Biochemical study of rapid discolouration mechanisms in Bison meat

鲜肉的颜色是消费者用来作为新鲜和卫生指标的一个重要属性，任何偏离正常颜色(例如樱桃红)的颜色都表明功能不佳和可能变质。肉色稳定性是野牛行业的主要担忧之一，因为在有氧零售包装下，野牛的颜色比牛肉更深，变色更快。因此，长期目标是通过监测客观和主观的颜色变化，全面了解决定不同包装下储存和零售陈列期间不同野牛肌肉肌红蛋白氧化/还原的因素。短期目标是：1)检测4-羟基-2-壬烯醛(HNE)、蛋白质氧化、非血红素铁和肌浆蛋白质组对两种不同稳定性的野牛肌肉在贮藏过程中颜色稳定性的影响；2)建立生化成分、氧化稳定性和肌浆蛋白与肌红蛋白氧化之间的关系；3)测试近红外反射光谱(NIRS)区分颜色稳定和不稳定的野牛肌肉的能力；4)研究一氧化碳气调包装(CO-MAP)对不同储藏期、不同色泽稳定性的野牛牛排生化成分和零售陈列特性的影响。死后骨骼肌中肌红蛋白的氧化还原生物化学特别复杂，其中出现的小生物分子可导致快速的色素氧化和表面变色；但其作用机制尚不清楚。野牛多不饱和脂肪酸含量较高，可促进氧化，产生HNE等反应性二次氧化产物，加速肌红蛋白氧化。这一过程可能涉及冷藏过程中蛋白质的氧化，血红素分子的分解，以及随后非血红素铁从卟啉环中释放，这也可能增加肉类系统的氧化不稳定性。此外，肌浆中抗氧化剂/促氧化剂成分蛋白(如硫氧还蛋白)之间的平衡变化可能会导致脂肪氧化，导致肉类变色。这些措施将与近红外光谱一起使用，以促进组织颜色稳定性的发展，并应用肌肉特有的加工策略，如新型包装(例如，CO-MAP)，以提高零售颜色稳定性。当然，随着对决定颜色稳定性的因素有了更好的了解，行业可以扩大鲜肉的销售，为消费者提供更一致、更可接受和更理想的产品。此外，三名本科生和两名理科硕士。学生将在我的计划下接受培训。从野牛身上获得的经验可以适用于其他物种，并缓解它们的颜色问题。

Fresh meat colour is an important attribute used by consumers as an indicator of freshness and wholesomeness, and any deviation of normal colour (e.g. cherry red) is indicative of poor functionality and possible spoilage. Meat colour stability is one of the major concerns in the bison industry, because it is darker and discolours more rapidly than beef under aerobic retail packaging. Consequently, the long-term objective is to gain comprehensive understanding of factors determining myoglobin oxidation/reduction in different bison muscles during storage and retail display under diverse packaging, by monitoring objective and subjective colour changes. The short-term objectives are: 1) to examine the effect of 4-hydroxy-2-nonenal (HNE), protein oxidation, non-heme iron, and the sarcoplasmic proteome on the colour stability of two bison muscles of diverse stability during storage; 2) to establish the relationship among biochemical components, oxidative stability and sarcoplasmic proteins to the oxidation of myoglobin during storage of two bison muscles; 3) to test the ability of near infrared reflectance spectroscopy (NIRS) to segregate bison muscles with stable vs. unstable colour; 4) to determine the effects of carbon monoxide modified atmosphere packaging (CO-MAP) on biochemical components and retail display characteristics of bison steaks from with different colour stability using different storage periods. The redox biochemistry of myoglobin in post-mortem skeletal muscles is particularly complex, where small biomolecules occur that can cause rapid pigment oxidation and surface discolouration; but, their mechanisms of action are not well understood. The higher polyunsaturated fatty acid content in bison could promote oxidation and generate reactive secondary oxidation products such as HNE, and accelerate myoglobin oxidation. This process could involve protein oxidation during refrigerated storage, breakdown of the heme molecule and the subsequent release of non-heme iron from the porphyrin ring, which might also increase oxidative instability in the meat system. Also, variations in the balance between antioxidant/pro-oxidant component proteins (e.g. thioredoxin) in the sarcoplasm could induce lipid oxidation and cause meat discoloration. These measures will be used along with NIRS in order to enable development of colour stability in tissue and apply muscle-specific processing strategies such as novel packaging (e.g. CO-MAP) for improving retail colour stability. Certainly, with better understanding of the factors that determine colour stability, industry can expand fresh meat sales, offering a more consistent, acceptable and desirable product to consumers. In addition, three undergraduate and two M.Sc. students will be trained under my program. The experiences gained with bison could be applicable to other species and mitigate their colour issues.