It has commonly been accepted that the most diagnostic region
characterizing the pectin and lignin constituents of fibers is the
1400–1800 cm−1 region of IR spectra (Wrobel-Kwiatkowska et al.,
2009). The characteristic band of pectin is that at 1733 cm−1, which
corresponds to the vibration ofthe free carboxyl group. The component
at about 1610 cm−1 corresponds to the symmetric stretching
vibrations of ionized COO− groups of pectins. It should be noted
that the degree of fiber retting (pectin release) follows the intensity of the pectin bands. Therefore, it was suggested that the data
for the pectin content measured by FT-IR is more precise than those
from the biochemical method.