Experimental and computational studies on the solvent-free reaction between ozone and glucose-glycine melanoidin

Date

10-2002

Degree

Bachelor of Science in Agricultural Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Ernesto J Del Rosario

Co-adviser

Rommel S. Talan

Committee Member

Aurea N. Miranda-Chu

Abstract

Melanoidin was prepared by heating an equimolar mixture of glucose and glycine (solvent-free) at 160 T for two minutes. It was dialyzed in deionized water, eluted through Sephadex G-75 column and then freeze-dried. The solid melanoidin was reacted with gaseous ozone at ambient temperature (-30 *C). Reduction in absorbance values of 29.26 % and 32.14 % at 280 nm and 475 nm, respectively, were obtained for the ozonized melanoidin in aqueous solution. The average molecular weight (MW) of melanoidin decreased by up to 10.2 % after ozonation based on Sephadex G-75 column chromatography; the elution peaks showed broadening due to increased polydispersity in the ozonized melanoidin. Both the decolorization and gel filtration results supported the Criegee ozonation mechanism. Both decolorization and MW values after the solvent-free ozonation of melanoidin were lower compared to literature values for the corresponding reaction in aqueous solution. The difference was attributed to the limited contact between the reactants for the solvent-free reaction. Infrared and UV-visible spectral simulations were carried out using HyperChem software for the probable molecular structure of the products of melanoidin ozonation. The results showed that the proposed structure of Yaylayan and Kaminsky (1998), showed closest agreement between the simulated and experimental IR spectra. The structure proposed for melanoidin by Kato and Tsuchida (1981) gave a simulated UV-visible spectrum closest to the experimental.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Document Type

Thesis

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