Primers to detect important yeasts
Yeasts present on the surface of smear cheeses play an important role in the development and flavour of a cheese. As well as having a direct effect on the quality of the cheese, they play a part in the overall microbial ecology of the surface flora. Dominant species keep others in check and a delicate dynamic population balance is maintained to achieve the tasty cheese the consumer expects. Moreover, when the competitor is a Listeria species, its control by yeast competitors can be crucial for consumer health. As part of the study of major yeasts on European smear cheeses, the EC-funded project, SCM isolated five separate strains. Researchers at the University of Caen Basse-Normandie developed specific polymerase chain reaction (PCR) primers for this sole purpose. These primers adhere onto specific regions of DNA at the start and the end of a sequence. Once this has occurred, the length of DNA can be replicated and then identified. The primers developed were compared to published sequences from international DNA sequence libraries. Two sequences were specifically designed for Geotrichum candidum (G. candidum), an important microbial representative in the food industry. This particular yeast is used widely in the cheese industry as a ripener. However, it can have devastating effects on food quality when present as a contaminant. As such, it can cause slimy rot in orchard and warehouse fruit. An unwelcome visitor in fruit and vegetable juice, it can cause degradation and spoilage. It is a psychrophile and therefore it proliferates in cold conditions, including refrigerated cakes and frozen vegetables. It is therefore expected that the use of the primers will greatly facilitate the study of the ripening process in food and help to prevent food spoilage. Use of primers rather than probes already developed will facilitate identification of these important microbes.
