Kinetic and spectroscopic (UV- vis and IR) studies on the ozonation of glucose-glycine melanoidin in buffered solution at pH 3.5, 5.0 and 6.5

Date

4-2004

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Ernesto J Del Rosario

Co-adviser

Hosea L. Matel

Committee Member

Jose Rene L. Micor

Abstract

Synthetic melanoidin was prepared from 1.0 M glucose, 1.0 M glycine and 0.5 M sodium carbonate. It was dialyzed in distilled water, eluted through Scphadex 0-75 column and then freeze-dried. The kinetics of ozonation of melanoidin was studied at pH 3.5, 5.0 and 6.5 based on the absorbance of the samples at 280 and 475 nm. The reaction was found to obey first order kinetics at 475 nm and half-order kinetics at 280 nm. The calculated rate constant at 475 nm was found to he higher than that at 280 nm. After two hours of ozonation, maximal decolorization efficiencies of 93.9%, 94.6% and 93.7% were obtained at 475 nm, while 56.4%, 56.2% and 55.2% were observed at 280 nm at pl I 3.5,5.0 and 6.5, respectively. The average molecular weight of melanoidin was reduced by up to 82.3%, 87.1% and 78.6% after two hours of ozonation at pH 3.5, 5.0 and 6.5, respectively. At the pH values used, an increase in pH of about 0.2 pH unit was observed after the ozonation process, which could be explained by the reaction of the buffer with ozone. From the UV-Visible spectra, the decrease in the intensity of absorption as well the shift to a lower wavelength of the 3.,,,,, at 290 - 300 nm suggests disappearance of the conjugated On the other hand, the increase in the intensity of C-0 stretch after ozonation of melanoidin indicates formation of ozonide due to action of ozone on the Cr--C of the melanoidin.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2004 C4 G83

Document Type

Thesis

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