Subcritical Water Hydrolysis of Citrus Pectin, Pea Protein Concentrate, and Their Mixture for Oligosaccharide and Peptide Production

• Author / Creator

  Vo, Hung Ha Phuoc

• Bioactive oligosaccharides and peptides have drawn great attention due to reported health benefits such as antidiabetic, anti-obesity, anticancer, anti-hypertensive, and antioxidant. The most common methods to produce oligosaccharides and peptides are enzymatic and acid hydrolysis which have multiple disadvantages such as being environmentally harmful, time consuming, expensive, and using complicated procedures. Therefore, the main objective of this thesis was to evaluate subcritical water processing as an ecofriendly technology to hydrolyze pectin and pea protein concentrate to obtain oligosaccharides and peptides, respectively. In the first study, citrus pectin was hydrolyzed at 135-200oC and 50 bar for 10-60 min using subcritical water, modified by either malic acid or citric acid, to obtain hexuronic acids and pectic oligosaccharides. The contents of hexuronic acids, pectic oligosaccharides, rhamnose, and the antioxidant activity of the obtained hydrolysates were determined. The results showed that with increasing temperature, the content of hexuronic acid significantly enhanced up to 0.63 g/g pectin at 200oC/50 bar/10 min in aqueous citric acid media. The main oligosaccharide in the hydrolysates was arabino-oligosaccharide with the highest content obtained at 160oC/50 bar/20 min with a molecular weight of 2.65 kDa. The main monosaccharide in the hydrolysates was rhamnose, which content increased at elevated temperature with a maximum value of 0.075 g/g pectin at 180oC/50 bar/10 min. In the second study, citrus pectin was added as a catalyst for pea protein concentrate hydrolysis due to its ability of releasing hexuronic acids into the media to obtain bioactive peptides. Subcritical water at 160-240oC and 50 bar for 10-60 min was employed. The degree of hydrolysis, the peptide size distribution, the hydrolysate antioxidant activity, the amino acid profile, the fluorescence intensity, and the total protein/peptide/amino acid content were determined. The degree of hydrolysis improved with increasing temperature with the highest value of 64.8% at 220oC/50 bar/10 min
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  using pectin as the catalyst compared to citric acid (27.2%). The peptide with molecular weight of 4.1 kDa was the dominant peptide in the hydrolysate. The DPPH- scavenging activity of protein hydrolysates using citric acid was significantly higher than the ones obtained with pectin. The hydrolysates with pectin, on the other hand, had significantly higher ferric reducing antioxidant activity than the ones obtained with citric acid, indicating that pectin and citric acid catalyzed the hydrolysis reaction in different patterns to produce peptides capable of accepting and donating hydrogen atoms, respectively

• Subjects / Keywords

  • Subcritical water
  • Peptide
  • Pea protein
  • Oligosaccharide
  • Citrus pectin

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-pz0e-wp82

• License

  This thesis is made available by the University of Alberta Library 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.