Cysteine-Induced pH-Dependent Formation of Thiols and Sulfides or 2-Acetylthiazole and Pyrazines during Thermal Treatment of N-(1-Deoxy-d-xylulos-1-yl)-alanine

Abstract

The influence of pH was studied on volatile flavor formation during thermal treatment of an Amadori rearrangement product (ARP) with or without the addition of cysteine (Cys). The formation of thiols and sulfides or 2-acetylthiazole and pyrazines induced by Cys during thermal degradation of ARP was pH-dependent. At low pH levels, the hydrolysis of Cys to hydrogen sulfide (H2S) was promoted, giving rise to the increase of thiols and sulfides with an obvious meaty aroma. However, alkaline conditions were beneficial for enhancing the cyclization or transformation of imine to the enol structure, which strengthened the formation of 2-acetylthiazole and pyrazines with a roasted and nutty aroma. The imine was derived from the nucleophilic addition of Cys and methylglyoxal (MGO) and subsequent decarboxylation. At pH 8, Cys-induced variation of the flavor profile was weakened during thermal degradation of ARP. Accordingly, the combinational effect of pH and added Cys could be beneficial for achieving the desirable flavors during thermal processing of ARP.

Promotion or Inhibition Effects of Exogenous Glutathione-Degraded Amino Acids on the Formation of 2,3-Butanedione and Pyrazines via Varied Pathways of Interaction with α-Dicarbonyl Compounds Derived from N-(1-Deoxy-d-xylulos-1-yl)-alanine

“…ARP was analyzed by a Bruker DRX 400 MHz spectrometer (Bruker BioSpin, Germany) operated at 25 °C, and 1 H and 13 C NMR spectra were obtained. The test conditions for NMR analysis of ARP were in accordance with the previous study, 19 and the data were processed through MestReNova software (version 9.0.1, Escondido, CA, USA). 19 Thermal Treatment of Reaction Systems.…”

“…The method for the preparation and purification of ARP was developed according to our published study. 19 In brief, xylose (0.4 mol/L) and Ala (0.2 mol/L) were completely dissolved in deionized water (100 mL), and then the pH of the resultant mixture was adjusted to 7.5 ± 0.1 with NaOH (6 mol/L). Then the solution was dehydrated with a rotary vacuum evaporator at 80 °C for 20 min after being heated at 80 °C for 60 min under ambient pressure.…”

“…The method for the preparation and purification of ARP was developed according to our published study . In brief, xylose (0.4 mol/L) and Ala (0.2 mol/L) were completely dissolved in deionized water (100 mL), and then the pH of the resultant mixture was adjusted to 7.5 ± 0.1 with NaOH (6 mol/L).…”

“…The test conditions for NMR analysis of ARP were in accordance with the previous study, 19 and the data were processed through MestReNova software (version 9.0.1, Escondido, CA, USA). 19 Thermal Treatment of Reaction Systems. Reaction systems of ARP (20 mmol/L) with or without GSH (20 mmol/L) addition were prepared, and the initial pH of the resultant mixtures was adjusted to 7.5 with a 3 mol/L NaOH solution before the heat treatment.…”

Maillard Reaction Process and Characteristic Volatile Compounds Formed During Secondary Thermal Degradation Monitored via the Change of Fluorescent Compounds in the Reaction of Xylose–Corn Protein Hydrolysate

“…ARPs and their degradation products, such as α-dicarbonyl compounds and other intermediates, can also be isolated, purified, and quantified, which would help us to infer the process of Maillard reaction. 11 Based on the dynamic changes in the concentration of Amadori compounds, the Maillard reaction pathway could be inferred, and the MRIs were selectively prepared by adjusting the reaction parameters. 12 However, for the Maillard reaction of the complex protein hydrolysates, multiple peptide fragments and free amino acids coexisted, and thereby various highly active precursors formed, which all made the isolation of intermediates difficult and their characterization impossible.…”