Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE 68583-0908, USA.
Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68503-0908, USA.
J Anim Sci. 2021 Jul 1;99(7). doi: 10.1093/jas/skab156.
The objective of this study was to evaluate effects of different levels of lipopolysaccharide (LPS)-mediated oxidative stress on fresh meat quality. Crossbred lambs (n = 29) were blocked by weight and fed a standard finishing ration for the duration of the study. Lambs were individually housed and treatment groups were administered one of three intravenous injections every 72 h across a three-injection (9-day) cycle: saline control (control), 50 ng LPS/kg body weight (BW) (LPS50), or 100 ng LPS/kg BW (LPS100). Rectal temperatures were measured to indicate inflammatory response. Lambs were harvested at the Loeffel Meat Laboratory and 80 mg of pre-rigor Longissimus lumborum were collected in control and LPS100 treatments within 30 min postmortem for RNA analysis. Wholesale loins were split and randomly assigned 1 or 14 d of wet aging. Chops were fabricated after aging and placed under retail display (RD) for 0 or 7 d. Animal was the experimental unit. LPS-treated lambs had increased (P < 0.05) rectal temperatures at 1, 2, 4, and 24 h post-injection. Transcriptomics revealed significant (Praw < 0.05) upregulation in RNA pathways related to generation of oxidative stress in LPS100 compared with control. A trend was found for tenderness (Warner-Bratzler shear force, WBSF; P = 0.10), chops from LPS50 having lower shear force compared with control at 1 d postmortem. Muscle from LPS50 treatment lambs exhibited greater troponin T degradation (P = 0.02) compared with all treatments at 1 d. Aging decreased WBSF (P < 0.0001), increased sarcoplasmic calcium concentration (P < 0.0001), pH (P < 0.0001), and proteolysis (P < 0.0001) across treatments. Following aging, chops increased discoloration as RD increased (P < 0.0001), with control chops aged 14 d being the most discolored. Chops from lambs given LPS had higher (P < 0.05) a* values compared with control at 14 d of aging. The L* values were greater (P < 0.05) in LPS100 compared with both LPS50 and control. Aging tended (P = 0.0608) to increase lipid oxidation during RD across either aging period. No significant differences (P > 0.05) in sarcomere length, proximate composition, fatty acid composition, or isoprostane content were found. These results suggest that defined upregulation of oxidative stress has no detriment on fresh meat color, but may alter biological pathways responsible for muscle stress response, apoptosis, and enzymatic processes, resulting in changes in tenderness early postmortem.
本研究旨在评估不同水平脂多糖（LPS）介导的氧化应激对鲜肉品质的影响。杂种羔羊（n = 29）按体重分组，在研究期间饲喂标准育肥日粮。羔羊单独饲养，每隔 72 小时给予三组静脉注射中的一组，共三组注射（9 天周期）：生理盐水对照（对照）、50ng LPS/kg 体重（BW）（LPS50）或 100ng LPS/kg BW（LPS100）。测量直肠温度以指示炎症反应。羔羊在 Loeffel 肉类实验室收获，在死后 30 分钟内，对照组和 LPS100 处理组中采集 80mg 预僵直腰最长肌进行 RNA 分析。分割胴体并随机分配 1 或 14 天湿老化。老化后制备肉块，并在零售展示（RD）下放置 0 或 7 天。动物是实验单位。LPS 处理的羔羊在注射后 1、2、4 和 24 小时的直肠温度升高（P < 0.05）。转录组学显示，与对照组相比，LPS100 中与氧化应激产生相关的 RNA 途径显著上调（Praw < 0.05）。LPS50 处理的羔羊在死后 1 天的嫩度（Warner-Bratzler 剪切力，WBSF；P = 0.10）有降低趋势，与对照组相比剪切力较低。与所有处理相比，LPS50 处理组的肌钙蛋白 T 降解更大（P = 0.02），在死后 1 天。老化降低了 WBSF（P < 0.0001），增加了肌浆钙离子浓度（P < 0.0001）、pH 值（P < 0.0001）和蛋白水解（P < 0.0001）。老化后，随着 RD 的增加，肉块的变色程度增加（P < 0.0001），14 天老化的对照肉块颜色最深。与对照组相比，LPS 处理的羔羊在 14 天老化时的 a值更高（P < 0.05）。与 LPS50 和对照组相比，LPS100 的 L值更高（P < 0.05）。RD 期间，老化有增加脂质氧化的趋势（P = 0.0608），无论老化期如何。未发现肌节长度、近似成分、脂肪酸组成或异前列腺素含量有显著差异（P > 0.05）。这些结果表明，氧化应激的明确上调对鲜肉颜色没有不利影响，但可能改变负责肌肉应激反应、细胞凋亡和酶促过程的生物途径，导致死后早期嫩度发生变化。
