Determination of the degree of esterification (DE) of pectin
using FourierTransform Infrared (FTIR) spectrometry
Samples containing pectin were desiccated prior to FTIR analy-
sis. FTIR spectra of the samples were recorded using a Bruker IFS66
instrument from 800 to 2000 cm−1. The measuring resolution was
3 cm−1. The resultant spectra were smoothed to remove the noise
and the second-derivative spectra were obtained using the OMNIC
E.S.P. 5.1 software.DE was determined according to Pappas et al.
(2004) equations:
where A1740 and A1630 were defined as the absorbance intensities of the bands for methyl-esterified and non methyl-esterified
carboxyl groups at 1740 cm −1 and 1630 cm−1, respectively.These
strong mixed peaks are caused by ester and carboxylic vibrations
(Manrique &Lajolo,2002).