ANSC 3421 Meat Science EXAM 2

chemical composition of Muscle

water 75% , Protein 20%, Fat 3%, minerals vitamins carbs 2% ((( matching question on exam)))

Protein 20%

1.) contractile = myosin + actin

2.) Sarcoplasmic = myoglobin + hemoglobin

3.) connective tissue = collagen + elastin

fat 3%

1. ) prime = 12%

2.) choice = 4.5%

3.) select = 3%

4.) standard = 2 %

minerals, vitamins, carbs 2% ( 4 items I,Z, B, G)

iron ( heme), zinc, B vitamins, glucose

Muscle

•A contractile organ comprised of muscle fibers, connective tissue and intramuscular fat

Three types of muscle tissue

skeletal, cardiac, smooth

skeletal muscle ** know for exam **

1. ) voluntary

2.) striated

3.) multi nucleated

purpose : •Responsible for body movements which produce locomotion

35% - 65% of carcass weight

cardiac muscle ** know for exam **

1.) involuntary

2.) striated

3.) branched

4.) intercalated discs

5.) single nucleated

6.) location = heart

Smooth muscle ** know for exam**

1.) involuntary

2.) not straited

3.) single nuclei

purpose : contained within blood vessels and extremely elastic and pliable

Structure of Skeletal Muscle

Skeletal Muscle Fibers

epimysium ( muscle) , perimysium ( muscle bundle), endomysium ( muscle fiber), sarcolemma, sarcomere, myofibril, myofilament

Myofibrils

contains 2 types of myofilaments : MYOSIN ( thick, remember myosin = 6 letters -1 = 5 thick is 5 letters)

ACTIN ( THIN, remember actin = 5 letters - 1 = thin , thin is 4 letters)

thick filaments

MYOSIN - constitute the A band of the sarcomere

THIN filaments

ACTIN, constitute the I band of the sarcomere

smallest contractile unit = WHAT?

sarcomere

I band (actin)

m line

H zone

myosin

actin

A band ( Myosin)

z line

proteins of the myofibril

Major contractile proteins ...

MYOSIN : constitutes 45% of myofibrillar protein ( light and heavy meromyosin)

ACTIN : constitutes 20% of myofibrillar protein ( G Actin or globular actin)

Know what the myosin structure looks like and the functionality of the "head" CONSTRUCTION OF MYOSIN

rod like tail and two globular heads

Heads: two smaller, LIGHT polypeptide chains that reach out and grab onto actin

Construction of Actin

G ACTIN : globular

F ACTIN : fibrous

two strands of F Actin coiled together to form a HELIX

1. tropomyosin ( the strand) 2. troponin ( allows for contraction to occur) binding sites)))

TROPOMYOSIN :

1.) one tropomyosin strand lies on the surface on each of the two coiled chains of F actin

2.) is wound around the actin

TROPONIN :

1.) molecules are bound to tropomyosin and contain calcium ion binding sites

2.) present in grooves of actin and lies along tropomyosin

Muscle Fiber Type / Red vs White

◦Leg muscles of chicken have a higher proportion of red fibers

◦Breast muscles of chicken have a higher proportion of white fibers

Connective Tissue

Purpose: HOLD VARIOUS PARTS OF THE BODY TOGETHER (MUSCLE TO BONE)

Collagen

1.) white in color

2.) susceptible to moist heat

Elastin

1.) Yellow in color

2.) Not susceptible to moist heat

Connective tissue layers of muscle

1.) Epimysium = surrounds entire muscle

2.) Perimysium = surrounds muscle bundle

3.) Endomysium = surrounds muscle fiber

KNOW DIAGRAM FOR EXAM

Partitioning of Fat

mesenteric fat = internal ( visceral)

Perinephric = Internal ( kidney, pelvic, heart)

Intermuscular = Seam

Subcutaneous = external

Intramuscular = marbling

Composition of Fat

1.) neutral lipids

2.) Saturated = no double bonds = aka bad fats ( beef and lamb)

3.) Unsaturated = one or more double bonds = aka good fats ( pork)

4.) Monounsaturated = one double bond

5.) Polyunsaturated = two or more double bonds

Contractile Proteins

actin and myosin

MYOSIN = THICK

ACTIN = THIN

Regulatory Proteins

tropomyosin and troponin

Structural Protein

Z Line

Contractile Proteins MYOSIN

MYOSIN ( thick)

myosin head moves back and forth to perform a muscle contraction

Contractile Proteins ACTIN

ACTIN ( thin)

myosin head attached to the actin

REGULATORY proteins / Tropomyosin

tropomyosin

* thin protein that lays around the actin protein

REGULATORY proteins / Troponin

troponin / 3 subunits

* TnT binds tropomyosin

* TnL inhibitory subunit

* TnC calcium binding subunit

Sacrolemma

membrane around the muscle fiber

sits just under the endomysium

Sarcoplasmic Reticulum

- STORES CALCIUM

- needed for contraction

Muscle contraction

* a signal travels down a nerve

* attached to individual muscle cells

* the signal is passed on the myoneural junction

* the sarcolemma depolarizes

muscle contraction

* the depolarization causes the SR to release Ca into the sarcoplasm

* the Ca will bind with troponin ( Tn)

* this causes a shift in the troponin tropomyosin ( Tm) complex

The ATPase of Myosin

The ATPase activity of Myosin

*ATP ( adenosine triphosphate) bind to the myosin head

*ATP hydrolysis to ADP + Pi " cocks" the myosin head

The ATPase activity of Myosin

* the myosin head attached to the exposed binding site on Actin

* Pi leaves causing the "power stroke"

* ADP is released causing a strong bond

The ATPase activity of Myosin

ATP reattaches to the myosin head causing the head to released from the myosin - actin binding site

Overview of the process

1.) the muscle fiber is stimulate

2.) where does the contraction start? ( brain) which sends a signal down the spinal cord to the nerve

3.) Sarcoplasm --> SR ( calcium inside) --> calcium released, Thin filaments move to middle of sarcomere, Ca + floods into the muscle itself. Calcium binds to troponin/ tropomyosin . once it attaches, the binding sites revealed.

Myosin cross bridges attach to active site on actin. After attachment, the cross bridges pivot, pulling the thin filaments. A fresh ATP replaces the ADP+Pi, allowing myosin and actin to detach. Energy from the splitting of the fresh ATP allows repositioning of the myosin head. Return to step 1

Overview again

1.) muscle fiber is stimulated

2.) Ca+ ions are relased

3.) Thin filaments move to middle of sarcomere

4.) muscle fiber contracts

5.) muscle tension increases

putting it all together

1.) signal travels down a nerve to a muscle cell

2.) nerve impulse is transferred to the sarcolemma of a muscle cell

3.) the sarcolemma depolarizes causing the SR to release Ca+ into the cytosol of the cell

4.) Ca+ binds to troponin (Tn)

5.) the Tn-Tm complex shifts the grove of the actin exposing the binding site

6.) myosin possess ADP+Pi to allow for contraction to occur

putting it all together

* myosin attaches to actin forming a weak bond

* Pi is released causing the power stroke

* ADP is released forming a tight rigor bond of actin and myosin

tender cuts *** know tender cuts vs tough cuts***

1.) Psoas major ( aka tenderloin / filet/ highest overall value)

2.) Infraspinatus ( flat iron / comes from the chuck section)

3.) Gluteus medius ( sirloin)

4.) Longissimus dorsi (ribeye / loin)

5.) Triceps brachii

tough cuts *** know tender cuts vs tough cuts***

1.) Deep pectoral ( brisket)

2.) Latissimus dorsi

3.) Trapezius

4.) Superficial pectoral

Actomyosin Effect

* sarcomere length

* muscle fiber diameter

Sarcomere Length

As contraction occurs, sarcomere length shortens

Electrical Stimulation

* electrical pulse sent through the carcass to increase tenderization

How does it work? uses up ATP to reduce ability of muscle to contract / speeds up the process of rigor mortis and pH decline

reduces the influence of cold shortening / high voltage results in some muscle tearing

Postmortem Aging

* enzymes are responsible for making meat products more tender over time

* CALPAIN aka termites = slowly eat away at the sarcomere

enzyme found within muscle that is commonly activated by Ca+

enzyme increase over time = degradation of proteins ( titin, desmin, nebulin)

CALPASTATIN aka exterminator = regulates calpains and prevents them from working. BOS INDICUS aka BRAHMAN CATTLE have higher amounts of calpastatin

Plant Enzymes

degrade either muscle proteins or connective tissue

* solubilize the muscle fibers most importantly contractile proteins ( actin and myosin)

* solubilize contractile proteins such as collagen

* can become too soft and mushy and develops off flavors

Enzyme PAPAIN ** KNOW THIS**

plant substrate PAPAYA active against muscle

Enzyme BROMELIN ** KNOW THIS **

plant substrate pineapple active against collagen

Enzyme FICIN ** KNOW THIS **

plant substrate FIG active against muscle and collagen

Muscle Fiber Diameter

* muscle fiber type is correlated to diameter and size

* smaller diameter fibers are more tender

Muscle fiber type and carcass location

high oxidative = red fiber types ( type I)

highly glycolytic = white fiber types ( type IIX)

Connective Tissue in Meat

•Connective tissue functions as structural support, nutrient storage, transport, defense, and repair to the body

•Connective tissue made of cells, ground substances, and protein fibers

•The protein fibers consist of

•collagen ( 55-95%)

• reticulin

• elastin

Locomotion muscles have higher collagen amount compared to support muscles

locomotion muscles = chuck and round

Support muscles = rib and loin

•Older animals have a greater amount mature collagen crosslinks

•The greater amount of mature collagen crosslinks means less collagen solubility leading to less tender meat

Collagen Affect on Tenderness

•Warner-Bratzler shear force (WBSF) is used to measure meat tenderness

•Shear force <3.9 = tender

•Shear force >4.6 = tough

the increase of collagen content strongly correlates to the increase of shear force values of raw meat

Blade Tenderization

•Physical severance of connective tissue and muscle fibers

• through multiple knives piercing through meat products

Problems

• increased shrinkage

• decrease shelf life

• concern with microbiological contamination

Bulk Density or Lubrication Effect : Marbling Theories

• bulk density : aka swiss cheese (marbling) allowing for a little bit of a break within the muscle proteins. Same as cooking a piece of steak with marbling, fat breaks down faster than muscle.

•Swiss Cheese

• lubrication effect aka Oil in an engine.

Bulk Density or Lubrication Effect : Marbling Theories

• insurance theory

•Higher quality grade proven to be more tender

• strain theory

•Puts tension on muscles fibers and bundles

National Beef Tenderness Survey Results

•Post-mortem aging

•Range from 1 to 358 days

•Mean of 20.5 days

National Beef Tenderness Survey Results

•Steak Tenderness

•Top Blade Steaks had lowest WBSF values and highest Consumer Panel scores

•Round Steaks had the highest WBSF values and Lowest Consumer Panel scores

•Strip Loin ranked higher than Ribeye for WBSF values

the protein responsible for the meat color is

myoglobin

Two main pigments

myoglobin and hemoglobin

ultimate pH and rate of pH decline postmortem

nature of group attached to the iron and the state of the iron

Myoglobin

* accepts oxygen from hemoglobin

* stores oxygen for use by the living muscle

•Contains a globin protein attached to a porphyrin ring containing a heme iron

•Nature of the group attached to the iron, and the state (covalent or ionic) of the iron determines meat color

Chemical Forms of Myoglobin ** know this for the exam**

DEOXYmyoglobin = purple

OXYmyoglobin = Red

METmyoglobin = brown

CARBOXYmyoglobin= red

DEOXYmyglobin ( DMb)

* heme Fe in Ferrous state

*uncut meat

* only water present to bind

* very LOW O2 tension required, typically associated with vacuum packaging

*•Purplish-red or purplish-pink color

•Nothing bond to the 6th binding site, Fe2+ / ferrous state

OXYmyoglobin ( OMb)

adding O2 to this product, not oxidization, but oxygenation oxidization results in the brown color

* Heme Fe is Ferrous state

* cut meat exposed to oxygen ( O2)

* no change in irons valence

* bright cherry red color

METmyoglobin ( MMb)

* oxymyoglobin is very unstable

* Oxidation of FERROUS Mb to FERRIC state

* complete oxygen consumption --> cellular respiration

* brown color

__NITROSYLHEMOCHROMOGEN *** KNOW THIS FOR EXAM ***

•is responsible for the stable cured-pink color of cured meats.

NITRIC OXIDE HEMOCHROME ** know this for exam **

Pure pink color associated with ham and pork products * do not need to know the graph ** know nitric oxide hemochrome

Factors Affecting Meat Color

* amount of myoglobin in the muscle

-Age: the lighter the color of the veal, the younger the carcass ( almost pink) VEAL < CALF < YOUNG BEEF < OLD BEEF

•Looses affinity for oxygen as age increases

-Species: (pork the least amount of myoglobin) PORK < LAMB < BEEF

-Type: SUPPORT < LOCOMOTION

Muscle pH

water retention or water holding capacity ( WHC)

High Muscle pH

•MORE H20 RETENTION = DARK COLOR

Low Muscle pH

LESS H20 RETENTION = LIGHTER COLOR

Vitamin E feeding of cattle

* prevents oxidation; retards conversion of myoglobin to METmyoglobin

History of Packaging

Pre WWII ◦ICE BOXES IN HOMES * KNOW PROS AND CONS FOR TYPE OF PACKAGING **

Protect Product from ...

contamination and deterioration

while providing ... product visibility and label information

Vacuum Packaging

primarily used in wholesale cuts directly from packer

Overwrap

mainly used in retail sales

Modified Atmosphere Packagin ( MAP)

mainly used in retail sales to increase shelf life

Packing Plant

§Equipment used today

-Multi-chamber, heat sealing

-Capacity: 30 pieces per minute

§Vacuum Packaging Bags

-Bone-Guard

-Non-heat vs. Heat shrink

-Improves product appearance

-Thickens bag for puncture resistance

•"Leakers"

-Improves barrier properties

Vacuum Packaging

* vacuum packaging for boxed beef

* O2 impermeable

* Moisture impermeable

* extends shelf life dramatically

Problems: changes meat color ( purplish red) , not often used in retail sales, low levels of O2 increases DEOXYmyoglobin , upon opening blooms back to normal color

Overwrap

used in retail settings: -allows for abundant oxygen levels, bright red pigment

- allows for very visible product

-Overwrap should have low water vapor transmission rate

•Problems

-May lose free water, causes purge

-High Oxygen availability increases aerobic bacteria growth

-These microorganisms compete for the oxygen and eventually turns the meat brownish (metmyoglobin)

- IN GOOD CONDITIONS, shelf life can be maintained for 5 to 7 days

Freezer Burn

• Evaporation of water

•Ice crystal formation on the surface of the food

•Delayed by

•Air tight packaging

•Manual defrost freezer

•Old, painty, cardboard flavor

•Flavor issue, not a food safety issue

MAP gas combinations

•High-Oxygen ( OXYmyoglobin)

•80% oxygen and 20% carbon dioxide

•Maintains strong oxymyoglobin color

•Decreases bacteria growth

• INDUCES lipid oxidation

•Carbon Monoxide

•0.4% carbon monoxide (CO), 30% carbon dioxide (CO2) and 69.6% Nitrogen (N)

•Maintains strong carboxymyoglobin color

•Decreases bacteria growth

• REDUCES lipid oxidation

CASE READY

-Individual slices are vacuum packaged or modified atmosphere packaged (MAP)

-Shipped to store, ready for display

RETAIL READY

-Subprimals fabricated into steaks/chops at retail and placed in case