A determination of the composition and structure of the polysaccharides fractions isolated from apple cell wall based on FT-IR and FT-Raman spectra supported by PCA analysis

Abstract

Generally in plants, cell wall polysaccharides are the main determinants of tissue properties and contents of an essential part of dietary fiber, prebiotics, or cosmetic ingredients. Therefore, evaluation of the content and structure of polysaccharides is crucial to understanding and controlling their functionality. Vibrational spectroscopy has already proven to be very useful in studying wall-based compounds. Here, it was proposed to use the FT-IR and FT-Raman spectra combined with PCA analysis to discriminate and distinguish pectic and hemicellulosic fractions isolated from apple parenchyma as an example. Reference measurements have been done on commercially available polysaccharides in order to identify relevant fingerprint bands. The similarities of different polysaccharide fractions from apple: water, imidazole, dilute alkali-soluble polysaccharides (WSP, ISP, DASP, respectively), and polysaccharides soluble in three potassium hydroxide concentration (KOHs) to the reference polysaccharides were found. In the case of both types of spectroscopy, the region below 1800 cm−1 was used to differentiate the samples. The results showed that the WSP, ISP, and DASP fractions have band patterns similar to the pectic polysaccharides, but also contain bands characteristic of polysaccharides containing arabinan and galactan. While the KOH fractions showed the greatest similarities to the hemicellulose polysaccharides, especially the glucomannan and xyloglucan. The results showed that FT-IR and FT-Raman spectra supported by PCA can be useful for studying the structure of polysaccharide fractions directly isolated from plant cell wall material.