Characterization of collagen cross-links that influence meat quality

消费者对肉的接受程度取决于肉的坚韧。 肉的韧性取决于肉中结缔组织或“软骨”的数量，坚韧的肉具有大量的结缔组织。 肉类中的结缔组织主要由蛋白质胶原组成，胶原在其分子之间形成交联，在整个肌肉中产生纤维网络，将肌肉蛋白质的收缩力转移到骨骼，从而在活动物中产生运动。 随着动物的成熟，胶原交联的复杂性增加，可被热降解的交联逐渐被热稳定的交联取代。 因此，现代畜牧业的做法是生产幼畜供食用。 这一战略生产出了嫩鸡肉和猪肉，但没有生产出嫩牛肉，因为非常年轻的牛不能产生足够的肉，这种做法是有利可图的。因此，只有30%的牛肉胴体足够嫩，可以用平底锅油炸，而剩下的70%则通过切碎成“碎牛肉”来嫩化。 研磨牛肉使其变嫩，但也会缩短其保质期，增加其水分流失，并增加其对细菌的接触。 牛肉也可以使用酶来降解胶原蛋白;然而，这些酶也会降解其他肌肉蛋白质，并产生“糊状”或“颗粒状”的熟牛肉。 该研究计划的第一个目标是表征不同年龄和生长速度的牛的牛肉中胶原蛋白交联的结构，以了解胶原蛋白交联的复杂性如何随着动物的年龄和生长而变化。 该研究计划的第二个目标是确定仅降解胶原蛋白并降低其热稳定性的酶。 了解胶原蛋白的交联结构，它如何受到动物年龄和生长速度的影响，并确定酶降解如何影响复杂交联中涉及的胶原蛋白，这对于创造新工艺来嫩化和增加高结缔组织牛肉的价值至关重要。 这项研究将为加拿大牛肉加工商提供新的产品差异化战略，并有助于增加加拿大在全球牛肉市场的份额。

Consumer acceptability of meat is governed by how tough the meat is perceived to be. The toughness of meat is determined by the amount of connective tissue or 'gristle' that is in the meat, with tough meat having large amounts of connective tissue. Connective tissue in meat consists primarily of the protein collagen, which forms cross-links between its molecules to produce a fibrous network throughout muscle that transfers the force of contraction from the muscle proteins to the bone to produce movement in the live animal. As animals mature, the complexity of the collagen cross-links increases, with cross-links that can be degraded by heat progressively replaced by cross-links that are heat stable. As a result, modern animal husbandry practices produce young animals for meat. This strategy has produced tender chicken and pork, but has not produced tender beef because very young cattle do not yield sufficient meat for the practice to be profitable. Consequently, only 30% of the beef carcass is tender enough to be pan-fried, while the remaining 70% is tenderized by mincing it into 'ground beef'. Grinding beef tenderizes it, but also reduces its shelf-life, increases its water loss and increases its exposure to bacteria. Beef can also be tenderized using enzymes to degrade collagen; however, these enzymes also degrade other muscle proteins and produce cooked beef that is 'mushy' or 'granular'. The first objective of this research program is to characterize the structure of the collagen cross-links in beef from cattle of different ages and growth rates to see how the complexity of the collagen cross-links changes as animals age and grow. The second objective of this research program is to identify enzymes that degrade only collagen and reduce its heat stability. Understanding the cross-link structure of collagen, how it is affected by animal age and rate of growth and identifying how enzyme degradation affects collagen involved in complex cross-links is crucial to creating new processes to tenderize and add value to high connective tissue beef. This research will provide new product differentiation strategies to Canadian beef processors and assist with increasing Canada's share of the global beef market.