Influence of gelation on the retention of purple cactus pear extract in microencapsulated double emulsions

A purple cactus pear (Opuntia ficus-indica) extract (CP) was encapsulated in double emulsions (DE) gelled with gelatin (DE-CP-G) and with gelatin and transglutaminase (DE-CP-GT), as well as in a DE with a liquid external aqueous phase (DE-CP), in order to study the retention of betanin as colorant agent. Both gelled DEs showed a predominantly elastic behavior,in contrast with DE-CP. The degradation rate constant of betanin was significantly higher in DE-CP-GT (90.2 x 10(-3) days(-1)) than in DE-CP-G (11.0 x 10(-3) days-(1)) and DE-CP (14.6 x 10(-3) days(-1)) during cold-storage (4 degrees C). A shift towards yellow color was found in all the systems during cold-storage (4 degrees C) and after thermal treatment (70 degrees C/30 min), especially in DE-CP-GT, denoting a higher degradation of betanin. Betalamic acid, cyclo-Dopa 5-O-beta-glucoside, 17-decarboxy-betanin and neobetanin were identified by UHPLC-MS/MS as degradation products of betanin.