Evaluation of sanitizer penetration and its effect on destruction of Escherichia coli O157:H7 in Golden Delicious apples

This study was conducted to determine the penetration of 5% trisodium phosphate solution at various depths within punctures and calyces of apples spot inoculated with Escherichia coli O157:H7 and the effect of solution agitation on destruction of the pathogen. Sanitizer solutions containing radiolabeled disodium phosphate (DSP32) were able to penetrate apple tissues through punctures and calyx cavities. However, agitation of the solutions did not result in significantly greater penetration in these areas (P > 0.05). Overall, there were 1.57- and 1.11-log reductions of pathogen cells within 4-h-old punctures treated with and without trisodium phosphate solution agitation, respectively. Sanitizer solutions were effective in destroying pathogen cells residing within the upper 4.2-mm region of the punctures. Destruction of pathogen cells within open and closed calyces occurred mainly within the basin and the upper 3 mm of the calyx cavity. Treatment with agitated sanitizer solution resulted in a 0.67-log reduction in pathogen concentration within open calyces. In contrast, treatment of closed calyces resulted in a 1.37-log reduction, mainly within the basin. Washing with water alone appeared to result in further penetration of the cells within calyces without significantly reducing the number of pathogen cells (P > 0.05). To develop more effective methods for reducing contamination on produce, it is important to know the extent of sanitizer penetration and its effect on destruction of pathogens.