Application of dielectric barrier discharge plasma for the reduction of non-pathogenic Escherichia coli and E. coli O157:H7 and the quality stability of fresh oysters (Crassostrea gigas)

Abstract

This study focuses on the efficacy of dielectric barrier discharge (DBD) plasma treatment (1.1 kV, 3 mm distance, N2 1.5 L/min) as a non-thermal intervention to reduce non-pathogenic Escherichia coli and E. coli O157:H7 in oysters (Crassostrea gigas). Exposure times of 10–30 min by the plasma against non-pathogenic E. coli and E. coli O157:H7 resulted in a log reduction of 0.31–1.01 and 0.18–0.62, respectively, in fresh oysters. In particular, exposure to DBD plasma for 60 min indicated 2.14 log reduction (99.28% reduction) of non-pathogenic E. coli and 1.19 log reduction (93.54% reduction) of E. coli O157:H7. D1-values for non-pathogenic E. coli and E. coli O157:H7 were 27.78 min and 50.08 min, respectively (R2 ≥ 0.98 by using a first-order kinetic model). The glycogen content (1.10–1.20 g/100 g) and texture profile (hardness, springiness, cohesiveness, resilience) of samples treated with DBD plasma did not differ significantly from that of the control (p > 0.05). Therefore, exposing oysters to DBD plasma for at least 60 min could be useful for reducing >99% of non-pathogenic E. coli and 90% of E. coli O157:H7 without causing any deleterious changes to the glycogen content and overall texture of fresh oyster.