Electrolyzed water and mild-thermal processing of Atlantic salmon (Salmo salar): Reduction of Listeria monocytogenes and changes in protein structure

Abstract

This study investigated the effect of different electrolyzed water (EO) solutions, including acidic electrolyzed water (AEW) and neutral electrolyzed water (NEW), alone and in combination with mild thermal processing (50, 55, 60, 65 °C) at different exposure times (2, 6, 10 min) on the reduction of Listeria monocytogenes on Atlantic salmon fillets. The effects of the EO water solutions on cell wall structures of L. monocytogenes and on the secondary structure of salmon protein were studied using Fourier Transform Infra-Red (FTIR) spectroscopy. Temperature and time significantly influenced the efficacy of the AEW and NEW. NEW has stronger antimicrobial properties as compared to AEW. The highest bacterial reduction was observed at 65 °C after 10 min for salmon treated with NEW, with a 5.6 log10 CFU/g reduction. Spectral features show that the secondary protein structures in salmon muscle treated with NEW were less affected than tissue treated with AEW as shown in a PCA model. In addition, the FTIR spectra for L. monocytogenes showed that the NEW and AEW affected cell wall properties differently; this might be due to the form of available chlorine in NEW and AEW and to AEW having a lower pH. In general, NEW showed better antimicrobial properties, particularly when combined with mild thermal processing than AEW and also caused less alteration in protein structure. The findings of this study may be used to improve the quality and safety of cured and smoked ready-to-eat fish products.