Tracking problem microbes

Food micro-organisms can compromise product safety or adversely affect quality. Knowing where and how problem microbes enter a food can help prevent recurrences and so better assure food safety and quality. Molecular biology techniques coupled with effective microbiological sampling constitute a powerful part of our expanding services in this area.

The approach is perhaps best recognised from its application to pathogens, such as Listeria, E. coli, Salmonella and Staphylococcus as Debra Smith of CCFRA's Food Hygiene Department explains: “It is well established that Listeria is naturally widespread in the environment and that some strains are persistent in food production areas. So if a product becomes contaminated with a strain of Listeria it is necessary to carry out careful and planned microbiological sampling of possible sources and to use a typing method to identify which source potentially caused the problem. It is then possible to target control measures at the source so that recurrences can be prevented. For example, if the issue was due to survival of Listeria on a food contact surface, we can use a variety of standardised tests to assess the efficacy of particular disinfectants for eliminating problem micro-organisms.”

“We use a RiboPrinter^TM to look at conserved genes and characterise bacterial isolates to help track sources of contamination” adds Suzanne Jordan of CCFRA's Microbiology Department. “The software is able to compare Riboprint^TM patterns from an unknown environmental sample with a database of over 6000 patterns representing almost 200 bacterial genera and over 1400 species. With only eight hours needed to obtain a Riboprint^TM of a bacterial colony, the power and speed of the approach is clear”.

The same principles of environmental sampling and reliable identification of problem organisms apply to spoilage, where quick and effective solutions can save food and drinks companies significant time and money, and help reduce product loss. Spoilage of foods by yeasts and moulds provides a good example, as it is a concern for some major categories of food. Saccharomyces, for example, is known to cause problems with soft drinks and Penicillium with baked goods. Dairy products and meats are also susceptible to yeast-mediated spoilage.

Recognising that understanding of the growth and cross-contamination mechanisms of yeasts and moulds in the factory environment is poor, we have initiated new research to underpin and strengthen assistance in this area. These include confirmation of the presence of mould contamination, isolation and purification of moulds, identification of moulds to species level and determination of mould survival characteristics – such as their tolerance to heat, acids and disinfectants. Molecular methods can complement traditional morphological approaches to mould identification. Again, when combined with factory visits by hygiene specialists the approach can enable the source of contamination to be pinpointed. Practical advice can then be given on the prevention of contamination and the problems that it causes.