Investigation of the interactions between sanitizers, surface characteristics, washing conditions, and bacteria for improving microbial safety of fresh produce

The aim of washing fresh produce with sanitizers is to enhance food safety and reduce the incidence of foodborne illness. There is an increasing interest in developing alternatives to replace chlorine for having a safe, environmentally friendly, and more effective sanitizing treatment. The efficacy of sanitizer wash could be influenced by surface characteristics of produce and washing conditions.; Acidic electrolyzed water (AEW), peroxyacetic acid (POAA), and ozone, as well as several combinations of the sanitizers were investigated for their effectiveness on inactivation of Escherichia coli O157:H7 and native microbial flora on selected produce. Their effects on other quality attributes of fresh-cut produce during storage were also studied. The inactivation mechanism of the sanitizers was investigated with a MFP-3D(TM) atomic force microscopy (AFM). A non-contact method using confocal scanning laser microscopy (CSLM) to quantitate surface roughness of fresh produce was developed. The influence of surface roughness on reduction of E. coli O157:H7 was examined. The changes in flow velocity, agitation rate, and washing time were investigated to ascertain their effects on E. coli O157:H7 removal from produce.; POAA exhibited the highest bactericidal ability in the reduction of E. coli O157:H7 populations on cantaloupes and fresh-cut apples, followed by AEW and chlorine. The sequential treatment of AEW followed by Calcium Ascorbate exhibited a good browning control ability and helped to extend shelf life of fresh-cut apples. The aqueous ozone followed by AEW wash was effective in initial natural flora population reduction on cilantro and maintained low microbial growth during storage. The different cell morphological changes of E. coli cells treated with POAA from that of AEW and chlorine indicate that POAA, AEW and chlorine may have different bactericidal mechanisms. The surface roughness value obtained from 3-D images reconstructed from 2-D images acquired with a CSLM was in good agreement with that measured with a surface profilometer. The surface roughness played an important role in the removal and inactivation of E. coli O157:H7 inoculated onto fresh fruits during sanitizing treatments. Washing condition tests showed that the residual bacterial population decreased with increasing agitation rate, flow velocity, and treatment time.