General Characteristics of Food Animal Origin

Question 1

The Yolk

Answer 1

1) Comprises 31% of the weight of an egg
2) Has a higher nutrient density than the white
3) Yolk supply flavor and mouthfeel
4) Contain all 3 lipids; Triglycerides, Phospholipids, and Sterols
5) The primary phospholipid is lecithin & the most well-known sterol is cholesterol
6) Primary protein in yolk = Vitellin
7) The yolks pigments = Xanthophylls
8) If the yolks have a higher carotenoid content, they are darker

Question 2

The White

Answer 2

1) Also known as Albumen
2) Over half of the protein in whites is Ovalbumin
3) White provide more protein than yolk

Question 3

Composition of milk (Water)

Answer 3

1) Milk is composed of water approximately 87-88%
2) If the water is removed, the shelf life of milk products is greatly extended

Question 4

Composition of milk (Carbohydrates)

Answer 4

1) Main carbo = Dissacharides Lactose
2) It is converted into lactic acid due to BACTERIAL fermentation

Question 5

Composition of milk (Fat)

Answer 5

1) Fat or Butterfat exists at level of 3-4% in whole milk
2) Fat globules are less dense than the water in the aqueous phase of milk
3) When emulsified during homogenization, there is an increase in the number of fat cells
4) Milk either carries or may be fortified to contain the fat-soluble vitamins, and it contains the pigments carotene and xanthophyll.
5) The fatty acid chains contain many short-chain
fatty acids such as saturated butyric acid, caproic, caprylic, and capric acids.

Question 6

Composition of milk (Protein: Casien)

Answer 6

• Protein represents 3–4% of the composition of milk
• Casein is the primary protein of milk, comprising approximately 80% of the milk protein.
• The caseins can be separated by acidification to a pH of 4.6 (the isoelectric point).
• At this pH, the caseins aggregate, since they are hydrophobic, are poorly hydrated and carry no net
charge
• Casein micelles are relatively heat stable and are not denatured by heat (at neutral pH) unless temperatures are very high and heating is prolonged.
• Caseins contain both hydrophobic and hydrophilic sections
• Caseins contain a high proportion of the amino acid proline
• Casein readily adsorb at an oil–water interface, forming a stable film that prevents coalescence of emulsion droplets -thus, they make excellent emulsifiers.

Question 7

Composition of milk (Protein: Whey)

Answer 7

• A second protein fraction of milk is the whey or serum
• It makes up approximately 20% of milk protein and includes the lactalbumins and lactoglobulins.
• Whey proteins are more hydrated than casein and are denatured and precipitated by heat rather than by acid.
• Other protein components of milk include enzymes such as lipase, protease, and alkaline phosphatase, which hydrolyze triglycerides, proteins, and phosphate esters, respectively.

Question 8

Composition of milk – vitamins

Answer 8

• Milk contains both water-soluble and fat-soluble vitamins.
• The nonfat portion of milk is especially plentiful in the B vitamin riboflavin
• Vitamin A is naturally in the fat component of whole milk.
• Whole milk is generally (98%) fortified with vitamin D.
• Low-fat and nonfat milk are fortified with both of these fat-soluble vitamins because milk fat is reduced or absent.

Question 9

Composition of milk – minerals

Answer 9

• Minerals such as calcium and phosphorus are present at levels of approximately 1% of milk
• Calcium is combined with the protein casein as calcium caseinate, with phosphorus as calcium phosphate and as calcium citrate.
• Other minerals present in milk are chloride, magnesium, potassium, sodium, and sulfur.

Question 10

MEAT-Protein Classification

Answer 10

• Myofibrillar Protein: Salt soluble protein, main
component of meat protein.

• Sarcoplasmic Protein: Water soluble protein.

• Stroma Protein: Connective tissue protein, the residue after extraction of the sarcoplasmic and myofibrillar
protein.

Question 11

Myofibrillar Protein

Answer 11

• Muscle is the group of bundles
• Bundle is the group of fibers
• Fiber is the group of myofibrils
• Myofibril is the continuous fibril (sarcomere)
• Fibril consists of thick filament (myosin) and thin filament (actin)
• Salt soluble component.
• The myofibrillar proteins present in the muscle in the largest amounts, that is, myosin, actin, tropomyosin, and the troponin.
• Contribute to the muscle contraction and functional properties of meats.

Question 12

1. myofibrillar proteins are composed of:

Answer 12

Myosin

Question 13

Myosin is generally considered the singly most important
because:

Answer 13

• Myosin is the principal of myofibrillar proteins, making up over 55% of the total, and it is located in the thick filament.
• The molecular weight of myosin is 200 kDa.
• In the formation of the network during setting, a major role is played by the aggregation of the myosin through different protein-protein interactions.

Question 14

Actin

Answer 14

• Actin is the myofibrillar protein of second highest
concentration and is found in the thin filaments along with tropomyosin and the troponin complex.
• The moleculer weight of actin is 45 kDa.
• Actin itself does not display the ability to form a gel.

Question 15

Z-line:

Answer 15

• Thin filament attach at one point so that they are all lined up with one another
• The Z-line is the dark line that runs perpendicular to the thin filaments
• It is simply a lot of sticky proteins that anchor the thin filaments in place
• a region within an I-band that defines the end of a sarcomere

Question 16

A-band:

Answer 16

• The dark band, where the myosin runs
• A region of a myofibril composed of thick filaments and thin filaments. At the center of the A-band, the H zone provides a space for the thick filaments to pull the thin filaments towards

Question 17

H zone:

Answer 17

• A region in the center of the sarcomere of the
myofibril composed almost exclusively of thick
filaments.
• During contraction H zone shrink in size as thin
filaments are pulled in to fill the space of the H
zone

Question 18

M line

Answer 18

The M line in the center of the sarcomere and A band is where proteins hold the thick myofilaments in position.

Question 19

I-band:

Answer 19

• A portion of the sarcomere contains the z line and contains thin filaments only.
• During contraction, the region of the I-band will shrink as the thin filament is pulled towards the center of each respective sarcomere by the thick filaments

Question 20

Stroma Protein

Answer 20

• The connective tissue surrounding the muscle
• Epimysium: Surrounding the group of muscles into meat.
• Perimysium: Surrounding the group of muscle fibers
(bundle) into muscle.
• Endomysium: Surround each of the muscle fibers into bundle

Question 21

Stromal proteins (connective tissue)

Answer 21

•10 - 15% of total muscle protein

•Stroma is the protein that forms connective tissue, it cannot be extracted by water, acid, alkaline, and salt solution.

•Responsible for holding the cells together,providing
an extracellular skeleton and contributing to the
general shape.

•The component of stroma are either collagen, elastin, or both.

Question 22

Collagen in stromal proteins

Answer 22

• Collagen has a usual amino acid composition
containing more than 12% of hydroxyproline.
• If collagen is heated for a long period, it changes
to a water soluble gelatin.
• When gelatin solution is seasoned and cooked,
it turns into jelly, desirable food in some
countries.

Question 23

Elastin in stromal protein

Answer 23

• Elastin is very resistant to moist heat and
cooking does not affect Elastin.
• Elastin is somewhat elastic and therefore found
in tissue where some flexibility is required.

Question 24

Importance of sarcoplasmic proteins

Answer 24

1. Enzyme activity
   • calpain - tenderization
   • postmortem glycolysis
   • pH change
   • potential flavor contributions from
   protein hydrolysis → hydrolized proteins
2. Color
   • myoglobin
   • responsible for all meat color variations, so a good
   understanding is critical in meat processing

Question 25

Pigments

Answer 25

• A variety of nitrogenous compounds contribute to the color of mammal muscles.
• The major contributor to color is the hemeprotein myoglobin. Hemeprotein is the pigments associated with the bright red surface color of meat.
• Other pigments such as the cytochromes and hemoglobin present in blood cells remaining in the muscle may make a minor contribution to meat color.

Question 26

Meat Color – Pigment Content

Answer 26

• Pigments
• Two main pigments: myoglobin and hemoglobin
• Majority of color is due to myoglobin

Question 27

So — what controls meat color?

Answer 27

1. Myoglobin concentration
2. Chemistry
   • Fresh meat color comes from
   • deoxymyoglobin - Fe++ - no ligand? (purple)
   • oxymyoglobin - Fe++ - oxygen attached at 6th position on heme (cherry red)
   • carboxymyoglobin - Fe++ – carbon monoxide at 6th position (cherry red)
   • metmyoglobin - Fe+++ - water (brown)

Question 28

Iridescence

Answer 28

Iridescence results in a shiny, rainbow-like
appearance on the surface of cooked meat
products.

This appearance is often associated with
green, red, orange, and yellow colors caused by
product surface microstructure and light
diffraction, not the myoglobin redox state.

Question 29

Shell

Answer 29

1) Outer covering of egg, composed largely of calcium carbonate

2) May be white or brown depending on BREED of chicken

Question 30

Yolk

Answer 30

1) Color varies with feed of the hen, but doesn’t indicate nutritive content

2) Major sorce of egg vitamins, minerals, and fats

Question 31

Vitelline (Yolk) Membrane

Answer 31

1) Holds egg yolk contents

Question 32

Chalazae

Answer 32

1) Twisted, cordlike strands of egg white

2) Achor yolk in center of egg

3) Prominent chalazae indicate FRESHNESS

Question 33

Air cell

Answer 33

1) Pocket of air formed at large end of egg

2) Caused by contraction of the contents during cooling after laying

3) Increases in size as egg ages

Question 34

Shell Membranes

Answer 34

1) Inner and outer shell membranes surround the albumen

2) Provide protective barrier against bacterial penetration

3) Air ccell forms between these two mwmbranes

Question 35

Thin Albumen

Answer 35

1) Nearest to the shell

2) Spreads around thick white of high-quality egg

Question 36

Thick Albumen

Answer 36

1) Major source of egg riboflavin and protein

2) Stands higher and spreads less in higher-grade eggs

3) Becomes indistinguishable from thin white in lower-grade eggs

Question 37

Sarcoplasmic Protein

Answer 37

• Water soluble component.
• Extracellular fluid liquid contains different types of enzyme, pigments, parvalbumins, antifreeze proteins, marine toxins, and NPN.
• ~ 30% of total muscle protein