Decontamination of low Aw foods and environments

A member subscription–funded project is evaluating and validating potential decontamination technologies for low water activity (Aw) foods. Traditionally, these foods, which include chocolate, nuts, seeds, cereals, and flour, have been regarded as microbiologically safe as a result of their inherent product characteristics. However, concern has been recently raised about the potential presence and survival of Enterobacteriaceae such as Salmonella, Escherichia coli and Cronobacter in low Aw foods.

Research is focusing on three decontamination strategies for cocoa beans, powders, herbs and dried pet foods: whole room ozonation; a combination of wetting and heat; and steam. As part of these methods, the D– and z–values of two strains of Salmonella attached to stainless steel surfaces were analysed to determine the time taken for significant log reductions of this bacterium.

In low Aw foods, D–values calculated for Salmonella strains were much higher than would be expected in a moist situation, where a process of 70°C for 2 minutes would be expected to achieve >6 log reductions in this organism. In low Aw foods, the D–value was 30 minutes at 115°C, showing the disparity between moist and dry conditions. These findings will help in developing guidelines for processors of low–moisture foods, including assessment and validation instructions for the thermal performance of selected industrial processes to establish their importance in microbial risk reduction.

Contact: Izabela Palgan
+44(0)1386 842149
izabela.palgan@campdenbri.co.uk