In simple terms, the muscles of the animal are the meat. The muscles are the numerous bundles of cells and fibers that can be contracted and expanded to produce the body’s movements. The three major types of muscles are the skeletal, cardiac, and smooth.
Skeletal muscles are linked to bone by bundles of collagen fibers known as tendons. The skeletal muscles are made up of several components referred to as muscle fibers. These fibers bundle together in various configurations that give them a striated appearance, such as grooves or parallel lines that may overlap in different directions. These fibers form the basic mechanism that controls muscle contraction.
Muscles contract; they never push because the fibers are too soft to propel bone forward. The animal’s body is constructed in such a way that when one muscle contracts an opposing muscle will relax, allowing movement. When both muscles relax at the same time, no movement occurs. And the location of these muscles will largely determine the amount of use they get.
While the skeletal muscles support the body structure and initiate movement, smooth muscles are found in the organs or the tubular system, such as the digestive tract, reproductive organs, circulatory system, and urinary tract. Lastly, the cardiac muscle is found in the heart.
From a carcass value perspective, skeletal muscles are the most important of the three types because of their quantity and desirability for human consumption.
This chapter will examine the major muscles found in a pig, how to identify them when you cut up a carcass, how to cut them into the most useable portions, and what to do with some of the less edible parts. Understanding the muscle terrain of your pig carcass will help you when cutting it up and dividing it into portions.
PIG MUSCLES AND BONES
More than 100 different muscles are found in a pig’s body. For general use, however, they are usually grouped into five major areas and then further broken down into specialty cuts, often depending on their marketing characteristics or potential.
This is what you will encounter when you begin deconstructing the carcass, also referred to as the fabrication process. This process will break down large portions of one area into smaller, more manageable pieces or cuts.
The five major areas include the shoulder (picnic and Boston butt), loin, hams, and belly or sides. The minor areas include the head, cheek and jowl, and the feet and hocks.
The five major divisions of a carcass can be further broken down into eleven sections, which will help identify the muscles and bones in that portion and allow us to discuss them in detail. While this only describes one-half of the carcass, you will remember that there will be an identical section on the other half; the two halves are mirror images of each other. We’ll start with the bones as they can be trimmed and used for soup stock or, in some cases, pickled.
• Tarsal bone—from the rear hock down to the toes. Each rear leg has seven bones. They are short, cubical bones of various sizes. It is sometimes called the hock joint. Two dewclaws suspend from the metatarsal bones in each rear foot.
• Tibia—are located just above the rear hock and below the femur, or the stifle. Pigs have two tibia bones, one located in each hind leg. It has a distinctive curve in the bone shaft. This is commonly referred to as the rear leg bone, hind shank, or hock bone.
• Femur—lies anterior (in front of) the tibia and below the hind leg, and it is often called the round bone or leg bone. There is only one in each hind leg. It is the largest and most massive of the long bones and has a larger shape at the top and bottom than of the cylindrical shaft. It also has a flat shape on the posterior (behind) side.
• Pelvis—made up of four different bone structures: the ischium, or aitchbone; the pubis; the coccygeal; and sacral vertebrae (often melded together in any reference as the tail).
• The ischium or aitchbone consists of one pair. This means they are fused together with tendons and tissue and are mirror images of each other—one found on each side of an imaginary center line. Although they slope slightly downward and inward, they are almost horizontal when viewed from the side.
• The pelvic girdle consists of three parts and the pubis is the smallest. It forms the forward part of the pelvic floor and, like the ischium, consists of one pair of bones.
• The tailbone consists of the twenty coccygeal vertebrae. These lie from the very tip of the tail to the sacral vertebrae nearest the pelvis.
• The sacral vertebrae consists of five fused vertebrae that are irregularly shaped. Because they are fused, they are often described as one bone—the sacrum. They attach to the lumbar vertebrae rather than the pubis bone.
• Lumbar vertebrae—often called the loin or lower back. The lower back position refers to the direction from the nose horizontally and not vertically. Pigs have six irregularly shaped bones in number, and they attach to the thoracic vertebrae in front and the sacral vertebrae in back.
• Thoracic vertebrae—form the part in front of the loin or lower back and up to the neck. This includes the shoulder area as they are referred to as the chine or featherbone, or rib vertebrae. The rib bones attach the thoracic vertebrae as they suspend downward.
• Ribs—consist of thirteen elongated and curved bones. They are arranged in pairs with one pair of the ribs (whole carcass) for each thoracic vertebrae. The first eight pairs fuse to the sternum and the other five attach to the thoracic vertebrae.
• Scapula—consists of one pair. It is referred to as the shoulder blade, blade bone, or the paddle bone because of its shape. It is a flat, smooth bone that attaches to the humerus only on the forward end. The rear part is not attached to any bone but is tied to muscles and tendons, which help facilitate a forward and backward front leg movement.
• Cervical vertebrae—also called the neck bones. Pigs have seven irregularly shaped bones of varying sizes. They attach at the skull at the front end and the thoracic vertebrae at the rear end.
• Humerus—or arm bone, is a single pair—one on each front leg—that extends from the shoulder down to the foreshank. It is a curved bone or shape, being larger at the top near the scapula and smaller near the foreshank. It looks like a backward S shape.
• Radius, or foreshank bone—the largest of the two forearm bones. It is gently curved and extends from the humerus to the metacarpal bones and is tied to the ulna, which lies right below it (behind it if viewed vertically).
• Ulna—also referred to as the foreshank bone and consists of one in each front leg. Like the radius, it is a long bone that extends from the humerus to the metacarpal bones of the lower leg. It lies behind or posterior to the radius and has a three-sided shaft.
• Metacarpal bones or cannon bones—lie below the knee to the front feet. Pigs have five bones in this point, but they are referred to as long bones. Two dewclaws descend from the metacarpal bones in each front foot.
• Carpal bones—found in the front legs and consist of six bones, which are arranged in two rows closest to the attachment point, consisting of four bones. In the farthest row, the second and third bones are fused and the fourth is separate.
• Skull—the head and consists of the cranium, which houses the brains; the mandible, or lower jaw, which works by muscle action for eating; and the sinuses, through which air flows to the lungs.
• Phalanges—the front and rear feet. They consist of three separate, relatively long and narrow bones.
• Hoof—not a bone but a covering that forms a protection over the lowest leg bones. The hooves act as shock absorbers to reduce the impact of the foot against any surface. They are made mostly of keratin and modified epidermal cells. The dewclaws do not have any practical purpose but can be skinned and boiled with bones for soup stock.
MUSCLES ARE MEAT
The skeleton supports the muscles, which are attached to the various bones by tendons and connective tissue. As long as the bone doesn’t break or the muscles don’t tear because of injury, the normal functions of the pig’s metabolic system will allow the muscles to expand and develop volume as the pig gets older.
These bones support movement, and although there are many divisions of the bones, there are also many divisions of the muscles to make that movement happen. Some muscles will get more use because of the bone they are attached to. For example, leg bones move more than the back bones so the shoulder muscles are more active than the loin muscles.
We can use the muscle divisions and divide the cuts into sections and identify their composition and how they can best be used. These can be classified generally as thoracic muscles, abdominal muscles, thigh muscles, and shoulder and neck muscles.
• Thoracic muscles are dominated by the pectoral muscles, both front and rear of the foreleg. These provide forward and backward movement. There is a broad muscle just behind the front legs that, even though it’s smaller, gives the foreleg great power for movement because of its length.
• Abdominal muscles help compress the abdominal wall and protect the internal organs from injury. Unlike the chest and lungs, the abdomen is not protected by skeletal bones. The internal organs are held in place by the pressure of the long abdominal muscles, which also help flex the trunk for turning. Pigs have three abdominal layers: the external and internal oblique, and the transverse muscle.
• The external oblique is a thin broad sheet of muscle covering the lower length of the abdomen.
• The internal oblique runs in an opposite direction of the upper layer.
• The transverse muscle is the innermost of the abdominal muscle layers.
The arrangement of the three layers gives the abdominal wall its strength. Because these are thin muscle layers and are well interspersed with fat deposits, they are difficult to trim out. Since this is where bacon comes from, they can be cut differently from other more voluminous muscles.
• Thigh muscles are large and contain the well-known hams. The femoral artery passes between the layers.
• Shoulder and neck muscles are prominent and extend from the back of the neck and jaw, and the back of the head through the shoulder to the humerus bone. The brachiocephalic muscle is a single muscle that attaches from the neck to the jaw and helps to raise and lower the mouth while eating.
These major muscle groups will be broken down later into specific muscle cuts, but for now this information will help you identify their general location. Once you begin to fabricate or cut up the carcass and deconstruct it into smaller cuts or pieces, you can keep this overview in mind. While it is not necessary to become an anatomical expert of a pig’s muscle structure, it will help you understand what the major areas are composed of.
MOVEMENT MAKES MUSCLE
As with any other animal used for meat, the most tender cuts or muscles are those that don’t get the most exercise or movement, such as the loin area, from which pork chops and pork loin are derived. Those muscles that get more use, such as the shoulders and hams, tend to have a higher bone-to-lean meat ratio than other cuts. This doesn’t mean they are less tender, although that is often the case with pigs raised on pasture or in open lots because they get more exercise than those raised in confinement systems. It usually means they need to be cooked differently than more tender cuts.
Pork cuts can be deboned or the bone left on when making cuts. This will be a personal preference. Although the majority of cuts found in the retail meat counters today are boneless, you will likely find that it is easier and quicker to deconstruct a carcass and get it into the freezer if each piece is not deboned. But if you have the help, time, talent, and dexterity, you may want to debone every cut. Bones can add flavor to the cut, especially in stews or moist cooking.
The two charts will tell you where the muscle is located and the bones involved. Knowing these names and locations will help you do a better job of carving up the carcass. There is no right or wrong way to cut up a carcass with home butchering since it will be for your family’s use and not for sale. The following methods described are only one option, and you can use it as a guide or create your own.
FOOD SAFETY
Before you dive into cutting up the carcass, you need to be aware of one principle that applies to all meat processing: the more you break down a carcass into smaller units, the more risk there is for bacterial exposure and contamination. As more muscle tissue becomes exposed to the environment around it, the risk and opportunity for bacteria to attach and grow increases.
A whole carcass has the minimum amount of exposed surface area. As large cuts are made, more area is exposed. When it is cut into smaller pieces, still more area is exposed. Simply put, the more meat is processed, the more it may be exposed to microorganisms. Using clean, sanitary equipment; clean table surfaces; and keeping work area temperatures low while working as quickly as possible will help reduce microbial activity.
This is the primary reason you need to keep in mind the three Cs. You need to keep it Cold, Clean, and Covered. There’s one additional C I like to include as well: keeping meat separate to prevent Cross-contamination.
KEEP IT CLEAN
Let’s start with keeping things clean. Strict sanitation is required before and after cutting any meat and processing it to prevent bacterial contamination and food-borne illnesses. It is especially important to handle raw meat in a sanitary environment to reduce the risk of bacterial growth while it is at room temperature. No meat is completely sterile, but using proper procedures will minimize your risks.
Once everything is ready, it’s a good idea to thoroughly wash your hands with soap and water before touching any meat or clean work surfaces. Remove any rings, jewelry, or other metal objects from your hands, ears, or other exposed body parts before cutting meat. Always rewash your hands between tasks, as well as if you come into contact with anything unsanitary: if you sneeze, use the bathroom, or handle materials not part of meat processing, you should rewash your hands.
KEEP IT COLD
Mismanagement of temperature is one of the most common reasons for outbreaks of food-borne diseases. Bacteria grow best at temperatures between 40º and 140ºF, so it is important that your fresh pork passes through this range quickly. Meat can be kept safe when it is hot or when it is cold, but not in between. It is best if the meat passes through this temperature range, whether being cooked or cooled, within four hours, but preferably less.
Store your raw meat in a refrigerator until you begin processing it. During the processing of most meat products, it will be essential to reach an internal temperature of 160ºF, as this effectively kills pathogenic bacteria. (Most, but not all, microorganisms are killed at 140ºF.) The less time you subject the meat to room or ambient temperatures the less risk there will be in it harboring harmful microorganisms that cause spoilage.
If meat is stored below 40°F, most of it can be kept safe from harmful bacteria for a short time. When frozen, most microorganisms that are present are merely dormant and can revive when thawed. If you have frozen the meat, it all should be processed as soon as possible and not refrozen to use later.
KEEP IT COVERED
One simple rule to acknowledge is that all foods have a diminishing shelf life after being opened or made, even if properly stored. However, you can lessen the effects on stored foods created by temperature, the type of wrapping used, and proper storage. The manner in which you cover, contain, or wrap foods prior to use and for storing will help determine how well they keep in a refrigerator, cupboard, or freezer.
Temperature will have the greatest effect on meat, especially as it increases. As previously mentioned, raw or cooked meat should be kept chilled until used. Even your refrigerator will not have consistent temperatures throughout. Interior drawers tend to have slightly higher temperatures than shelves. The door shelves are also generally warmer because of their exposure to room temperatures once they are opened. It is better not to store highly perishable foods such as meat in the drawers or doors of your refrigerator.
PREVENTING CROSS-CONTAMINATION
Cross-contamination occurs when one food comes in contact with another and has the potential of spreading bacteria from one source to another. This can take the form of several variations: both can be raw or one can be raw and one cooked. Cross-contamination could be between meats, vegetables, seafood, eggs, or poultry, or it can occur when surfaces have had mutual contact, such as placing one food on a plate, counter, or cutting board, removing it, and then placing another food on the same surface without washing the surface in between. It can also occur between knives that have not been cleaned between uses and even in your grocery cart if juices happen to leak from one package to another. You can take several steps to avoid cross-contamination of pork or any other foods.
PREVENTING AND RETARDING BACTERIAL GROWTH
Although sanitation and the three (or four) Cs dynamics are routine components of pork processing, misuse or incomplete application of any one of them can be detrimental. Preventing and retarding the development of harmful organisms should be your primary objective while handling raw pork. Consuming microorganisms that have grown and propagated in meat can cause serious illness or even death. This concern should not be taken lightly. When health problems surface relating to eating meat products, it is generally a result of intoxication or infection.
Intoxication occurs when the heating or processing fails to kill the microbes in question. Those that are able to survive can produce a toxin that, when eaten by humans, can produce illness. One example is undercooked meat. Infection occurs when an organism such as salmonella or listeria is consumed due to contamination.
Several types of toxins exist, including exotoxins and endotoxins. Exotoxins are located outside of the bacterial cell and are composed of proteins that can be destroyed by heat through cooking. Exotoxins are among the most poisonous substances known to humans. These include Clostridium botulinum, which causes tetanus and botulism poisoning.
Endotoxins attach to the outer membranes of cells but are not released unless the cell is disrupted. These are complex fat and carbohydrate molecules, such as Staphylococcus aureus, that are not destroyed by heat.
Bacteria are the most common and important organisms that can grow on meat. Not all bacteria are bad, however, as according to a 2007 New York University study, the human body may carry as many as 180 different kinds of bacteria on its surface. Although molds and yeasts can affect meat quality and cause spoilage, their effect is far less significant or life threatening than toxins or bacteria. Molds typically cause spoilage in grains, cereals, flour, and nuts that have low moisture content or in fruits that have a low pH. Yeasts will not have a significant effect on meat because of the low sugar or carbohydrate content of muscle. They need high sugar and carbohydrate levels to affect a change.
Several parasites may cause a problem if the pork is undercooked or improperly processed. A parasite infection will occur in the live animal before it occurs in a human. There is one swine-related parasite that you should be aware of. This includes Trichinella spiralis. Trichinosis is a parasite that can live in swine muscle and may be transferred to humans through raw or undercooked pork. Using and maintaining recommended cooking temperatures and times will destroy these parasites.
MOISTURE AND OXYGEN
Moisture in meat is essential for palatability, but it is also a medium for microbial growth. The level of moisture in fresh pork is high enough to provide spoilage organisms with an ideal environment for growth. Researchers have found that moisture levels of at least 18 percent will allow molds to grow in meat. Drying meats through a smoking or cooking process will typically eliminate any concerns with moisture.
Oxygen is necessary for animals to survive but is an unwelcome agent when processing pork. Yeasts and molds are aerobic microbes that need oxygen to grow. Anaerobic microbes grow when oxygen is present, and this group can be deadly because it includes clostridium, which produces a toxin, and a group called putrifiers, which degrade proteins and produce foul-smelling gases.
Drying is one procedure to follow when processing pork because it acts as an inhibitor of enzyme action by removing moisture. When moisture is removed, enzymes cannot efficiently contact or react with the meat fibers or particles. Without this interaction, bacteria, fungal spores, or naturally occurring enzymes from the raw meat cannot grow to proportions that can cause severe illness. Minute traces may still be present, but with no growth, they lie dormant. However, lying dormant does not mean they can’t resume growth if moisture or temperature conditions are introduced that are favorable to them.
MUSCLES AND MOLECULAR TRANSFORMATION
Muscles are meat, and their texture and the fats found in the bodies of pigs are largely reflective of their diets.
The position of the muscles on the skeleton has a significant impact on the texture of meat. For example, muscles that create movement, such as the front and hindquarters in pigs, receive more exercise than the loin or belly areas. The more exercise or movement a muscle uses, the more blood flow is needed. This, in turn, creates a darker color meat because of the flow of hemoglobin, which delivers oxygen to the muscle. The more hemoglobin (sometimes referred to as myoglobin) a muscle contains, the darker color the muscle will be.
The muscles of a harvested pig go through a molecular transformation once the heart stops. This can influence the muscle texture. With the cessation of blood and oxygen flow, the muscle pH begins to gradually drop. This occurs because the glycogen reserves within the animal’s muscles are depleted and then converted to lactic acid. Because oxygen is no longer available to the muscle cells, lactic acid levels rise, the pH begins to drop, and the reserves of creatine phosphates diminish.
Creatine phosphates aid in muscle movement, and when they are no longer available, the muscle filaments can no longer slide over one another and the muscle becomes still and rigid, resulting in a condition known as rigor mortis.
Soon after your pig is harvested, the muscle undergoes a gradual change in pH and will decline from a normal pH of 7.0 to 5.5. This decline results from a loss of glycogen held within the muscle and its conversion to lactic acid. The degree of acidity or alkalinity (pH) will have an effect on the growth of microorganisms. Most of these will thrive at a pH that is nearly neutral (7.0) than at any other level above or below it. Meat pH can range from 4.8 to 6.8, but microorganisms generally grow slower at a pH of 5.0 or below. This acidity level can act as a preservative in some instances and is generally not a concern unless there is a long delay in processing the carcass at room temperatures.
The amount of time it takes a pig’s muscles to reach their final pH levels are influenced by several factors. These include the cooling rate of the carcass and the extent of the animal’s struggle at the time of death. Cooling affects the time because metabolism is slowed when the carcass is subjected to lower temperatures. Finally, the animal’s activity level immediately prior to the killing will affect the pH, with less activity prolonging the period of pH decline.
Understanding these factors affecting meat quality is not intended to discourage you from processing your own meat. Rather, it is meant to increase your awareness to the potential for problems resulting from mishandling or inadequately processing your pig. Humans have been safely butchering and handling the meat for their families for generations because they understood the basic principles to preserve meat properly.
CALM ANIMAL HANDLING
It is important to handle your animal calmly before slaughter. We’ve already talked about setting up a pen to place your pig in a day or two before the butchering is scheduled. Reducing its physical stress before slaughter also reduces the chance of adrenaline increasing in its system and affecting the meat quality. The reasoning is simple.
Research shows that animals that are stressed immediately before slaughter call upon glycogen in the muscle and liver to meet muscle energy demands. If a pig is excited or stressed just before you kill it and before the muscle glycogen levels return to normal, the excess glycogen is converted to lactic acid and the pH drops faster than normal, resulting in a pale, lean color.
If your pig is under stress for 24 hours or longer before slaughter, it will likely use up all of its muscle glycogen because of prolonged muscle energy demands. This will result in a lower level of glycogen in the muscle when slaughtered and a lower level of lactic acid in the muscle. The pH will then remain high and the meat will be dark-colored, making it less attractive. Calm, safe handling measures are needed to ensure normal muscle energy demands and to avoid abnormal increases and decreases in pH levels.
TO KEEP BONES OR NOT
There are about as many reasons to keep the bones intact in the meat cut as there are to cut them out. The choice will be yours, and there may be some advantages to leaving them in, such as with cooking pork chops.
When deconstructing the carcass, you will be cutting through various bones to create smaller pieces for cooking, packaging, or storing. Prior to packaging, you may keep the bones in or cut them out. The cuts can be frozen, and when thawed for use at a later date, they can be trimmed of the bone. Cutting out the bones will take more work at butchering time.
The main reason for keeping the bone intact with the meat cut is the flavor and texture it can add to dishes. The marrow on the inside of all bones consists of albumen and collagen, along with blood cells. When heated, these substances release gelatin, which creates flavors for soups, stock, and stews. Leaving bones on the meat helps conduct heat to aid in cooking the cut thoroughly. It also helps prevent the meat from drying out. Boneless meat typically cooks faster than meat on the bone because it doesn’t need to heat the bone itself. The choice is yours whether to keep the bones intact or to take them out.