Carbon isotopic characterization of cider CO2 by isotope ratio mass spectrometry: a tool for quality and authenticity assessment
A. I. Cabañero, Laboratorio Arbitral Agroalimentario. Ministerio de Agricultura, Alimentación y Medio Ambiente, C/Aguarón 13, 28023 Madrid, Spain.
The cider market is an important sector of the food industry in certain regions. Adulteration of cider can happen in several ways: for example, by the addition of sugar, or of exogenous CO2 to certain types of cider. Because such practices are not allowed by either Spanish legislation or the legislation of other countries, it is essential to study possible methods to detect these unauthorized practices. For this purpose a procedure was required to study the stable carbon isotopic composition of CO2 in cider.
A liquid sample of cider was transferred to a vial and CO2 from the headspace of the vial was analyzed using a peripheral device interfaced to an isotope ratio mass spectrometer. Separation of the CO2 from water and ethanol was achieved using a gas chromatography column located in the peripheral device.
The values for repeatability and reproducibility obtained indicated the robustness of the method, which is required for routine analysis. Ninety cider samples from various origins were analyzed, most of which showed a 13C content consistent with the declared origin. The δ13C ranged from −24.80‰ to −20.89‰ for ciders with endogenous carbon dioxide (−22.74 ± 0.79‰) and −37.13‰ to −26.00‰ if industrial CO2 was added. Several samples were also suspected of C4 sugar addition prior to the fermentation.
A fast, accurate and simple method for cider adulteration detection was developed. The addition of exogenous CO2 as well as C4 sugar addition prior to fermentation could be detected. The method showed advantages over existing methods in term of simplicity (no sample preparation and very long-term stability of the sample), speed (less than 10 min/sample) and precision ((r ≤0.32 and R ≤0.42). Copyright © 2012 John Wiley & Sons, Ltd.