Modulating bioactive compounds and antioxidant potential in coffee beans: impact of roasting on amino acids, phenolics, proteins, and caffeine

Abstract

Abstract This study investigates the impact of different roasting conditions on the chemical and functional properties of Colombian coffee beans, focusing on phenolic compounds, caffeine, antioxidant activity, proteins, and amino acids. Coffee samples roasted under five levels—light, medium, city, French, and Italian—were analysed using HPLC, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and trolox equivalent antioxidant capacity assays. The results revealed a significant degradation of total chlorogenic acids (CQAs) with roasting intensity, exceeding 90% reduction in Italian roasts, particularly 5-CQA. In contrast, caffeine content remained relatively stable across all roast levels. Antioxidant capacity was maintained up to city roast but declined significantly in French and Italian roasts. Protein analysis showed that unroasted beans had detectable bands (32 and 22 kDa) corresponding to α- and β-chains, which disappeared in all roasted samples, indicating protein denaturation. Additionally, free amino acid content dropped markedly from 130.70 mg/100 g in green beans to 75.18 mg/100 g in the darkest roast. These findings suggest that moderate roasting (light to city) can preserve key bioactive compounds and antioxidant properties while enhancing flavour, making it optimal for functional coffee production. The study recommends further investigation into the bioavailability of thermally degraded phenolics and the sensory implications of roast-driven compositional changes in coffee.