Nanoemulsions of Mentha piperita L. essential oil in combination with mild heat, pulsed electric fields (PEF) and high hydrostatic pressure (HHP) as an alternative to inactivate Escherichia coli O157: H7 in fruit juices

摘要

This study was performed in order to obtain and characterize nanoemulsions of Mentha piperita L. essential oil (n-MPEO) to assess its efficacy in combination with mild heat (MHT) (50, 52, 54 degrees C;10 min), pulsed electric fields (PEF) (20, 25, 30 kV/cm; 150 mu s), and high hydrostatic pressure (HHP) (150, 200, 300 MPa; 15 min) treatments in causing a 5-log(10) reduction in survival counts (from 7 to & 2 log(10) CFU/mL) of Escherichia toll O157:H7 in guava and mango juices. The droplets of n-MPEO were & 200 nest and showed good stability for 4 months at 4 degrees C. The n-MPEO at 5.0 mu L/mL displayed a more efficacious long-term antimicrobial activity than suspensions of MPEO (s-MPEO). Combined treatments of s-MPEO or n-MPEO and MHT, PEF, or HHP acted synergistically against E. coli. Nevertheless, combined treatments with n-MPEO showed the same or even higher efficacy than those with s-MPEO (up to 1-additional log(10) reduction). Thus, by using nanoemulsions, lower doses of antimicrobial compounds (up to 4 times) or milder MHT (up to 4 degrees C), PEF (up to 5 kV/cm) and HHP (up to 100 MPa) treatments can be applied, while still guaranteeing the microbial safety of tropical fruit juices.