Measurement of 13C/12 C Ratios of Sugars, Malic Acid, and Citric Acid as Authenticity Probes of Citrus Juices and Concentrates
abstract The carbon-13 content of sugars, malic acid, and citric acid has been determined in authentic orange, lemon, and tangerine juices. After a cleanup step, sugars and organic acids were separated from each other by an anion-exchange process, and pure malic and citric acids were isolated by preparative reversed-phase liquid chromatography. This method has been applied to the stable isotope analysis of citrus juice samples of different botanical and geographical origins and of different years. Correlations between the carbon isotope ratios of all metabolites have been found, and typical ranges for the differences in δ13C values between them have been defined for each fruit. These data provide new tools for detecting adulterations that cannot be detected by the conventional carbon-13 method with the whole juice.
