Impact of thermally induced wall breakage on the structural properties of water-soluble polysaccharides in chickpeas

The present work aimed to elucidate the influence of wall breakage induced by thermal processing on the molecular, structural, and antioxidant activities of water-soluble polysaccharides in chickpeas. Different extents of cell wall disruption were observed by fluorescence microscopy in chickpea cotyledons. Moreover, a decreasing fluorescence intensity of cell wall fragments was observed in the flour residues upon heat fluidization, autoclaving, and microwave heating, and the polysaccharide extraction rates were increased by 31.47%, 25.52%, and 9.79%, respectively. Furthermore, WPUCP, WPHCP, WPMCP, and WPACP (water-soluble polysaccharides from unprocessed, heat fluidized, microwaved, and autoclaved chickpeas, respectively) were RG-I (rhamnogalacturonan-I)-enriched pectic polysaccharides composed of galactose, arabinose, galacturonic acid, and rhamnose. After chickpea thermal processing, the degrees of branching decreased to 2.87, 3.79, and 2.53 in WPHCP, WPMCP, and WPACP, respectively, and the molecular weights were reduced by 46.46%, 24.83%, and 59.91%, respectively. Structural analysis showed that the semicrystalline regions of WPHCP, WPMCP, and WPACP were slightly damaged without changing the functional groups, but their thermal stability decreased. Interestingly, WPACP formed an ordered conformation (microporous network structure) through the formation of hydrogen bonds. Moreover, the antioxidant activities of WPHCP, WPMCP, and WPACP were enhanced, and the strongest radical scavenging activity was observed for WPHCP.

Automated summary

The present study aimed to investigate the influence of thermal processing on the water-soluble polysaccharides in chickpeas. It was found that thermal processing caused cell wall breakage and increased the extraction rate of polysaccharides. However, it also led to a decrease in branching degree and molecular weights, as well as changes in the structure and thermal stability of polysaccharides. Interestingly, thermal processing enhanced the antioxidant activities of the polysaccharides.