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A predictive spatial model for roasted coffee using oxygen isotopes of α‐cellulose
Author(s) -
Driscoll Avery W.,
Howa John D.,
Bitter Nicholas Q.,
Ehleringer James R.
Publication year - 2020
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8626
Subject(s) - cellulose , chemistry , isotopes of oxygen , coffee bean , oxygen isotope ratio cycle , isotope ratio mass spectrometry , relative humidity , coffea arabica , green coffee , stable isotope ratio , isotope , oxygen , mass spectrometry , food science , chromatography , botany , nuclear chemistry , organic chemistry , meteorology , physics , quantum mechanics , biology
Rationale Fraudulent region‐of‐origin labeling is a concern for high‐value, globally traded commodities such as coffee. The oxygen isotope ratio of cellulose is a useful geographic tracer, as it integrates climate and source water signals. A predictive spatial model (“isoscape”) of the δ 18 O values of coffee bean cellulose is generated to evaluate coffee region‐of‐origin claims. Methods The oxygen isotope ratio of α‐cellulose extracted from roasted coffee beans was measured via high‐temperature conversion elemental analyzer/isotope ratio mass spectrometry (TC‐EA/IRMS) and used to calculate the δ 18 O value of coffee bean water. The 18 O enrichment of coffee bean water relative to the δ 18 O value of local precipitation was modeled as a function of local temperature and humidity. This function was incorporated into a mechanistic model of cellulose δ 18 O values to predict the δ 18 O values of coffee bean cellulose across coffee‐producing regions globally. Results The δ 18 O values of analyzed coffee bean cellulose ranged from approximately +22‰ to +42‰ (V‐SMOW). As expected, coffees grown in the same region tended to have similar isotope ratios, and the δ 18 O value of coffee bean cellulose was generally higher than the δ 18 O value of modeled stem cellulose for the region. Modeled δ 18 O values of coffee cellulose were within ±2.3‰ of the measured δ 18 O value of coffee cellulose. Conclusions The oxygen isotope ratio of coffee bean cellulose is a useful indicator of region‐of‐origin and varies predictably in response to climatic factors and precipitation isotope ratios. The isoscape of coffee bean cellulose δ 18 O values from this study provides a quantitative tool that can be applied to region‐of‐origin verification of roasted coffee at the point‐of‐sale.