Decontamination method using heat and relative humidity for radish seeds achieves a 7-log reduction of Escherichia coli O157:H7 without affecting product quality

Abstract

We developed a novel decontamination method to inactivate Escherichia coli O157:H7 on radish seeds without adversely affecting seed germination or product quality. The use of heat (55, 60, and 65 degrees C) combined with relative humidity (RH; 25,45, 65, 85, and 100%) for 24h was evaluated for effective microbial reduction and preservation of seed germination rates. A significant two-way interaction of heat and RH was observed for both microbial reduction and germination rate (P < 0.0001). Increases in heat and RH were associated with corresponding reductions in E. coli O157:H7 and in germination rate (P < 0.05), The order of lethality for the different treatments was generally as follows: no treatment <55 degrees C/25-65% RH 60 degrees C/25-45% RH 65 degrees C/25% RH <55 degrees C/85% RH = 60 degrees C/65% RH <55 degrees C/100% RH = 60 degrees C/85-100% RH = 65 degrees C/45-100% RH. The most effective condition, 65 degrees C/45% RH, completely inactivated E. coli O157:H7 on the seeds (7.0 log CFU/g reduction) and had no significant effect on the germination rate (85.4%; P > 0.05) or product quality. The method uses only heat and relative humidity without chemicals, and is thus applicable as a general decontamination procedure in spout producing plants where the use of growth chambers is the norm. (C) 2015 Elsevier B.V. All rights reserved.