Qualitative and varietal characterization of pomegranate peel: High-value co-product or waste of production?

Fruit peel (i.e. pericarp + mesocarp) is the most abundant by-product of the agri-food pomegranate processing chain. In recent decades, pomegranate fruit peel is attracting a lot of attention due to the presence of bioactive molecules suitable to be used in the production of food supplements. This study aimed at investigating and characterizing the nutritional and nutraceutical quality of the peels of seven important pomegranate cultivars selected considering the fruit ripening period (early, medium and late), the type of cultivar (sweet, semi-acid and acid cultivar), and the seed hardness. Early (Purple Queen, Acco, and 29–101) and medium (MR100) ripening cultivars showed higher percentages of crude fiber (>2.2%) than the late ripening cultivars (Wonderful, Kingdom and ME17). The highest content of organic acids, punicalagin and its derivates were observed in the peel of acid and semi-acid cultivars (Wonderful, Kingdom and Acco). Acco fruit peel exhibited the highest antioxidant and radical scavenging activity (1.30 and 0.88 mmol Trolox g−1 on a dry weight basis d.w., respectively) as well as total soluble polyphenol (249 mg GAE g−1 d.w.) content. No consistent relationship considering sugar concentration and mineral composition was observed. The wide quantitative and qualitative diversity of bioactive compounds and nutrients observed in the analysed fruit peels showed that the overall biochemical profile is genotype dependent. So far, the findings of this research further highlighted that pomegranate fruit peel contains a wide variety of beneficial compounds, thus showing a high potential in terms of nutrients and nutraceutics, so confirming the importance of pomegranate fruit peels for pharmaceutical and medical purposes.