Rapid Authentication of Coffee Blends and Quantification of 16‑O‑Methylcafestol in Roasted Coffee Beans by Nuclear Magnetic Resonance

• Published in: Journal of agricultural and food chemistry Vol. 62; no. 51; pp. 12309 - 12314
• Main Authors: Schievano, Elisabetta, Finotello, Claudia, De Angelis, Elisabetta, Mammi, Stefano, Navarini, Luciano
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24.12.2014; American Chemical Society, Books and Journals Division
• Subjects: Coffea - chemistry; Coffea arabica; Coffea canephora; Coffee - chemistry; coffee beans; Cooking; detection limit; Diterpenes - analysis; esterification; Food Contamination - analysis; Magnetic Resonance Imaging - methods; nuclear magnetic resonance spectroscopy; Plant Extracts - analysis; quantitative analysis; Seeds - chemistry; Coffea canephora var. Robusta; coffee blends; food control; 16-O-methylcafestol; qHNMR
• DOI: 10.1021/jf505013d
• ISSN: 0021-8561; 1520-5118

Roasted coffee is subject to commercial frauds, because the high-quality Coffea arabica species, described as “100% Arabica” or “Highland coffee”, is often mixed with the less expensive Coffea canephora var. Robusta. The quantification of 16-O-methylcafestol (16-OMC) is useful to monitor the authenticity of the products as well as the Robusta content in blends. The German standard method DIN 10779 is used in the determination of 16-OMC in roasted coffee beans to detect C. canephora in blends, but it is laborious and time-consuming. Here, we introduce a new method that provides a quantitative determination of esterified 16-OMC directly in coffee extracts by means of high-resolution proton nuclear magnetic resonance spectroscopy. Limit of detection and limit of quantitation were 5 and 20 mg/kg, respectively, which are adequate to detect the presence of Robusta at percentages lower than 0.9%. The proposed method is much faster, more sensitive, and much more reproducible than the DIN standard method.