Development of a process for the production of a betalain-based colouring foodstuff from cactus pear

Since no process has yet been established for the production of cactus pear juice, the present work aimed at the development of a betalain-based colouring foodstuff from Opuntiaficus-indica cv. 'Gialla' and cv. 'Rossa' of two seasons applying unit operations typical for fruit juice production. Complete separation of the peels from the pulp and removal of seeds were achieved by carborundum peeling of the frozen fruits and subsequent passing through a finisher. Furthennore, for improved filtration of cactus pear juice different enzyme preparations were tested to degrade pectic-like substances. To monitor quality changes in the course of processing, juice samples were analysed after each processing step in terms of colour and selected chemical parameters. While lightness (L*) and chroma (C*) increased during processing for both cultivars, hue angle (h degrees) remained unchanged for the yellow cultivar 'Gialla'.. but a slight shift towards red was observed for the red cultivar 'Rossa' after pasteurisation. Unexpectedly, even after repeated thermal treatment neither non-enzymatic browning nor HMF formation was observed in juices from both cultivars. (c) 2005 Elsevier Ltd. All rights reserved.