Amadori and Heyns rearrangement products are currently produced as crude Maillard reaction mixtures, due to lack of convenient procedures for their synthesis. The objective of this study was to develop a synthetic strategy based on polymer-supported synthesis that allows the production of different derivatives of these sugar-amino acid conjugates. The strategy involved coupling of poly(ethyleneglycol) mono methyl ether (PEGME) with N-protected (t-BOC) amino acid through catalysis by DCC (dicyclohexylcarbodimide) to form a polymer bound ester of the amino acid (89% yield with beta-alanine), followed by deprotection of the t-BOC group through a novel microwave-assisted hydrolysis process in high yields (98%). After the deprotection, the polymer-based amino acid was neutralized by triethyl amine treatment, followed by room temperature reaction with selected reducing sugars or sugar analogs, for 48 hrs to produce polymer bound ARP in 75% yield (using acetol). The final product was cleaved by methanolysis using sodium methioxide in 65% yield. The reactions were monitored by spectroscopic analysis and the intermediates were identified by FTIR, Py/GC/MS and 1H NMR.

A water-methanol solution of glycine and scD-glucose was refluxed for seven hr. The solvent was evaporated under vacuum at room temperature and the residue was dialyzed against distilled water. After dialysis, the solvent was evaporated under vacuum at room temperature. The non-dialyzable fraction was further fractionated by gel filtration. The process yielded three polymeric materials (10,000 $<$ M $<$ 20,000) whose purity was verified by HPLC. The isolated polymers were further analyzed by UV-VIS and FTIR spectroscopy and by pyrolysis/GC/MS. Elemental analysis indicated that polymer A has the following empirical formula $ rm C sb6H sb{11}N sb1O sb4$ and polymers B1 and B2 have the same empirical formula as glucose $ rm C sb1H sb2O sb1.$ The origin of nitrogen containing polymer A was assigned to Amadori intermediate or to some of its derivatives and the origin of polymers B1 and B2 was assigned to Glucosone and to 3- or 1-deoxyglucosones; common non-nitrogen containing reactive intermediates during Maillard reaction. Plausible mechanisms were proposed for the formation of polymers.

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published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Pyrolysis/GC/MS was utilized as an integrated reaction, separation and identification system to study the thermal degradation products of non-volatile Maillard flavor precursors. Model systems of scL-phenylalanine (aromatic amino acid), glycine and scL-alanine (aliphatic amino acids), scL-serine ($ beta$-hydroxy amino acids) and scL-methionine (sulphur containing amino acid) were investigated. Quartz tube pyrolysis of scD-glucose/amino acid or dicarbonyl/amino acid mixtures shortened the analysis time (from hours to minutes) and eliminated the need for extraction since the volatiles generated from the precursors are directly transferred into the GC column. / Phenylalanine Amadori product and different model systems containing phenylalanine and different reducing sugars were studied. Ribbon pyrolysis was used to study the effect of temperature (150, 200, 250$ sp circ$C) on the efficiency of formation of initial pyrolysis products from phenylalanine and Amadori phenylalanine. Quartz tube pyrolysis was used at 250$ sp circ$C to enhance the secondary reactions. These studies revealed the formation of pyridine and naphthalene derivatives such as 3,5-diphenylpyridine, 1(2)-naphthaleneamine, N-methyl-1(2)-aminonaphthalene, 1-aminoanthracene, 2$ sp prime$-phenyl-pyrrolo (4,5-A) dihydronaphthalene, 1(2)-(N-phenethyl)napthaleneamine and 1(2)-(N-phenethyl-N-methyl)naphthaleneamine. / Model studies using scD- ($ sp{13}$C) glucoses and a series of dicarbonyl compounds with labeled ($ sp{15}$N/$ sp{13}$C) glycines and ($ sp{15}$N/$ sp{13}$C) alanines identified a new chemical transformation of $ alpha$-dicarbonyls, that lead to the addition of alkyl groups from the amino acid to the $ alpha$-dicarbonyl compounds, instead of the amino group as in the case of the Strecker type interaction between the two reactants. Thus, glyoxal and pyruvaldehyde can be transformed into pyruvaldehyde and 2,3-butanedione respectively, by glycine and 2-ketobutanal and 2,3-pentanedione respectively, by scL-alanine. The labeled glycine model studies indicated that methyl substituted pyrazines and pyrazinones formed in the model systems, have a common intermediate. Two pathways of pyrazinone formation were distinguished based on the labeling experiments, one involving the reaction of three moles of glycine and the other the interaction of the dipeptide glycylglycine with an $ alpha$-dicarbonyl compound. / A major product of the reaction of scD-glucose with excess glycine was detected by Py/GC/MS analysis and subsequently synthesized and isolated using focused microwave irradiation at atmospheric pressure conditions. Spectroscopic analysis by NMR, FTIR, MS and UV in conjunction with labeling studies have indicated the unknown compound to be 5-hydroxy-1,3-dimethyl-2 (1H) -quinoxalinone. The labeling studies indicated the incorporation of ten carbon atoms (six from sugar, one C-1 atom of glycine, and three C-2 atoms of glycine) and two nitrogens. / scL-Serine was found to be a unique amino acid generating in the absence of sugar a variety of heterocyclic compounds. Under pyrolytic conditions scL-serine can be viewed as a potential mixture of glycine, alanine, serine, formaldehyde and dicarbonyl compounds. / Model studies with scL-methionine provided evidence that methional (Strecker aldehyde) generated under Quartz tube pyrolysis undergoes secondary reactions with amino compounds generating 1,3-thiazines or 3-substituted pyridine in a similar fashion to that of scL-phenylalanine systems where 3-substituted pyridines were also identified. (Abstract shortened by UMI.)

The physicochemical parameters of fifteen honey samples from a wide range of botanical origins were characterized to identify the influence of composition on the formation of alpha-dicarbonyl compounds during heating. Color, pH, moisture content, water activity, hydroxymethylfurfural (HMF), sugar and amino acid content were determined before and after storage at various time and temperatures. The effects of storage time and temperature on the formation of Maillard reaction product were also investigated. Analysis of the data has indicated that they have a significant impact on the rate of production of Maillard related compounds such as alpha-dicarbonyls and HMF. The content of free amino acids was also decreased 'over time with concomitant increase in color intensity. Furthermore, nine alpha-dicarbonyl compounds were detected in honey samples. The analysis of these compounds after derivatization with o-diaminobenzene resulted in the identification of three previously unreported derivatives in honey such as 3-deoxypentulose, 1,4-dideoxyhexulose and 3,4dideoxyglucosone-3-ene. More importantly, the detection of 5-hydroxycyclohexane-1,2,4-trione was to our knowledge the first cyclic alpha-dicarbonyl compound ever reported in literature. Characterization of this molecule by different mass spectrometric techniques and spiking experiments provided evidence that supported the precursor, the structure and proposed mechanism of formation.

The present study investigated the possibility of using an electrolytic cell to prevent nonenzymatic browning in lemon juice products. A single-strength, a double strength and a triple-strength lemon juice were subjected to four different current densities (0.116, 0.231, 0.463 and 0.926 A/m$ sp2)$ for 30 minutes using an electrolytic cell. Dissolved oxygen level, conductivity, redox potential, pH in juices and the voltage applied to the electrodes required to maintain constant current density through the cell were monitored. Juice samples were taken at 0, 5, 15 and 30 minutes and then stored for one month at 30$ sp circ$C. / After one month of storage, juice samples were assessed for browning and quality alteration. The chemical indices used were the browning index and concentrations in furfural and 5-hydroxymethylfurfural (HMF). Although redox potentials and concentrations in dissolved oxygen were significantly reduced by the electrolytic cell treatment, none of the electrochemical treatments significantly retarded detrimental reactions in juices over the storage period. Initial levels in dissolved oxygen and redox potential do not seem to have any significant effect on browning or chemical quality deterioration in lemon juices. Thus, the present study suggests that nonenzymatic browning in lemon juice products may be due to factors other than oxidative reactions.

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