Effect of Additional Amino Acids on the Cysteine-Xylose Maillard Reaction to Form Volatile Flavor Compounds

This study investigated effect of adding serine, glutamic acid, or glycine to the "cysteine-xylose" system on formation of volatile flavor compounds via the Maillard reaction, aiming to provide guidance for meat animals breeding, meat food processing, and meat flavorings preparation. For the different Maillard reaction systems, their reaction extents were assessed by measurement of UV absorption at 294 and 420 nm, color difference values, pH, and the remaining xylose in the reaction solutions. Volatile flavor compounds generated were comparatively analyzed by solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) and aroma extract dilution analysis in gas chromatography-olfactometry (AEDA/GC-O) in combination with partial least squares regression correlation analysis (PLSR) and odor activity value (OAV) calculation. The results showed that addition of each of the three amino acids in four times the molar concentration of cysteine, the reaction extents of the Maillard reaction systems were enhanced. Addition of glycine caused the most browning of the reaction solution, followed by that of serine and glutamic acid. On the other hand, formation of volatile flavor compounds also increased as well with addition of the three amino acids. Especially, addition of glutamic acid produced the highest amount of sulfur-containing meaty compounds, where the odor-active compounds of them had greater dilution factors and the key aroma compounds (OAV≥1) of them exhibited larger OAVs. With increasingly adding the three amino acids in "cysteine-xylose" system, amounts of sulfur-containing key aroma compounds generated in the reaction systems first rose then fell, whereas amounts of the pyrazine key aroma compounds ascended all the way. As serine and glutamic acid each were in four times cysteine concentration, and glycine was in two times cysteine concentration, the sulfur-containing key aroma compounds were maximally yielded in the reaction systems, respectively. In conclusion, among the three amino acids, glutamic acid caused the weakest browning reaction whereas benefitted generation of sulfur-containing meaty compounds.