An Automated Solid-Phase Microextraction--Gas Chromatography--Mass Selective Detection Approach for the Determination of Sugar-Amino Acid Reaction Mechanisms

Beiträge Zur Tabakforschung International/Contributions to Tobacco Research

Dube

et al. 2019

SummaryEmployment of 1-hydroxy-acetone as a carbon source and NH4OH as a source of base and nitrogen, has enabled arrays of pyrazines to be synthesized. Reaction conditions such as temperature, time, carbon/nitrogen mole ratios and pH were optimized to maximize the quantity of pyrazines, thereby providing the synthesis of at least 19–20 structurally different pyrazines. Addition of amino acids, selected aldehydes, and hydrolyzed tobacco-derived F1 protein has positively impacted the array of pyrazines from both qualitative and quantitative aspects. Results further showed that by changing the carbon source from 1-hydroxy-acetone to 1-hydroxy-2-butanone and/or 2-hydroxy-3-butanone, control of the type of pyrazines being synthesized could be realized in that the qualitative and quantitative distributions of the pyrazine array were shifted to higher molecular weight derivatives. A relatively large scale reaction (1.5 L) employing optimized parameters yielded > 2 g of a diverse array of pyrazines dominated by multiple dimethylpyrazine derivatives. While systematically varying reaction conditions and reagent mole ratios can predictably alter the distribution and yield of pyrazines, the two most overwhelmingly significant factors governing these two pyrazine product characteristics included the structure of the carbon source and the presence or absence of aldehydes and free amino acids.

Section: Reaction Using Acetol (1-hydroxyacetone)supporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optimal Synthesis of Substituted and Branched Pyrazines via Reaction of Alpha Hydroxy Ketones with Selected Nitrogen Sources

Ashraf‐Khorassani

Beiträge Zur Tabakforschung International/Contributions to Tobacco Research

Dube

et al. 2019

“…Recently, alternative sources of carbon atoms in pyrazines formed during the heating of amino acids and sugars have been described. Specifically, the presence of the branched alkyl side chain pyrazines has been unambiguously attributed to the presence of certain amino acids in aqueous‐based heat‐treated formulations 12, 14, 20–22. The branched alkyl side chains have been unambiguously linked to the alkyl group located on certain amino acids such as valine, leucine and isoleucine.…”

Section: Introductionmentioning

confidence: 97%

Sugar and selected amino acid influences on the structure of pyrazines in microwave heat‐treated formulations

Steichen

2005

J Sci Food Agric

The amount and type of selected sugars and selected amino acids have been shown to significantly impact the structure of headspace-volatile pyrazines produced in aqueous microwave heat-treated formulations. Selection of sugar and amino acid can dictate the structure, yield and distribution of headspace-volatile pyrazines. Under the same reaction conditions and sugar to ammonium hydroxide ratios, rhamnose was found to produce more pyrazines than did high-fructose corn syrup (HFCS). With rhamnose, the yield of pyrazines approached 4500 µg mL −1 . Formulations selectively enriched in ethyldimethylpyrazines can be prepared by stepwise substitution of HFCS with rhamnose. Formulations preferably enriched in methyl-and dimethyl-(3-methylbutyl)-as well as methyl-and dimethyl-(2-methylpropyl)pyrazines were prepared through selective combinations of rhamnose/HFCS and amino acids. Stepwise substitution of HFCS with rhamnose coupled with the use of selected amino acids allowed for the control of the yield, structure and distribution of volatile pyrazines in microwave heat-treated aqueous formulations. Reaction temperature was also found to significantly influence pyrazine yield and distribution. Statistical modeling of the reaction yields as functions of reaction variables produced surfaces with acceptable modeling coefficients. Mechanisms were postulated to account for the increased yields and selected distributions pyrazines when rhamnose was employed.

“…In the vast majority of these cases, pyrazine and methylpyrazine dominate the quantitative and qualitative array of pyrazines produced in these model reactions. These two pyrazines, from a physical property and sensory perspective, are generally viewed as less desirable (8,9). Reaction protocols that significantly reduce or eliminate their presence in a pyrazine array and result in a corresponding increase of other substituted pyrazines of higher molecular weight, thereby having desirable sensory properties, would be viewed very positively for flavor applications.…”

Section: Introductionmentioning

confidence: 99%

Optimization of α-Hydroxyketone and Pyrazine Syntheses Employing Preliminary Reactions of Glucose and Buffer Solutions

Ashraf‐Khorassani

Beiträge Zur Tabakforschung International/Contributions to Tobacco Research

Dube

et al. 2019

SummaryGlucose and selected phosphate buffers have been reacted employing systematic variations in reaction temperature and time (150–160 °C for 60–90 min) to optimize the yield of acetol. This mixture was reacted further with NH4OH, systematically varying reaction conditions and reagent ratios to optimize pyrazine yield. The highest yield of pyrazine was obtained when 1 g of glucose was reacted with 25 mL of buffer at 150–160 °C for 60 min, which in turn was reacted with 1 mL of concentrated aqueous NH4OH at 120–130 °C for 17–18 h. Higher temperatures and higher concentrations of glucose caused a decrease in the yield of pyrazines. The addition of hydrolyzed tobacco-derived F1 protein as a secondary source of nitrogen increased the yield of pyrazines by 2–10% depending on F1 protein concentration. Furthermore, the addition of any α-hydroxyketone, similar in structure to acetol, as a pure reagent to the reaction mixture not only increased the yields of pyrazine by ranging from 25–100 % depending on the reagent concentration, but also significantly altered the qualitative and quantitative distribution of the pyrazines. With all of the reaction parameters examined (reaction time, temperature, reagent ratios, etc.) the most significant impacts on both pyrazine yield and distribution were noted when: 1) glucose was pre-reacted with buffer, 2) hydrolyzed F1 protein was added as a second nitrogen source, and 3) when pure α-hydroxyketones were employed as co-reagents. Use of these reaction parameters was found to dramatically shift the pyrazine distribution toward higher molecular weight resulting in a pyrazine array having more desirable physical and sensory attributes.