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

Abstract 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 °C; 10 min), pulsed electric fields (PEF) (20, 25, 30 kV/cm; 150 μs), 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 10 CFU/mL) of Escherichia coli O157:H7 in guava and mango juices. The droplets of n-MPEO were  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 °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. Industrial relevance The exploration of a series of different delivery systems of antimicrobial compounds in food products improves their antimicrobial efficacy and aids in the establishment of successful combined treatments for food preservation. The preparation of nanoemulsions of MPEO not only enhances the compound's stability, but also its antimicrobial efficacy (20% reduction in treatment time as compared with non-emulsified MPEO). Valuable synergistic effects that can be observed when combining n-MPEO with MHT, PEF, or HHP (up to 2.5- additional log 10 reductions) reveal alternatives to traditional treatments that are successful because they help reduce treatment intensity, thereby helping to avoid adverse effects on juice quality without compromising food safety.