Thymol Fumigation in Combination with Modified Atmosphere Packaging as an Alternative to SO2 Treatment on the Decay Prevention and Pericarp Browning of Longan Fruit

Abstract

Microbial decay and pericarp browning are the major concerns that limit the postharvest life of longan fruit. The most effective and inexpensive way to prevent these limitations is SO2 fumigation, however, due to its safety and regulatory issues other alternatives should be tested. Thymol is a natural antimicrobial compound reportedly being effective against a wide range of microorganisms. However, due to its highly volatile and peculiar taste in food, there is a need to develop a technique that effectively releases the vapors without affecting its sensory quality. In this study a device was designed for the controlled release of thymol and then evaluated for its ability to prevent the decay and pericarp browning of longan. Thymol vapors were obtained from the slurry prepared from 5 g of thymol with 5 mL of distilled water in 180 mL glass jar. Jar was hermetically sealed and allowed for 24 h to accumulate the required amount of vapors in the headspace. Thymol fumigated fruit were packaged with a specific high gas permeable film that creates the desired modified atmospheres (MAs) were compared with non-fumigated fruit packaged in similar packaging and stored in air at 27 °C. In-package gas composition, decay incidence (DI) and pericarp browning (BI) were evaluated during storage. Equilibrium MAs of reduced O2 and elevated CO2 were established in all packages. Thymol significantly (P 0.05) prevented DI and BI and resulted in the longer shelf life of 8 d as compared to non-fumigated fruit in packaging (6 d). The combined effects of thymol fumigation and modified atmosphere packaging can be used as alternative to SO2 treatment which may also be applied to other fruits. Combination with low temperature storage will enhance the effectiveness of thymol for long-term storage.