- Methylglyoxal binds to amines in honey matrix and 2′-methoxyacetophenone is released in gaseous form into the headspace on the heating of manuka honey
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Reports on the thermal stability of manuka honey in terms of food processing have been few. This study investigated changes in nine characteristic chemicals of manuka honey during heating. Among these, methylglyoxal (MGO) and 2′-methoxyacetophenone (MAP) were significantly decreased by heating at 90 °C. To elucidate the mechanism for this decrease, artificial honey was prepared from sugars and water with MAP or MGO and then heated. The decrease of MGO was enhanced with L-proline, lysine, or arginine derivatives, accompanied by formation of 2-acetyl-1-pyrroline, MGO-derived lysine dimer, or argpyrimidine, respectively, suggesting that an amino–carbonyl reaction is one pathway for the loss of MGO. The decrease of MAP in the artificial honey depended on the volume of headspace in a vessel. MAP from heated manuka honey was also detected in the gas phase, indicating that MAP was vaporized. Heating could thus reduce the beneficial and/or signature molecules in honey.
- Kato, Mai,Kato, Yoji,Kawai, Masaki,Kishi, Yui,Miyoshi, Noriyuki,Nagata, Akika,Okano, Yayako,Shimizu, Michiyo,Suga, Naoko,Yakemoto, Chisato
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Read Online
- An expeditious, high-yielding construction of the food aroma compounds 6-acetyl-1,2,3,4-tetrahydropyridine and 2-acetyl-1-pyrroline
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The key compound responsible for the aroma of bread, 6-acetyl-1,2,3,4- tetrahydropyridine (1), has been constructed in an efficient three-step procedure from 2-piperidone in an overall yield of 56%. Compound 1 was liberated in the final step under basic conditions. A related synthetic route produced 2-acetyl-1-pyrroline (2), the principal component of cooked rice, in 10% overall yield.
- Harrison, Tyler J.,Dake, Gregory R.
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Read Online
- Efficient Analysis of 2-Acetyl-1-pyrroline in Foods Using a Novel Derivatization Strategy and LC-MS/MS
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2-Acetyl-1-pyrroline (2-AP) is a key odorant in many foods, such as aromatic rice and wheat bread, with a very low odor threshold of 0.05 μg/L in water. The small molecule with a popcornlike, roasty odor is generated biologically or by Strecker degradation within the Maillard-reaction cascades during thermal food processing with methylglyoxal and 1-pyrroline as the main direct precursors. Numerous gas-chromatographic methods for the analysis of 2-AP have been published, but the reactivity of the compound leads to discrimination or degradation during sample workup. We developed a novel derivatization method for 2-AP with o-phenylenediamine followed by HPLC-MS/MS analysis of the resulting stable quinoxaline. The precision (7%), repeatability (14%), recovery (92%), linearity (0.79-500 μg/kg), limit of detection (LOD, 0.26 μg/kg), and limit of quantitation (LOQ, 0.79 μg/kg) were validated for rice matrix and were excellent as compared with those of methods published before. With the novel method, 2-AP levels in typical foods like aromatic rice (131 μg/kg), wheat bread (18 μg/kg), brown bread (18 μg/kg), rye bread (18 μg/kg), and popcorn (38 μg/kg) were determined.
- Jost, Tobias,Heymann, Thomas,Glomb, Marcus A.
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p. 3046 - 3054
(2019/03/11)
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- 2 - acetyl -1 - pyrroline synthetic method
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The invention discloses a synthesis method of 2-acetyl-pyrroline. The synthesis method comprises the following steps of: (1), dissolving pyrrolidine-2-formonitrile hydrochloride in inorganic alkali liquor, carrying out extraction for a plurality of times, combining organic layers, adding a drying agent for drying and dehydrating, filtering, and removing volatile components in filtrate to obtain an intermediate product; (2), dissolving the intermediate product obtained in the last step into an organic solvent, dropwise adding tert-butyl hypochlorite to carry out halogenating reaction, then adding potassium tert-butoxide to carry out elimination reaction, filtering and removing volatile components in filtrate to obtain pyrroline-2-formonitrile; (3), dissolving the pyrroline-2-formonitrile in an organic solvent, adding a Grignard reagent to carry out Grignard reaction, then adding acid liquor to carry out hydrolysis, carrying out extraction for a plurality of times, combining organic layers, adding a drying agent for drying and dehydrating, filtering, and removing volatile components in the filtrate to obtain a product. The synthesis method disclosed by the invention is simple and easy to implement, and high in yield; he obtained product is very high in purity, low in energy consumption and lower in cost.
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Paragraph 0037; 0039; 0042
(2017/08/25)
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- New short and general synthesis of three key Maillard flavour compounds: 2-Acetyl-1-pyrroline, 6-acetyl-1,2,3,4-tetrahydropyridine and 5-acetyl-2,3-dihydro-4H-1,4-thiazine
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A new general synthetic route towards three key Maillard flavour compounds, namely 2-acetyl-1-pyrroline, 6-acetyl-1,2,3,4-tetrahydropyridine and 5-acetyl-2,3-dihydro-4H-1,4-thiazine, was developed. The key step in the process is the methylenation reaction of azaheterocyclic carboxylic esters by means of dimethyltitanocene, giving rise to intermediate vinyl ethers which can be considered as excellent and stable precursors for the title compounds, as a simple acidic treatment of these precursors suffices to release the characteristic Maillard flavours.
- Deblander, Jurgen,Van Aeken, Sam,Adams, An,De Kimpe, Norbert,Abbaspour Tehrani, Kourosch
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p. 327 - 331
(2015/01/30)
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- New short and general synthesis of three key Maillard flavour compounds: 2-Acetyl-1-pyrroline, 6-acetyl-1,2,3,4-tetrahydropyridine and 5-acetyl-2,3-dihydro-4H-1,4-thiazine
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A new general synthetic route towards three key Maillard flavour compounds, namely 2-acetyl-1-pyrroline, 6-acetyl-1,2,3,4-tetrahydropyridine and 5-acetyl-2,3-dihydro-4H-1,4-thiazine, was developed. The key step in the process is the methylenation reaction of azaheterocyclic carboxylic esters by means of dimethyltitanocene, giving rise to intermediate vinyl ethers which can be considered as excellent and stable precursors for the title compounds, as a simple acidic treatment of these precursors suffices to release the characteristic Maillard flavours.
- Deblander, Jurgen,Van Aeken, Sam,Adams, An,De Kimpe, Norbert,Abbaspour Tehrani, Kourosch
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p. 327 - 331
(2014/08/18)
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- METHOD FOR SYNTHESISING 2-ACETYL-1-PYRROLINE AND THE STABLE PRECURSOR THEREOF, OPTIONALLY ISOTOPICALLY MARKED
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The present invention relates to a method for synthetizing a compound of the following formula (I): wherein R is a methyl or ethyl group, n is 1 or 2, and X is a CH2 or CD2 group, from a compound of the following formula (II): wherein R and n are as defined above, and also relates to a method for assaying the compounds of the formula (I) using a corresponding deuterated derivative as an internal reference, as well as to the use of ketal derivatives of compounds of the formula (I) as a stable precursor, in particular in a flavoring composition.
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Page/Page column 9
(2012/05/04)
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- δ1-pyrroline-5-carboxylic acid formed by proline dehydrogenase from the Bacillus subtilis ssp. natto expressed in Escherichia coli as a precursor for 2-acetyl-1-pyrroline
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Proline dehydrogenase (PRODH) catalyzes the biosynthesis of Δ1-pyrroline-5-carboxylic acid (P5C). The Bacillus subtilis subsp. natto gene for the proline dehydrogenase (BnPRODH) was cloned and expressed in Escherichia coli. Nucleotide sequence analysis of the clone revealed an open-reading frame that encodes 302 amino acid polypeptide with a calculated molecular mass of 34.5 kDa. The deduced amino acid sequence showed sequence similarity to bacterial PRODH and PutA of E. coli. The BnPRODH gene was cloned into pET21b and was expressed at a high level in E. coli BL21-(DE3). The expressed protein was purified by using nickel ion affinity column chromatography to homogeneity before characterization. The purified recombinant BnPRODH was used to produce P5C. Model system composed of P5C and methylglyoxal was set up to study the formation of 2-acetyl-1-pyrroline. Our data showed that P5C, derived from the conversion of L-proline by the purified recombinant PRODH, might react directly with methylglyoxal to form 2-AP. P5C/methylglyoxal pathway represents the first report of a biological mechanism by which 2-AP may be synthesized in vitro by PRODH.
- Huang, Tzou-Chi,Huang, Yi-Wen,Hung, Hui-Ju,Ho, Chi-Tang,Wu, Mei-Li
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p. 5097 - 5102
(2008/02/12)
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- A general method for the synthesis of the most powerful naturally?occurring Maillard flavors
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The natural flavors 2-acetyl-1-pyrroline 1a, 2-propionyl-1-pyrroline 1b, 2-acetyl-3,4,5,6-tetrahydropyridine 1c, 2-acetyl-2-thiazoline 1d, 2-propionyl-2-thiazoline 1e, and the artificial flavor 2-acetyl-5,6-dihydro-4H-1,3-thiazine 1f have been prepared by catalytic SeO2 oxidation of the corresponding cyclic imines 6a-c and sulfur cyclic imines 7a-c using TBHP as co-oxidant. The oxidation of the pyrrolines 1a and b is completely regioselective. Professional olfactory evaluation together with the odor threshold of the new flavor 1f is reported.
- Fuganti, Claudio,Gatti, Francesco G.,Serra, Stefano
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p. 4762 - 4767
(2007/10/03)
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- Process for the preparation of 2-acetyl-1-pyrroline, the basmati rice flavorant
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The present invention provides a process for preparing of 2-acetyl-1-pyrroline, the principle aroma component of basmati and other varieties of scented rice, and also of processed cereal and grain products, said flavor chemical is of great value, in the art of application of flavor to foodstuffs like rice and bakery products.
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Page column 5
(2010/11/30)
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- Formation of odorants in Maillard model systems based on L-proline as affected by pH
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Formation of the odorants acetic acid, 4-hydroxy-2,5-dimethyl-3-(2H)-furanone (HDMF), 6-acetyl-1,2,3,4-tetrahydropyridine (ATHP), and 2-acetyl-1-pyrroline (AP) was monitored by isotope dilution assays at pH 6, 7, and 8 in Maillard model reactions containing glucose and proline (Glc/Pro) or the corresponding Amadori compound fructosyl-proline (Fru-Pro). In general, higher yields were obtained at pH 7 and 8. Acetic acid was the major odorant with up to 40 mg/mmol precursor followed by HDMF (up to 0.25 mg/mmol), the formation of which was favored in the Fru-Pro reaction systems. On the contrary, ATHP (up to 50 μg/mmol) and AP (up to 5 μg/mmol) were more abundant in Glc/Pro. However, the sensory relevance of the two N-heterocycles was more pronounced on the basis of odor activity values, confirming their contribution to the overall roasty note of the reaction samples. It was also found that formation and decomposition of Fru-Pro were faster at pH 7 as compared to pH 6, explaining in part the preferred formation of the four odorants studied under neutral and slightly alkaline conditions. After 4 h of reaction at pH 7 in the presence of proline, about one-fourth of the glucose was consumed leading to acetic acid with a transformation yield of almost 40 mol %.
- Blank, Imre,Devaud, Stephanie,Matthey-Doret, Walter,Robert, Fabien
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p. 3643 - 3650
(2007/10/03)
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- Flavor Contribution and Formation of the Intense Roast-Smelling Odorants 2-Propionyl-1-pyrroline and 2-Propionyltetrahydropyridine in Maillard-Type Reactions
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Application of aroma extract dilution analysis on two different model mixtures of proline and glucose, reacted under aqueous or dry-heating conditions, revealed 2-propionyl-1-pyrroline (PP) and 2-propionyltetrahydropyridine (PTHP; occurring in two tautomers), besides 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine, as important roast-smelling odorants in both mixtures. A comparison of the isotope distribution in PP and PTHP formed from either 13C6-labeled or unlabeled glucose suggested a formation pathway for both odorants from the same intermediate, 1-pyrroline, when reacted with either 2-oxobutanal (yielding PP) or 1-hydroxy-2-butanone (yielding PTHP). 2-Oxobutanal, a possible precursor of 1-hydroxy-2-butanone, was shown to be formed in high yields (29 mol %) by reacting acetaldehyde and glycolaldehyde, two well-known degradation products of carbohydrates.
- Hofmann, Thomas,Schieberle, Peter
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p. 2721 - 2726
(2007/10/03)
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- 2-Oxopropanal, Hydroxy-2-propanone, and 1-Pyrroline - Important Intermediates in the Generation of the Roast-Smelling Food Flavor Compounds 2-Acetyl-1-pyrroline and 2-Acetyltetrahydropyridine
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On the basis of labeling experiments with [13C]6-glucose/unlabeled proline as well as quantitative data obtained in model studies using stable isotope dilution assays, 1-pyrroline and hydroxy-2-propanone were identified as effective intermediates in generating the roast-smelling food odorant 2-acetyltetrahydropyridine (ATHP; two tautomers). Synthesis of the key precursor compound, 2-(1-hydroxy-2-oxo-propyl)pyrrolidine, and studies on its degradation confirmed the important role of this intermediate in ATHP formation. Boiling of the intermediate for 30 min in aqueous solution generated >30% of ATHP on a molar basis. 1-Pyrroline and 2-oxopropanal were confirmed as important intermediates in the generation of the further roast food odorant, 2-acetyl-1-pyrroline (AP). On the basis of results of labeling experiments with [13C]6-glucose/unlabeled proline, two different mechanisms could be proposed. One leads to AP via 2-(1,2-dioxopropyl)pyrrolidine as the precursor with elimination of the aldehyde group in 2-oxopropanal as carbon dioxide. The other one suggests elimination of carbon-2 of the pyrroline ring. The latter mechanism was further established by a result showing that from the reaction of 2-methyl- 1-pyrroline with 2-oxopropanal AP was also generated.
- Hofmann, Thomas,Schieberle, Peter
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p. 2270 - 2277
(2007/10/03)
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- New and Convenient Syntheses of the Important Roasty, Popcorn-like Smelling Food Aroma Compounds 2-Acetyl-1-pyrroline and 2-Acetyltetrahydropyridine from Their Corresponding Cyclic α-Amino Acids
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Novel straightforward syntheses have been developed supplying the important food odorants 2-acetyl-1-pyrroline (AP) and 2-acetyltetrahydropyridine (ATHP) in high yields. The four-step reaction sequence starts from the N-shielded cyclic a-amino acids L-proline and pipecolinic acid, respectively, which, in the first step, are converted into the N-shielded 2-acetyl derivatives. Removing the shielding group with trifluoroacetic acid afforded the 2-acetylpyrrolidine and 2-acetylpiperidine trifluoroacetate, respectively, which, upon increasing the pH of their aqueous solutions to 7.0, are spontaneously oxidized in high yields into AP (43% based on L-proline) or ATHP (35% based on pipecolinic acid), respectively, by air oxygen. The latter step is an important hint at the last step in the yet unclear formation pathways of both odorants in foodstuffs.
- Hofmann, Thomas,Schieberle, Peter
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p. 616 - 619
(2007/10/03)
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- Novel syntheses of the major flavor components of bread and cooked rice
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A new synthetic pathway toward the Maillard flavor compounds 6-acyl-1,2,3,4-tetrahydropyridines and 2-acetyl-1-pyrroline is presented. The reaction sequence involves deprotonation of a vicinal diimine and subsequent alkylation with an N,N-diprotected ω-bromoalkylamine, followed by deprotection and intramolecular transimination of the functionalized intermediate. Acidic workup affords the above-mentioned heterocycles, which are principal flavor constituents of bread and cooked rice, respectively. In addition, the synthesis of the more stable diethyl acetal of 2-acetyl-1-pyrroline is described.
- De Kimpe, Norbert,Keppens, Marian
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p. 1515 - 1519
(2007/10/03)
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- Penicillin acylase-mediated synthesis of 2-acetyl-1-pyrroline and of 2-propionyl-1-pyrroline, key roast-smelling odorants in food. Inclusion complexes with i-cyclodextrin and their NMR and MS characterization
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The synthesis of the strong natural roast odorants 1 and 2 is achieved from the C-6 isomeric alcohols 16 and 21 via the acetylenic C-6 and C-7 amines 8 and 9. Key step in the process is the hydrolysis of the W-phenylacetamides 12 and 13 by means of immobilized penicillin acylase, which affords the l-amino-4,5-diketones 14 and 15, spontaneously ring closing to 1 and 2. These latter compounds form inclusion complexes with/?-cyclodextrin, as demonstrated by NMR measurements in deuterated water and FAB-MS spectra.
- Favino, Tito Fabrizio,Fronza, Giovanni,Fuganti, Claudio,Fuganti, Daniela,Grasselli, Piero,Mele, Andrea
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p. 8975 - 8979
(2007/10/03)
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- Synthesis of 2-Acetyl-1-pyrroline, the Principal Rice Flavor Component
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A new straightforward synthesis of 2-acetyl-1-pyrroline, the principal rice flavor component with a cracker-like flavor, is reported.The reaction sequence involves the conversion of pyrrolidine into tripyrroline, subsequent hydrocyanation of the latter into 2-cyanopyrrolidine, oxidation into 2-cyano-1-pyrroline, and Grignard addition of methylmagnesium iodide, affording an overall yield of 16-19percent from pyrrolidine.In similar way, 2-propionyl-1-pyrroline, a recently discovered flavor component of popcorn, was prepared in addition to several higher analogues, i.e., 2-acyl-1-pyrrolines.Also, the synthesis of 2-(acetyl-d3)-1-pyrroline, a deuterated derivative of the rice flavor compound which is useful for the stable isotope dilution assay, is described.
- Kimpe, Norbert G. De,Stevens, Christian V.,Keppens, Marian A.
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p. 1458 - 1461
(2007/10/02)
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- Process for preparing 2-acetyl-1-aza-1-cycloalkenes useful as flavor components for bread and rice
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Straightforvard and inexpensive syntheses of 2-acetyl-1-aza-1-cycloalkenes usefull as bread and rice flavor components, i.e. 2-acetyl-1,4,5,6-tetrahydropyridine and 2-acetyl-1-pyrroline, respectively, comprise the following steps : oxidation of cyclic amines to cyclic imines; subsequent cyanation of cyclic amines to 2-cyano-1-azacycloalkanes ; oxidation of 2-cyano-1-azacycloalkanes to 2-cyano-1-aza-1-cycloalkenes; synthesis of 2-acetyl-1-aza-1-cycloalkenes by a Grignard reaction. These syntheses give rise to the title compounds, free of side products, in a way easily amenable to industrial production.
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