{"id":22,"date":"2015-08-21T21:55:28","date_gmt":"2015-08-21T21:55:28","guid":{"rendered":"http:\/\/opentextbc.ca\/meatcutting\/?post_type=chapter&p=22"},"modified":"2019-07-03T22:50:06","modified_gmt":"2019-07-03T22:50:06","slug":"composition-of-meat","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/meatcutting\/chapter\/composition-of-meat\/","title":{"raw":"Composition of Meat","rendered":"Composition of Meat"},"content":{"raw":"Meat muscle, which is what we eat, is made of [pb_glossary id=\"588\"]fibres[\/pb_glossary]<\/strong>, bound together with connective tissue, that are mainly linked to other groups of muscles or directly to the animal\u2019s bone structure. Muscle contains 60% to 70% moisture, 10% to 20% protein, 2% to 22% fat, and 1% ash, depending on type and species.\r\n\r\nOn larger bones (such as the shanks of larger animals), it is easy to see the muscle groups in bundles (if cut on the cross-section) surrounded by [pb_glossary id=\"558\"]collagen[\/pb_glossary] <\/strong>fibres and a much heavier connective tissue ([pb_glossary id=\"581\"]elastin[\/pb_glossary]<\/strong>) that forms a thin covering (called [pb_glossary id=\"668\"]silverskin[\/pb_glossary]<\/strong>) separating muscle groups or a [pb_glossary id=\"681\"]tendon[\/pb_glossary]<\/strong> at the ends of the muscle group (Figure 1). The tendon is attached to the bone at or near a bone joint (Figure 2).\r\n\r\n[caption id=\"attachment_23\" align=\"aligncenter\" width=\"500\"]\"Figure<\/a> Figure 1. Crosscut of beef shank showing muscle fibres.[\/caption]\r\n\r\n[caption id=\"attachment_24\" align=\"aligncenter\" width=\"500\"]\".\"<\/a> Figure 2. Bone with tendon attached (left) and muscle removed (right).[\/caption]\r\n\r\nThe muscle fibres are known as [pb_glossary id=\"629\"]myofibrils[\/pb_glossary]<\/strong>, which are composed of thick and thin filaments arranged in a repeating pattern alongside the other myofibrils (Figure 3). One unit of a bundle is called a [pb_glossary id=\"664\"]sarcomere[\/pb_glossary]<\/strong>, or little muscle. The thick filaments are the contractile protein [pb_glossary id=\"631\"]myosin[\/pb_glossary]<\/strong>.<\/em> The thin filaments, known as [pb_glossary id=\"525\"]actin[\/pb_glossary]<\/strong>, contain two other proteins called [pb_glossary id=\"687\"]troponin[\/pb_glossary]<\/strong> and [pb_glossary id=\"686\"]tropomyosin[\/pb_glossary]<\/strong> that help regulate muscle contraction.\r\n\r\n[caption id=\"attachment_25\" align=\"aligncenter\" width=\"500\"]\".\"<\/a> Figure 3. 1007 Muscle Fibres (large) by OpenStax College - Anatomy & Physiology, Connexions Website. June 19, 2013. Licensed under CC BY 3.0 via Wikimedia Commons[\/caption]\r\n\r\nThe amount of connective tissue in meats and its [pb_glossary id=\"670\"]solubility[\/pb_glossary]<\/strong> (the degree to which it is dissolved during the cooking process) can directly influence the tenderness of meat muscle. For example, as an animal ages, it has more connective tissue and therefore experiences [pb_glossary id=\"565\"]cross-linking[\/pb_glossary]<\/strong>, an increase in connective tissue that becomes highly insoluble. This is why older animals are usually tougher and younger animals are more tender.\r\n\r\nThe most tender cuts from a beef animal, such as tenderloin, strip loin, and top sirloin from the beef hind quarter, can be prepared using a [pb_glossary id=\"578\"]dry heat cooking method[\/pb_glossary]<\/strong>. In contrast, tougher cuts from the front quarter of beef that have more collagen connective tissue, such as the blade, shoulder, and shank, require a [pb_glossary id=\"626\"]moist heat[\/pb_glossary] <\/strong>or [pb_glossary id=\"559\"]combination cooking method[\/pb_glossary]<\/strong>, which breaks down collagen into a [pb_glossary id=\"599\"]gelatin[\/pb_glossary] <\/strong>form when cooked in water at temperatures of over 80\u00b0C (176\u00b0F). The collagen dissolves in the water, which is why stocks made from animal bones and connective tissue have body and thicken when cooled. (We discuss cooking potential and tenderness in more detail later in the book.)\r\n\r\nHeavy collagen, such as tendons at the ends of muscle groups and the protein elastin, does not break down under this cooking process and is therefore insoluble in water. In addition to silverskin and tendons, there is a specific piece of heavy collagen (also known as the [pb_glossary id=\"535\"]backstrap[\/pb_glossary])<\/strong> that is yellow in colour and located along the upper backbone from the base of the skull to the end of the rib cage in all meat animals (Figure 4).\r\n\r\n[caption id=\"attachment_26\" align=\"aligncenter\" width=\"500\"]\".\"<\/a> Figure 4. Backstrap location on lamb rack.[\/caption]\r\n\r\nFats are deposited all over certain parts of the animal and contribute to the shelf life, flavour, and colour of dry aged meats. Fat in beef meat muscle is called intramuscular<\/strong> fat<\/strong> and appears as a pattern of wavy lines, commonly known as marbling <\/strong>(Figure 5).<\/a>\r\n\r\n[caption id=\"attachment_703\" align=\"aligncenter\" width=\"400\"]\".\"<\/a> Figure 5. Poster indicating marbling in USDA Beef grades. [image description]<\/a>[\/caption]Well-marbled meat usually indicates that the cooked meat will be juicy and tender, and the amount of marbling is a factor that is used to determine the grade of beef, specifically for the A grades. Beef grading is discussed in detail later in the book.\r\n

Image descriptions<\/h1>\r\n<\/a>Figure 5. Poster indicating marbling in USDA Beef grades.<\/strong>\r\n\r\nA guide to understanding the fat content of USDA grades of beef.\r\n