Biochemical study the formation of key flavor precursors in various skeletal muscles post-mortem

生肉没有熟肉的香气，因为典型的香气主要是在烹饪过程中产生的。事实上，这些风味化合物是通过生肉中存在的天然前体在加热过程中发生化学反应而产生的。在这些天然风味前体中，糖和糖磷酸盐，特别是五种碳糖(戊糖)在通过美拉德反应产生熟肉所需的香气和风味方面发挥了重要作用。然而，导致这些戊糖在肉类中形成的生化途径并不完全清楚。核糖是一种五碳糖，也是肉类中一种关键的风味前体，其形成的公认途径是通过肌肉中的ATP在死后分解，但不能解释肉类中存在的所有戊糖的形成。例如，核酮糖-5-磷酸、核糖-5-磷酸、木糖已在不同类型的肉类(鸡肉、牛肉和兔)中被发现，但它们的生化来源尚不清楚。生物化学途径，如磷酸戊糖途径，很可能参与其中，并可能依赖于肌肉和/或物种。此外，目前还不清楚肉类调理如何影响关键风味前体浓度的形成和/或随时间的演变，以及这一步骤在多大程度上取决于肌肉/物种。NSERC的这项发现建议旨在使用化学和生化方法来阐明选定的生化反应在选定的骨骼肌死后产生关键风味前体(戊糖)中的作用。通过对白肉(鸡胸肉和腿肉)和加拿大常见的瘦肉红肉(野牛和麋鹿)的比较研究，首先阐明了所选择的生化反应对肉类风味的重要性的肌肉和/或物种依赖性；其次，研究了肉类调理对每种肉类关键风味前体的影响。模型系统将被用来研究候选风味前体在所选肉类中的作用以及它们对每种所选肌肉的特征香气和风味的贡献。这一研究计划将有助于了解肉类风味前体的形成，并最终有助于风味遗传标记的选择。

Raw meat has none of the aroma of cooked meat as the characteristic aroma is largely generated during cooking. In fact, the flavor compounds are generated via chemical reactions occurring between natural precursors present in raw meat during heating. Among these natural flavor precursors, sugars and sugar phosphates, and particularly five carbon sugars (pentoses) play a major role in generating the desirable aroma and flavor of cooked meat via the Maillard reaction. However, the biochemical pathways leading to the formation of these pentoses in meat are not fully understood. The accepted route for the formation of ribose, a five carbon sugar and a key flavor precursor in meat via the breakdown of ATP in muscle post-mortem, cannot explain the formation of all pentoses present in meat. For instance, ribulose-5-phosphate, ribose-5-phosphate, xylulose have been identified in various types of meat (chicken, beef and rabbit) while their biochemical origins remain unexplained. Biochemical pathways such as the pentose phosphate pathway may well be involved and could be muscle and/or species dependent. In addition, it is not clear how meat conditioning affects the formation and/or evolution of key flavor precursors' concentrations with time, and to what extent this step is muscle/species dependent. This NSERC discovery proposal aims to employ chemical and biochemical approaches to clarify the role of selected biochemical reactions in generating the key flavor precursors (pentoses) in selected skeletal muscles post-mortem. A comparative study using both white meat (chicken breast and leg) and popular Canadian lean red meats (bison and elk) is designed to elucidate firstly, the muscle and/or species dependency of the selected biochemical reactions important for meat flavor and secondly, to study the effect of meat conditioning on key flavor precursors in each type of meat. Model systems will be employed to investigate the role of candidate flavor precursors in selected meats and their contribution to the characteristic aroma and flavor of each selected muscle. This research program will help to understand the formation of flavor precursors in meat and will ultimately help with selection of genetic markers for flavor.