Luigi Mondello and colleagues said current methods cannot reliably discriminate between the natural and synthetic version of the main aroma compound.
The most valuable species is Tuber magnatum Pico (better known as “Alba white truffle”), in which bis(methylthio)methane is the key aroma compound.
Synthetic bis(methylthio)methane has been approved by the World Health Organization as a food additive but some foods made with this cheaper compound may still command a premium price if consumers believe they contain authentic white truffles.
Italy and France investigate truffle sector
The issue is not hypothetical as Italian and French authority investigations to verify truffle conformity this year shows.
The price of a kilo of truffle is between €500 and €1,200, according to La Direction générale de la concurrence, de la consommation et de la répression des frauds (DGCCRF) in France.
The fungi are usually used as flavouring additives due to distinctive aroma.
Italian and French investigations revealed fraudulent practice involving two managers from French and Italian establishments that were customers and suppliers to each other and had family ties.
Following this intervention, the French manager agreed to distance company activities with the Italian operator and review labelling of truffle products sold.
In the control, 42 items were analysed, mostly products containing truffles, truffle juice or flavour.
It revealed labeling defects in more than half of the cases as 16 products did not comply with rules, five did not correctly inform the consumer about nature of the truffle used and three were deficient in truffles compared to the amount announced.
DGCCRF said the offense rate is explained by operators not taking into account a 2016 revision of labelling requirements and planting areas being insufficient in terms of demand.
Truffle growers are considering a label or brand to give product quality assurances to the consumer.
Carbon isotope ratios
Researchers exploited differences in carbon isotope ratios between plant- and petroleum-derived versions of bis(methylthio)methane.
They optimized the technique of multidimensional gas chromatography coupled to combustion-isotope ratio mass spectrometry (GC-C-IRMS).
An HS-SPME MDGC-C-IRMS with simultaneous quadrupole MS detection was applied to resolve the coelution occurring with other components.
The team used the method to compare the carbon isotope ratios of bis(methylthio)methane from 24 genuine white truffles harvested at different locations in Italy, two commercial intact truffles and 14 commercial samples of pasta, sauce, olive oil, cream, honey and fresh cheese flavoured with truffle aroma were analysed.
The approach discriminated between foods that contained synthetic truffle aroma or a mixture of synthetic and natural aromas and it could distinguish among products containing white truffle and those with other species of the fungus.
Source: Anal. Chem., 2018, 90 (11), pp 6610-6617
“Multidimensional Gas Chromatography Coupled to Combustion-Isotope Ratio Mass Spectrometry/Quadrupole MS with a Low-Bleed Ionic Liquid Secondary Column for the Authentication of Truffles and Products Containing Truffle”
Authors: Danilo Sciarrone, Antonino Schepis, Mariosimone Zoccali, Paola Donato, Federico Vita, Donato Creti, Amedeo Alpi and Luigi Mondello