Use of FT-IR Spectra and PCA to the Bulk Characterization of Cell Wall Residues of Fruits and Vegetables Along a Fraction Process

Abstract

This study focuses on the analysis of polysaccharide residues from the cell walls of fruits and vegetables: tomato, potato, pumpkin, carrot and celery root. An alcohol-insoluble residue was prepared from plant material by extraction using the hot ethyl alcohol method and then cell wall fractions soluble in trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate, sodium carbonate and alkaline solution were sequentially extracted. Infrared spectroscopy combined with Fourier transform (FT-IR) was used to evaluate differences among cell wall residues and among species after each step of sequential extraction of pectins and hemicelluloses. Additionally, pectic substances were identified using an Automated Wet Chemistry Analyser. Principal component analysis (PCA) was applied to FT-IR spectra in two regions: 1,800–1,200 cm⁻¹ and 1,200–800 cm⁻¹ in order to distinguish different components of cell wall polysaccharides. This method also allowed us the possibility of highlighting the most important wavenumbers for each type of polysaccharide: 1,740, 1,610 and 1,240 cm⁻¹ denoting pectins or 1,370 and 1,317 cm⁻¹ denoting hemicelluloses and cellulose, respectively.