Meat Principles of Food Science and Processing 2024 Lecture 5 PDF

1 Meat Dr. Mohamed Elsaadany 17  Types of Meat Meat from animals such as beef cattle, sheep, and pig serves as an important source of complete protein. Meat from other animals, such as goat, rabbit, deer, elk, moose, horse, and squirrel, is less commonly eaten. 1. Beef Be...

1 Meat Dr. Mohamed Elsaadany 17  Types of Meat Meat from animals such as beef cattle, sheep, and pig serves as an important source of complete protein. Meat from other animals, such as goat, rabbit, deer, elk, moose, horse, and squirrel, is less commonly eaten. 1. Beef Beef originates from cattle that are classified according to age and gender. - Steers. Male cattle that are castrated - Bulls. uncastrated males - Heifers and cows. Heifers, females that have not borne a calf. cows, female cattle that have borne calves, is less desirable - Calves. Calves 3 to 8 months old are too old for veal and too young for beef. - If they go to market between 8 and 12 months, their meat is referred to as baby beef. - Veal. comes from the young calves of beef cattle, either male or female, between - the ages of 3 weeks and 3 months. It has milky flavor, pale color, and tender - texture. 2. Lamb and Mutton - Lamb and mutton are the meat of sheep. lamb comes from sheep less than 14 months old, and mutton from those over 14 months. Dr. Mohamed Elsaadany 18  COMPOSITION OF MEATS Structure of Meat Meats are composed of a combination of water, muscle, connective tissue, adipose (fatty) tissue, and often bone. 1. Muscle Tissue - Most of the protein in animals is found in their muscles - Muscles are made up of muscle fibers. - The characteristics of muscles are an important consideration in deciding how the meat should be prepared. - If the muscle fibrils are small, the result is finer muscle bundles, which give the meat a very delicate, soft consistency. Dr. Mohamed Elsaadany 19 Types of Meat Dr. Mohamed Elsaadany 20  COMPOSITION OF MEATS Muscle Contraction and Relaxation - Muscle fibrils play an important role in muscle contraction and relaxation. - The muscle fibril is separated into segments called sarcomeres, The sarcomeres contain two proteins, actin (thin) and myosin (thick), that are alternately aligned. - It is thought that muscle contraction occurs when the sarcomeres shorten as the thick and thin filaments “slide” past each other, forming another protein called actinomyosin 2. Connective Tissue - is a part of ligaments and tendons, and also acts as the “glue” that holds muscle cells together. The most abundant protein in connective tissue is collagen - Collagen It is tough and fibrous, but converts to a gel when exposed to moist heat. The - other two main types of connective tissue proteins are elastin and reticulin. Effect of Collagen on Tenderness - Cuts high in connective tissue are naturally tough and need to be properly prepared in - order to become more tender. Meat of neck, shoulders, legs, and flank, contain more collagen and tend to be tougher than muscles from the loin, or lower back, and rib areas, which get less exercise. Dr. Mohamed Elsaadany 21  COMPOSITION OF MEATS Effect of Age on Tenderness Collagen concentration also increases as animals age, which is why meat from older animals is tougher. tougher cuts require slow, moist heating at low temperatures to convert, or hydrolyze, the tough connective tissue to soft or gelatin. 3. Adipose (Fatty) Tissue Adipose tissue is, simply, fat. When it appears on the outside of meat, this fat is known as cover fat. Fat found within muscles is called intramuscular fat or marbling. Fat content is dependent on the source animal’s genetics, age, diet, and exercise, and on the cut of the meat. Well-marbled beef fetches a higher price Fat Color and Texture Fat is white in younger animals, and turns progressively more yellow as the animals age because of the presence of carotenoid pigments in the feed. Dr. Mohamed Elsaadany 22  Meat color The color of meat is derived from pigment containing proteins, chiefly myoglobin and, to a lesser extent, hemoglobin. The red color of meat also increases as the animal ages Exposure of meat to oxygen changes the color of myoglobin, and therefore the meat to bright red and after while it become brownish-red. Cooking meat initially converts the color of raw meat to bright red then denaturing to grayish brown. Storing cooked meat too long causes the meat to turn yellow, green, or faded. The food industry uses several methods to keep meat products from turning brown. – One such method is the addition of nitrites to processed meats. Extractives: Meat derives some of its flavor from nitrogen compounds called extractives. these including creatine and creatinine, urea and uric acid that all water soluble Dr. Mohamed Elsaadany 23  Purchasing Meats To ensure that consumers are purchasing meat that is safe, governmental laws require the inspection of animal carcasses. In addition to this mandatory inspection for safety, meat may also voluntary assigned yield grades and quality grades to assist consumers in selection. Organic Meats Organic meat is defined as being derived from cattle fed only milk, grasses, and grains from birth to slaughter Dr. Mohamed Elsaadany 24  Purchasing Meats The grading of meat is not under government mandate or control, but is a strictly voluntary procedure that the meat packer or distributor may have done under contract with the USDA. Yield grade: The amount of lean meat on the carcass in proportion to fat, bone, and other inedible parts. Dr. Mohamed Elsaadany 25  Tenderness of Meats Overall, natural meat tenderness is due to factors such as the cut, age, and fat content. – Meats can also be treated to make them more tender. – Preparation temperatures and times also have an influence on tenderness. Dr. Mohamed Elsaadany 26  Tenderness of Meats Natural Tenderizing Rigor mortis: From the Latin The particular cut of the for “stiffness of death,” the meat temporary stiff state Age (connective tissue following death as muscles concentration) contract. Heredity and diet Marbling Aging: Ripening that occurs Slaughtering conditions when carcasses are hung in Aging refrigeration units for longer periods than that required for the reversal of rigor mortis. Dr. Mohamed Elsaadany 27 Rigor Mortis Dr. Mohamed Elsaadany 28  Postmortem changes in muscles Postmortem Changes in the Muscle 1. Chemical changes ( Metabolic changes) 2. Physical properties changes ( meat/tissue texture) Pre-rigor mortis Rigor mortis Post Rigor Stage Meat pH - ATP decreased - Lactic acid deposits in the cells - pH decrease - Glycogen decreases to an extent - Extensibility of muscle increases - Rigor Mortis Occurs Dr. Mohamed Elsaadany 29  minimizing the Shortening How to minimize the Shortening (actomyosin cross-link formation?) 1. The meat is hung on the carcass after slaughter to stretch the muscles. This minimizes the formation of actomyosin cross-links. (more later). 2. Pre-rigor temperature is controlled to minimize fiber shortening. The optimum temperature is between 59 F and 68 F (15–20 C). Above this temperature, increased shortening occurs. Below it, “cold shortening” occurs. At low temperatures, the sarcoplasmic reticulum pump is unable to pump calcium ions out of the sarcoplasm, and so contraction occurs.(more later). Dr. Mohamed Elsaadany 30 Meat cuts Dr. Mohamed Elsaadany 37  Preparation of Meats Meat should be sponged clean of any moisture with paper towels and trimmed of fat before being prepared. Doneness of meats can be determined by a combination of time/weight charts, color changes, internal temperature, and touch. Tender meats are best prepared by dry heat (roasting/baking, broiling, grilling, pan-broiling, and frying), whereas moist-heat methods (braising, simmering, stewing, and steaming) are best for tougher cuts. Processed Methods Before the advent of refrigeration, meat is preserved by such processing methods as curing, smoking, canning, and drying. Dr. Mohamed Elsaadany 38  Changes During Heating Cooking meats at the correct temperature for the right amount of time will maximize their tenderness, juiciness, and flavor. Exposing meat to high temperatures for too long will toughen, shrink, and harden meat because such exposure shortens muscle fibers, denatures proteins, and causes the meat to dehydrate. Carry-over cooking: The phenomenon in which food continues to cook after it has been removed from the heat source as the heat is distributed more evenly from the outer to the inner portion of the food. Doneness Various methods are used to determine doneness and sometimes more than one method is used. include internal temperature, time/weight charts, color changes, and touch. Dr. Mohamed Elsaadany 39  Touch as a test for doneness. Touch Doneness can be determined by the firmness of the meat. Pressing lightly on the center of the lean tissue can help to determine whether the meat is rare, medium, or well done. Dr. Mohamed Elsaadany 41  Cooking methods Tender cuts are usually prepared by one of the dry- heating methods: – Roasting (baking) – Broiling – Grilling – Panbroiling – Frying Dr. Mohamed Elsaadany 42  Cooking methods Frying Sautéing, pan-frying, and deep-frying are suitable for tender, small pieces of meat that are low in fat or that have a breaded coating. Dr. Mohamed Elsaadany 43  Cooking methods Less tender cuts of meat are usually prepared by moist-heat methods such as: – Braising – Simmering/stewing – Steaming Microwave ovens are usually not the best option for cooking meats, except for thawing and reheating leftovers. Dr. Mohamed Elsaadany 45  Storage of Meats Meat contains high percentages of water and protein, both ideal for the growth of microorganisms. – Consequently, meat should be stored in the refrigerator or freezer. Meats are best refrigerated at just above freezing between 0° to 2°C. Wrapping Meat (meats are packaged with plastic wrap) can be refrigerated in their original wrap for up to two days. Dr. Mohamed Elsaadany 46