Aroma binding and stability in brewed coffee: A case study of 2-furfurylthiol

The aroma stability of fresh coffee brew was investigated during storage over 60 min, there was a substantial reduction in available 2-furfurylthiol (2-FFT) (84%), methanethiol (72%), 3-methyl-1H-pyrole (68%) and an increase of 2-pentylfuran (65%). It is proposed that 2-FFT was reduced through reversible chemical binding and irreversible losses. Bound 2-FFT was released after cysteine addition, thereby demonstrating that a reversible binding reaction was the dominant mechanism of 2-FFT loss in natural coffee brew. The reduction in available 2-FFT was investigated at different pH and temperatures. At high pH, the reversible binding of 2-FFT was shown to protect 2-FFT from irreversible losses, while irreversible losses led to the reduction of total 2-FFT at low pH. A model reaction system was developed and a potential conjugate, hydroxyhydroquinone, was reacted with 2-FFT. Hydroxyhydroquinone also showed 2-FFT was released after cysteine addition at high pH.