Basics of Meat Science

Basics of Meat Science

Basics of Meat Science

Jay B. Wender, Ph.D. American Meat Processors Association

introduction

Muscles are highly specialized tissues used to provide structural support, generate movement, and maintain metabolic processes for the full functioning of animals. Muscles are highly organized tissues that supply energy for contraction and transmit that contraction motion to the skeleton.

Over the years, meat has been defined in various ways by different authors. Meat is generally defined as animal tissue suitable for use as food. This definition includes all processed and manufactured products that can be manufactured by these organizations. Meat is considered a source of high-quality protein. The word protein comes from the Greek word proteos, meaning ‘primary’, suggesting how important protein is to human nutritional well-being. The characteristics of meat provide meat processors with the opportunity to manipulate proteins to provide specific processed meat products.

muscle composition

Lean meat, or muscle tissue, contains on average 70-75% water, 19-23% crude protein, 3-2% fat, and about 1% each of minerals and carbohydrates.

moisture

Water is the single biggest contributor to muscle weight and is easily lost in meat. The moisture retained by meat is called water retention capacity (WHC). The physical and chemical structure of meat is related to the amount of water it retains. Moisture can be classified as bound moisture, fixed moisture, and free moisture.

Bound water is water held directly by chemical bonds to meat proteins and accounts for 4-5% of the total water found in muscle. This water remains tightly bound to muscle proteins through severe mechanical or other physical forces.

The fixed moisture is retained indirectly by electrically charged reactive groups in the meat proteins. For meat processors, the more moisture in a fixed state, the better the product’s ability to retain moisture and thus the higher its longevity. The amount of water fixed in meat can be approximately 35-75%.

Free water is water retained by muscle membranes and capillary action. Meat processing, such as grinding or grinding, damages the muscle membrane, causing the meat to release this free moisture. The loss of free moisture from the retail area is called drip loss or purge. The goal of meat processors is to convert free moisture into a fixed state.

protein

Muscle proteins can be classified into several categories based on their location within the structure of muscles and myofibers, their physicochemical properties (e.g. solubility), and their functionality in relation to further processing of meat. Muscle proteins form three large groups of proteins called myofibrillar proteins, sarcoid proteins, and connective tissue or matrix proteins.

Myofibrillar proteins are mainly myosin, actin, tropomyosin, m protein, alpha-actinin, beta-actinin, c protein, troponins T, I, C, and other minor proteins associated with myofibers but present in very small amounts. It consists of: Myosin and actin account for 65% of total muscle proteins, with tropomyosin and troponin each contributing an additional 5% and the remaining 25% comprised of other regulatory and structural proteins. Other myofibrillar proteins, consisting primarily of myosin and actin, are also called “water-soluble proteins” because they can dissolve in neutral salt solutions.

Glycoproteins are composed of myoglobin, hemoglobin, cytochrome proteins, and various endogenous enzymes. These proteins make up 30-35% of total muscle protein. Glycoproteins are soluble in low-salt solutions but insoluble in water. Because these proteins are sometimes extracted with pure water, the name “water-soluble proteins” has become common. Myoglobin is probably the most important protein in meat because it is responsible for meat color, which is associated with product quality. Myoglobin consists of a globular protein part (globin) and a non-protein part called the heme ring. The heme portion of the pigment plays a special role in determining meat color depending on the oxidation state of the iron within the heme ring.

Matrix proteins, or connective tissue proteins, are composed primarily of collagen and elastin. Collagen is the single most abundant protein in mammals and is present in bones, skin, tendons, cartilage, and muscles. Collagen, elastin, and lipoproteins of cell membranes are among the most important connective tissue proteins in muscle. In muscle, connective tissue is composed primarily of collagen proteins and serves as an extracellular support for the fibers.

province

Fat is also the main component of muscle/meat. Fat is one of the most variable components of meat. Fat is a very high energy compound and contributes not only to calories but also to the flavor, juiciness and texture of meat. The amount of fat can vary greatly depending on the animal as well as the cut or cut of meat. The difference in flavor depending on the species is said to be due to the different fat composition of each species.

Fat is found throughout the carcass or meat cuts. External fat is present on the surface of the carcass or cuts and is also called back fat. Intermuscular fat exists between the muscles within an area and is also called deep fat. Intramuscular fat is a lump of fat inside a muscle, also known as marbling. Marbling contributes to the flavor and juiciness of meat. The amount of visceral fat, also known as kidney, pelvic, and heart fat, is utilized in the equation to determine the meat quality grade of a beef carcass.

Lipids or fats are composed of glycerol and fatty acids. Fatty acids are attached to glycerol molecules. Animal fat consists mostly of triglycerides, which account for most of the total lipids in animal fat. Triglyceride means three fatty acids attached to a glycerol molecule. One fatty acid is esterified to each hydroxyl (O++) portion of the glycerol molecule. You can have lipids that are monoglycerides (one fatty acid per glycerol molecule) or diglycerides (two fatty acids per glycerol molecule).

Fatty acids are chains of repeating methyl units with an acid (carboxyl) group at one end. Fatty acids are named or classified into two general categories: One is a classification based on the number of carbons in the chain length. Fatty acids range from 4 carbons in chain length to 24 carbons in chain length. Fatty acids are also classified according to whether they are saturated or unsaturated. A carbon atom (to put it simply) has four reactive sites. If all four reaction sites are filled with hydrogen or another carbon, it is considered saturated. If the reactive site on the carbon atom does not contain three hydrogens, it is unsaturated. Unsaturated fatty acids have a double bond between carbons because they lack two hydrogen atoms. Polyunsaturated fatty acids have two or more double bonds in their chain length.

mineral

Meat of all species contains about 1% minerals. Mineral content does not fluctuate significantly throughout the life of the animal, regardless of changes in other compositions, etc. From a nutritional standpoint, red meat is an excellent source of iron and zinc, as well as many other minerals. Remember that myoglobin contains iron as an important part of its structure. Calcium is essential for muscle contraction, but it is contained in only small amounts. Therefore, meat is not considered a good nutritional source of calcium.

muscle structure

Meat can be divided into three muscle types: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscles are organs of the muscular system that account for most (35-65%) of the carcass weight of meat animals and are attached directly or indirectly to bones. Smooth muscles are the muscles that make up the digestive tract. The heart is made up of cardiac muscle.

From an economic perspective, skeletal muscle is the most important of the three types of muscle. These muscles facilitate movement or provide support to the body. The smallest independent cellular units of mature skeletal muscle are called fibers. Skeletal muscle is a very complex contractile system composed of cylindrical multinucleated muscle fibers (cells) of varying length, surrounded by a layer of connective tissue called the endomysium. These bundles of muscle fibers are surrounded by a connective tissue sheath known as the perimysium, and the entire muscle is surrounded by a denser connective tissue sheath called the epimysium.

The structural complexity of a muscle may consist of smaller functional parts of the muscle, including muscles, muscle bundles, myofibers (or cells), myofibrils, and myofibrillar filaments. Each muscle fiber contains hundreds of muscle fibers.

Myofibers are linear arrays of cylindrical sarcomas, surrounded at both ends by a membrane system that is an elaborate extension of the myofibrillar plasma membrane or sarcomas. These extensions of the pore membrane, called transverse tubules or t-tubules, allow the pore membrane to contact the ends of each muscle fiber.

The sarcoids, located between the t-tubules, are covered with special endoplasmic reticulum called endoplasmic reticulum, which contain high concentrations of Ca2+. Interaction within the sarcoid with Ca2+ released from the endoplasmic reticulum causes muscle contraction.

The process by which muscle is converted into meat

During and after slaughter, which is considered post-mortem slaughter, many chemical and structural changes occur that affect the quality and performance of the meat. This change is called the process of converting muscle into meat. Glycogen (animal starch) from living animals is transported from the liver to the muscles. When energy is needed for contraction, glycogen is converted to ATP. For this reaction to occur, oxygen must be present in the system. Remember, myoglobin stores oxygen in your muscles that can be used to produce ATP. Even after death, the reactions described above continue as long as oxygen is present in the body. If the blood is removed during slaughter and is depleted of oxygen and cannot be replenished, additional ATP cannot be produced. When ATP is depleted, thick and thin filaments become locked together and glycogen is converted to lactic acid. Lactic acid builds up in meat until most of the glycogen is used up.

After slaughter, stiffness occurs in the muscles. Postmortem changes occur as ankylosis progresses. When ATP is depleted and the thick and thin filaments of muscle fibers become locked together, the muscle is said to be stiff. Additionally, when spasticity sets in, the muscles shorten and become locked in place. The muscles or meat become shortened or partially contracted and the thick and thin filaments become loose, making the meat very tough. In addition to structural changes, the build-up of lactic acid lowers the pH of the meat and makes it more acidic. Living muscle has a pH of about 7, which is neutral acidity, but after death, the pH drops to 5.4 to 5.7 under normal conditions.

meat quality

A drop in pH affects the overall quality of the final meat product. pH affects the meat’s ability to retain moisture and can also affect its color.

Protein functionality is a general term defined as physicochemical properties that influence the processing and behavior of protein systems as judged by the quality attributes of the final product. It is a concept that encompasses the characteristics of meat components that are important as raw materials up to the manufacturing stage when processed meat products are made. The main functional properties are: (1) water binding capacity (or water retention capacity): (2) fat stabilization (or fat emulsification): (3) interparticle bonding capacity (or protein gelation); (4) Development of desirable color characteristics.

water retention capacity

When discussing water retention capacity, it is worth emphasizing once again that proteins create the main mechanism for retaining water in meat products. Myofibrillar protein is the most important protein for water binding in meat. This protein has a net negative charge. A concept or term you should be familiar with is isoelectric point (pl). This is the pH where the positive charge is equal to the negative charge. The isoelectric point of meat is approximately 5.2. As lactic acid builds up and lowers the pH of the meat, the pH approaches its isoelectric point. When the pH reaches 5.2, the difference between positive and negative charges gradually decreases. When the positive and negative charges are equal, the water holding capacity reaches its lowest level.

fat oil painting

Meat emulsions are made by grinding or finely chopping meat and water and adding sodium chloride to form a fine homogenate into which animal fat (mainly pork fat) is dispersed. The addition of ingredients plays an important role in the formation and stability of meat emulsions. The typical procedure begins with adding the lean meat containing the most myofibrillar proteins to the mince. In successful meat emulsions, water-soluble myofibrillar proteins, especially myosin or actomyosin complexes, are generally considered to be the main emulsifiers. These myofibrillar proteins are salt soluble, so for the most effective response, the salt content should be 4 to 4.5% of the lean meat.

Solubilized (extracted) myosin gives the minced meat paste its sticky adhesion. Lean meat contains about 75% water, but additional amounts are usually added for myosin extraction. A portion (about half) of ice or water is added to the extracted myosin. Water can become trapped in the open muscle fiber structure and bind to the negative charges of the proteins.

Once the temperature rises to 7°C (45°F), you will need to add any remaining ice or water to allow it to absorb into the meat tissue. You should then continue to chop as you add fatty meat and other ingredients until the final emulsion temperature is between 13°C (55°F) and 18°C ​​(64°F). When all steps are successfully completed, the fat is completely emulsified, so that the soluble myofibrillar proteins completely coat each fat particle, and during the heat treatment, the proteins are denatured and bound to all the fat.

If stable emulsification is not achieved, evidence of unemulsified fat, unbound moisture or gelatin will remain on the surface or interior of the final cooked product. Unemulsified fat may be present as fat (fat cap) on the ends of the sausage or as a thin grease coating on the surface of the sausage.

protein gelation

Gelation of myofibrillar proteins is the most important property that occurs in restructured, molded and sausage products and is also responsible for the texture, viscoelastic properties, meat juices and stabilization of fat emulsions of processed products. When heat is applied, a series of events occur in the muscle fiber proteins used in processed meats. A conformational change occurs during thermal denaturation of actomyosin.

Protein-protein interactions are functional events that can be related to the structural integrity of meat products through ordered aggregation by heat. This aggregation is twofold, involving the head portion of the myosin at temperatures between 30°C and 50°C and the rod portion in the temperature region above 50°C. It is important to minimize moisture, fat, protein and salt in the produced meat paste and pH and muscle changes in the raw meat ingredients.

color

The color of meat is an important quality characteristic. Myoglobin is the pigment or color of meat. Myoglobin is red, and the color is determined by the concentration of myoglobin in the muscle. Myoglobin can exist in three states: reduced myoglobin, oxymyoglobin, and metmyoglobin. Reduced myoglobin refers to myoglobin without oxygen attached. On the other hand, metmyoglobin refers to iron molecules oxidized to a different state (from iron, Fe++ to iron, Fe+++).

Meat takes on different colors depending on the presence or absence of oxygen in the myoglobin molecule. After slaughter, meat is in an oxygen-deprived state, that is, there is no oxygen attached to the myoglobin molecules. This is reduced myoglobin and has a purple color. After cutting meat, when the surface is exposed to oxygen in the air, myoglobin absorbs this oxygen and becomes bright red, oxymyoglobin. The reaction of adding oxygen to myoglobin is called oxygenation by chemists.

Packaging films used for fresh meat are designed to be oxygen permeable to maintain their vibrant red color. Fresh meat, such as beef, often turns a dark reddish-brown color when left in the butcher section. This color is undesirable because it reminds consumers of spoiled meat. This color is the result of myoglobin going through an oxidation process to form metmyoglobin. The oxidation process changes the iron in the myoglobin molecule from the iron (Fe++) state to the iron (Fe+++) state.

conclusion

The structure and composition of meat influences its selection for specific purposes. Fresh meat is selected for different reasons than the meat selected to make processed meat products. Some factors considered when selecting meat for a specific purpose are the age of the animal at harvest, amount of connective tissue, overall quality, marbling, color, and the lean to fat ratio of the raw material. Overall, knowledge of the basic concepts of meat science and processed meat can help you produce high-quality, desirable meat products.

reference

Romans JR, Jones KW, Costello WJ, Carlson CW, Ziegler PT. 1985. The meat we eat. 12th ed. Danville, Illinois; Interstate Printers and Publishers, Inc.

Reference

Romans JR, Jones KW, Costello WJ, Carlson CW, Ziegler PT. 1985. The Meat We Eat. 12th ed. Danville, IL; The Interstate Printers and Publishers, Inc.

Basics of Meat Science – Nassau Foods, Inc