MODEL REACTIONS ON ROAST AROMA FORMATION .11. HEATING OF SERINE WITH SELECTED SUGARS AND SUGAR DEGRADATION PRODUCTS IN AN AUTOCLAVE

After reaction of serine with glucose, fructose, diacetyl or cyclotene in an autoclave at 120-degrees-C, 150-degrees-C, or 180-degrees-C 338 volatile compounds (aliphatic and carbocyclic carbonyls, furans, furanones, pyranones, phenols, pyridines, pyrazines and pyrroles) were identified. The total amounts of some of these compound classes were determined and compared. Serine forms, beside glycolic aldehyde, also aminoethanol and some aliphatic aldehydes which lead to the formation of a great many compounds. Fructose obviously forms, under same conditions, more methylglyoxal than glucose, but generally the degradation products are identical. With rising temperature the number and amounts of reaction products increased some of which, like furylpyrazine and furfurylpyrazine, additionally required special intermolecular condensations. Diacetyl at 180-degrees-C obviously forms dimeric condensation products which, by further reactions, yield benzene compounds, 3-hydroxy-2,5,6-trimethylpyridine, 2-acetyl-4,5-furan and 2-acetyl-4,5-pyrrole. Cyclotene itself forms during heating numerous derivatives by condensation-, dehydration- or hydrogen-transfer reactions. By reaction with NH3 from serine, these derivatives formed imines which, by further reactions, yielded cyclopentapyrazines and dicyclopentapyrazines. Some mechanisms are proposed for the formation of pyrrolylalkanols, pyrrolopyrazines and products mentioned here.