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Why asparagine needs carbohydrates to generate acrylamide
Varoujan A Yaylayan1, Andrzej Wnorowski, Carolina Perez Locas
1Department of Food Science and Agricultural Chemistry, McGill University, 21,111 Lakeshore, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9. varoujan.yaylayan@mcgill.ca
Journal of Agricultural and Food Chemistry
|March 6, 2003
Summary
Asparagine alone forms maleimide when heated. However, with reducing sugars, asparagine generates acrylamide via a decarboxylated Amadori product, a key finding for food chemistry.
Area of Science:
- Food Chemistry
- Organic Chemistry
- Chemical Kinetics
Background:
- Asparagine thermally decomposes primarily to maleimide.
- Acrylamide formation from asparagine is limited by intramolecular cyclization.
- The role of reducing sugars in acrylamide generation from asparagine requires elucidation.
Purpose of the Study:
- To investigate the mechanism of acrylamide formation from asparagine in the presence of reducing sugars.
- To identify the key intermediates and reaction pathways involved.
- To understand how reducing sugars promote acrylamide formation.
Main Methods:
- Fourier-transform infrared (FTIR) spectroscopy for model reactions.
- Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) with labeling studies.
- Analysis of thermal decomposition products of asparagine and its reactions with reducing sugars.
Main Results:
- The primary thermal decomposition product of asparagine is maleimide, not acrylamide.
- Reducing sugars facilitate acrylamide formation from asparagine.
- A decarboxylated Amadori product of asparagine and reducing sugars is identified as the key acrylamide precursor.
- Formation of the precursor involves Schiff base cyclization to oxazolidin-5-one followed by low-energy decarboxylation.
Conclusions:
- Acrylamide formation from asparagine is significantly enhanced by reducing sugars.
- The decarboxylated Amadori product is the critical intermediate, bypassing competing cyclization reactions.
- Elevated temperatures are necessary to cleave the C-N bond in the intermediate to yield acrylamide.