A predictive spatial model for roasted coffee using oxygen isotopes of α-cellulose.
RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020;
34:e8626. [PMID:
31658500 DOI:
10.1002/rcm.8626]
[Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 09/11/2019] [Accepted: 10/03/2019] [Indexed: 06/10/2023]
Abstract
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 δ18 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 δ18 O value of coffee bean water. The 18 O enrichment of coffee bean water relative to the δ18 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 δ18 O values to predict the δ18 O values of coffee bean cellulose across coffee-producing regions globally.
RESULTS
The δ18 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 δ18 O value of coffee bean cellulose was generally higher than the δ18 O value of modeled stem cellulose for the region. Modeled δ18 O values of coffee cellulose were within ±2.3‰ of the measured δ18 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 δ18 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.
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