A Look into the Future of Meat Science
¨ What is meat?
o
All animal tissues that are suitable for use as a food
§ All processed or manufactured products prepared from
these tissues are included.
o
The major component of meat is muscle
§ adipose, epithelial, connective, and nervous tissue
o
Nutritious food
§ What are the 6 classes of nutrients?
·
vitamins, minerals, proteins, carbohydrates, fat, water
§ meat is rich in protein, iron, B vitamins, and vitamin A
(liver).
(Polar bears livers are so high in vitamin A it can kill you if consumed)
§ provides all of vitamin B12 that needs to be consumed
§ Anthropologists report that 10,000 years ago, humans
began growing crops leading to larger populations.
·
These people who
mainly ate plants lacked essential nutrients which led to higher infant
mortality rates, shorter life spans, more infectious diseases, widespread
anemia, and bone mineral disorders.
§ Why do we benefit biologically from meat?
·
to replenish the body, we need to consume things that are chemically similar=beef
§ What do the scriptures say?
·
Genesis 9:3
·
D&C 49:18-21
·
D&C 59:16-20
·
Genesis 9:11 (JST)
¨ Meat Industry
o
It is not enough
to learn the current industry practices!
§ The industry changes so you must be able to know the basic concepts and apply them in different situations.
o
What is the
livestock industry without the meat industry? Dairy
o
The breeding and
rearing of poultry and livestock, along with forage and grain production for
these animals’ represents 60% of total agricultural production.
o
The food industry
represents the largest private sector the U.S. economy in terms of total assets,
employment, and gross receipts.
§ The meat industry earns 28% of the food industry receipts.
¨ Is science really needed in the meat industry?
o
manufacturing of meats used to be an art; now it is a science.
o
Today
manufacturing of meat products requires knowledge of…
§ farm animal production systems
§ animal welfare
§ growth hormones
§ preservatives
§ sustainability
§ food safety
§ human diseases
¨ Current and future challenges
o
In the next 40 years we will have to produce more food than we have in the last 10,000 years.
o
Bill Gates, who
has donated over $1.4 billion in efforts to improve agriculture in other
countries said, “Environmentalists are standing in the way of feeding humanity
through their opposition to biotechnology, farm chemicals, and nitrogen
fertilizer”.
o
There are
currently almost 7 billion people on earth.
§ It is predicted in 2050 the population will be between 9-10 billion
§ The UN-FAO predicts we will need to double our current production of meat.
¨ How are we going to overcome these challenges?
o
Future research in meat science is going to focus on biochemical, microbiological, biotechnological disciplines.
o
According the
experts, we need to focus on 5 priorities for the future of meat science
research
§ 1)the nutritional role of meat in a healthy diet
§ 2)the ongoing perception and realities of food safety and risk
§ 3)the effect of a growing animal rights movement worldwide
§ 4)the sustainability and environmental effects for various systems for producing meat animals
§ 5)the palatability, safety, and healthfulness of the resulting meat
o
A panel of
international scientists published in Science
that world leaders need to dramatically change their notions of sustainable
agriculture, get beyond popular biases against agriculture biotechnology, and
regulate genetically modified crops based on the best available science.
Nutritive Value of Meat 1.3
¨ Nutrient classes
o
Protein
§ What is a protein?
·
Proteins are large molecules consisting of one or more amino acid chains that are an essential part of a living organism. Protein accounts for 20% of total body weight
·
Building block = amino acids (there are 20 of them)
§ Where are proteins found in muscle?
·
myofibrils
· sarcoplasmic proteins (fluid inside a muscle cell)
o
Sarcoplasm is the
cytoplasm of striated muscle.
§ Why is regular protein consumption vital?
· we don't store amino acids and they are essential for building and repairing
§ Meat has high protein content and is a high quality
protein source also!
·
High quality
means…
o
amino acids are in amounts equivalent to our needs
o
highly digestible
o
easily absorbable
· 95-100% digestible
(while plant proteins are 65-75% digestible)
§ Essential amino acids are those that cannot be
synthesized
·
phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, arginine, leucine, lysine
o
Fat
§ Is fat necessary for a diet?
·
YES! (limited amounts) Every cell has fat and cholesterol
§ Fat is naturally found in our bodies and is necessary
for…
·
cell membranes
·
energy storage
·
vitamin storage
·
essential fatty acids
o
linoleic, arachidonic, linolenic
§ Types of fat in meat
·
saturated (lots of hydrogen bonds=hydrogenated)
·
unsaturated (double bonds)
·
poly unsaturated
o
More than one
double bond/fatty acid
§ Cholesterol
·
component of meat lipids
·
Naturally
component of cell membranes
·
Want no more than
300 mg intake/day.
§ Can be dangerous!
·
amount of fat consumed is linked with cancer and is a little higher with animal fats
o
Carbohydrates
§ Constitute less than 1% of the weight of fresh meat.
·
present as glycogen and lactic acid
§ Processed meats are the only meat products that may
contain carbohydrates.
o
Minerals
§ Meat is a good source of all minerals except calcium.
§ Iron
·
Regular intake is
important.
·
Iron from meat is
in a readily available form
o
heme iron = readily absorbable
·
Meat also
contains an unidentified factor that increases the absorbable iron from
none-heme sources.
o
Other
iron-containing foods must be consumed at the same time as meat to increase
iron absorption from other sources.
§ Zinc
·
More than 40% of
dietary intake of zinc comes from red meat, poultry, and fish.
·
Plant food
replacing meat in the diet increases phytate in the diet.
o
phytate reduces zinc uptake by the intestinal cells
·
essential for growth, wound healing, immunity, taste acuity, and DNA synthesis
§ Diets sufficient in meat consumption also likely fill
requirements for…
·
sodium
·
potassium
·
magnesium
·
selenium
o
Vitamins
§ All B complex vitamins are present in meat.
·
Thiamine,
riboflavin, niacin, vitamin B6, and vitamin B12 are present in highest
quantities.
·
Poor source of A,
D, E, K.
¨ Variety and Processed Meats
o
Liver is a rich
source of…
§ vitamin A
§ iron
§ niacin
§ riboflavin
o
liver is recommended to be a normal part of our diet
o
low fat and fat free trends can be a money maker= charge more
o
Most nutritionists
only consider a small population at risk for hypertension by consuming
processed meats.
¨ Nutrient retention during heating
o
Water soluble
vitamins are retained at greater amounts with dry cooking methods compared to
moist cooking methods.
o
Nutrients lost
from dripping can be salvaged for more complete use of nutrients. Use in gravy or stew.
Muscle Structure 1.4
o Smooth
§ involuntary, slow moving
§ one nuclei per muscle cell
o Cardiac
§ involuntary
§ found in the heart
one nuclei per muscle cell
§ Resembles both smooth and skeletal muscle
o Skeletal
§ voluntary muscle whose contraction causes skeletal movement.
Striated
Dark and light bands
Many nuclei per cell
¨ Skeletal Muscle
o Connective tissues
§
· Tissue covering the muscle.
§ epimysium
· Connective tissues inside muscle surrounding fascicles.
§ perimysium
· Connective tissue found inside fascicles.
endomysium
· Muscle cells are found inside the endomysium.
o Muscle cell
§ aka myofibers or muscle fibers
· Because the cells are longer than they are wide.
· can be several centimeters long
§ Multinucleated
· Why?
o so the proteins don't have to travel so far
§ Sarcolemma
· muscle cell membrane
§ T-tubules
· Invaginations in the sarcolemma
§ Sarcoplasm
· Cytoplasm of muscle fibers.
· 75-80% water
· Also contains…
o numerous proteins
o ribosomes
o glycogen (glucose chains)
o lipids
o other stuff
§ Nuclei
· Occur about every 5 μm.
· Located just beneath the sarcolemma.
· Figure 2.6
§ Myofibril
· long thin rods inside the myofiber/muscle cell
· bathed in sarcoplasm
· extend the entire length of the myofiber
· Two types of myofilaments…
o Actin and Myosin.
o they work together to cause muscle contraction
· Myofibril structure
o Sarcomeres
o One sarcomere
· Major proteins associated with myofibers…
o Over 20 different proteins.
§ 6 main proteins.
o Actin and myosin are the main contractile proteins.
o Troponin and tropomyosin are the major regulatory proteins.
o Actin
§ referred to as the thin filament
§ Figure 2.11
§ Tropomyosin strand extends across the whole groove of the actin filament.
§ Troponin occurs every 7-8 G-actin molecules.
o Myosin
§ referred to as the thick filament
o Cytoskeletal proteins
§ Titin
· Extend from the M line to the Z disc.
· Thought to be the scaffold for sarcomere development.
· Thought to be responsible for the resting tension of the sarcomere.
· elastic in the I band
· inelastic in the A band
· Does that make sense?
§ Nebulin
· Extends from the A band to the z disc.
· Plays a role in organizing thin filaments in developing muscle.
· Stabilizes thin filaments in muscle.
· May also anchor thin filaments to the Z disc.
· Sarcoplasmic reticulum
o Equivalent to the ER of other cell types.
o Forms a closely meshed network with myofibrils.
o flattened reservoir for calcium
o Figure 2.13
o Other organelles
§ Mitochondria
· powerhouse, creates energy
· Figure 2.13
§ Lysosomes
· Small vesicles capable of digesting the cell and its contents. (full of enzymes)
§ Golgi complex
· the UPS of the cell. It controls where things go.
Muscle's Associated Tissues 1.5
¨
Epithelial
Tissues
o
lines the surface of the body and organs
o
Of tissue types
present in the animal, epithelial tissue contributes the least to meat.
o
Characterized as
having little extracellular (outside the cell) material.
o
cell shape varies
§
Figure 2.16
¨
Nervous tissue
o
constitutes less than 1% of meat
o
Functions of the
tissue prior to slaughter and during slaughter influence meat quality.
o
Nervous tissue is
categorized as being part of either…
§
central nervous system
·
Brain and spinal
cord.
§
peripheral system
·
Nerve fibers in
other parts of the body.
o
Neuron features –
Figure 2.17
§
Axon- can be several feet long
§
Motor end plate- communicates with muscle cells
§
Cell body- (the signal is received in the dendrite)
o
Synapses
§
Interdigitating
areas where neurons are not joined, but rather exchange chemical substances
that causes a message to be passed on very quick!
¨
Connective tissue
o
Widely
distributed in the body.
§
Found in…
·
Skeleton
·
Framework of…
o
organs
o
blood vessels
o
lymph vessels
·
Sheaths
surrounding…
o
tendons
o
nerve trunks
o
muscles
·
attaches the skin
to the body
·
adipose tissue is
a specialized type (fat is a type of connective tissue)
·
huge role in
muscle
o
Connective tissue
is…
§
Characterized as
having relatively few cells and considerable extracellular substance.
§
Extracellular
substance varies between a soft jelly to a tough fibrous mass.
o
1) Connective
tissue proper
§
Connective
tissues that are fibrous and surround muscles, muscle bundles, and muscle
fibers.
§
Consists of…
·
ground substance
·
imbedded cells
·
extracellular fibers
§
Ground substance
·
Viscous solution
containing soluble glycoproteins.
·
synovial fluid between joints
§
Embedded cells
·
fixed or wandering cells (fat cells or immune system cells)
§
Extracellular
fibers
·
collagen and elastin
·
Types of
structures
o
Dense connective
tissue
§
Dense irregular
connective tissue
§
Dense regular
connective tissue
o
Loose connective
tissue
·
Collagen
o
most prevalent protein in our bodies
o
makes up 20-25% of total body protein
o
Figure 2.18 –
where it comes from.
o
Major component
of tendons and ligaments.
o
Networks of
collagen fibers are present n essentially all tissues and organs.
o
Over 12 different
kinds of collagen.
o
Not all types of
collagen form fibers.
§
Some form large
fibers, fine fibers, non fibrous, or even chicken wire-like sheath.
·
Figure 2.19 –
Type IV collagen
o
amount of connective tissue parallels physical activity
§
What does this mean
for meat quality?
o
something that sees more physical activity would mean more connective tissue and lesser quality.
§
What does this
mean for meat quality?
o
There are over 12
different types of collagen.
§
Connective tissue
cells
·
Fibroblasts
·
Mesenchymal Cells
o
potential to become fibroblasts or adipoblasts
·
Adipose Tissue
o
brown fat (for significant in new babies because it keeps them warm) and white fat
o
2) Supportive
connective tissues
§
Bone and
cartilage.
o
Cartilage
§
Collagen fibrils
form a fine network in the cartilage matrix.
·
These fibrils
constitute as much as 40% of the cartilage.
o
Bone
§
The extracellular
matrix of these connective tissues is calcified.
§
Figure
2.22
o
Blood
and lymph
§
Blood
and lymph, with their respective vessells are derived from connective tissues.
§
Blood
constitutes roughly 7% of the body weight.
o
While connective
tissues might seem different from one another, they have many similarities in
composition and function.
Adipose Tissue and Muscle Fiber Types 1.6
¨
Adipose Deposits
o
There are four
major fat depots in animals…
§
1) visceral (KPH=kidney, pelvic, and heart fat)
§
2) subcutaneous (under the skin)
§
3) intermuscular (seam fat between muscles)
§
4) intramuscular (perimysial tissue, fat between muscle fibers=marbling)
¨
Muscle Fiber
Types
o
Red muscle fiber
types
§
greater lipid content
§
red color due to greater myoglobin content
§
type I and II A myosin fibers
Slow twitch: can go for long distances and uses fat for energy
o
White muscle
fiber types
§
glycolytic
§
white in color
§
larger than red
§
type IIx(D) and type II B
Fast twitch: uses sugar for energy
Fast twitch: uses sugar for energy
o Table 2.1
¨
What is growth?
o
The normal
process of increase in size, produced by accretion of tissues similar in
constitution to those of the original tissue or organ.
o
Fattening and
growth are different.
o
Hypertrophy
§ enlargement of existing cells
o
Hyperplasia
§ increase in cell number
o
Accretionary growth
§ increase in extracellular material (found outside the cell)
o
Development
§ Gradual progression from a lower to a higher stage of
complexity, as well as gradual expansion in size.
o
Differentiation
§ where cells and organs acquire completely individual characteristics
o
Maturation
§ Where cells become fully developed and reach the
highest stage of complexity.
o
Senescence
§ where cells have lost their power of division and growth
o
Figure 3.1 –
Typical growth curve
¨
Myogenesis- creation of muscle
¨
Muscle
development during pregnancy
If there are nutrient restrictions during the second trimester or secondary myogenesis, we see that it actually decreases the number of muscle fibers the fetus develops. This decreases the muscle mass later in its development as well. It altered the animals genetic potential but it still has good genes to pass on to its offspring. It is not as critical during primary myogenesis because the focus in the developing fetus is not on muscle growth. The fetus is tiny but during secondary myogenesis it grows rapidly hence the need for adequate nutrition.
If there are nutrient restrictions during the second trimester or secondary myogenesis, we see that it actually decreases the number of muscle fibers the fetus develops. This decreases the muscle mass later in its development as well. It altered the animals genetic potential but it still has good genes to pass on to its offspring. It is not as critical during primary myogenesis because the focus in the developing fetus is not on muscle growth. The fetus is tiny but during secondary myogenesis it grows rapidly hence the need for adequate nutrition.
Fat and Muscle Development 1.7
¨
Fat development
o
Intramuscular fat
is the last fat depot to develop.
o
Visceral fat is
the first fat depot to develop.
o
Mature adipocytes
are up to 120 times the size of the primitive cell.
¨
Prenatal growth
o
Figure 3.7
¨
Postnatal growth
o
Figure 3.8
o
Figure 3.9
§ Proteins in muscle are:
·
1) sarcoplasmic proteins- rapid turnover
·
2) myofibrillar proteins- intermediate turnover- proteins in a myofiber (contractile and regulatory)
·
3) stromal proteins- nearly inert (collagen)
¨
Factors
influencing carcass composition
o
Genetics- anything over 40% is highly heritable. Through genetic selection we can increase the composition of the carcass.
Doubling muscled cattle- they have twice as many muscle fibers and hardly any marbling in them.
§ Table 3.5
§ Figure 3.10
§ Figure 3.11
o
Physiological age
o
Nutrition
§ Table 3.6
§ Compensatory growth
o
Hormones
§ Β-andrenergic agonists
· shifts nutrients from fat to muscle. Probably will be lesser meat quality because the intramuscular fat (marbling) will be the first fat depot to go.
§ Testosterone
· encourages muscle growth and discourages fat development.
§ Estrogen
· promotes fat development and doesn't affect muscle development positively or negatively.
§ Synthetic estrogens
· encourages lean growth in steers and whethers.
o
Environment
§ Stress = less performance
Muscle Contraction 1.11
Muscle Contraction 1.11
¨ Calcium
o
Resting state
versus contractile state
§ 1000 times greater Ca concentration in sarcoplasm
during contraction
o
Myosin structure
has two heads and is the thick filament
o
Motor end plate- where the nerve connects to the muscle fibers
§ Acetylcholine released- message that the neuron releases
·
leads to sodium influx in the cell
·
sodium influx leads to a calcium release
o
Affects troponin
§ Three subunits
·
C – binds calcium
·
T – binds tropomyosin
·
I – interacts with actin to inhibit actin and myosin interactions
§ Troponin are the nails on tropomyosin
·
Determines where
tropomyosin is on the actin strand
·
Tropomyosin
prevents myosin from crawling forward
§ High calcium concentration
·
Causes
conformation change in troponin allowing tropomyosin to move out of the way
§ Low calcium concentration
·
Troponin in its
standard confirmation, causing tropomyosin to block myosin
o
Affects muscle in
the three following ways
1)
2)
3)
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