Investigation of changes in non-traditional indices of maturation in Navel orange peel and juice using GC-MS and LC-QTOF/MS

Abstract

Changes in non-traditional indices of maturity, such as flavonoids and volatile compounds, during maturation were studied in Navel orange. Navel oranges were obtained at four stages of maturation, and non-volatile and volatile compounds in the peel and juice were analysed using liquid chromatography coupled with a quadrupole time-of-flight detector (LC-QTOF/MS) and gas chromatography with mass spectrometry and a flame ionisation detector (GC-MS/FID), respectively. Twenty-eight non-volatile and 62 volatile compounds in the peel as well as 22 non-volatile and 11 volatile compounds in the juice were found to have significant changes (p < 0.05) in abundances during maturation. Notably, most flavonoids (e.g. narirutin) and limonoids (e.g. nomilin) showed decreasing abundances during maturation. For volatile compounds, majority of detected alcohols peaked in abundances during middle maturation stages, while almost all detected aldehydes peaked at full maturity. Most terpenes peaked at earlier maturation stages in juice extracts compared to peel oil extracts. This comprehensive study could facilitate selection of Navel oranges for the extraction of valuable bioactive or flavour contributing compounds that are of interest to fragrance, flavour and nutraceutical industries.

Keywords: Citrus; Composition; GC–MS; LC-QTOF/MS; Maturity; Navel orange; Non-volatile compounds; Volatile compounds.