Optimization of high pressure processing-assisted extraction of pectic polysaccharides from three berries

High pressure processing (HPP) is a promising assistive method to extract pectic polysaccharides with high rhamnogalacturonan I (RG-I) domain and berries are sources of such pectic polysaccharides. This study extracts pectic polysaccharides from goji berry, raspberry, and cranberry, examines how HPP influences the pectic polysaccharide structure of three berries and provides a basis for the extraction and modification of pectic polysaccharides of specific structure and bioactivity. An orthogonal test was performed to optimize the HPP-assisted alkali method to extract the high yield and high RG-I content pectic polysaccharides from three berries. Structural information of pectic polysaccharides extracted by HPP method and conventional methods were compared from the perspectives of monosaccharide composition, molecular weight, FTIR and NMR. For raspberry, the optimal conditions consisted of a pressure of 500 MPa, a pH of 13, and a pressure-holding time of 12 min, while the optimal conditions for goji berry and cranberry were both 400 MPa, pH 13, 15 min. Under the optimal conditions, the yields for goji berry, raspberry, and cranberry were 10.49%, 16.63%, and 17.52%, respectively, and RG-I contents were 81.85%, 83.30%, and 63.22%, respectively. HPP showed an effect to degrade HG backbones and side chains and increase the RG-I content to some extent. HPP-assisted alkali method was revealed to be an efficient method to extract high RG-I content pectic polysaccharides, especially for cranberry, and was a potential method to modify pectic polysaccharide structure in a certain way.