Imbalance of the redox system and quality of tilapia fillets subjected to pre-slaughter stress.

Elenice Souza Dos Reis Goes,Pedro Luiz De Castro,Ricardo Pereira Ribeiro,Ana Carolina Pelaes Vital,Marcio Douglas Goes,Jorge Antônio Ferreira De Lara,Juan J Loor

doi:10.1371/journal.pone.0210742

Elenice Souza Dos Reis Goes, Pedro Luiz De Castro + Show 5 more

Open Access

https://doi.org/10.1371/journal.pone.0210742

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Abstract

The objective of this study was to evaluate the effect of oxidative stress on the instrumental and sensory quality of Nile tilapia fillets. The experiment was conducted in a 2x2 factorial arrangement, evaluating densities (60 and 300 kg m-3) and depuration times (1 and 24 hours) in a total of four treatments. The serum levels of cortisol and gene expression levels of catalase (CAT), glutathione peroxidase (GPx) and 70 kDa heat shock protein (HSP70) as well as the pH, color, tenderness, water-holding capacity and sensory analysis of the fillets were evaluated. High density (300 kg m-3) resulted in higher mean cortisol levels, lower expression of CAT and GPx enzymes as well as higher expression of HSP70. Fish under this treatment also exhibited fillets with greater tenderness, higher lightness, lower redness and lower sensory acceptance. The longer depuration time (24 hours) resulted in lower expression of the CAT and GPx enzymes and fillets with higher lightness. The water-holding capacity was not affected by the different treatments. Therefore, low density and longer depuration times are recommended for decreased stress and improved quality of fillets.

Highlights

Stress is a condition of high aerobic energy demand to supply the body’s maintenance mechanisms during activation for adaptation and resistance of the body to stressful conditions [1]
Imbalance of the redox system and quality of tilapia fillets at pre-slaughter can increase the degree of protein denaturation and, increase the access of proteolytic enzymes to protein substrates, leading to faster muscle softening, which is detrimental for fish muscle [6]
A recent study has shown that CAT, glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities are significantly lower in pale, soft and exudative (PSE) chicken meat, which makes this type of meat more susceptible to proteolysis and protein oxidation [11]

Summary

Introduction

Stress is a condition of high aerobic energy demand to supply the body’s maintenance mechanisms during activation for adaptation and resistance of the body to stressful conditions [1]. In addition to denaturation and proteolysis, muscle proteins undergo oxidative damage after slaughter and subsequent meat aging [7]. Oxidation may play a role in controlling the proteolytic activity of enzymes and may be linked to meat tenderness [9]. Endogenous antioxidant factors, such as enzymes, control oxidation in muscle tissues [8]. Enzymes, such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), can neutralize meat oxidation [10]. A recent study has shown that CAT, GPx and SOD activities are significantly lower in pale, soft and exudative (PSE) chicken meat, which makes this type of meat more susceptible to proteolysis and protein oxidation [11]

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