Effects of Essential Oils and Hydrolates on the Infectivity of Murine Norovirus

The use of natural substances with antiviral properties might reduce foodborne viral
diseases. In this study, we evaluated the virucidal effect of Citrus limon and Thymus serpyllum essential
oils (EOs) and of Citrus Limon, Thymus serpyllum and Thymus vulgaris hydrolates on murine norovirus
(MNV), a human norovirus surrogate. To assess the virucidal effect of these natural substances,
the reduction in viral infectivity was estimated by comparing the TCID50/mL of untreated viral
suspension and the viral suspension treated with hydrolates and EOs at different concentrations. The
results showed a natural loss of infectivity of the untreated virus after 24 h of approx. 1 log. The EO
(1%) of T. serpyllum, and hydrolates (1% and 2%) of T. serpyllum and T. vulgaris immediately caused a
reduction in MNV infectivity of about 2 log but did not provide a further significant decrease after
24 h. Instead, the EO (1%) and hydrolate (1% and 2%) of C. limon exerted an immediate reduction
in the viral infectivity of about 1.3 log and 1 log, respectively, followed by a further reduction in
infectivity of 1 log after 24 h for the hydrolate. These results will allow for the implementation of a
depuration treatment based on the use of these natural compounds.