Effect of Roasting Degree on Major Coffee Compounds: A Comparative Study between Coffee Beans with and without Supercritical CO2 Decaffeination Treatment

Abstract

Coffee is a beverage that is consumed worldwide, and the demand for decaffeinated coffee has increased in recent years. This study aimed to investigate the effect of roasting conditions on the concentration of physiologically active compounds in coffee beans with and without supercritical CO2 decaffeination treatment. Decaffeination treatment markedly reduced caffeine concentration and slightly reduced trigonelline concentration in the coffee beans, whereas the concentrations of chlorogenic acids (chlorogenic acid, cryptochlorogenic acid, and neochlorogenic acid) were largely unchanged. Roasting was performed using a hot-air coffee roaster machine and the coffee beans were treated at different peak temperatures (125–250℃), different hold times at the peak temperature (120–240 s), and different temperature increase times to reach the peak temperature (60–180 s). Roasting conditions such as long hold and long temperature rise times at high temperatures (≥ 225℃) significantly degraded coffee compounds except for caffeine, with similar degradation rates between non-decaffeinated and decaffeinated coffee beans. In contrast, the L* value of decaffeinated coffee decreased with less thermal history compared to that of non-decaffeinated coffee. This allowed for the complete roasting of decaffeinated coffee with a lower thermal history compared to those of non-decaffeinated counterparts, suppressing the degradation of several coffee compounds. For example, comparing the similar L* values between coffee beans with and without decaffeination treatment, it was found that the former tended to contain more chlorogenic acid. Generally, decaffeination results in the loss of physiologically active compounds along with caffeine, which is a major concern. However, this study showed that appropriate control of decaffeination and roasting conditions can limit the degradation of several valuable coffee compounds, such as trigonelline and chlorogenic acid.