熟制牛肉提前褐变现象（PMB）容易误导消费者的判断，导致牛肉热杀菌不彻底，造成大肠杆菌O157:H7等致病菌的感染，严重影响消费者的安全。高氧气调包装是造成该现象的主要因素，但是其影响机制尚不明确。课题组前期研究发现，高氧气调包装下脂肪氧化加快了冷却牛肉褐变。在此基础上，本项目拟建立冷却牛肉高氧气调包装（80%O2+20%N2）模型，结合CO气调包装、真空包装和托盘包装，探究不同条件下牛肉熟制后的肉色变化规律和PMB现象的分子机制。该研究重点通过脂质组学和蛋白组学的结合分析，揭示不同氧化状态下的脂质变化和蛋白表达变化，阐明PMB现象的分子机制；结合体外模拟氧化实验，采用圆二色谱、拉曼色谱和差示扫描量热法研究脂质氧化对肌红蛋白二级结构和热稳定性的影响；通过以上结果的相关性分析，明确脂质氧化促进肌红蛋白氧化的途径，揭示PMB现象的发生分子机制，为熟制牛肉PMB现象的改善提供理依据。

Premature browning (PMB) will lead the consumer to make a wrong judgment on the doneness of beef cooking which will lead to the survival of O157：H7 and other pathogens. High oxygen modified atmosphere package (HiOx-MAP) is one of the most serious causes of this problem. However, the mechanism is not clear. It was found that HiOx-MAP accelerated the beef browning in our previous research. Based on this finding, four different packages including HiOx-MAP, CO-MAP, vacuum package and over wrap will be applied on chilled beef during storage, to find the cooked color changes, and to find the mechanism of this problem. Proteomics and lipidomics will be used together to find out the changes of lipid and protein under different conditions. The structure and heating resisting ability of myoglobin will be analyzed based on in vitro experiment and that above using circular dichroism spectrum (CD) and differential scanning calorimetry (DSC) methods. Based on the correlation analysis of the results above, the pathway of how lipid oxidation accelerates the myoglobin oxidation will be found and the mechanism of PMB problem will also be explained. The results of this research will be useful for PMB color control.