Antioxidant Generation during Coffee Roasting: A Comparison and Interpretation from Three Complementary Assays

Area of Science:

• Food Chemistry
• Analytical Chemistry

Background:

• Coffee is a significant source of dietary antioxidants, with compounds present in green beans and others formed during roasting.
• Routine analytical methods for quantifying coffee's total antioxidant capacity are not universally accepted.

Purpose of the Study:

• To adapt and validate three complementary assays (Folin-Ciocalteu, ABTS, ORAC) for routine antioxidant capacity assessment.
• To determine the antioxidant capacities of coffee bean extracts across different roasting stages.

Main Methods:

• Adaptation and validation of Folin-Ciocalteu (FC), ABTS, and ORAC assays for beverage analysis.
• Measurement of antioxidant capacity in coffee bean extracts subjected to various roasting levels.

Main Results:

• All three assays demonstrated a progressive increase in antioxidant capacity from green beans to light roast coffee.
• Melanoidin formation during roasting contributed more to antioxidant capacity than chlorogenic acid (CGA) degradation.
• Assays showed variability in quantifying green bean antioxidant capacity relative to gallic acid (GA), but less so with CGA.

Conclusions:

• Coffee roasting enhances overall antioxidant activity, with melanoidins playing a key role.
• The choice of reference antioxidant (GA vs. CGA) impacts assay results, highlighting different sensitivities to various antioxidant molecules.
• Validated assays provide a reliable method for assessing antioxidant changes during coffee processing.