Use of FT-IR spectroscopy to follow the effect of processing in cell wall polysaccharide extracts of a sun-dried pear

The sun-dried pear is a traditional Portuguese food product with unique organoleptic characteristics. In order to understand the modifications that occur during the drying process, cell wall extracts were prepared from dried and fresh tissues. Cell wall polymers were solubilised from the CWM by sequential extraction with aqueous solutions of CDTA, Na2CO3, and KOH, with increasing strengths, to leave the cellulosic residue. The polysaccharides present in the different extracts were characterised by sugar analysis and by FT-IR spectroscopy in the region between 1200 and 850 cm-1. The spectra analysis followed by chemometrics allowed us to distinguish the fresh from the sun-dried pear extracts in CDTA, Na2CO3, and KOH precipitates. These extracts contain pectic polysaccharides rich in GalA and Xyl-rich hemicellulosic polysaccharides (xylans). The selection of the most important wavenumbers allowed us to identify the spectral region related to GalA in pectic polysaccharide extracts in the range between 1120 and 990 cm-1. This study shows the potential of the FT-IR spectroscopy and multivariate information in the discrimination of cell wall extracts from dried and fresh pears.