Fourier Transform Infrared
and Physicochemical Analyses
of Roasted Coffee
- Publication date
- Publisher
Abstract
In this study, Brazilian coffee beans processed to different
stages
of roast at 210, 220, 230, and 240 °C were analyzed for pH value,
titratable acidity, moisture content, and color lightness. Fourier
transform infrared (FTIR) spectroscopy, in conjunction with principal
component analysis, was conducted to study the effects of process
time and temperature on the IR-active components of the acetyl acetate
extract of the roasted coffee. The results showed that high-temperature–short-time
resulted in higher moisture content, higher pH value, and higher titratable
acidity when the beans were roasted beyond the start-of-second-crack
stage, as compare to low-temperature–long-time process (LTLT).
The LTLT process also resulted in greater IR absorbance for aldehydes,
ketones, aliphatic acids, aromatic acids, and caffeine carbonyl bands
on the FTIR spectra. Clusters for principal component score plots
were well separated, indicating that the changes IR-active components
in the coffee extracts, due to the different roasting treatments,
can be discriminated by the FTIR technique. On the basis of the loading
plots of principal components, changes of IR-active compounds in the
coffee extract at various stages of roasting were discussed