Graduate Thesis Or Dissertation

 

The preparation of common prebiotic oligosaccharides with defined degree of polymerization Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5q47rw889

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  • Prebiotics are a subset of dietary fiber that is growing in demand within the food industry. The health benefits of prebiotics have been well established, leading to the increase in its incorporation into various food products. Given the importance of prebiotics as functional ingredients, it is important to understand their sensory properties. However, such knowledge is not well established because commercially available prebiotics are a mixture of saccharides with varying degree of polymerization (DP), including mono- and disaccharides. The goals of this research were to develop fractionation methods to prepare common prebiotic oligosaccharides [i.e., fructooligosaccharides (FOS), galacto-oligosaccharides (GOS), and xylooligosaccharides (XOS)] with well-defined DP from commercially available prebiotic oligosaccharides mixtures and to conduct chemical analysis to characterize the fractionated prebiotic oligosaccharides. To achieve the first goal, column chromatography was performed following principles of adsorption chromatography, whereby the analyte adsorbed to the surface of the stationary phase, then desorb and elute from the column by using a gradient mobile phase. During the chromatography run, cellulose was used as the stationary phase, whereas ethanol/water mixtures were used as the mobile phase. The packing material and solvents were selected based on their Generally Recognized as Safe (GRAS) status. The mobile phase was delivered to the column as a step gradient within the range of 85%-55% ethanol. The percentage used was determined by the solubility of the oligosaccharide, which were impacted by their chemical structures with heterogenous saccharides being more soluble (i.e., FOS, GOS) than homogenous saccharides (i.e., XOS). The specifics for chromatography conditions (i.e., sample load, volume of solvent, and mobile phase composition) differ based on the class of oligosaccharide and were tailored to best fit the separation capabilities of each oligosaccharide. It was important to find a balance between resolution, which impacted yield, and time taken for the chromatography run. Although the amount produced had relatively low (30-75%) recovery, the study made use of the fact that economical preparation does not require baseline resolution since the commercially available starting materials were relatively inexpensive. To confirm the identify and purity of the fractionated oligosaccharide preparations (FOS DP3, FOS DP4, GOS DP3, GOS DP4, XOS DP2, XOS DP3, and XOS DP4), various chemical analyses were performed. These included total carbohydrate analysis, moles quantification, nuclear magnetic resonance (NMR), and high-performance liquid chromatography (HPLC). Total carbohydrate analysis found that each prebiotic fraction was approximately 99-100% carbohydrate on a dry weight basis. Results from the moles quantification experiment and NMR analysis confirmed that the DP corresponds with the targeted profile for each oligosaccharide. HPLC results further verified the identity and purity for each oligosaccharide preparation through comparison with commercially available standards. Overall, this research produced and characterized seven fractions of prebiotic oligosaccharides with distinct chemical structure. This economical method of obtaining purified, fractionated prebiotic oligosaccharide is valuable to researchers interested in studying the properties of prebiotic oligosaccharides with specific chain lengths.
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