Flavonoids in pigmented orange juice and second-pressure extracts.

Flavanone glycosides (FGs) and polymethoxylated flavones (PMFs) have been studied in pigmented orange (Citrus sinensis) juices and second-pressure extracts (SPEs) by high-performance liquid chromatography and diode array detector. Detection was performed simultaneously at two different wavelengths: 278 nm (for determination of FGs) and 325 nm (for determination of PMFs). Qualitative distribution patterns of FGs and PMFs in juices and SPEs were similar, although the quantitative results are quite different. An increased narirutin/hesperidin ratio after centrifugation and the presence of high amounts of PMFs in SPEs, which remain unchanged after centrifugation, were observed. Therefore, a simple and affordable procedure to distinguish an orange juice from SPEs was proposed.