Chemical Mapping of Essential Oils, Flavonoids and Carotenoids in Citrus Peels by Raman Microscopy.

Citrus peels, by-products in large quantity, are rich in various functional and beneficial components which have wide applications. Chemical analysis of these components in citrus peels is an important step to determine the usefulness of the by-products for further applications. In this study, we explored Raman microscopy for rapid, nondestructive, and in situ chemical mapping of multiple main functional components from citrus peels. The relative amount and distribution in different locations (flavedo, albedo, and longitudinal section) of 3 main functional components (essential oils, carotenoids, and flavonoids) in citrus peels were systematically investigated. The distribution profiles of these components were heterogeneous on the peels and varied between different species of citrus peels. Essential oil was found mainly existed in the oil glands, while carotenoids were in the complementary location. Some flavonoids were observed in the oil glands. This study showed the capability of Raman microscopy for rapid and nondestructive analysis of multiple bio-components without extraction from plants. The information obtained from this study would assist the better production and application of the functional and beneficial components from citrus by products in an effective and sustainable manner.

PRACTICAL APPLICATION: This study indicated the capability of Raman microscopy for rapid and nondestructive analysis of multiple bioactive components in plant tissues. The information obtained from the study would be valuable for developing effective and sustainable strategy of utilization of citrus peels for further applications.