Micro December 2018

3M Petrifilm Rapid E. coli /Coliform Count Plate

ISO 4832:2006

95% CI g

Cont. level a

Matrix

Mean b

s r

RSD r

Mean

s r

RSD r

Mean diff. f

LCL h

UCL i

c

d

Ready- made- sandwiches

High

4.852

0.077

1.587

4.868

0.076

1.561

-0.016

-0.055

0.023

Low Med High Low Med High Low Med High Low Med High Low Med High

1.877 2.887 4.852 1.877 2.887 4.934 1.874 2.900 4.852 2.563 3.631 4.303 1.831 2.877 4.801

0.067 0.076 0.077 0.067 0.076 0.028 0.089 0.055 0.077 0.226 0.146 0.107 0.053 0.067 0.077

3.570 2.632 1.587 3.570 2.632 0.567 4.749 1.897 1.587 8.818 4.021 2.487 2.895 2.329 1.604

1.891 2.909 4.853 1.901 2.902 4.908 1.864 2.909 4.881 2.717 3.626 4.477 1.863 2.894 4.829

0.046 0.064 0.084 0.055 0.067 0.049 0.080 0.053 0.077 0.063 0.079 0.097 0.088 0.062 0.060

2.433 2.200 1.731 2.893 2.309 0.998 4.292 1.822 1.578 2.319 2.179 2.167 4.724 2.142 1.242

-0.013 -0.022 -0.001 -0.024 -0.015 0.025 0.010 -0.017 -0.029 -0.154 0.005 -0.174 -0.032 -0.017 -0.029

-0.076 -0.052 -0.021 -0.089 -0.032 -0.012 -0.043 -0.026 -0.084 -0.414 -0.113 -0.303 -0.154 -0.084 -0.071

0.050 0.008 0.018 0.042 0.001 0.063 0.063 -0.009 0.025 0.106 0.124 -0.044 0.090 0.049

Raw veg with dressing

Chicken feed

Soybean meal

Stainless steel

Sealed concrete

0.014 a All matrices are artificially contaminated. An uncontaminated level was not tested, as per ISO 16140-2, Microbiology of the food chain — Method validation — 1 Part 2: Protocol for the validation of alternative (proprietary) methods against a reference method. 2 b Mean of five replicate portions, plated in duplicate, after logarithmic transformation: Log 10 [CFU/g + (0.1)f]. 3 c Repeatability standard deviation. 4 d Relative standard deviation for repeatability. Reported as a percentage. 5 e ISO 4832:2006, Microbiology of food and animal feeding stuffs -- Horizontal methods for the enumeration of coliforms – Colony- count technique. 6 f Mean difference between the candidate and reference methods. 7 g Confidence interval based on paired statistical analysis. 8 h 95% Lower confidence limit for difference of means. 9 i 95% Upper confidence limit for difference of means.

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