Targeted and non-targeted detection of lemon juice adulteration by LC-MS and chemometrics

ABSTRACT

Economically motivated adulteration (EMA) of lemon juice was detected by LC-MS and principal component analysis (PCA). Twenty-two batches of freshly squeezed lemon juice were adulterated by adding an aqueous solution containing 5% citric acid and 6% sucrose to pure lemon juice to obtain 30%, 60% and 100% lemon juice samples. Their total titratable acidities, °Brix and pH values were measured, and then all the lemon juice samples were subject to LC-MS analysis. Concentrations of hesperidin and eriocitrin, major phenolic components of lemon juice, were quantified. The PCA score plots for LC-MS datasets were used to preview the classification of pure and adulterated lemon juice samples. Results showed a large inherent variability in the chemical properties among 22 batches of 100% lemon juice samples. Measurement or quantitation of one or several chemical properties (targeted detection) was not effective in detecting lemon juice adulteration. However, by using the LC-MS datasets, including both chromatographic and mass spectrometric information, 100% lemon juice samples were successfully differentiated from adulterated samples containing 30% lemon juice in the PCA score plot. LC-MS coupled with chemometric analysis can be a complement to existing methods for detecting juice adulteration.

KEYWORDS:

• Lemon juice
• adulteration
• LC-MS
• Orbitrap
• principal component analysis
• chemometrics

Acknowledgements

The authors would like to thank Dr Artemio Z. Tulio, Jr and Zhaobin Wang for performing the total titratable acidity, °Brix and pH measurements; Jing Bai and Xuelin Zhang from the Illinois Institute of Technology for preparing lemon juice samples; Dr Kevin Kubachka from the USFDA Forensic Chemistry Center for providing IRMS knowledge; and Dr Ralf Tautenhahn from Thermo Fisher Scientific, Inc. for technical support.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

This project was supported in part by an appointment to the Research Participation Program at the Center for Food Safety & Applied Nutrition administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the US DOE and the USFDA.