FENNEL (FOENICULUM VULGARE) ESSENTIAL OIL AS A NATURAL BIOACTIVE IN MODIFIED CASSAVA STARCH COATINGS: A SUSTAINABLE STRATEGY TO EXTEND PAPAYA SHELF LIFE

Biopolymer coatings represent a sustainable alternative for extending the postharvest life of climacteric fruits, whose losses are largely driven by fungal diseases such as anthracnose and by the toxicity and resistance limitations of synthetic pesticides. This study formulated and characterized a biodegradable coating based on modified cassava starch (3%, w/v) incorporated with fennel (Foeniculum vulgare) essential oil (1,500 ppm) and evaluated its application on papayas (Carica papaya L.) stored at 10 °C for 16 days. Coating formulation was guided by a Box-Behnken design (15 runs) varying essential oil concentration (2–4%, w/w), surfactant hydrophilic-lipophilic balance (10–15), and agitation time (10–30 min), with coating adhesion to the fruit as the response. Five treatments were compared: uncoated control, coating without essential oil applied by immersion (CRI) or spraying (CRS), and coating with essential oil applied by immersion (ROI) or spraying (ROS). Mass loss, firmness, soluble solids, pH, titratable acidity, color, respiration rate, and ethylene production were monitored every 4 days, and coatings were characterized by rheology, contact angle, DSC, and TGA, including a 180-day stability study at ambient and refrigerated temperatures. Spray-applied coatings (CRS, ROS) showed better adhesion and visual integrity, whereas immersion produced film cracking and ROI led to fruit deterioration. ROS restricted mass loss to 1.91–8.64% over storage, below the 14.22% observed for CRI, and showed the lowest firmness decline, with the sharpest reduction only after 12 days, against 6 days for the other treatments. Color parameters remained stable in all coated fruits, while only the control changed significantly, indicating delayed ripening. Anthracnose developed in control and ROI fruits after 16 days, whereas sprayed coatings prevented injuries. Coatings behaved as pseudoplastic emulsions (Herschel-Bulkley, R² = 0.9868–0.9974), and essential oil incorporation raised apparent viscosity from 31 to 245 mPa·s and the melting temperature from 131.73 to 137.77 °C, confirming matrix-oil compatibility and improved thermal stability, with residual mass of 15% against 0.5–1.63% for oil-free coatings. The emulsion remained stable for six months without contamination, and contact angles were consistently higher under refrigeration (84.89° to 51.82° over 180 days). Spray application of the modified cassava starch coating enriched with fennel essential oil ensured superior adhesion and preservation, constituting a suitable methodology to extend papaya shelf life with natural bioactive inputs.

Acknowledgments: This work was funded in part by the Cearense Foundation for the Support of Scientific and Technological Development (FUNCAP, grant MLC-0191-00087.01.00/22, SPU No. 06264875/2022) and by the National Council for Scientific and Technological Development (CNPq, grant 303540/2023-0), with support from the Brazilian Agricultural Research Corporation (Embrapa) and the Federal University of Ceará (UFC).