Methional
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propanal_200.svg)
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| General | ||||||||||||||||
| Surname | Methional | |||||||||||||||
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| Molecular formula | C 4 H 8 OS | |||||||||||||||
| Brief description |
light yellow smelly liquid |
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| properties | ||||||||||||||||
| Molar mass | 104.17 g mol −1 | |||||||||||||||
| Physical state |
liquid |
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| density |
1.043 g cm −3 (25 ° C) |
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| boiling point |
165-166 ° C |
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| Refractive index |
1.483 (20 ° C) |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C | ||||||||||||||||
Methional is a colorless liquid organic chemical compound and a breakdown product of the sulfur-containing amino acid L - methionine . Methional is an important odor-determining component in potato chips. Traces of methional can also be found in black tea and in products made from green tea. Methional contains the functional groups of an aldehyde and a thioether .
Occurrence
Methional occurs in the Concord grape variety , asparagus , baked potatoes, wheat and other bread, Swiss cheese, cocoa, roasted hazelnuts and peanuts and other foods.
Methional is an odorous substance that z. B. forms reducible sugars and amino acids in the (thermally induced) Maillard reaction . It is formed from α-dicarbonyl compounds (intermediate products of the complex Maillard reaction) with L- methionine:
CH 3 SCH 2 CH 2 (NH 2 ) CHCO 2 H + O → CH 3 SCH 2 CH 2 N = CCO 2 H + H 2 O CH 3 SCH 2 CH 2 N = CCO 2 H + H 2 O → CH 3 SCH 2 CH 2 CHO + NH 3 + CO 2
Methional easily breaks down into acrolein and methyl mercaptan . The latter is usually quickly oxidized to dimethyl disulfide by atmospheric oxygen . Dimethyl disulfide is partly responsible for the taste of potatoes.
L- methionine is oxidized non-enzymatically to methional, ammonia and carbon dioxide by flavins and light .
physiology
Methional acts as an allosteric modulator of the taste receptor from the two proteins T1R1 and T1R3 . On human receptors, its potency is exceeded by 3- (methylthio) butanal.
Extraction and presentation
A large-scale Michael addition of methyl mercaptan to acrolein provides methional:
CH 3 SH + H 2 C = CHCHO → H 3 CS (CH 2 ) 2 CHO
use
From methional is racemic DL methionine by means of a Strecker synthesis produced on an industrial scale (reaction with hydrogen cyanide and ammonia ).
Individual evidence
- ↑ a b c d e f data sheet 3- (Methylthio) propionaldehyde, ≥97%, FG from Sigma-Aldrich , accessed on April 12, 2014 ( PDF ).
- ↑ a b Entry on 3- (Methylthio) propanal in the GESTIS substance database of the IFA , accessed on July 23, 2016(JavaScript required) .
- ↑ a b Faith C. Belanger, Rong Di & Daphna Havkin-Frenkel (2009) Increasing the Methional Content in Potato through Biotechnology, Biotechnology in Flavor Production, 185–188, doi : 10.1002 / 9781444302493.ch9 .
- ↑ Shmuel Yannai: Dictionary of Food Compounds with CD-ROM . Chapman & Hall / CRC, Boca Raton 2004, ISBN 1-58488-416-9 , pp. 932 .
- ↑ SF Yang, HS Ku, HK Pratt (1967) Photochemical Production of Ethylene from Methionine and Its Analogues in the Presence of Flavin Mononucleotide, The Journal of Biological Chemistry, 242, 5274-5280.
- ↑ Toda Y et al: Positive / Negative Allosteric Modulation Switching in an Umami Taste Receptor (T1R1 / T1R3) by a Natural Flavor Compound, Methional . In: Sci Rep . 8, No. 1, August 2018, p. 11796. doi : 10.1038 / s41598-018-30315-x . PMID 30087430 . PMC 6081381 (free full text).
- ↑ Charles Hurd, Leon Gershbein (1947) Reactions of mercaptan with Acrylic and Methacrylic Derivatives, Chemical Laboratory of Northwestern University, 69, 2328-2335.