Quantitation of key odorants in arginine/cysteine-glucose Maillard reactions

Unlike many other named reactions in organic chemistry, the Maillard reaction is not a clearly defined single pathway. Instead, it is one of the most complex processes in food chemistry. Maillard reactions studied in the literature over the last fifty years have focused either on simple model systems or complex culinary processes. The next step in our understanding of Maillard reactions is to bridge the gap between these simple and complex systems. By adding more than one amino acid to a model system, we aim to better understand the different mechanisms for which certain aroma compounds are formed. In this study, L-arginine and L-cysteine were selected as the two amino acids in the thermal reaction with glucose. Found most abundantly in turkey and chicken, arginine is a basic, polar amino acid that has not been well studied in terms of its generation of volatile compounds from the Maillard reaction. In contrast, L-cysteine, an amino acid found in meat and poultry, has been studied in detail. Using different reaction conditions, the key odorants from several arginine-cysteine/glucose model studies were identified and quantified by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). Attention was given to the extraction procedure used for the isolation of the aroma compounds. The methodology of Likens-Nickerson extraction, better known as steam distillation extraction (SDE), has often been used in the literature to isolate the aroma compounds from Maillard reactions. A comparison of several data sets will show that solvent assisted flavor evaporation (SAFE) is a more preferred method for the isolation and recovery of a wide range of key odorants. This is evident in the quantitation of hydrophilic, mercapto acids, including 2-mercaptopropionic acid and 3-mercaptopropionic acid. The physico-chemical properties (log10Pow) and the mechanisms of formation will be discussed for both compounds. Finally, the mechanisms of formation for additional key odorants identified by GC-MS and GC-O will be proposed. A strategy to prove these mechanisms and ideas for supplementary reactions will be briefly discussed.M.S.Includes bibliographical reference