Changes in stable isotope ratios in PDO cheese related to the area of production and green forage availability: the case study of Pecorino Siciliano

RATIONALE: Labeled cheese characteristics reflect the territory features and the feeds supplied to animals. No studies have investigated the variations of cheese stable isotope ratios within a PDO area and few studies focused on the effect of animal feeding system. For traceability purposes, it is important to know how and whether these issues affect SIRs in a PDO cheese. METHODS: Thirty-six Pecorino Siciliano cheese samples were collected in three east-Sicilian areas (Catania, Iblei and Nebrodi) during grazing and stall-feeding seasons. Herbage, hay and concentrate supplied to animals were also sampled. The stable isotope ratios of C, N, H, O and S were measured on the defatted cheese and on each feed using an isotope ratio mass spectrometer coupled with an elemental analyser. RESULTS: Multivariate analysis, performed by using the stepwise procedure to C, N, H, O and S SIRs, selected S and N SIRs as those allowing the best discrimination among the three areas (Catania, Iblei and Nebrodi). The discriminant model correctly classified the 97.2% of the cheeses. The discrimination of the feeding system (presence or absence of green forage) was less efficient; it correctly classified the 86.1% of the cheeses samples to their respective group. Carbon and oxygen isotope ratios allowed the best discrimination between the two systems. CONCLUSIONS: This study widens the horizons related to cheese PDO authentication. It demonstrates that the variability in element SIRs could produce a geographic discrimination even within a PDO area; this leads to the research of new tools in the traceability issue, such as the isoscape approach. Moreover, this study suggests that SIRs determination could be useful also for discriminating cheese arising from a stall feeding system from cheese produced on a green forage-based feeding system, which gives benefit in terms of environmental impact, animal welfare and human health.