Amadori compound generation

K. Eichner, M. Reutter, and R. Wittmann, Detection of Amadori compounds in heated foods, in Thermally Generated Flavors Maillard, Microwave, and Extrusion Process, T. H. Parliment, M. J. Morello, R. J. McGorrin (eds), American Chemical Society, Washington, DC, 1994, 42-54. 

M27. Mossine, V. V., Linetsky, M., Glinsky, G. V., Ortwerth, B. J., and Feather, M. S., Superoxide free radical generation by Amadori compounds The role of acyclic forms and metal ions. 

As indicated previously, primary and secondary amines can also react with carbonyl compounds to form a mixture of compounds containing small molecules and polymers. The small molecule compounds obtained from an aldose and an amine have the common name Amadori products because the Amadori rearrangement is involved in their formation. The compounds generated from ketoses and amines are known as Heyns products (although the differentiation Amadori/Heyns is not always considered). The mechanism for the reaction of primary amines with a reducing sugar can be formulated as follows ... 

In this reaction the glycosylamines are transformed into the Amadori compounds. The elimination of the amine from the Amadori compounds may generate a-dicarbonyl compounds that are the source of further condensations and formation of browning polymers. This may be expressed by reactions of the type ... 

The new compounds formed from these reactions still contain reactive carbonyl groups that can continue the condensation and generate browning polymers. Pyrolysis studies were done on several Amadori compounds from this class [11-13], such as 1-deoxy-1-[(S)-2-(3-pyridyl)-1-pyrrolidinyl]-p-D-fructose [11). However, the nondializable melanoidin from this type of reaction received less interest. 

Tobacco leaf has a complicated chemical composition including a variety of polymers and small molecules. The small molecules from tobacco belong to numerous classes of compounds such as hydrocarbons, terpenes, alcohols, phenols, acids, aldehydes, ketones, quinones, esters, nitriles, sulfur compounds, carbohydrates, amino acids, alkaloids, sterols, isoprenoids [48], Amadori compounds, etc. Some of these compounds were studied by pyrolysis techniques. One example of pyrolytic study is that of cuticular wax of tobacco leaf (green and aged), which was studied by Py-GC/MS [49]. By pyrolysis, some portion of cuticular wax may remain undecomposed. The undecomposed waxes consist of eicosyl tetradecanoate, docosyl octadecanoate, etc. The molecules detected in the wax pyrolysates include hydrocarbons (Cz to C34 with a maximum of occurrence of iso-Czi, normal C31 and anti-iso-C32), alcohols (docosanol, eicosanol), acids (hexadecanoic, hexadecenoic, octadecanoic, etc ). The cuticular wax also contains terpenoids such as a- and p-8,13-duvatriene-1,3-diols. By pyrolysis, some of these compounds are not decomposed and others generate closely related products such as seco-cembranoids (5-isopropyl-8,12-dimethyl-3E,8E,12E,14-pentadecatrien-2-one, 3,7,13-trimethyl-10-isopropyl-2,6,11,13-tetradecatrien-1al) and manols. By pyrolysis, c/s-abienol, (12-Z)- -12,14-dien-8a-ol, generates mainly frans-neo-abienol. 

In mixtures of amino acids and sugars, meat flavor can be developed via different pathways. Cysteine does not only generate meat flavor via keto-L-cysteines but it reacts also with (the decomposition products of) the Amadori compounds of other amino acids to produce meat flavors that are of comparable intensity (5). This means that there are at least two major pathways to meat flavor development in such Maillard reaction systems ... 

Another approach to overcome the flavor instability problem is the in situ generation of die unstable flavor compounds just prior to consumption of die product. In principle, this is possible with ketopentosese-L-cysteines as the flavor precursors. Unfortunately, this approach is frustrated by the high costs of the pure Amadori compounds and dieir relatively low reactivity in products under kitchen conditions (Figure 4). 

In theory, a crude cysteine-sugar reaction product with a high content of Amadori compoimd can also be used as a flavor precursor system. However, to avoid off-flavor formation, the cysteine-xylose reaction has already to be discontinued before 75% of the maximum Amadori compound concentration has been achieved. Moreover, dilution with other precursors and/or a flavor carrier is necessary for acceptable stability. In some cases, the use of mixtures of cysteine with Amadori compounds of other amino acids (5) can also be a suitable alternative for the in situ generation of meat flavors. 

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