Dissertation
ADSORPTIVE RECOVERY OF POLYPHENOLIC ANTIOXIDANTS FROM WINERY BY-PRODUCTS USING POLYETHYLENE GLYCOL (PEG) GRAFTED SILICA PARTICLES
Doctor of Philosophy (PhD), Washington State University
01/2019
Handle:
https://hdl.handle.net/2376/111103
Abstract
The potential to use concentrated polyphenols extracted from grape pomace as a dietary supplement is high due to the polyphenols’ remarkable health-promoting characteristics. However, the widespread utilization of polyphenols from grape pomace is limited by inefficient recovery. This dissertation aims to develop and characterize a new purification process for the effective recovery of polyphenols from grape pomace extract. To achieve our goal, a novel adsorbent and co-solvent elution method were designed to recover polyphenols from grape pomace extract. First, a methoxy polyethylene glycol (mPEG) ligand capable of forming hydrogen bonds with polyphenols was grafted onto silica particles which were then used as an adsorbent. Grafting bare silica with mPEG introduced a high number of ether sites which facilitate hydrogen bonding between polyphenols and mPEG ligands; an increase in the adsorption capacity was therefore achieved by 7.1- and 11.4-fold compared to bare silica. Second, a series of binary solvent systems using PEG-200 or PEG-400 and water or ethanol as a co-solvent was developed for the effective release of polyphenols from mPEG-grafted silica particles. Approximately 99.9% of the adsorbed polyphenols was recovered using 50% PEG-400-ethanol co-solvent. Polyphenols recovered with mPEG-grafted silica particles showed up to ~12-fold higher potency in comparison to grape pomace extract. The higher potency seen in PEG co-solvent eluted polyphenols was attributed to enrichment of gallic acid, procyanidin-B2, and myricetin. In the last section, characterization of the adsorption of polyphenols extracted from grape pomace onto mPEG-grafted silica particles was performed. The adsorption isotherms, thermodynamics, and kinetics of the adsorption process were investigated. The adsorption was well-described with the Langmuir isotherm model and the adsorption process is exothermic, thermodynamically favorable, and spontaneous. Kinetics of the polyphenol adsorption are well-described with Lagergren’s pseudo-first-order rate model. Use of the Weber and Morris model suggested that both intraparticle diffusion and external mass transfer limitations play a role in regulating the adsorption of polyphenols onto mPEG-grafted particles. Favorable thermodynamics of the adsorption, rapid kinetics, and a strong affinity of mPEG grafted silica particles to polyphenols demonstrate that these particles can potentially be used in commercial applications for purification of polyphenols from grape pomace.
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Details
- Title
- ADSORPTIVE RECOVERY OF POLYPHENOLIC ANTIOXIDANTS FROM WINERY BY-PRODUCTS USING POLYETHYLENE GLYCOL (PEG) GRAFTED SILICA PARTICLES
- Creators
- Ayca Seker
- Contributors
- Shulin Chen (Advisor)Manuel Garcia Perez (Committee Member)Brian Clowers (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Systems Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 167
- Identifiers
- 99900581706601842
- Language
- English
- Resource Type
- Dissertation