Free carotenoid and carotenoid ester composition in native orange juices of different varieties

Introduction. Among the citrus species, C. sinensis has been the most studied given its importance in terms of production and its industrial application in juices. Some of orange juice's organoleptic and functional properties, which make it an attractive product for the consumer, are due to its carotenoid composition. Xanthophylls can be found in either their free form (as the carotenes are found) or in a more stable fatty acid esterified form in the case of mono-and polyhydroxylated xanthophylls. Detection of adulteration of orange juices is of concern to consumers, regulatory agencies and citrus processing industries, and the study of carotenoid ester composition has been proposed to evaluate fruit products' authenticity. In this study, we report on the native (carotenoid esters and free carotenoids) carotenoid profile of orange juices of eight different varieties. Materials and methods. Monovarietal fresh orange juices were obtained from squeezing mid-season oranges (Citrus sinensis varieties: Bionda, Brasiliana, Moro, Ovale, Sanguinello, Tarocco, Valence and Washington) cultivated and supplied by a local producer. After the extraction of the carotenoids from the samples, the analyses were carried out by HPLC-DAD-APCI-MS. Results and discussion. The results showed that, in the juices studied, the xanthophylls were mostly esterified (93% of the total carotenoid mean content). The different varieties investigated showed variations in their carotenoid contents. The total carotenoid contents ranged from 2.42 mu g.g(-1) in the Washington variety to 15.8 mu g.g(-1) in the Valencia variety. Among the monoesters, the Valencia variety showed the highest violaxanthin ester amounts (61%), the Brasiliana variety showed the highest. beta-cryptoxanthin ester content (86.9%) and the Tarocco variety had the highest luteoxanthin ester amount (75.7%). Moreover, in general, in the Brasiliana, Ovale, Sanguinello, Valencia and Washington varieties, the monoester contents were higher than the diesters, whereas in the Bionda, Moro and Tarocco varieties the opposite was determined. To the best of our knowledge, this is the first time that this analytical approach has been applied to characterising, both qualitatively and quantitatively, the whole carotenoid pattern (carotenoid esters and free carotenoids) in orange juices from the Bionda, Brasiliana, Moro, Ovale, Sanguinello, Tarocco, Valence and Washington varieties. This contribution could also be used to establish authenticity markers among orange varieties that could potentially be used to prevent adulteration.