Evaluation of colour properties and chemical quality parameters of cactus juices

The chemical composition and visual appearance of cactus fruits from the genera Opuntia and Hylocereus were investigated. Colour properties were assessed in solutions with pH ranging from 1 to 8 and expressed as chroma, hue and colour shade. Between pH 3 and 7, all samples were stable as indicated by hue and chroma values. The colour shade of the red juice of Opuntia ficus-indica cv. 'Rossa' was in the range of red beet preparations hitherto most commonly used for colouring low-acid food commodities. Hylocereus was characterized by purplish hues, whereas the juice from O. ficus-indica cv. 'Gialla' displayed a yellow tonality. An improved spectrophotometric method for pigment quantification was proposed. Betacyanin contents were 525.3, 73.9 and 1.3 mg/l in juices from Hylocereus polyrhizus, Opuntia ficus-indica cv. 'Rossa' and O. ficus-indica cv. 'Gialla', whereas betaxanthins amounted to 48.3, 36.4 and 5.3 mg/l in O. ficus-indica cv. 'Gialla', O. ficus-indica cv. 'Rossa', and H. polyrhizus, respectively. Although the colourless fruits from O. ficus-indica cv. 'Bianca' and H. undatus could not be considered as a colour source, selected quality parameters were also investigated with respect to their nutritional value. To the best of our knowledge, this is the first report about the chemical quality parameters of H. polyrhizus and H. undatus.