Characterization of collagen cross-links that influence meat quality

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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.