Meat Flashcards
What is the definition of meat?
Animal tissue used for food
What types of meat are there?
- Red meat (beef, pork, veal, lamb/mutton, horse)
- poultry (chicken, turkey, duck)
- fish/seafood
- other types (deer, bears, dog, cats, worms, grubs)
What is the world’s leading meat?
Pork with 106,103 metric tons produced
What is the leading meat in the U.S.?
Poultry at 20,130 metric tons
What is smooth muscle?
Smooth muscle is muscle tissue where the muscle fibers are not highly ordered. They comprise the walls of the digestive tract, capillaries, etc.
What is involuntary striated muscle?
This is cardiac muscle that makes up the heart.
Striated means this muscle is “striped” and layered.
What is voluntary striated muscle?
This is skeletal muscle that have alternating dark and white bands.
What are myofibers?
Myofibers are muscle fibers. They are the structural unit of muscle.
What is the sarcolemma?
the excitable outer cell membrane of muscle fibers
Describe the nuclei in muscles.
Voluntary striated muscles have multiple nuclei, while smooth and involuntary striated muscle have just one nuclei.
What are myofibrils?
long fibers of contractile filaments in myofibers
the basic rod-like unit of a muscle fiber
They permit each cell to do work
What is the sarcoplasm?
The liquid portion of the cell.
What is the endomysium?
The thin layer than surrounds each muscle cell/fiber.
What is the perimysium?
The perimysium is the connective tissue layer that wraps around several muscle cells and forms a bundle (both primary and secondary).
What is the epimysium?
The layer that surrounds the entire muscle.
What is a sarcomere?
The smallest functional contractile unit.
It contains several hundred filaments, and is located between z-lines.
It can also be defined as the distance between two z-lines.
What’s the function of the myofibrils and what are they composed of?
Myofibrils permit each cell to do work. They are composed of actin and myosin.
What is actin?
Actin is the thin filaments of myofibrils. They appear as light bands.
What is myosin?
Myosin is the thick filaments of the myofibrils. They appear as dark bands.
Describe the sliding-filament theory.
When muscles contract, the actin and myosin filaments slide together and the sarcomere decreases in length. However, the actin and myosin filaments do not change length during contraction, they slide together. Contraction is regulated by the calcium ion concentration in the sarcoplasmic reticulum.
What is the sarcoplasmic reticulum?
This is the layer that surrounds the myofibrils.
What is the role of ATP in muscle contraction?
- keeps actin and myosin separated
- provides energy for contraction
Describe the anaerobic reactions of muscle contraction.
ATP <–> ADP + Energy
Phosphocreatine <–> Creatine + Energy
Glycogen (glucose) <–> lactic acid + energy
Anaerobic reactions produce less energy than aerobic reactions.
Describe the aerobic reactions of muscle contraction.
Glycogen + o2 –> h2o + co2 + energy
Lactic acid + o2 –> h20 + co2 + energy
fatty acid + o2 –> h20 + co2 + energy
Produces more energy than anaerobic reactions.
What is rigor mortis?
The stiffening of the carcass by intense shortening of the muscle fibers (no longer have enough energy to relax).
What is the resolution of rigor?
When the carcass relaxes due to autolysis (self breakdown). The muscle is more tender here due to the enzymatic breakdown of muscle protein.
The muscle becomes as tender as pre-rigor muscle.
What is rigor completion?
This is the point where the muscle is at its maximum toughness and maximum contraction.
What enzymes are involved in rigor mortis?
Calpains and cathepsins are the enzymes involved in autolysis
At what pH does resolution of rigor occur and calpains and cathepsins become active?
pH=5.6
What happens to the water binding capacity of muscle as the pH drops?
Water binding capacity drops. This explains why packaged meat sometime has free water at the bottom of the packaging.
Why does pH drop in meat after death?
pH initially drops during rigor mortis because once an animal dies, all aerobic reactions halt and lactic acid builds up.
What is the purpose of aging meat?
to improve tenderness and flavor
What relationships exist when aging meat?
time and temperature
aging and microbial spoilage
What are some methods of aging meat?
- 7-14 days at 35 degrees F
- 2-3 days at 60-68 degrees F utilizing UV light (higher risk for microbial growth)
- additional proteolytic enzyme - papain - helps tenderize the meat
- wet aging - meat is retained in its own fluids
What percent of meat is water?
75%
What percent of meat is protein?
19%
What percent of meat is lipids?
4%
What percent of meat is carbohydrates?
1%
What percent of meat is minerals?
1%
What percent of meat are the total solids?
25%
What percent of meat are solids non-fat (SNF)?
21%
Discuss lipids in monogastrics
These lipids reflect diet and are 54% unsaturated and 46% saturated in pig fatty acids for instance.
Describe ruminant lipids
Ruminant lipids are more uniform.
In cows, the fatty acids are 46% unsaturated and 54% saturated.
Describe lipids in poultry.
66% unsaturated and 34% saturated
What is oleic?
the most common fatty acid found in meat
Describe the nutritional value of meat.
It ranks third in protein value after eggs and milk.
What is actomyosin?
the major protein in meat
What is myoglobin?
A meat protein that transports o2 and co2 within muscle
What are some of the minor meat proteins?
troponin, tropomyosin, enzymes, nucleoproteins, collagen
Inedible proteins: collagen, elastin, keratin
What is the major carbohydrate in meat?
Glycogen (before rigor)
Lactic acid (during rigor)
Other carbs include glucose derivatives.
What vitamins are prominent in meat?
Vitamin B12, niacin, riboflavin, Vitamin B6
Beef is high in Vitamin B12
Pork is high in thiamine
What minerals are provided by meat?
Fe, Zn, K, S, Na, Cl, Mg, Ca, P
The main ones are Fe and Zn
Mg, Ca, and P are mostly in bone
How is meat quality determined and what criteria is used?
- color and texture
- aroma and flavor
- juiciness
- tenderness
What affects meat color?
Myoglobin is most responsible for meat color.
Used muscles are darker because they have more myoglobin in them (myoglobin is dark).
Color is also affected by the pH
Unused muscle is lighter in color because there is less myoglobin present
What are the desirable meat colors?
- Beef - bright, cherry red
- Pork - grayish pink
- Mutton - light pink
- Veal - pinkish brown
- Poultry - golden, yellow
What affects meat’s aroma and flavor?
- subtle combinations that are organoleptic
- volatile compounds that are liberated by heating
- water soluble and fat soluble compounds; have different influences, fats have more influence on flavor
What is juiciness and how does it relate to meat?
Juiciness is defined as the wetness produced by the release of meat fluids.
It is second to tenderness is importance as a palatability factor.
It is greatly affected by cooking procedure.
Meats that have more marbling are typically juicier.
What factors influence flavor?
Cooking procedure and marbling
What is tenderness and how does it relate to meat?
Tenderness is a measurement of how easily meat can be cut or chewed. It is also measured as resistance to sheer force.
What factors influence meat tenderness?
- Connective tissue - more connective tissue leads to less tender meat
- Cooking method - myofibrils become tougher with heat while connective tissues become more tender with heat
- time and temperature of storage - variable effects
- muscle fiber coarseness - small fibers may become more tender, but connective tissues are still the main determinant
- Age - tenderness decreases the older the animal gets
What are some pre-slaughter factors that influence meat quality?
- Heredity: tenderness is a highly heritable trait
2 Physiological:
- age: younger animals are more tender; older animals are tougher and have stronger flavor
- hormonal balance: in younger animals, hormones are not a large factor; in older animals, hormones can have an effect on meat quality - Feeding and management: a major factor
- Slaughtering and stress: less stress means the animal has higher glycogen stores and better rigor resolution
What post-slaughter factors affect meat quality?
- Chilling: ensures quality and makes meat easier to cut
2: Aging: for monogastrics, they have a higher unsaturated fat content, and aging may cause an oxidized flavor; otherwise, aging improves tenderness - Freezing: inhibits growth of microorganisms; theorized that ice crystals may help with tenderness
- Electric stimulation: makes rigor more uniform by contracting muscles at the same time; improves color and tenderness
What is the dressing percentage?
The amount of carcass usable for meat.
Dressing percentage = (carcass weight/live weight) x 100
What are some common dressing percentages?
Sheep: 50%
Cattle: 60-62%
Swine: 72%
Describe meat inspection
Meat inspection is a mandatory practice that is paid for by taxes. It is carried out by the Food Safety and Inspection Service (FSIS), which is a division of the USDA.
The Wholesome Meat Act of 1967 requires every slaughtered animal to be inspected.
The purpose is to ensure meat is wholesome and suitable for consumption to protect public health.
Some evaluation factors are that the meat is free of disease, the facilities are clean and sanitary, and the meat is properly packaged and labeled.
Describe meat grading
Meat grading is optional, and paid for by meat packers who want it. It follows USDA guidelines, and is based on aspects of meat desired by consumers.
What are private grades?
These are grades followed by some packers. They do not always follow USDA guidelines.
Describe how the USDA Grades quality grades of beef.
Beef is evaluated based on palatability, flavor, and tenderness. It is also based on maturity and marbling.
The grades are prime (most marbling), choice, select, and standard (least marbling).
Describe USDA yield grades for beef.
This measures the quantity of boneless, closely trimmed retail cuts of meat from the animal.
It is based on fat, area or rib-eye-muscle, and weight.
Grades: 1, 2, 3,4 ,5
Describe pork grades under the USDA.
Yield and quality are in one grade together. The grades are based on backfat, muscling, and lean cuts.
Grades: U.S. 1-4
Describe USDA poultry grades.
Grades are A, B, and C.
Whole birds are typically grade A.
How is meat marketed?
- Whole carcass
- Wholesale/retail: boxed products are sold; based on primal cuts such as ribs, chuck, loin, brisket
- kosher and halal meats: based on religious guidelines
- variety meats: includes organs, like heart or liver
What are some common meat pathogens?
Salmonella (most common), campylobacter, E. coli, Listeria (can grow at colder temp ranges, ex. on lunchmeats)
What are the recommended cooking temperatures for meat?
For ground products, and internal temp of 160 degrees F is recommended.
Other types of meat are at a lesser concern for internal temp.
Describe Hazard Analysis Critical Control Points (HACCP)
A systematic approach to food safety that identifies and eliminates hazards at various points in food production and processing.
