Essential oil composition, antibacterial activity and postharvest application of Portulacaria afra essential oil for enhancing shelf life and quality of citrus fruits

Abstract

Moazzam Anees, Muhammad Rizwan Tariq, Muhammad Saleem Haider and Azeem Intisar*

The current study examines the extraction of the essential oil from <i>Portulacaria afra</i>, with a particular focus on its use as a coating material to enhance the postharvest attributes and shelf life of citrus (<i>citrus reticulata</i>). Essential Oils (EOs) were obtained through the microwave assisted distillation process and analyzed by means of Gas Chromatography-Mass Spectrometry (GC-MS), which demonstrated a wide variety of bioactive compounds. Notably, twenty-nine compounds were successfully identified in the extracted essential oil. The main constituents were palmitic acid (36.95%), linoleic acid (8.83%), and 5-methyl-2-furancarboxaldehyde (8.82%). Antibacterial assays demonstrated significant inhibitory effects of <i>P. afra</i> oil against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>, supporting its potential application as natural antimicrobial agent. Subsequently, the essential oils were formulated into coatings and applied to citrus fruits. The coated fruits were assessed for a comprehensive array of postharvest quality parameters, including visual appearance, color, aroma, gloss, taste, firmness, weight loss, titratable acidity, pH, ascorbic acid content, total soluble solids, and the activities of antioxidant enzymes such as Superoxide Dismutase (SOD), Peroxidase (POD), and Catalase (CAT). The findings demonstrated that all the essential oil coatings were very effective in delaying senescence, maintenance of organoleptic properties, and microbial spoilage relative to the untreated controls. P. afra coating showed better behavior in most parameters, especially in terms of maintaining firmness, lessening weight loss, increasing vitamin C retention and controlling oxidative stress by increasing POD and CAT activity.