The increase in ORP of NEO water may be attributed to the formation of free radicals in liquid when exposed to ultrasound.
The application of ultrasound leads to cavitation, a phenomenon accompanied by transient and very high temperature and pressure localized spots; and these conditions lead to the thermal dissociation of the aqueous solution resulting in the production of free radicals (Riesz & Kondo, 1992; Earnshaw, 1998; Kentish & Ashokkumar, 2011).
Free radicals, being oxidizing agents as other oxidants formed in the NEO water, results in a greater total amount of oxidants when compared to reducing agents in the solution, causing the NEO water to have a higher ORP after ultrasound treatment.
Increased ORP of EO water has been reported to increase its antimicrobial efficacy (Huang et al., 2008; Hricova et al., 2008; Liao