Abstract: In order to study the effect of roasting temperature, duration and pH on the degradation of chlorogenic acid in coffee beans during processing, Arabica green coffee beans were roasted to different degrees. Changes in the pH, mass loss, moisture content, and the contents of 3-O-caffeoylquinic acid (3-O-CQA), 5-O-caffeoylquinic acid (5-O-CQA), 4-O-caffeoylquinic acid (4-O-CQA) and three isochlorogenic acids of samples induced by roasting at different temperatures for different durations were analyzed. The degradation kinetics of 3-O-CQA, 4-O-CQA and 5-O-CQA was modelled and validated using chemical reaction models. The results showed that moisture content and mass loss rate of roasted coffee beans respectively decreased and increased with roasting temperature and duration. The 3-O-CQA content decreased significantly with roasting temperature and time (P < 0.05). Compared with raw coffee beans, the content of 4-O-CQA and 5-O-CQA increased firstly and then decreased with the temperature rises, but decreased significantly with roasting duration (P < 0.05). The contents of 5-O-CQA and 4-O-CQA were significantly negatively correlated with pH and roasting duration (P < 0.05), and 3-O-CQA content was significantly negatively correlated with roasting temperature and duration (P < 0.05) but significantly positively correlated with moisture content (P < 0.05). The interaction of roasting temperature and duration showed a very significant effect on the degradation of chlorogenic acid (P < 0.001). The thermal degradation of chlorogenic acid and its two isomers followed a first-order kinetic model. In the chemical reaction models, 3-O-CQA was converted into 5-O-CQA and 4-O-CQA, and the concentrations of all three compounds decreased significantly with increasing pH and temperature (P < 0.05). The interaction between temperature and pH had a significant effect on chlorogenic acid degradation (P < 0.001). In short, the interaction of roasting temperature, duration and pH can promote the rapid degradation of chlorogenic acid in roasted coffee beans.

Key words: interaction; roasted coffee beans; chlorogenic acid; degradation; isomer conversion