Differences in the composition of phenolic compounds, carotenoids, and volatiles between juice and pomace of four citrus fruits from Southern Italy

Processing citrus fruits into juice generates large amounts of byproducts, mainly pomaces. This study aimed to investigate the composition in phenolic compounds, carotenoids, and volatiles of juices and pomaces of citruses from Southern Italy, i.e., mandarin, lemon, orange, and bergamot. Targeted approaches were employed. Results indicated that lemon provided the juice with the greatest phenolic content (357 ± 51.3 mg kg-1 FW). It was abundant in eriocitrin (90.9 ± 10.8 mg kg-1 FW) and isorhamnetin 3-O-rutinoside (47.3 ± 8.03 mg kg-1 FW). Likewise, lemon pomace was the richest in phenolics (886 ± 43.2 mg kg-1 FW), mostly narirutin (130 ± 14.7 mg kg-1 FW). As regards carotenoids, mandarin and orange pomaces were equally (p > 0.05) prominent sources of the compounds, providing primarily lutein and β-cryptoxanthin. Bergamot accumulated great amounts of volatile compounds. In particular, bergamot juice was rich in monoterpenes, e.g., α- pinene (375 ± 62.7 mg kg-1 FW). This study investigated for the first time the carotenoid and volatile profiles of bergamot. Since, citrus pomaces contained great amounts of phytochemicals, they should find new applications in the food, cosmetics, and pharmaceutical industries.