Abstract
A comparative IR spectral study was conducted with synthetic melanoidins which were prepared from various ratios of sugars and amino acids and a pseudomelanoidin which was prepared from sugar only. A significant resemblance was observed between the pseudomelanoidin and the melanoidin prepared from a high (9:1) sugar ratio (type 1). Another series of melanoidins (type 2) consists of those prepared from an "excess" of amino acid (9:1 and 1:1). Type 1 showed the presence of carbonyl and hydroxyl groups as well as aromatic vibrations. The same groups were detected in the spectrum of the pseudomelanoidin. These features were observed in a very low concentration in the type 2 melanoidins. Carboxylic groups are present in pseudomelanoidin and in both types of the melanoidins. However, the acid strength of this group is high in melanoidin of type 2, but low in type 1 and in the pseudomelanoidin. The nitrogen atom which is involved in the melanoidin structure is present as a tertiary amine. Heat treatment of KBr discs containing glycine, galactose and a mixture thereof revealed that galactose was converted into pseudomelanoidin; a mixture of galactose-glycine yielded the corresponding melanoidin of type 2; no reaction was observed with glycine.
Original language | English |
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Pages (from-to) | 117-125 |
Number of pages | 9 |
Journal | Organic Geochemistry |
Volume | 9 |
Issue number | 3 |
DOIs | |
State | Published - 1986 |
Keywords
- galactose
- glycine
- infrared spectroscopy
- Maillard reaction
- melanoidins