AOAC-RI ERP Book Micro Jan 19 2017

g sample size) were inoculated with E. coli O157:H7 at a concentration aimed to achieve a targeted level of contamination. The inoculation levels targeted were chosen in order to meet the targeted POD values for the different inoculation levels. The concentrations achieved through inoculation were found to be 2.584 x 10 -2 MPN/g for the high inoculation level of spinach and 4.740 x 10 -2 MPN/g for the high inoculation level of sprouts, according to the MPN analysis (Table 2). In addition to this, the AOAC fractional positive criterion (POD between 0.25 and 0.75) was met, providing evidence that the inoculation procedure was successful for spinach and sprouts (Table 5, Table 9). Review of the POD calculation outcomes for the spinach candidate method (200 g Spinach Analyzed via the 3M TM MDA) and reference method (200 g Spinach Analyzed via the FDA BAM Ch. 4A) shows that the 95% confidence intervals contained 0.000 at all inoculation levels for the dPOD CP , comparing the ‘screening stage’ and ‘confirmation stage’ of the candidate method, and the dPOD C , comparing the candidate method and reference method (Table 5). Because of this, for the candidate method, the POD CP values were not significantly different from their corresponding POD CC values. Based on this outcome, it can be stated that the probability of detecting a positive result in the “screening stage” of the candidate method was not significantly different from the probability of detecting a positive result in its “confirmation stage” at any of the inoculation levels tested. Additionally, for the candidate method versus the reference method, the POD C values were not significantly different from their corresponding POD R values. Based on these outcomes, by fulfilling the criteria to contain 0.000 within the 95% confidence intervals, it can be stated that the probability of detecting a positive result in the candidate method was not significantly different from the probability of detecting a positive results in the reference method. Thus, the candidate method and the reference method can be considered equivalent, based on the AOAC International guidelines. Also, the lack of false positive or false negatives (Table 4 ) when comparing the ‘screening stage’ and the ‘confirmation stage’ of the candidate method further supports the adequacy of the method. Review of the POD calculation outcomes for the sprout candidate method (25 g Spinach Analyzed via the 3M TM MDA) and reference method (25 g Spinach Analyzed via the FDA BAM Ch. 4A), shows that the 95% confidence intervals contained 0.000 at all inoculation levels for the dPOD CP , comparing the ‘screening stage’ and ‘confirmation stage’ of the candidate method, and the dPOD C , comparing the candidate method and reference method (Table 9). Because of this, for the candidate method, the POD CP values were not significantly different from their corresponding POD CC values. Based on this outcome, it can be stated that the probability of detecting a positive result in the “screening stage” of the candidate method was not significantly different from the probability of detecting a

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