Effect of citral nanoemulsion on the inactivation of Listeria monocytogenes and sensory properties of fresh-cut melon and papaya during storage

Abstract

This study evaluated the survival of Listeria monocytogenes on fresh-cut melon and papaya treated with citral nanoemulsion (CN) during 7 days of storage at 4, 8, 12, and 16 °C. CN was prepared by catastrophic phase inversion, and fresh-cut melon and papaya were artificially inoculated, resulting in 5 log cfu/g of L. monocytogenes. Then, they were treated with 0.30 (CN-0.3) and 0.15 (CN-0.15) μL/mL of CN. CN presented droplet size below 200 nm, monodisperse distribution, and negative surface charge. CN-0.3 reduced the L. monocytogenes counts more efficiently, with counts below the detection limit (1 log cfu/g) in both fruits after 48 h at 4 °C, and 72 h at 8 °C and 12 °C. At 16 °C, L. monocytogenes counts were below the detection limit for CN-0.3 after 120 h in papaya, but it survived the other treatments for 7 days. Both CN-0.3 and CN-0.15 decreased the indigenous microbiota. Scanning electron microscopy (SEM) showed bubbles in L. monocytogenes membrane and cell disruption in fruits treated with CN-0.3. Finally, CN-0.3 treated melon and papaya showed greater brightness, herbal flavor and aroma, firmness, and juiciness, as well as lower sugar and organic acid profile changes than the control samples during storage. Results indicate citral nanoemulsion's efficiency in controlling L. monocytogenes growth on fresh-cut melon and papaya stored at refrigerated temperatures without negatively influencing the sensory parameters.

Keywords: Citral; Food safety; Fresh-cut fruit; Listeria monocytogenes; Natural antimicrobial.