Composition of discarded Sicilian fruits of Opuntia ficus indica L.: Phenolic content, mineral profile and antioxidant activity in peel, seeds and whole fruit

Sicily (Italy) is the second producer of Opuntia ficus-indica (OFI) fruits after Mexico. To date, huge quantities of fruit are discarded during the selection for the fresh market, generating a large amount of by-product to be valorized. This study aimed to investigate on the composition of OFI discarded fruits from the main Sicilian productive areas, over two harvesting periods. Peel, seeds and whole fruit samples were characterized in terms of minerals and phenolic compounds through ICP-OES and HPLC-DAD-MS. Potassium, calcium and magnesium were the most abundant elements and peel samples showed the highest values. Seventeen phenolic compounds were detected in peel and whole fruit, including flavonoids, phenylpyruvic and hydroxycinnamic acids, while only phenolic acids were found in the seeds. A multivariate chemometric approach highlighted a correlation between the mineral and phenolic content and the different parts of the fruit as well as a significant influence of productive area.