2.7. Fourier Transform Infrared Spectroscopy (FTIR) analysis
Pectin particles were mixed with KBr (1:100) and pressed into
KBr pellets before FTIR analysis. FTIR spectra Nicolet 5700 (Thermo
Fisher Scientific, USA) was applied at the absorbance mode in the
frequency range of 4000–400 cm1 at a resolution of 4 cm1. The
absorption spectra were obtained after denoising and baseline
correction.
2.8. Determination of physico-chemical properties of pectin
2.8.1. Intrinsic viscosity and viscosity-average molecular weight (MV)
Intrinsic viscosity was measured with an Ubbelohde capillary
viscometer with a capillary diameter of 0.58 mm (Jiaojiang Glass
Instrument Co., Taizhou, China) at 25 ± 0.1 C. 0.1 M phosphate
buffer (pH = 7.0) was used as the solvent. 3.0 mg of dried sample
was dissolved in 10 mL solvent. According to the efflux time of
the pectin solution (t) and the solvent (t0), the relative viscosity
(gr = t/t0) was obtained. Specific viscosity was calculated from the
formula gsp = (t t0)/t0. Intrinsic viscosity could be obtained by
one point method according to the following equation