapsulating agent ratio (1:1e5:1) and inlet air temperature (100e140 C), and the dependent variables were the polyphenol, betacyanin and betaxanthin encapsulation efficiencies. The CP total polyphenol, betacyanin and betaxanthin contents were 73.2 ± 1.0 mg gallic acid equivalent/ 100 g, 22.4 ± 0.31 mg/100 g and 7.6 ± 0.12 mg/100 g, respectively. A 5:1 ratio of CP/encapsulating agent at 100 C and 140 C inlet air temperatures were the optimal conditions for the CP-SPI and CP-(SPI þ MD) systems, respectively; for the CP-(SPI þ I) system, the ratio and the inlet optimal air temperature were 4:1 and 105 C, respectively. The stability of the powders obtained under optimal conditions for each systemwas studied at 60 C in the dark. Increased polyphenols and decreased betalains were observed in all systems during storage, and the yellow pigments (betaxanthin) were more stable than the red pigments (betacyanin).