Álvarez-Armenta A, Pacheco-Aguilar R, López-Zavala AA, Corona-Martínez DO, Sotelo-Mundo RR, García-Orozco KD, Ramírez-Suárez JC. The greening reaction of skipjack tuna (
Katsuwonus pelamis) metmyoglobin promoted by free cysteine during thermal treatment.
PeerJ 2022;
10:e13923. [PMID:
35996665 PMCID:
PMC9392451 DOI:
10.7717/peerj.13923]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 07/29/2022] [Indexed: 01/19/2023] Open
Abstract
Background
Tuna muscle greening is a problem that occurs after heating. A hypothesis has been postulated to address this problem, involving a conserved Cys residue at position 10 (Cys-10) present on tuna myoglobin (Mb) that is exposed during the thermic treatment, forming a disulfide bond with free cysteine (Cys) in the presence of trimethylamine oxide (TMAO), resulting in the greening of the tuna Mb.
Methods
We present a study using skipjack tuna (Katsuwonus pelamis) metmyoglobin (MbFe(III)-H2O) where the effect of free Cys (1-6 mM), TMAO (1.33 mM), and catalase on the greening reaction (GR) was monitored by UV-vis spectrometry during thermal treatment at 60 °C for 30 min. Moreover, the participation of Cys-10 on the GR was evaluated after its blocking with N-ethymaleimide.
Results
The GR occurred in tuna MbFe(III)-H2O after heat treatment with free Cys, forming sulfmyoglobin (MbFe(II)-S) as the responsible pigment for the tuna greening. However, the rate constants of MbFe(II)-S production depended on Cys concentration (up to 4 mM) and occurred regardless of the TMAO presence. We postulate that two consecutive reactions involve an intermediate ferrylmyoglobin (promoted by H2O2) species with a subsequent MbFe(II)-S formation since the presence of catalase fosters the reduction of the rate reaction. Moreover, GR occurred even with blocked Cys-10 residues in tuna Mb and horse Mb (without Cys in its sequence).
Discussion
We found that GR is not exclusive to tuna Mb´s, and it can be promoted in other muscle systems. Moreover, Cys and thermal treatment are indispensable for promoting this pigmentation anomaly.
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