Method of producing a pectic polysaccharide isolate enriched in rhamnogalacturonan-I

A method of producing a hydrolysed pectic polysaccharide isolate enriched in rhamnogalacturonan-I, the method comprising:

• (a) obtaining a pectin-rich substrate:
• (i) selected from pomace, aqueous extract of pomace, and combinations thereof,
• (ii) obtained from one or more crops selected from apple, pear, carrot, and chicory without the use of organic solvent, and
• (iii) comprising at least 3% by weight of dry matter of pectic polysaccharides having a backbone consisting of galacturonic acid residues and rhamnose residues, the rhamnose residues being contained in a backbone consisting of galacturonic acid residues and rhamnose residues, said rhamnose residues being contained in alpha (1→4)-galacturonic-alpha (1→2)-rhamnose residues;
• (b) subjecting the pectin-rich substrate to enzymatic treatment, comprising one or more pectinases selected from pectin lyase (EC 4.2.2.10), pectate lyase (EC 4.2.2.2), endo-polygalacturonase (EC 3.2.1.15), exopolygalacturonase (EC 3.2.1.67 and EC 3.2.1.82) to partially hydrolyse the pectic polysaccharides;
• (c) subjecting an aqueous liquid containing the partially hydrolysed pectic polysaccharides to solid-liquid separation to produce a liquid fraction comprising partially hydrolysed pectic polysaccharides, said solid-liquid separation employing a solid-liquid separation technique selected from sedimentation, decanting, centrifugation, hydrocyclones, filtration, and combinations thereof;
• (d) subjecting the liquid fraction comprising the partially hydrolysed pectic polysaccharides to ultrafiltration using an ultrafiltration membrane having a molecular weight cut-off in the range of 5 to 100 kDa;
• and
• (e) recovering and drying the ultrafiltration retentate, the recovered ultrafiltration retentate preferably contains galacturonic acid residues and rhamnose residues in a molar ratio of not more than 6:1.