Researchers in Spain have developed a quick and easy method to detect toxic Aspergillus fungi in contaminated food. 

Alfredo Sanz-Medel and his colleagues at the University of Oviedo have produced a test that relies on room-temperature phosphorescence (RTP) and speeds up the testing from up to ten days to less than two.

The RTP test does not use fluorescence, and therefore does not require the harsh conditions of current methods. Additionally, the slower time-scale of RTP enables the faster-occurring fluorescent emission to be filtered out, improving the selectivity of detection. The group were able to separate toxic cultures from non-toxic strains within 36 hours of contamination, much faster than fluorescence-based approaches.

Moulds of the Aspergillus genus are commonly found as contaminants in foodstuffs intended for humans and animals. Some of these species have the ability to produce aflatoxins, a class of compounds with a wide range of very harmful effects. The development of screening methods for the quick identification of these strains is of great present interest, said Sanz-Medel.

Fluorescence methods currently used for detecting aflatoxin-producing strains require the samples to be grown in a nutrient medium that favours toxin production. The toxin-producing colonies fluoresce blue under ultra-violet light. These methods usually require 3-10 days to provide a result. In any case, getting detectable fluorescence levels requires certain conditions, such as a lack of oxygen and the presence of metal atoms.

According to Sanz-Medel, this method provides a simpler and faster method for aflatoxin screening than classical microbiological techniques, and shows the great analytical potential of RTP.

Michael Spencelayh