Exam 3 Flashcards
Post Mortem Aging
widely used practice occurs to some degree by default in all meat products
essentially is the controlled rotting of meat products to increase tenderness
protease enzymes (calpain) are released in muscle & degrade protein structure *A specific process (no mush)
amount of degradation influences tenderness & other eating quality characteristics (can be controlled to a degree)
Aging process length
28 days 95% key response of aging process complete (typically)
Tensor Fasciae Latae
tri-tip
not a lot of difference between quality grades regarding tenderness
should buy cheaper meat if selling for fundraising purposes, no need to buy prime if the tenderness difference is neglible
marbling and aging
higher marbling means a quicker aging response
Aging Definition
a naturally occurring process by which meat is held under controlled temperatures for a period of time. This allows enzymatic activity (calpain) to degrade complex proteins changing flavor and tenderness
meat kept above freezing (28 degrees F for meat)
Dry aging
hold the meat under refrigeration
no packaging
dry surface of meat
pro: easy, excellent flavor development (oxidation of fats)
con: surface dehydration, significant trim loss, need larger store space for inventory
Wet aging
hold meat under refrigeration
vacuum packaging
wet surface
pro: no yield loss, easy to transport
con: limited flavor development, need vacuum packaging system
*no difference in tenderness between wet and dry only flavor
Dry vs wet aged fabrication
meat price (cost is the most expensive thing in a meat plant
wet aged beef is cheaper (less loss)
dry aged beef is more expensive (less product) considered a luxury item
Physical tenderization
mimicking enzymatic aging
method of suspension: tenderstretch, tendercut
electrical stimulation: physical destruction, prevents cold shortening
hydrodyne: uses explosives to send shock waves through water (not very practical)
blade needle or pin tenderization
Blade/Needle tenderization
also known as needling, cubbing can be included: done by costco
cuts through the muscle fibers and connective tissue
usually done on low grade meat
most effective means of breaking down connective tissue
very commonly used for food service cuts: especially sirloin
food safety concerns: transferring pathogens from the surface of the meat to the interior of the muscle
needle tenderized meat needs to be cooked to a greater degree of doneness
Seasoned and marinated
application of various seasonings and coatings/breading to meat products
fajita marinades, rosemary seasoned rack of lamb, pork carnitas
usually incorporated into enhanced products that need added value, flavor improvement, and or tenderness improvement
Batter and Breading
application of seasonings and coating/breading to meat products
utilizes advanced milling techniques
adds significant value (cheap weight) to products
adds significant caloric content
adds convenience and flavor
General Composition of meat
water: 70-75%
proteins: 20-25%
lipids: 1-6% (IM fat)
carbohydrates: 1% (glycogen: postmortem pH changes)
inorganic constituents: 1% (iron, vitamin B)
Muscle Proteins
three major groups based on solubility:
sarcoplasmic proteins: 25-30% (cytoplasm of meat, determines meat color)
myofibrillar proteins 50-60%
stromal proteins 10-20% (connective tissue)
Sarcoplasmic Proteins
25-30%
water-soluble
enzymes and myoglobin (color)
Myofibrillar Proteins
50-60%
salt soluble
actin and myosin
Stromal proteins
10-20%
insoluble, requires stong acid/alkali
collagen and elastin (connective tissue)
Muscle function
muscle comprises 30-40% of an animals body mass: the largest organ mass in the body of vertebrates
primary functions:
movement: locomotion, digestion, breathing, vision, circulation
support: tonic contraction
maintenance of body temp: metabolic activity produces heat
dietary protein source: muscle foods
Basic muscle types
Skeletal: voluntary
cardiac: involuntary
smooth: involuntary
Skeletal muscle
voluntary
in meat science, a basic knowledge of the structure and function of skeletal muscle is required to understand the basis for differences in meat quality and various functional processing of meat
Levels of Muscle organization (5)
1) skeletal muscle: surrounded by epimysium
2) muscle bundle: surrounded by perimysium
3) muscle cells (fiber): surrounded by endomysium
4) myofibril: surrounded by sarcoplasmic reticulum (not a connective tissue)
5) sarcomere: the contractile unit
Muscle design
collection of individual cells: muscle fibers encased “harnessed by a highly organized network of connective tissue (provides structural integrity)
Connective Tissue is subdivided into “sheaths” that encase:
the entire muscle (perimysium)
bundles of muscle fibers, blood vessels, neurons, fat cells (perimysium)
individual muscle fibers (endomysium)
IM fat location
intramuscular fat is located on the perimysium
marbling in meat consist of groups of IM fat cells deposited in the perimysium in close proximity to blood vessels
Connective tissue in muscle
2% collagen
0.1% elastin
Collagen Characteristics
the structural unit of collagen is tropcollagen
tropocollagen molecule is a triple helix consisting of three polypeptide chains (glycine-proline-hydroxyproline)
repeating tripeptide
Structure of collagen
repeating tripeptide: glycine-proline-hydroxyproline
as collagen matures it forms stable crosslinks which increases its tensile strength
therefore as the animal matures more crosslinks are formed and meat gets tougher
differences among muscles in collagen content
increasing hydroxyproline (collagen) content
psoas major (tenderloin): least amount most tender
longissimus dorsi (ribe eye)
rectus femoris
triceps brachii
superdigital flexor (shank): greatest amount least tender
Elastin
rubbery protein (connective tissue) that is abundant in structures that require the ability to stretch (ligaments, arteries & veins, abdominal wall, lungs, skin)
contains two unique amino acids: Desmosine and Isodesmosine which from cross-links
is very resistant to extremist in alkalinity, acidity, and heat: very stable protein (more so than collagen)
elastin fibers are capable of stretching to several times their original length but quickly resume their original length when tension is released
Muscle cell=?
MYOFIBER
myofibers are long and cylindrical in shape
length ranges from a few mm up to several cm
diameter ranges from 10 to more than 100 microns
multinucleated: nuclei located at the periphery just beneath the sarcolema
designed to shorten resulting in movement
sarcolema
cell membrane
sarcoplasm
cytoplasm of the muscle cell (water, proteins, lysosomes, glycogen granules, lipid droplets, ribosomes)
nuclei
muscle cells are multinucleated, elliptical nuclei are located near cell periphery
myofibrils
contractile machinery of cell, comprised of contractile units called sarcomeres
sarcoplasmic reticulum and T-tubules
highly developed endoplasmic reticulum unique to muscle cells
membrane-bound around the myofibril
sits just under the endomysium
stores Ca in the relaxed muscle
transverse T-tubules: invaginations of the sarcolemma that form a “communication channel” into the interior of a muscle fiber
structure and banding features of Myofibrils
muscle cells (fibers) are packed with smaller rod-like organelles called myofibrils
myofibrils occupt over 80% of cell volume
myofibrils show distinct alternating light (I) and dark (A) bands
I band
light band containing just thin filament
(actin, troponin, tropomyosin, titin, nebulin)
A band
dark band containing an overlap of thin and thick filaments
(actin, myosin, M line)
Z line
a dense thin line that bisects the I band
z filaments composed of alpha-actinin
anchor the thin filaments on each side of the Z line
a key primary structural element of myofibril
the area for one Z line to another is referred to as the sarcomere
Z lines form the lateral boundaries for repeating contractile units
H zone
light zone with the A band
region in which there is no overlap of thick and thin filaments: just thick filament
psuedo H zone
dark region bisecting the H zone where the M line holds the thick filaments together
M line
very thin dark line withing the pseudo H zone
M line holds the thick filaments in position
Muscle contraction
involves shortening of the sarcomeres
thick and thin filaments slide across one another bringing Z lines closer together