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

Abstract

The contribution of glutathione (GSH) and free amino acids degraded from GSH to the generation of pyrazines and 2,3-butanedione was illustrated during their interaction in the thermal treatment of the Amadori compound of alanine and xylose (ARP). GSH-degraded amino acids, glutamic acid (Glu), cysteine (Cys), and glycine (Gly), but not pyroglutamic acid (pGlu), could effectively capture α-dicarbonyls to facilitate the formation of pyrazines when ARP was heated with GSH. Deoxypentosones, the precursors of 2,3-butanedione, were largely consumed in the ARP–GSH model by the interaction with GSH and its degradative Cys compared with the ARP model. The addition of GSH and deoxypentosones inhibited the further degradation of deoxypentosones, resulting in less formation of 2,3-butanedione and other α-dicarbonyl compounds. Meanwhile, the reaction between GSH-degraded Cys and deoxypentosones to form sulfur-containing compounds such as thiols accelerated the consumption of deoxypentosones; thereby, the formation of 2,3-butanedione was severely interfered. However, this inhibition was compensated for by the GSH-degraded Gly through the addition between Gly and MGO and the subsequent deamination. The involvement of exogenous GSH could simultaneously boost the yields of 2,3-butanedione and pyrazines compared with those of ARP heated alone. As the degree of GSH degradation strengthened in the ARP-thermal-degraded GSH models, the yields of both pyrazines and 2,3-butanedione steadily increased.

Disclosing the Nitrogen Sources via Isotope Labeling Technique and the Formation Mechanism of Pyrazine and Alkylpyrazines during the Heat Treatment of N-(1-Deoxy-d-xylulos-1-yl)-alanine and Exogenous Alanine

“…The interaction between exogenous and regenerated amino acids might complicate the formation pathway of the pyrazines, making it challenging to pinpoint the source of the formed pyrazines. Therefore, in order to reveal the contribution of regenerated and exogenous Ala to the formation of diverse pyrazines, 15 N-Ala was used as an exogenous amino acid to clarify the origin of the nitrogen as well as the pathway for the participation of exogenous Ala in the formation of pyrazines.…”

“…Chemicals. D-Xylose (Xyl), sodium chloride, 15 N-labeled L-alanine ( 15 N-Ala), L-alanine (Ala), 15 N-labeled L-glycine ( 15 N-Gly), and Lglycine (Gly) were obtained from Aladdin Chemical Reagent Co, Ltd. (Shanghai, China). Methylglyoxal (40% in H 2 O) and glyoxal (40% in H 2 O) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).…”

“…13 And more importantly, some research results suggested that the supplement of exogenous peptides/amino acids could effectively promote the yields of pyrazine compounds during the controlled flavor formation of ARP. 14,15 However, the reaction preference of different αdicarbonyls with selected amino acids to form respective pyrazines remains unclear. Also, the formation mechanism of pyrazines stimulated by exogenous amino acids or peptides needs to be further explored.…”

“…The intervention of extra-added Ala on the production of pyrazines from thermally treated Ala-ARP under alkaline conditions was analyzed. 15 N-labeled Ala was employed as an exogenous Ala to react with Ala-ARP, and thereby, the nitrogen sources of formed pyrazines were distinguished. Further research was conducted to investigate the reactivity difference between GO and MGO with Ala. During the thermal treatment of ARP with or without exogenous Ala, the dynamic changes of pH, regenerated and exogenous Ala, as well as α-dicarbonyls were also monitored.…”

Exogenous Alanine Promoting the Reaction between Amadori Compound and Deoxyxylosone and Inhibiting the Formation of 2-Furfural during Thermal Treatment

“…During the thermal reaction of methionine-glucose-ARP and exogenous methionine, the oxidation of methionine could competitively inhibit the oxidation of dihydropyrazines to form pyrazines, but promote the conversion of dihydropyrazines to ethyl or long-chain substituted alkylpyrazines with the involvement of aldehyde . Our previous studies have revealed that exogenous cysteine and glutathione (acting as browning inhibitors) can interfere with the pyrazines and 2,3-butanedione formation via diverse pathways of interaction with α-DCs degraded from alanine-xylose ARP. , However, the aforementioned studies predominantly focused on the exogenous amino acids containing reactive groups in their side chain (including sulfhydryl and hydroxyl) or exogenous peptides accompanied by hydrolysis of peptide bonds, which made the pathways of their participation in ARP flavor formation more special, while the role of exogenous amino acids without reactive side chains in ARP degradation was ignored. To model the Maillard reaction well, alanine was selected.…”