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

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 2(2) statistical factorial design for each system (CP-SPI, CP-(SPI + MD) and CP-(SPI + I)) was used. The independent variables were the CP/encapsulating agent ratio (1:1-5:1) and inlet air temperature (100-140 degrees 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 degrees C and 140 degrees C inlet air temperatures were the optimal conditions for the CP-SPI and CP-(SPI + MD) systems, respectively; for the CP-(SPI + I) system, the ratio and the inlet optimal air temperature were 4:1 and 105 degrees C, respectively. The stability of the powders obtained under optimal conditions for each system was studied at 60 degrees 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). (C) 2014 Elsevier Ltd. All rights reserved.