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.

No description available.

The ability of Pyrolysis-GC/MS analytical system---developed earlier to study the mechanism of Maillard reaction---was further enhanced to include chemical ionization, tandem mass spectrometry and a sample pre-concentration trap essential to detect minor components. Furthermore, the sample delivery during Py-GC/MS analysis was optimized and its relevance to the study of aqueous Maillard model systems was also characterized. The results of these investigations have indicated that the use of higher values of carrier gas flow rates or high constant pressures, during Py-GC/MS analysis can increase the total number of peaks and total area counts of the pyrograms. The influence of the reaction phase on the mechanism of formation of Maillard products was studied by comparison of 13C-label incorporation patterns of the common products formed in model systems consisting of labeled glycine and D-glucoses subjected to both pyrolysis and heating in aqueous solutions. Although pyrolysis reaction produced higher number of products, however, the major pathways of formation of variety of important Maillard products followed the same mechanism under both pyrolytic and aqueous systems. Furthermore, the advantages of the optimized system, were demonstrated both in the investigation of the mechanism of Maillard reaction, using L-serine and L-threonine as model systems and in the study of formation of Maillard generated carcinogens and chemical markers. Analyses of the pyrolysis products of [13C-1], [13C-2] and [13C-3] labeled L-serines and L-threonines have indicated the presence of three initial degradation pathways. Decarboxylation followed by deamination; a retro-aldol reaction and dehydration followed by isomerization, deamination and hydrolysis leading to the formation of pyruvic and 2-ketobutanoic acids. Interestingly, the amino carbonyl interaction between the resulting pyruvic acid and the aminoethanol can lead to the formation of an Amadori product i

Some New Zealand indigenous plants may offer unique qualities that can be used to secure an exclusive niche in the alcoholic drinks market in the same way that Scotch whisky and tequila are strongly identified with the country of origin, Scotland and Mexico. Tequila is a spirit distilled from a fermented agave, dry adapted lily. Agave is in the family Agavaceae, a notable New Zealand member of which is the common cabbage tree or ti kōuka (Cordyline australis). Similarly, to the agave having a fermentable core, ti kōuka has carbohydrate (inulin) content in its young stems and roots that can be hydrolysed in acidic suspensions or by enzyme hydrolysis to yield fructose. The main objective of this thesis was to systematically research the feasibility of the production of a tequila-like spirit from ti kōuka stem, profiling the chemical properties of the spirit with a view of future commercial production of an iconic New Zealand spirit. The initial stage of the thesis focused on extracting inulin from the ti kōuka stem and hydrolysing (by both acid and enzyme) it to yield reducing sugar. The sugar concentration yielded was too low (~ 10 to 15%) to be fermented and distilled economically. Rather, the ti kōuka extract was evaporated to produce flavoured products by the Maillard reaction, a reaction between amino acids and sugars. The flavoured compounds were then infused with potable ethanol. In outline, the dried stem was hydrolysed with an inulinase at 60°C for 1 hour. The pH was adjusted to 10 with sodium hydroxide and evaporated at 60°C for 65 hours. The dried extract was reconstituted with water, centrifuged and the supernatant infused with portable ethanol to yield final different concentrations of 80, 67, 57 and 50%. The ethanol treatments simultaneously extracted flavour and colour to varying degrees. Next, sugars and amino acids were analysed in the ti kōuka stems by liquid chromatography. The most abundant sugar present in the ti kōuka after inulinase hydrolysis was fructose and the dominant amino acids were arginine, leucine, lysine, and aspartic acid/aspargine and glutamic acid/glutamine. Amino acids and reducing sugar were also analysed at different stages of the spirit production. The reducing sugar content decreased during each step of the process. The relative concentrations of arginine, leucine and lysine decreased while that of aspartic and glutamic acids increased during the whole process of making the spirit. Model systems were then used to simulate the reactions taking place between the amino acids and reducing sugar present in the ti kōuka extract. The colour of the models became darker as a function of time, accumulating more brown pigment containing the flavoured compounds. Increasing the pH and concentration of the amino acids in the reaction mixture also increased the browning pigment formation. Dichloromethane and n-pentane and diethyl ether solvent extraction of the spirits and analysis of volatiles by gas chromatography- mass spectrometry revealed that the chemical profiles of the spirits were different from those of the commercial spirits, gin, tequila and whisky. Sensory evaluation was performed on four variations of the spirit, and demonstrated that the creations were consumer-acceptable. The costs and other issues involved in producing and marketing such a spirit were identified, the major selling point being geographical exclusivity.

Some New Zealand indigenous plants may offer unique qualities that can be used to secure an exclusive niche in the alcoholic drinks market in the same way that Scotch whisky and tequila are strongly identified with the country of origin, Scotland and Mexico. Tequila is a spirit distilled from a fermented agave, dry adapted lily. Agave is in the family Agavaceae, a notable New Zealand member of which is the common cabbage tree or ti kōuka (Cordyline australis). Similarly, to the agave having a fermentable core, ti kōuka has carbohydrate (inulin) content in its young stems and roots that can be hydrolysed in acidic suspensions or by enzyme hydrolysis to yield fructose. The main objective of this thesis was to systematically research the feasibility of the production of a tequila-like spirit from ti kōuka stem, profiling the chemical properties of the spirit with a view of future commercial production of an iconic New Zealand spirit. The initial stage of the thesis focused on extracting inulin from the ti kōuka stem and hydrolysing (by both acid and enzyme) it to yield reducing sugar. The sugar concentration yielded was too low (~ 10 to 15%) to be fermented and distilled economically. Rather, the ti kōuka extract was evaporated to produce flavoured products by the Maillard reaction, a reaction between amino acids and sugars. The flavoured compounds were then infused with potable ethanol. In outline, the dried stem was hydrolysed with an inulinase at 60°C for 1 hour. The pH was adjusted to 10 with sodium hydroxide and evaporated at 60°C for 65 hours. The dried extract was reconstituted with water, centrifuged and the supernatant infused with portable ethanol to yield final different concentrations of 80, 67, 57 and 50%. The ethanol treatments simultaneously extracted flavour and colour to varying degrees. Next, sugars and amino acids were analysed in the ti kōuka stems by liquid chromatography. The most abundant sugar present in the ti kōuka after inulinase hydrolysis was fructose and the dominant amino acids were arginine, leucine, lysine, and aspartic acid/aspargine and glutamic acid/glutamine. Amino acids and reducing sugar were also analysed at different stages of the spirit production. The reducing sugar content decreased during each step of the process. The relative concentrations of arginine, leucine and lysine decreased while that of aspartic and glutamic acids increased during the whole process of making the spirit. Model systems were then used to simulate the reactions taking place between the amino acids and reducing sugar present in the ti kōuka extract. The colour of the models became darker as a function of time, accumulating more brown pigment containing the flavoured compounds. Increasing the pH and concentration of the amino acids in the reaction mixture also increased the browning pigment formation. Dichloromethane and n-pentane and diethyl ether solvent extraction of the spirits and analysis of volatiles by gas chromatography- mass spectrometry revealed that the chemical profiles of the spirits were different from those of the commercial spirits, gin, tequila and whisky. Sensory evaluation was performed on four variations of the spirit, and demonstrated that the creations were consumer-acceptable. The costs and other issues involved in producing and marketing such a spirit were identified, the major selling point being geographical exclusivity.

Zugl.: Berlin, Techn. Univ., Diss., 2006

Thesis (Ph. D.)--University of Rhode Island, 2003. / Typescript. Includes bibliographical references (leaves 170-182).

Thesis--Berlin. / Vita.

Techn. Universiẗat, Diss., 2000--Berlin.