Subcritical water extraction and reaction of bioactive pectic polysaccharides

• Author / Creator

  Valdivieso, Carla S

• Natural pectic polysaccharides have drawn considerable attention as promising multifunctional materials for food, pharmaceutical and biomedical uses. Pectic polysaccharides production, however, involves the utilization of inorganic acids such as sulfuric, hydrochloric and nitric acids. The objective of this study was to isolate novel bioactive pectic polysaccharides from pomegranate Punica granatum L. biomass using a subcritical binary fluid system as well as to obtain pectin-based sols under subcritical water conditions prior to the production of pectin-based 2D films or 3D cryogel structures. Pomegranate pectic polysaccharides (PPs) were extracted using a semi-continuous subcritical water system at 100-140˚C, 50 bar and 5 mL/min with binary solvent systems (aqueous citric acid or aqueous ethanol) and, pectin-based sols were formed within a stirred-tubular subcritical water batch reactor at 100˚C and 70 bar. The variables evaluated were yield, galacturonic acid content, degree of esterification and anti-oxidant properties of isolated pomegranate pectic polysaccharides. Pectin-based sols were then used to obtain films and cryogels. The physico-chemical, mechanical, optical and functional properties of such gels were determined. These results showed that subcritical water and the above subcritical binary aqueous systems at 120˚C/50 bar and 30 min favored the extraction of bioactive pomegranate pectic polysaccharides with high galacturonic acid content (>70%) and degree of esterification (>60%). The total phenolic content and the anti-oxidant activity of extracted PPs were 152.9 mg GAE/g PPs and I %DPPH >87%, respectively. Pectin-based sols obtained with subcritical aqueous citric acid at 100˚C/70 bar led to flexible films with tensile strength, percent elongation and phenolics release capacity comparable to pectin-based films produced by the traditional sol-gel method. Subcritical sol formation and freeze-dried gel integration led to lightweight and highly porous bioactive pectin-based cryogels. Through this thesis, subcritical water technology has shown to be a versatile, environment-friendly and sustainable alternative that can be used for pomegranate biomass conversion into value-added products as well as in combination with other processes to obtain novel biocomposite materials.

• Subjects / Keywords

  • Bioactive films
  • Extraction
  • Pectic polysaccharides
  • Pomegranate biomass
  • Subcritical water

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R37659T2F

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.