Trends in technology, trade and consumption likely to impact on microbial food safety

Current and potential future trends in technology, consumption and trade of food that may impact on food-borne disease are analysed and the key driving factors identified focusing on the European Union and, to a lesser extent, accounting for the United States and global issues. Understanding of factors is developed using system-based methods and their impact is discussed in relation to current events and predictions of future trends. These factors come from a wide range of spheres relevant to food and include political, economic, social, technological, regulatory and environmental drivers. The degree of certainty in assessing the impact of important driving factors is considered in relation to food-borne disease. The most important factors driving an increase in the burden of food-borne disease in the next few decades were found to be the anticipated doubling of the global demand for food and of the international trade in food next to a significantly increased consumption of certain high-value food commodities such as meat and poultry and fresh produce. A less important factor potentially increasing the food-borne disease burden would be the increased demand for convenience foods. Factors that may contribute to a reduction in the food-borne disease burden were identified as the ability of governments around the world to take effective regulatory measures as well as the development and use of new food safety technologies and detection methods. The most important factor in reducing the burden of food-borne disease was identified as our ability to first detect and investigate a food safety issue and then to develop effective control measures. Given the global scale of impact on food safety that current and potentially future trends have, either by potentially increasing or decreasing the food-borne disease burden, it is concluded that a key role is fulfilled by intergovernmental organisations and by international standard setting bodies in coordinating the establishment and rolling-out of effective measures that, on balance, help ensure long-term consumer protection and fair international trade. Keywords: Microbial food safety; Food technology; Globalizatio

Comparing nonsynergy gamma models and interaction models to predict growth of emetic Bacillus cereus for combinations of pH and water activity values

This research aims to test the absence (gamma hypothesis) or occurrence of synergy between two growth-limiting factors, i.e., pH and water activity (aw), using a systematic approach for model selection. In this approach, preset criteria were used to evaluate the performance of models. Such a systematic approach is required to be confident in the correctness of the individual components of the combined (synergy) models. With Bacillus cereus F4810/72 as the test organism, estimated growth boundaries for the aw-lowering solutes NaCl, KCl, and glucose were 1.13 M, 1.13 M, and 1.68 M, respectively. The accompanying aw values were 0.954, 0.956, and 0.961, respectively, indicating that equal aw values result in similar effects on growth. Out of the 12 models evaluated using the preset criteria, the model of J. H. T. Luong (Biotechnol. Bioeng. 27:280–285, 1985) was the best model to describe the effect of aw on growth. This aw model and the previously selected pH model were combined into a gamma model and into two synergy models. None of the three models was able to describe the combined pH and aw conditions sufficiently well to satisfy the preset criteria. The best matches between predicted and experimental data were obtained with the gamma model, followed by the synergy model of Y. Le Marc et al. (Int. J. Food Microbiol. 73:219–237, 2002). No combination of models that was able to predict the impact of both individual and combined hurdles correctly could be found. Consequently, in this case we could not prove the existence of synergy nor falsify the gamma hypothesis

Factors influencing the accuracy of the plating method used to enumerate low numbers of viable micro-organisms in food

This study aims to assess several factors that influence the accuracy of the plate count technique to estimate low numbers of micro-organisms in liquid and solid food. Concentrations around 10 CFU/mL or 100 CFU/g in the original sample, which can still be enumerated with the plate count technique, are considered as low numbers. The impact of low plate counts, technical errors, heterogeneity of contamination and singular versus duplicate plating were studied. Batches of liquid and powdered milk were artificially contaminated with various amounts of Cronobacter sakazakii strain ATCC 29544 to create batches with accurately known levels of contamination. After thoroughly mixing, these batches were extensively sampled and plated in duplicate. The coefficient of variation (CV) was calculated for samples from both batches of liquid and powdered product as a measure of the dispersion within the samples. The impact of technical errors and low plate counts were determined theoretically, experimentally, as well as with Monte Carlo simulations. CV-values for samples of liquid milk batches were found to be similar to their theoretical CV-values established by assuming Poisson distribution of the plate counts. However, CV-values of samples of powdered milk batches were approximately five times higher than their theoretical CV-values. In particular, powdered milk samples with low numbers of Cronobacter spp. showed much more dispersion than expected which was likely due to heterogeneity. The impact of technical errors was found to be less prominent than that of low plate counts or of heterogeneity. Considering the impact of low plate counts on accuracy, it would be advisable to keep to a lower limit for plate counts of 25 colonies/plate rather than to the currently advocated 10 colonies/plate. For a powdered product with a heterogeneous contamination, it is more accurate to use 10 plates for 10 individual samples than to use the same 10 plates for 5 samples plated in duplicat

The application of the Appropriate Level of Protection (ALOP) and Food Safety Objective (FSO) concepts in food safety management, using Listeria monocytogenes in deli meats as a case study

To establish a link between governmental food safety control and operational food safety management, the concepts of the Appropriate Level of Protection (ALOP) and the Food Safety Objective (FSO) have been suggested by international bodies as a means of making food safety control transparent and quantifiable. The purpose of this study was to investigate how the concepts of ALOP and FSO could be applied in practice. As a case study, the risk of severe listeriosis due to consumption of deli meat products in the Netherlands was taken. The link between these concepts was explored for two situations following a “top-down” approach, using epidemiological country data as a starting point, and a “bottom-up” approach, using data on the prevalence and concentration of the pathogen at retail as a starting point. Models based on both approaches were able to describe the link between ALOP and FSO and our results showed that meaningful estimations are feasible, although interpretations need to be made with care. For the top-down approach, the mean estimated value derived for ALOP was 3.2 cases per million inhabitants per year (95% CrI: 1.1-6.6). For the bottom-up approach, ALOP values ranged considerably, 4.7-55 (with 95% CrI ranging from 2.9-162), depending on the input parameters selected. The level of detail considered in the stochastic models considerably influenced the ALOP and FSO estimates. As best practice it is recommended to develop both approaches, although depending on the application context one may appear more appropriate than the other

Distribution of Cronobacter spp. in industrial batches of powdered infant formula and the impact of sampling approaches

Objectives - The three objectives of this study are: first, to investigate how Cronobacter spp. are distributed throughout a recalled and a normal batch of powdered infant formula (PIF); second, to investigate the occurrence of conglomerations of Cronobacter spp. cells, since conglomerations of cells with high concentrations may impact on risk assessment and public health; and third, to investigate the performance of typical sampling plans. Results - In the recalled batch the concentrations Cronobacter spp. versus the filling time was assessed by 415 samples of 333 g using the MPN technique. In 58 % of the samples, concentrations were below the detection limit of -2.52 log CFU/g. However, specifically within three time intervals MPN concentrations were estimated varying between -2.52 and 0.66 log CFU/g. In addition 2290 samples of 1 g were investigated by plating, and 8 were found to contain Cronobacter spp. above the detection limit of 0.52 log CFU/g. These samples were originating from packages filled at the time interval with also the highest MPN concentrations. The two largest conglomerations were 123 and 560 cells in 1 g of PIF. In 99% of the samples from the normal batch, concentrations were below the detection limit. Various sampling plans were evaluated for the contamination data from the recalled batch. Keeping the total sample weight constant at 300 g and increasing the number of random samples from 1 to 300, increased the probability of detection from 0.38 till 1.00. Conclusions - Cronobacter spp. was distributed heterogeneously within a recalled batch of PIF with parts of the batch with no detectable contamination, and parts of the batch with concentrations up to 2.75 log CFU/g. The presence of conglomerations of Cronobacter spp. cells occurred with a low frequency. Taking more and smaller samples, keeping the total sampling weight constant, considerably improved the performance of the sampling plans to detect such a type of contaminated batch

Effects of preculturing conditions on lag time and specific growth rate of Enterobacter sakazakii in reconstituted powdered infant formula

Enterobacter sakazakii can be present, although in low levels, in dry powdered infant formulae, and it has been linked to cases of meningitis in neonates, especially those born prematurely. In order to prevent illness, product contamination at manufacture and during preparation, as well as growth after reconstitution, must be minimized by appropriate control measures. In this publication, several determinants of the growth of E. sakazakii in reconstituted infant formula are reported. The following key growth parameters were determined: lag time, specific growth rate, and maximum population density. Cells were harvested at different phases of growth and spiked into powdered infant formula. After reconstitution in sterile water, E. sakazakii was able to grow at temperatures between 8 and 47°C. The estimated optimal growth temperature was 39.4°C, whereas the optimal specific growth rate was 2.31 h-1. The effect of temperature on the specific growth rate was described with two secondary growth models. The resulting minimum and maximum temperatures estimated with the secondary Rosso equation were 3.6°C and 47.6°C, respectively. The estimated lag time varied from 83.3 ± 18.7 h at 10°C to 1.73 ± 0.43 h at 37°C and could be described with the hyperbolic model and reciprocal square root relation. Cells harvested at different phases of growth did not exhibit significant differences in either specific growth rate or lag time. Strains did not have different lag times, and lag times were short given that the cells had spent several (3 to 10) days in dry powdered infant formula. The growth rates and lag times at various temperatures obtained in this study may help in calculations of the period for which reconstituted infant formula can be stored at a specific temperature without detrimental impact on healt