Visualization of oil cells and preservation during drying of betel leaf (piper betel) using hot-stage microscopy

Abstract

Piper betel, a well-known and widely used herb of tropical Asiatic countries, contain several bioactive constituents that possess therapeutic uses and health-promoting properties. The postharvest losses of 35% to 70% are reported due to biomass spoilage, fungal infections and dechlorophyllations. Controlled dehydration to retain the oils in the natural cellular matrix for further extraction is a potential solution for these avoidable postharvest losses. Therefore, the present investigation was undertaken to determine the impact of dehydration on microstructural changes, shrinkage and swelling of the cellular matrix, retention of oil reserves/glands, and implications for extraction yield. The betel leaf samples were dehydrated at 40, 50 and 60 °C using a hot-stage under a microscope to report microstructural changes. The moisture balance instrument was deployed to determine the drying rate at the macro level, and separately hot air drying was conducted to elucidate the drying of bulk betel leaves and its impact on oil retention. Visual inspection during dehydration gave an insight into the preservation of the oil cells/reserves. The result indicated that oil cells/reserves in the epidermal layer and traverse section of the petiole were protected and preserved during dehydration at 40 to 50 °C and were ruptured at 60 °C. The same was reflected through the yields and composition of the extracts obtained by Supercritical fluid extraction.

Keywords:

• Hot-stage microscopy
• glandular trichomes (pearl glands)
• oil reserves/oil cells
• essential oils

Acknowledgment

The authors are grateful for financial support through the Prof. M. M. Sharma Doctoral fellowship for providing the Ph. D./Research grant. The authors also thank Shri. Suvendu Parida for the keen interest in the project and the support rendered from time to time, including providing free raw material, Betel Leaves.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.