A new research paper has outlined the use of gas chromatography and chemometrics in detecting fraud in Italian grappa spirit.
In ‘An Authentication Study on Grappa Spirit’ by Silvia Adruini, Alessandro Zappi, Marcello Locatelli, Salvatore Sgro and Dora Melucci, Italian researchers developed a method to authenticate grappa using alcohol measurement and gas chromatography analysis.
“Grappa” is a traditional Italian spirit drink produced from the distillation of fermented grape marc and seeds after winemaking. In the EU Spirit Drink Regulations, “grappa” is a protected name, and it has to be produced from Italian cultivated and processed grapes.
A chemometric model was created and validated with the aim of verifying the authenticity of two suspicious samples of a product labelled as “grappa”. In all, 123 spirit samples were analysed to train and test the model. Samples were both grappa and other spirits as wine, grain, apple, and pear spirits.
For the linear discriminant analysis (LDA) model test, both cross-validation and the projection of 29 of the analysed samples (not used for the training phase) were applied, in both cases with a NER higher than 97%. The suspicious samples projected onto the LDA model were classified as “wine spirit”, demonstrating that they were different from the grappa samples used for the model training.
However, two further one-class modelisation analyses carried out on the single classes, “grappa” and “wine spirit”, demonstrated that the suspicious samples were very different also from the wine spirit samples. Therefore, the suspicious samples may probably be considered adulterated grappa samples rather than wine spirit samples sold as grappa.
Of these, 43 were “grappa” and the others were spirit drinks from wine, grapes, apples and pears. The samples were divided into a training set (94 samples) of a chemometric model using LDA, and a validation set (29 samples) was used to test the model and gave good discrimination between the different types of spirits.
Two suspicious samples of “grappa” seized by Italian customs were also examined and analysed. Visual examination revealed differences in the cork closures and barcodes. The analytical results on the chemometric model indicated the two samples were wine spirit rather than “grappa”.
The chemometric approach has already been successfully applied several times for authentication purposes, for example in honey or saffron samples. Nowadays, chemometrics is largely used in analytical research, and also the American Food and Drug Administration is starting to recommend its use in analytical procedures.
This research started from a case study. The Italian Customs and Monopolies Agency (Agenzia delle Dogane e Monopoli) seized a batch of bottles of spirit labelled as “Italian grappa”; however, some suspicions arose about the authenticity of such products, due to the flavour of the spirit not compliant with the usual one perceived by some consumers. Therefore, the chemical law parameters of the suspicious samples were analysed and compared to those of other grappa samples.
Some other classes of spirits that can be used to adulterate the grappa were analysed in the same way. Thus, a multivariate classification model was computed and validated to predict the belonging spirit-class of the suspicious samples.
