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Gas stunning with CO2 affected meat color, lipid peroxidation, oxidative stress, and gene expression of mitogen-activated protein kinases, glutathione S-transferases, and Cu/Zn-superoxide dismutase in the skeletal muscles of broilers

Xu, Lei, Zhang, Haijun, Yue, Hongyuan, Wu, Shugeng, Yang, Haiming, Wang, Zhiyue, Qi, Guanghai
Journal of animal science and biotechnology 2018 v.9 no.1 pp. 37
blood serum, breast meat, breast muscle, breasts, carbon dioxide, color, correlation, cortisol, enzyme activity, gene expression, genes, glutathione transferase, lipid peroxidation, lipid peroxides, meat quality, messenger RNA, mitogen-activated protein kinase, nitrogen, oxidative stress, oxygen, skeletal muscle, storage, storage temperature, stunning methods, superoxide dismutase, thiobarbituric acid-reactive substances, triiodothyronine
BACKGROUND: Meat color and lipid peroxidation are important traits related to meat quality. CO₂ concentration is a critical factor that can affect meat quality in the commercial use of gas stunning (GS). However, the effect and mechanism of CO₂ stunning on meat color and lipid peroxidation during long-term storage remain poorly studied. We aimed to study the effects of GS methods, especially CO₂ concentration, on meat color and meat lipid peroxidation in broilers during long-term storage at 4 °C and to explore the potential mechanism of meat color change via lipid peroxidation and the inner lipid peroxide scavenging system. METHODS: Eighteen broilers were sacrificed after exposure to one of the following gas mixtures for 90 s: 40% CO₂ + 21% O₂ + 39% N₂ (G40%), 79% CO₂ + 21% O₂ (G79%), or no stunning (0% CO₂, control). Meat color, serum variables, enzyme activities, and the gene expression of mitogen-activated protein kinase (MAPK), nuclear factor-erythroid 2-related factor 2 (Nrf2), glutathione S-transferase (GST) and superoxide dismutase (SOD) were determined. RESULTS: The concentrations of serum triiodothyronine (T3, P = 0.03) and the ratio of serum free triiodothyronine/free thyroxine (FT3/FT4, P < 0.01) were decreased, whereas levels of serum cortisol (P < 0.01) were increased in the 40% CO₂ group compared with the control group. Additionally, the thiobarbituric acid-reactive substances (TBARS) ₃ d (P < 0.01) and TBARS ₆ d (P = 0.01) in breast meat and the TBARS ₃ d in thigh meat (P < 0.01) were increased in the 40% CO₂ group compared with the control group. Serum T3 was negatively correlated with TBARS₆ d both in the breast and thigh meat (r = − 0.63, P < 0.01 and r = − 0.47, P = 0.05 respectively). T3/T4 was negatively correlated with TBARS₆ d in the breast meat and in the thigh meat (r = − 0.57, P = 0.01; and r = − 0.53, P = 0.03 respectively). Compared with the control group, Lightness (L*) ₁ d (P = 0.03) and L*₉ d (P < 0.01) were increased, whereas total chromatic aberration (E*) ₁ d (P = 0.05) and E*₃ d (P < 0.01) were decreased in the breast meat of both the G40% and G79% groups. The values of yellowness (b*) ₃ d (P = 0.01), b*₆ d (P < 0.01) and E*₆ d (P < 0.01) in the thigh meat were lower in both the G40% and G79% groups than in the control group. In the breast muscle, the mRNA levels of c-Jun N-terminal kinase 2 (JNK2, P = 0.03), GSTT1 (P = 0.04), and SOD1 (P = 0.05) were decreased, and the mRNA levels of JNK1 (P = 0.07), Nrf2 (P = 0.09), and GSTA3 (P = 0.06) were slightly lower in both the G40% and G79% groups compared with the control group. However, among these genes, only the mRNA level of JNK1 was decreased in the G40% group compared with the control group and the G79% group (P = 0.03) in the thigh muscle. CONCLUSIONS: Compared with the control group, meat color quality in the breast meat was decreased, and the expression of genes in the MAPK/Nrf2/ARE (antioxidant responsive element) antioxidant pathway in breast muscle was partly suppressed by GS of both 40% and 79% CO₂. However, oxidative stress and meat lipid peroxidation during storage were aggravated by GS with 40% CO₂ compared to GS with 79% CO₂ and no GS.