12 January - 20 June 2016

Clostridium botulinum spore loads in food lower than previously thought

In a study from the Institute of Food Research (IFR), it was found that typical loadings of Clostridium botulinum (C.Bot) spores in minimally processed chilled foods were found to be lower than previously thought. C.Bot is a particularly virulent food contaminant, with a single spore capable of germinating and eventually causing botulism poisoning.

In a study from the Institute of Food Research (IFR), it was found that typical loadings of Clostridium botulinum (C.Bot) spores in minimally processed chilled foods were found to be lower than previously thought. C.Bot is a particularly virulent food contaminant, with a single spore capable of germinating and eventually causing botulism poisoning.

An optimised technique for analysis of these spores using enrichment followed by PCR is well suited to enumeration of samples with 10 – 100 spores/kg. From literature, samples were typically referenced as containing numbers of spores in this range, with outliers being uncommon.

In a study of nearly 500 samples, the majority of samples were shown to have spore loading more in the range of 1 – 10 spores/kg, challenging the capabilities of the optimised technique. To overcome the challenges arising from analysing samples near the limit of quantification, the team employed Bayesian statistical techniques and data from previous studies to quantify the expected spore loads in the samples.

The data obtained from this study, combined with heat-treatment techniques, incubation conditions and growth time, was used to perform a risk based study to evaluate potential shelf life of raw ingredients and prepared chilled foods.

As the loading of spores in the raw food samples was found to be significantly lower, this means that the required food treatment of chilled food products can be softened from the typical 90°C/10min treatment for chilled foods with an expected shelf life of 10 days, to a shorter or cooler treatment.

These softened conditions provide cost savings for food manufacturers through reduction in energy input, but also means a more desirable product for the consumer.

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