Total phenolics, ascorbic acid, and betalain contents of differently colored cactus pear clones (nine Opuntia ficus-indica [L.] Mill. clones and one O. robusta Wendl. clone) were investigated and related to their respective antioxidant potential assessed by Trolox-equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays. TEAC and ORAC values were very highly correlated with each other and also with values for total phenolics, betalain contents, and ascorbic acid concentrations. Total phenolics had the greatest contribution to ORAC and TEAC values. High-performance liquid chromatography (HPLC)-diode array detector (DAD)-tandem mass spectrometry (MS/MS) measurements of cactus pear juices permitted the differentiation of the clones based on variations in pigment patterns and betalain concentrations. The red and yellow betalains were absent in lime green colored cactus fruits. The ratio and concentration of these pigments were responsible for the yellow, orange, red, and purple colors in the other clones. Progeny of purple and lime green colored parents were characterized by 12% and 88% of plants bearing lime green and purple fruit, respectively. This implies that the genes for betalain production were lacking in the lime green fruits but could be provided by a parent with a complete set of genes, that is, purple fruits. Besides known pigments typical of Cactaceae, two unexpected betalains were identified. Whereas gomphrenin I was found for the first time in tissues of cactus plants, methionine-betaxanthin has never been described before as a genuine betalain. In addition to their alleged health-promoting properties, various combinations of yellow betaxanthins and red-purple betacyanins may allow the development of new food products without using artificial colorants.

No abstract

No abstract

No abstract

The impact of heating at 75, 85, and 95 • C during 60 min on overall color and betalain retention of yellow-orange cactus pear (Opuntia ficus-indica [L.] Mill. cv. 'Gialla') juice after a 24-h color regeneration period was investigated. The addition of 0.1% isoascorbic acid prior to heating minimized color alteration as well as betalain degradation to a significant level. A correlation between the total betaxanthin retention and the indicaxanthin/isoindicaxanthin ratio was detected in heated juice samples, thus proving the indicaxanthin/isoindicaxanthin ratio as a valuable indicator of thermally treated cactus pear juices. Notably, the same ratio was instrumental for retrospectively calculating the initial betaxanthin content. Additionally, storage experiments over a period of 6 mo were conducted. Samples kept in the dark exhibited notably better color and pigment retentions as compared to illuminated samples. A significantly stabilizing effect was also observed in samples with isoascorbic acid fortification. While indicaxanthin and betanin were predominantly degraded through hydrolytic cleavage upon both heat exposure and storage, isomerization was only marginal for betanin. In contrast, 2-decarboxy-betanin formation was exclusively found for nonfortified heated samples while decarboxylated indicaxanthin could not be detected. Thermal treatment and pigment regenerationAliquots of 20 mL cactus pear juice (pH 4) with and without addition of 0.1% isoascorbic acid were heated in a water bath at 75, 85, and 95 • C under continuous stirring in a 100-mL round-neck glass sealed with a rubber stopper for 5, 10, 15, 30, 45, and 60 min, respectively. Immediately after heating, samples were cooled in an ice bath for 90 s to stop further degradation. Following a period