Chapter 18
Formation of Sulfur-Containing Flavor Compounds from [ C]-Labeled Sugars, Cysteine, and Methionine Downloaded by KTH ROYAL INST OF TECHNOLOGY on November 22, 2016 | http://pubs.acs.org Publication Date: July 29, 1994 | doi: 10.1021/bk-1994-0564.ch018
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R. Tressl , E. Kersten , C. Nittka , and D. Rewicki
Institut für Biotechnologie, Technische Universität Berlin, Seestrasse 13, 13353 Berlin, Germany Institut für Organische Chemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany The formation of furans, thiophenes, furanones, thiophenones etc. was investigated in a series of [1(or 6)- C]-glucose and [1- C]-arabinose/ cysteine and methionine model experiments. The labeled compounds were analyzed by capillary GC/MS and NMR-spectroscopy. From their structures the degradation pathways via different reactive intermediates (e.g. 3-deoxyaldoketose, 1-deoxydiketose) and fragmentations were evaluated. Besides the transformations to flavor compounds via identical labeled precursors, major differences in the flavor compounds result from specific Strecker reaction sequences. Major unlabeled compounds e.g. 3mercaptopropionic acidfromcysteine and 4-methylthiobutyric acid from methionine demonstrate transamination/reduction, and the formation of pyruvate and 2-mercaptopropionic acid from [1- C]-glucose/cysteine indicates β-elimination. 13
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Cysteine- and methionine-specific Maillard products are important sulfur containing flavor compounds in meat and roasted coffee. Their formation pathways were postulated from the results of model experiments of cysteine, methionine, sugars and the corresponding degradation products (7). According to the specific Strecker degradation of cysteine (2) many compounds like 3,5-dimethyl-l,2,4-trithiolane, 3methyl-l,2,4-trithiane and l,2,3-trithia-5-cycloheptene result from cysteine without the participation of a fragment from carbohydrates (3). During Strecker degradation of methionine, 3-methylthiopropanal is generated and undergoes a cleavage into propenal, propanal and methylmercaptan or a transformation into sulfur compounds (4,5). In the initial phase of the Maillard reaction, D-glucose (or D-arabinose) and cysteine form Schiff bases, which undergo keto-enol tautomerism, allylic dehydration and deamination into α-dicarbonyls (Scheme 1). To some extent the Schiff bases are cleaved into C2-, C3- and C4-fragments, which may react as precursors. Therefore, the formation pathways of individual sulfur compounds can not be elucidated without labeling experiments. For this purpose [1- C]-labeling experiments are most suitable (6,7). In this paper we demonstrate [l(or 6)- C]-D-glucose/L-cysteine, [1- C]-Darabinose/L-cysteine and [l- C]-D-glucose/L-methionine model experiments, which were carried out comparable to the corresponding L-proline and hydroxyproline experi13
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0097-6156/94/0564-0224$08.00/0 © 1994 American Chemical Society
Mussinan and Keelan; Sulfur Compounds in Foods ACS Symposium Series; American Chemical Society: Washington, DC, 1994.
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Downloaded by KTH ROYAL INST OF TECHNOLOGY on November 22, 2016 | http://pubs.acs.org Publication Date: July 29, 1994 | doi: 10.1021/bk-1994-0564.ch018
18.
TRESSL E T AL.
Sulfur-Containing Flavor Compounds
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ments (7). The described model reactions lead to [ C]-labeled products from which substantial conclusions on their formation routes can be drawn. For this determination the distribution, position and extent of the [ C]-labeling of selected compounds were analyzed by mass spectrometry. Thermal degradation of cysteine and methionine in water (3), in addition with thiamin (8), and with a-dicarbonyls (5) were carried out and numerous volatiles were identified. 13
Strecker Degradation, β-Elimination and Transamination of Cysteine/ Methionine during Heating with [l(or 6)- C]-D-Glucose 13
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During Strecker degradation of [l- C]-D-glucose with primary α-amino acids, pyrroles and pyridinols are formed as major products (6). 4-Aminobutyric acid and peptide bound lysine are transformed into [ CHO]-2-formyl-5-hydroxymethylpyrroles (9). Amino acids like Val, Ile, Leu, Phe and Met are transformed into 2-[ CHO]pyrrole lactones (10). Equimolar amounts of cysteine (methionine) and [l(or 6)- C]D-glucose were heated for 1,5 h at 160°C in aqueous solution at pH 5. The volatiles were extracted with pentane/ether and analyzed as described (7). In Table I selected (unlabeled) Strecker degradation products from cysteine and methionine are summarized. Pyruvat (1), 2- and 3-mercaptopropionic acids (2, 3) from cysteine as well as 2-oxo-5-thiahexanoic acid (4) and 5-thiahexanoic acid (5)frommethionine, 13
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Mussinan and Keelan; Sulfur Compounds in Foods ACS Symposium Series; American Chemical Society: Washington, DC, 1994.
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SULFUR COMPOUNDS IN FOODS
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Table I. Strecker Degradation Products from [l- C]-D-Glucose with Cysteine or Methionine N o
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formation [ppm] with C Met
compound
600
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H S
N^ o H
3
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180
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H
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Scheme 6. Formation of thiofuraneol in [l- C]-D-glucose/Cys Maillard experiments Acknowledgements This work was supported by the AIF (Koln). Literature cited 1. Tressl, R.; Helak, B.; Martin, N.; Kersten, E. In Thermal Generation ofAromas; Parliment, T.H., McGorrin, R.J., Ho, C.-T., Eds.; ACS Symp.Series 409; American Chemical Society, Washington, DC, 1989, 156-171. 2. Kobayasi, N.; Fujimaki, M. Agric. Biol. Chem. 1963, 29, 698. 3. Shu, C.-K.; Hagedorn, M.L.; Mookherjee, B.D.; Ho, C.-T. J. Agric. Food Chem. 1985, 33, 438. 4. de Rijke, D.; van Dort, J.M.; Boelens, H. In Flavour '81; Schreier, P., Ed.; Proceedings of the 3rd Weurman Symposium, Munich 1981; Walter de Gruyter, Berlin-New York, 1981, 417-431. 5. Martin, N. Ph.D. Thesis, Technische Univ. Berlin, 1989. 6. Nyhammar, T.; Olsson, K.; Pernemalm, P.-A. Acta Chem. Scand. 1983, Β 37, 879. 7. Tressl, R.; Helak, B.; Kersten, E.; Rewicki, D. J. Agric. Food Chem. 1993, 41, 547. 8. Werkhoff, P.; Brüning, J.; Emberger, R.; Güntert, M.; Köpsel, M.; Kuhn, W.; Surburg, H .J.Agric. Food Chem. 1990, 38, 777. 9. Tressl, R.; Kersten, E.; Rewicki, D. J. Agric. Food Chem., in press. 10. Tressl, R.; Helak, B.; Kersten, E.; Nittka, C. In Recent Developments in Flavor and Fragrance Chemistry; Hopp, R., Mori, K., Eds.; Proceedings of the 3rd International Haarmann & Reimer Symposium, Kyoto 1992; Verlag Chemie, Weinheim, New York, Basel, Cambridge, 1993; 165-181. 11. Anet, E.F.L. J. Adv. Carbohydr. Chem. 1964, 19, 181. RECEIVED March 23, 1994
Mussinan and Keelan; Sulfur Compounds in Foods ACS Symposium Series; American Chemical Society: Washington, DC, 1994.
