Application of carbon and hydrogen stable isotope analyses to detect exogenous citric acid in Japanese apricot liqueur

•Carbon and hydrogen stable isotope analyses can detect citric acid in liqueur.•Carbon stable isotope analysis can detect citric acid originating from C3 plants.•Hydrogen stable isotope analysis can detect citric acid from C3 and C4 plants.•Our analyses will help control the authenticity of Japanese apricot liqueurs.

Japanese apricot liqueur manufacturers are required to control the quality and authenticity of their liqueur products. Citric acid made from corn is the main acidulant used in commercial liqueurs. In this study, we conducted spiking experiments and carbon and hydrogen stable isotope analyses to detect exogenous citric acid used as an acidulant in Japanese apricot liqueurs. Our results showed that the δ13C values detected exogenous citric acid originating from C4 plants but not from C3 plants. The δ2H values of citric acid decreased as the amount of citric acid added increased, whether the citric acid originated from C3 or C4 plants. Commercial liqueurs with declared added acidulant provided higher δ13C values and lower δ2H values than did authentic liqueurs and commercial liqueurs with no declared added acidulant. Carbon and hydrogen stable isotope analyses are suitable as routine methods for detecting exogenous citric acid in Japanese apricot liqueur.