Unveiling the synergistic effect of combining low and high frequency electric fields for microbiological safety in liquid food processing. (August 2021)

• Record Type: Journal Article
• Authors: Rezaeimotlagh, Adel; Resch, Marlies; Kuchel, Rhiannon P.; Biazik, Joanna; Ziuzina, Dana; Bourke, Paula; Cullen, P.J.; Trujillo, Francisco J.
• Is Part Of: Journal of food engineering. Volume 303(2021)
• Publication Date: 2021-08
• Subjects: Electric field processing -- Radio frequency -- Ultrashort thermal heating -- Synergy -- Electron microscopy -- Emerging food processing technologies; Food industry and trade -- Periodicals; Food -- Analysis -- Periodicals; Aliments -- Industrie et commerce -- Périodiques; Aliments -- Analyse -- Périodiques; Aliments -- Recherche -- Périodiques; 664.005
• DOI: 10.1016/j.jfoodeng.2021.110588
• Languages: English
• ISSNs: 0260-8774

Abstract

Abstract: The synergistic effect of combining low and high radio frequency electric fields processing on Escherichia coli ( E. coli ) inactivation in liquid food was investigated. We show that by processing with low frequency (LF) at 12.5 kV cm −1 and 40 °C, followed by high frequency (HF) at 2.1 kV cm −1 and 65 °C, a synergistic effect on E. coli inactivation in saline water was achieved yielding approx. 5 log reduction and metabolic activity of 8.01 ± 4.34%. When similar treatment was applied to cranberry juice, an inactivation of 5.13 ± 0.21 log10 was achieved. Electron microscopy revealed that when both LF and HF treatments were applied alone, they disrupted the bacterial cell wall ultrastructure, with HF treatment additionally degrading cytoplasmic components. The sequential combination of LF and HF processes led to greater ultrastructural damage of E. coli as indicated by the observed perforation and rupture of the cell walls as well as leakage of cytoplasmic content. Graphical abstract: Image 1 Highlights: A continuous HF chamber for thermal processing at 13.56 MHz was designed. Sequential combination of LF and HF treatments ensured food safety due to synergism. LHF achieved synergy attacking multiple targets within E. coli cells. The synergy was due to the accumulating effects of electromagnetic fields. Inactivation in cranberry juice met microbiological safety requirement by US-FDA.