TY - JOUR
T1 - Actual distribution of Cronobacter spp. in industrial batches of powdered infant formula and consequences for performance of sampling strategies
AU - Jongenburger, I.
AU - Reij, M.W.
AU - Boer, E.P.J.
AU - Gorris, L.G.M.
AU - Zwietering, M.H.
PY - 2011
Y1 - 2011
N2 - The actual spatial distribution of microorganisms within a batch of food influences the results of sampling for microbiological testing when this distribution is non-homogeneous. In the case of pathogens being non-homogeneously distributed, it markedly influences public health risk. This study investigated the spatial distribution of Cronobacter spp. in powdered infant formula (PIF) on industrial batch-scale for both a recalled batch as well a reference batch. Additionally, local spatial occurrence of clusters of Cronobacter cells was assessed, as well as the performance of typical sampling strategies to determine the presence of the microorganisms. The concentration of Cronobacter spp. was assessed in the course of the filling time of each batch, by taking samples of 333 g using the most probable number (MPN) enrichment technique. The occurrence of clusters of Cronobacter spp. cells was investigated by plate counting.
From the recalled batch, 415 MPN samples were drawn. The expected heterogeneous distribution of Cronobacter spp. could be quantified from these samples, which showed no detectable level (detection limit of -2.52 log CFU/g) in 58% of samples, whilst in the remainder concentrations were found to be between -2.52 and 2.75 log CFU/g. The estimated average concentration in the recalled batch was -2.78 log CFU/g and a standard deviation of 1.10 log CFU/g. The estimated average concentration in the reference batch was -4.41 log CFU/g, with 99% of the 93 samples being below the detection limit. In the recalled batch, clusters of cells occurred sporadically in 8 out of 2290 samples of 1 g taken. The two largest clusters contained 123 (2.09 log CFU/g) and 560 (2.75 log CFU/g) cells. Various sampling strategies were evaluated for the recalled batch. Taking more and smaller samples and keeping the total sampling weight constant, considerably improved the performance of the sampling plans to detect such a type of contaminated batch. Compared to random sampling, stratified random sampling improved the probability to detect the heterogeneous contamination.
Highlights
¿ Sampling results are clearly different in a recalled and reference batch of powdered infant formula (PIF). ¿ Cronobacter spp. are heterogeneously distributed in the recalled batch of PIF. ¿ Clusters of cells are present with a low frequency (8 out of 2290 samples). ¿ Taking more and smaller samples improves the performance of the sampling plans. ¿ Compared to random, random stratified sampling improves the detection probability.
AB - The actual spatial distribution of microorganisms within a batch of food influences the results of sampling for microbiological testing when this distribution is non-homogeneous. In the case of pathogens being non-homogeneously distributed, it markedly influences public health risk. This study investigated the spatial distribution of Cronobacter spp. in powdered infant formula (PIF) on industrial batch-scale for both a recalled batch as well a reference batch. Additionally, local spatial occurrence of clusters of Cronobacter cells was assessed, as well as the performance of typical sampling strategies to determine the presence of the microorganisms. The concentration of Cronobacter spp. was assessed in the course of the filling time of each batch, by taking samples of 333 g using the most probable number (MPN) enrichment technique. The occurrence of clusters of Cronobacter spp. cells was investigated by plate counting.
From the recalled batch, 415 MPN samples were drawn. The expected heterogeneous distribution of Cronobacter spp. could be quantified from these samples, which showed no detectable level (detection limit of -2.52 log CFU/g) in 58% of samples, whilst in the remainder concentrations were found to be between -2.52 and 2.75 log CFU/g. The estimated average concentration in the recalled batch was -2.78 log CFU/g and a standard deviation of 1.10 log CFU/g. The estimated average concentration in the reference batch was -4.41 log CFU/g, with 99% of the 93 samples being below the detection limit. In the recalled batch, clusters of cells occurred sporadically in 8 out of 2290 samples of 1 g taken. The two largest clusters contained 123 (2.09 log CFU/g) and 560 (2.75 log CFU/g) cells. Various sampling strategies were evaluated for the recalled batch. Taking more and smaller samples and keeping the total sampling weight constant, considerably improved the performance of the sampling plans to detect such a type of contaminated batch. Compared to random sampling, stratified random sampling improved the probability to detect the heterogeneous contamination.
Highlights
¿ Sampling results are clearly different in a recalled and reference batch of powdered infant formula (PIF). ¿ Cronobacter spp. are heterogeneously distributed in the recalled batch of PIF. ¿ Clusters of cells are present with a low frequency (8 out of 2290 samples). ¿ Taking more and smaller samples improves the performance of the sampling plans. ¿ Compared to random, random stratified sampling improves the detection probability.
KW - enterobacter-sakazakii
KW - spatial-distribution
KW - food
KW - contamination
KW - milk
KW - microorganisms
KW - design
KW - beef
KW - rna
U2 - 10.1016/j.ijfoodmicro.2011.08.003
DO - 10.1016/j.ijfoodmicro.2011.08.003
M3 - Article
SN - 0168-1605
VL - 151
SP - 62
EP - 69
JO - International Journal of Food Microbiology
JF - International Journal of Food Microbiology
IS - 1
ER -