Antimicrobial activity of lime oil in the vapour phase against Listeria monocytogenes on ready-to-eat salad during cold storage and its possible mode of action

Abstract

This study investigated the antimicrobial activity of lime oil (LO) at 50, 100, and 200 μl to control microbial spoilage and the survival of Listeria monocytogenes on ready-to-eat (RTE) mixed vegetable salads in 1-L glass boxes for 7 days in a refrigerator (~4 °C). The bacteriostatic properties of L. monocytogenes were investigated by cell constituent release analysis and crystal violet assays, which are related to the bacterial cell wall and cell membrane. Scanning electron microscopy (SEM) was used to study the morphology of L. Monocytogenes, and the components of LO in treated RTE mixed vegetable salads using were studied by gas chromatography-mass spectrometry (GC-MS). The results indicated that LO at 100 μl L−1 could inhibit cell cultures and reduce the growth of L. monocytogenes (⁓104 cfu ml−1) on RTE salads in refrigerated conditions by 0.6–1.5 log10 cfu g−1. The results revealed that LO affected bacterial cell permeability and cell membrane integrity. The treated cells showed serious detrimental defects in their membrane morphology. Furthermore, α-terpineol, terpineol and limonene were confirmed as the key components that inhibited bacteria during cold storage. The quality of RTE salads stored with LO in a 1-L glass box showed good results, and the consumers also accepted the salads with a hedonic score (~6.1 ± 0.7) rated as ‘like slightly’ for sensory evaluation.