Cultivation line and fruit ripening discriminations of Shiikuwasha (Citrus depressa Hayata) peel oils using aroma compositional, electronic nose, and antioxidant analyses

- Cultivation line and fruit ripening discriminated the peel oils of Shiikuwasha.
- Shiikuwasha peel oils of three cultivation lines possess distinct aroma components.
- The concentration of the 14 main aroma components fluctuates during fruit ripening.
- MS-based e-nose analysis confirms the aroma profile differentiation.
- Antioxidant activities decrease with fruit ripening.

Shiikuwasha peel oils from three cultivation lines ('Izumi kugani', 'Katsuyama kugani', and 'Ogimi kugani') and four fruit-ripening stages were differentiated in terms of their aroma and antioxidant profiles. Each cultivation line had a distinctive profile of aroma components, and ripening stages affected the variations in the concentrations of their main constituents such as limonene, γ-terpinene, p-cymene, and linalool. Hyphenated total ion masses, obtained by a mass spectrometry (MS)-based electronic nose (e-nose) technique, effectively discriminated the peel oils according to their genetic and seasonal diversities, and generated several discriminant variables such as m/z 119, 135, and 149. The e-nose plots were generally alike with regard to the statistical profile of the compositional aroma compounds identified, wherein unripe oils of the early September harvest of the 'Izumi kugani' and 'Ogimi kugani' lines presented distinctive aroma profile clusters compared to the other Shiikuwasha oils. Moreover, despite fruit ripening, the 'Katsuyama kugani' peel oil was closely related to that of the 'Ogimi kugani' line. The antioxidant functions of Shiikuwasha peel oils declined with ripening, as seen from the oxygen radical absorbance capacity (ORAC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity assays. Additionally, the total phenolic contents of the oils were positively associated with their ORAC values.