Tracking Aromatic Volatile Biomarkers Through Coffee Bean Postharvest Stages

TL;DR

This review explores how aromatic volatile compounds in coffee beans change during postharvest stages, offering a chemical basis for monitoring quality and processing.

Contribution

The paper provides a comprehensive overview of volatile biomarkers across coffee postharvest stages, linking them to processing quality and technological standardization.

Findings

Volatile compounds like aldehydes and esters serve as biomarkers for ripeness and fermentation balance.

Pyrazines and thiols during roasting reflect the bean's postharvest history and roast degree.

Volatile biomarkers can help differentiate coffee lots and monitor oxidation stability during drying.

Abstract

This review synthesizes recent evidence on the generation and behavior of volatile biomarkers throughout the main postharvest stages of coffee, highlighting their potential for technological standardization. During harvest, aldehydes, furans, and lactones reflect ripeness and the presence of physiological defects, thereby influencing the formation of other volatile groups in subsequent stages. During pulping and fermentation, the metabolism of yeasts and lactic and acetic acid bacteria produces alcohols, acids, and esters (such as 2-phenylethanol, ethyl acetate, and methyl phenylacetate), which function as biomarkers of proper mucilage management and a balanced initial fermentation. In drying, the evolution of aldehydes derived from lipid oxidation and the retention of aromatic esters provide insights into dehydration kinetics and the stability of green coffee against oxidation. Finally, during roasting, volatile pyrazines, furans, thiols, and phenols integrate the entire postharvest history of the bean and enable inferences about roast degree, thermal overexposure, and final aroma development. Overall, the volatile biomarkers described here provide a robust chemical basis for objective monitoring of the postharvest process and the differentiation of coffee lots, although further studies are needed to define critical ranges by origin and processing system, standardize analytical methodologies, and quantitatively link these compounds to commercial quality parameters.

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