Burgundy truffles - fungi that range among the most expensive foods in the world - do not accumulate radioactive pollution, making the delicacy found in Europe safe for consumption, a new study has found.
Some forest mushrooms, such as wild porcini, can accumulate dangerous levels of radioactivity from the soils they grow in.
However, until now it was unclear if the same was true for truffles, which are highly prized as a delicacy for their hazel-nutty flavour and intense aroma.
Researchers analysed Burgundy truffles collected in central Europe and found they contain only negligible amounts of radioactive caesium, being safe for consumption.
The 1986 Chernobyl nuclear disaster in Ukraine released substantial quantities of radioactive particles, especially caesium-137 (137Cs).
Transported by winds and deposited by heavy rainfall, the caesium polluted large swaths of the European continent.
“Much of the continent’s topsoil layers are still radioactively contaminated,” said lead author Ulf Buntgen, from the Swiss Federal Research Institute.
However, that does not seem to affect the subterranean Burgundy or summer truffles (Tuber aestivum).
“We were very positively surprised that all specimens we analysed exhibited insignificant values of 137Cs,” said Buntgen.
This result is surprising because many types of fungi, including truffles, grow underground in and draw nutrients from soil prone to accumulating radioactive pollution.
Researchers said that in regions where the radioactive fallout after Chernobyl was most intense, not only mushrooms but also higher components in the food chain, including game meat of red deer and wild boar, still have excess values of 137Cs.
They analysed 82 Burgundy truffles collected across Europe between 2010 and 2014.
The samples were harvested by trained truffle dogs in several natural habitats and plantations in Switzerland, Germany, France, Italy and Hungary.
All samples had negligible radioactivity, with 137Cs values ranging below the detection limit of 2 becquerels per kilogramme.
This is far below the tolerance value of 600 becquerels per kilogramme, meaning the truffles are safe for consumption, at least in the areas the researchers sampled from.
The researchers are unsure how their results would change if they had collected samples in areas with even higher 137Cs deposition, such as parts of Belarus or central Austria.
They speculate that the reason Burgundy truffles are less susceptible to radioactivity contamination than other fungi could be due to the way Tuber aestivum uptakes nutrients from the soil compared to other types of mushrooms.
The study was published in the journal Biogeosciences.