School Science Lessons
Chicken Project 2
Updated: 2009-11-28
Please send comments to: J.Elfick@uq.edu.au
Table of contents
2.6 0 Hatching chickens
22.0
Prepare
chickens for food
22.1 Prepare eggs for food
2.6 0
Hatching chickens
2.6.1 Hatching an egg
2.6.2 Measure the eggs
2.6.3 Incubators, brooders
2.6.4 Development of chicken embryo
2.6.5 Record chicken development
2.6.6 Sexing a chicken
2.6.7 Care for chickens
2.6.8 Castrated capon raising the chicks as a
eunuch mother
22.0
Prepare
chickens for food
Domestic fowls used for food are called poultry, e.g. chickens, ducks,
geese, turkeys.
22.1 Receiving poultry supply and thawing
22.2 Grading and packaging poultry
22.3 Poultry grades
22.4 Poultry composition
22.5 Poultry structure
22.6 Preparation prior to cooking poultry
22.7 Cooking poultry
22.8 Quality points of poultry
22.9 Drawing a chicken
22.10 Trussing a chicken
22.11 Jointing a chicken
22.12 Chopping a chicken Chinese style
22.13 Boning a whole chicken breast
22.14 Carving a chicken
22.1 Prepare
eggs for food
22.15 Enjoy eggs every day!
22.16 Genetically modified organisms (GMOs) and
chicken feed
22.17 Egg grades
22.18 Egg sizes
22.19 Boiled eggs
22.20 Nutritional value
22.21 Cholesterol and fat in eggs
22.22 Contamination by bacteria
22.23. Egg allergy
22.24 Food labels
2.6.1 Hatching an egg
See diagram 50. 11: Parts of an egg
1. Keep records of the egg during the 21 days to hatching. Measure and
record the weight and length of the egg on days 3, 7, 14 and 21. Use a
strong light to see the developing chick. They call this candling
because formerly people used a candle to see if the chicks were alive
and developing properly. Note the heart of the developing chick already
beating by day 7. Note the change in the weight of the egg but no
change in the length of the egg. The mass changed because reserve
materials were broken down into carbon dioxide and water by
respiration. The carbon dioxide and water vapour could diffuse though
tiny pores in the shell causing the loss of weight.
2.6.2 Measure
the eggs
See diagram 50. 6. 5: Egg callipers
Weigh a fertilized egg and record in a table. Measure the length of the
egg with a pair of calliper and record in the table. Record the weight
and length of the egg each day. Note whether the weight changes and
whether the length changes. Weight decreases how is it lost? Food is
broken down during respiration to carbon dioxide and water and these
can both diffuse through the egg membranes and the shell to cause
weight loss. At the end of three days remove one egg and crack it
carefully. Put the contents into a shallow saucer. A three day embryo
will usually show the heart already beating. It may continue to beat
for half an hour. Remove an egg at day 7, day 14 and day 20 to study
the development of the embryo. Leave eggs for 21 days to hatch. When
the first cracks in the egg appear at day 21, the chicken is about to
hatch. The chicken cracks the egg with its egg tooth, a hard lump on
its beak. Find the egg tooth in a day 20 chicken.
2.6.3 Incubators, brooders
1. Make a cardboard box incubator
See diagram 50. 6. 3.1: Simple
electric incubator
Use a large and small cardboard box. Cut one end from the small box.
Cut a 15 cm2
window in a side of the large box. Cut a slit in the top of the smaller
box and suspend an electric lamp in it by a long electric cord. Put the
small box inside the larger box and pack newspaper between them. The
open end of the small box must fit against the side of the large box in
which you cut the window. Put a thermometer in the box so that you can
read it through the glass window.
2. Make a Styrofoam cool box
incubator
See diagram 50. 6. 3.2: Warm brooder,
electric incubator | See diagram 50. 6. 3.3: Brooder drinker, feeder box
Make a hole in the side of a Styrofoam box to fit a 40 watt light bulb
socket. Put aluminium foil on the bottom of the box. Put a piece of
wire mesh across the box. Make air holes in the sides and in the lid of
the incubator. Also, make a hole in the Styrofoam for a thermometer.
Maintain a constant temperature of 38oC in the incubator for
21 days. Use different sized bulbs and change the newspaper to regulate
the temperature. Put a dish of water in the incubator. Put 12 fertile
eggs in the incubator. After three days remove one egg and carefully
crack it open into a dish. Study the beating heart. It may continue to
beat for half an hour. Remove an egg every three days and observe the
development of the embryo. Leave eggs for 21 days to hatch.
2.6.4 Development of chicken embryo
1. Hold a light close to the egg so that you can see through it. As the
chicken develops, see its outline or shadow. Put the egg inside the
incubator and close the lid. The temperature should be 40oC.
Roll the
eggs every 12 hours to stop the yolk sticking to the shell. 2. Study an
unfertilized egg. Put a flat dish or Petri dish on black paper. Break
open a hen's egg. Note the yellow yolk and the clear part. you commonly
call the clear part the "white" of an egg because it turns white when
cooked. On the yolk see a small white patch. In the centre of this
white patch, too small to see with the eyes, is a nucleus. This is
where the chicken starts to develop. 3. Development of the chick in the
egg
Before egg laying:
Fertilization
Division and growth of living cells
Segregation of cells into groups of tissues
Between laying and incubation: No growth, stage of inactive embryonic
life
During incubation:First day
16 hours: First sign of resemblance to a chick embryo
18 hours: Appearance of alimentary tract
20 hours: Appearance of vertebral column
21 hours: Beginning of formation of nervous system
22 hours: Beginning of formation of head
24 hours: Beginning of formation of eye
Second day:
25 hours: Beginning of formation of heart
35 hours: Beginning of formation of ear
42 hours: Heart begins to beat
Third day
60 hours: Beginning of formation of nose
62 hours: Beginning of formation of legs
64 hours: Beginning of formation of wings
Fourth Day: Beginning of formation of tongue
Fifth Day: Formation of reproductive organs and differentiation of sex
Sixth Day: Beginning of formation of beak
Eighth Day: Beginning of formation of feathers
Tenth Day: Beginning of hardening of beak
Thirteenth Day: Appearance of scales and claws
Fourteenth Day: Embryo gets position suitable for breaking the shell
Sixteenth Day: Scales, claws, and beak becoming firm and horny
Seventeenth Day: Beak turns towards the air cell
Nineteenth Day: Yolk sac begins to enter body cavity
Twentieth Day: Yolk sac completely drawn into body cavity
Twenty-first Day: Hatching of chick
2.6.5 Record chicken development
See diagram 50.6.5.1: Feathering record
Weigh a newly hatched chicken and record the weight result in a table.
Use callipers to measure the height of the chicken from the top of its
head to its feet. Keep a chicken diary to record the weight, height and
behaviour of the chicken each day for the first three weeks. Describe
the change in colour or shape of its feathers. Describe how the chicken
walks when it first hatches and how this changes later. Describe its
"cheep"cry when newly hatched and how its voice changes later. Describe
how it pecks at its food, and drinks its water. Record any other
observations about the chicken. Record changes in the mass of the
chicken from day 1to day 20. Plot a graph of the changes in weight.
Plot a graph for the changes in the height of the chicken.
2.6.6 Sexing a chicken
For "sexing the chicken", turn the chicken over in the palm of the hand
with its head is pointing towards you. Try to find the opening
underneath its tail. Use the thumbs to fold down the feathers. Fold the
skin down around the opening but do not press too hard. If the chicken
is a male, you can probably see the penis like a small piece of thread.
When you cannot see a penis, then the chicken is a female.
2.6.7 Care for chickens
See diagram 50. 6. 3.2: Warm brooder
A hen sitting on eggs keeps them warm. When the chickens hatch, they
huddle under the hen for warmth and protection. If no mother hen, keep
the chickens warm with a heater in a brooder. This is a box with a
heater or light. The heater or light keeps the chickens warm. Give the
chickens food and clean water. Use shallow dishes for the food and
water. At first give the chickens a handful of chicken mash. Each day,
add more food to the dish each day and provide clean water.
2.6.8 Castrate
capon raising the chicks as a eunuch mother
A cock can be a mother. In a village in the north of Anhui Province in
China they ran an enterprise for raising chicks. The peasants could use
the castrated capon to protect and raise the chicks. People bought the
chicks from the hatchery. They gave rice liquor to the castrated capon
and the chicks in the same roost. Later, the chicks, which had never
seen their mother were getting impressions of the image, movement,
sound and temperature of the castrated capon. The chicks jostled
forcefully under the wings of the castrated capon as if in their
mother's bosom. The castrated capon clucked like a hen. Later it
protected the chicks and taught them to peck, call, defence themselves
and preserve heat. The effect was better than a hen. Peasants sum up
their experience and think it had three merits:
1. The castrated capon not only has large body and many feathers, but
also can raise 40 to 50 chicks, as many as two hens do.
2. It can raise
chickens for a long time. A hen raises the chicks only for a month, but
the castrated capon can do it for half a year until the chicks grow up
and weigh 1 to 2 kg.
3. The castrated capon is more daring, fiercer and
more thoughtful than cats and will not let cats get close to the
chicks. They can even wrestle with an eagle so they can raise the
chicks' survival rate.
22.1 Receiving poultry
supply and thawing
Poultry is supplied dressed or ready-to-cook, i.e. plucked and
eviscerated (innards removed) and without head or feet. Use fresh
poultry as soon as possible or be held for not longer than 3 days in a
refrigerator at 1oC. Take care that poultry is not left out
at room temperature when delivered. Store frozen poultry at -1oC.
Remove it from the freezer 18 to 24 hours before it is required for
food. Thaw it in a refrigerator. However, you can thaw it at room
temperature for 6 hours but not in warm water. If the poultry has been
wrapped in plastic, do not remove it before thawing, but remove poultry
from shipping cartons and spread out for easier thawing. Place the
poultry on trays to catch the melt and use the birds within 24 hours.
Never re-freeze poultry so it can be eaten later. Never buy
partially-thawed poultry or fresh poultry that is "sticky".
Refrigerate eggs, use them within two
weeks, cook them thoroughly, and never consume raw eggs.
22.2 Grading and packaging
poultry
Poultry is usually sold by numbers related to the weight of the bird
and rise in steps of 100 grams, e.g. No. 10 weighs 1 kg and No. 11
weighs 1.1 kg (1100 g). The size of the bird chosen for eating depends
on how it is to be used on the menu. Larger birds have more meat in
relation to the carcase than smaller birds, i.e. greater proportion of
meat compared with the weight of the bones.
22.3 Poultry grades
Grade 1. Roasting chickens, broilers, are the best quality chickens and
are 7 to 9 weeks old. The skin is unbroken and the birds are packed
without feet or giblets.
Grade 2a. Catering grade chickens are similar in quality and tenderness
to roasting chickens but the skin is broken during processing. Broken
wing tips and minor bruising to form small red patches may be seen.
Grade 2b. Chicken pieces may be cut from the poultry and sold. Pieces
may also be cut from the best parts of birds that have broken bones or
severe bruising during processing. Pieces may be bone-in or boneless
and may include all parts of the bird or as specified, i.e. chicken
breast, chicken wings, chicken thighs (drumsticks).
Boiling fowls are 1. Layer hens weighing about 1.3 kg formerly used in
egg production, 2. Meat breeder hens up to 65 weeks old and weighing 2
to 3 kg.
Boiling fowls are suitable for poaching and for dishes where only the
flesh is required.
22.4 Poultry composition
The edible meat consists of muscle surrounded by connective tissues and
fat deposits. Bone supports this muscle structure. The skin of poultry
is edible but some people are offended if served cooked poultry skin.
Poultry meat may be dark meat and light meat. Chicken breasts
from young birds have a higher niacin content than lean meat. Dark meat
is a better source of riboflavin and thiamine than white meat. The
differences in food value between dark meat and
white meat are not important but some people prefer to eat light or
dark meat, male or female poultry, particular parts of the carcase.
Poultry fat deposited on the muscle and under the skin makes the meat
more tender and more juicy. The fats improves meat flavour unless
it is old poultry with excessive fat. Older female birds have more fat
and fuller breasts than males.
22.5 Poultry structure
Connective tissue surrounds the meat muscle fibre and holds it
together. Older birds and more active birds (village birds and roaming
birds) have more connective tissue, and less tender meat. However, some
people prefer the taste of "free-range" birds. Breast meat has
connective tissue than leg muscles so it cooks faster than the leg
meat. However, breast meat has less fat than leg meat and will become
dry from long cooking unless the moisture lost during cooking is
replaced by basting, or using methods to moisture, e.g. aluminium foil
over the breast. Limited exercise helps to fatten the birds and they
become ready for eating at an earlier age. They attain desirable market
weights in a relatively short period of time and possess
characteristically tender, fleshy muscles.
22.6 Preparation prior to
cooking poultry
Ready to cook poultry should not require picking of pin-feathers, or
imilar type cleaning. It is wise, however, to Inspect all poultry after
thawing for the presence of any spongy red lung tissue inside the back,
loose membrane, pin-feathers or skin defects, remove these if present.
Some chickens, turkeys and ducks may have necks and giblets wrapped and
packed In the body cavity. Remove these, inspect and rinse. Wash
poultry inside and out under cold running
water and drain. Chickens to be used for deep fat frying must be
thoroughly dry. Keep at a minimum, the time the cut parts are exposed
to open air at room temperatures. If it is necessary to hold cooked
chicken for any time before serving, refrigerate.
22.7 Cooking poultry
Dry-heat methods include pan frying and roasting.
If roasting, thoroughly cook poultry with low temperature. Under-cooked
poultry is very prone to attack from bacteria. Thighs (drumsticks)
require longer cooking than breasts. While the thighs complete cooking,
the breast and skin have a tendency to become dry. Therefore, the
technique known as basting is used in poultry cooking. Basting adds
moisture to the skin and breasts and facilitates the browning and
roasting process. Prepare thawed and cleaned chickens, turkeys and
ducks for roasting by rubbing with salt and pepper. Spread over the
entire inner and outer surfaces. Really excellent seasonings that are
not cooked Inside the birds can be prepared. Roasting with stuffing
requires longer cooking periods. Prior to roasting, poultry should be
trussed by folding the wing tip under the wing stick and locking in
place against the back of the bird. Legs, too, must be secured in
place. Place birds into roasting pans and pour over melted
dripping. Do not pour melted dripping over ducks as these birds are
rich in fat. Baste frequently while cooking.
Cooking times and temperatures: 30 to 40 minutes per kg at 163oC.
22.8 Quality points of
poultry
8.1 The breast of the bird should be plump.
8.2 The vent end of the breast-bone must be pliable.
8.3 The flesh should be firm.
8.4 The skin to be white, unbroken and with a faint bluish tinge.
8.5 Any blue discolouration with an attendant stickiness and smell Is a
sign of deterioration in quality. Boiling fowls usually show marked
signs of toughness, for example the end of the breast bone is firm and
hard, and the skin usually shows an abundance of long hairs before
singeing. The legs are covered with large shiny, hard scales.
22.9 Drawing a chicken
Singe the bird with a flame. Make an incision down the length of the
neck. Pull out the windpipe and crop. Cut the neck off close to the
body, pulling the skin to one side and leaving a piece to fold over the
back. Place the bird on its back. Enlarge the vent opening and remove
the remaining organs and through this opening, i.e. the gizzard,
intestines, heart and liver with the gall bladder attached to it. Do
not break the gall bladder. Remove the lungs, the spongy masses lying
between the ribs in the hollows of the backbone. Take out the kidneys.
Open and clean the gizzard, heart, neck and liver in cold water.
22.10 Trussing a chicken
See diagram 22.10: Trussing a chicken
Trussing is often omitted when preparing poultry for cooking as the
bird's shape is set to some extent during processing. However, trussing
is desirable as an aid to the presentation of whole birds and for
poaching. Cut off the first joint of the legs and press them down close
to the
sides of the chicken. Fasten with a skewer or tie with string. Secure
the wings by running a skewer through the joint of one wing right
through the body to the other wing, or tie close to the body with fine
string, or fold wings underneath the back. To truss a fowl for boiling,
cut off the whole leg except for the
thigh, the end bones of which tuck into the apron. Tie the wings with
string close to the body.
A trussing needle is not necessary if the following procedure is
adopted.
1. Open the carcase at the vent and remove the fat adhering to the
Inside near the parson's nose. Take out the neck (if any) and make sure
the cavity is empty.
2. Open out the skin of the neck and remove the wishbone using the
fingers and a small knife.
3. Fold the skin of the neck under and turn the wing tips underneath
the bird to hold the neck skin in place.
4. Place the bird on the bench and press the legs down into the body.
5. Pass a string under the bird and cross the ends over bringing them
out under the drumsticks so that the strings lie in the creases along
the breast.
6. Turn the bird over and bring the strips up from under the wings.
7. Tie off the ends across the backbone.
7.1 When trussing by this method the knuckle joints should be left on
but must be removed prior to serving.
7.2 Removal of the wishbone assists in carving the breast. It also
avoids the risk of small splinter bones if the bird is to be cut up.
22.11 Jointing a chicken
To joint a raw chicken slit the skin round the junction of leg and body
and remove the legs. Cut off the wings together with a piece of breast
close to the joint. Then cut the breast from the back and cut it in
half lengthways through the bone. If a large chicken cutg in half again
crossways. Trim the back and cut in half. The legs may be cut again at
the joint..
1. Remove the legs. Place the chicken breast side up, pull one leg away
from the body and cut through the skin between the body and the thigh,
and then cut between the ball and socket. Bend the leg firmly outwards
and cut through between the joint, thus giving the thigh and drumstick.
The leg may also be left in one piece, which is known as the Maryland.
Repeat this procedure with the other leg.
2. Remove the wings. Press one wing against the body, making both parts
of the shoulder joint visible beneath the skin. Cut between the ball
and socket of the joint, then pull the wing outwards and cut down
through the skin at the base of the wing. Repeat this procedure with
the other wing.
3. Remove the breast from the carcase. Place the blade of the knife
inside the cavity and pierce one side between the shoulder joint and
the rib cage. Cut parallel to the backbone and through the rib cage.
Repeat this procedure on the other side. Pull the breast away from the
back to expose the shoulder bones. Cut between the shoulder bones to
detach the breast. The back may be cut into two or left whole and used
for making stock.
4. Cut the breast in half. Place the breast skin side up and cut into
two lengthways. If the bird is large the breast may be cut again across
the width yield 4 to 6 breast portions.
22.12 Chopping a chicken
Chinese style
1. Place the chicken, breast side up, on a wooden chopping board. With
a cleaver cut through the centre of the chicken, just to one side of
the breast bone. The-chicken should now be divided Into two equal
portions.
2. Take one side of the chicken, cut in half, between the thigh and
wing section.
3. Remove wing, by pulling back and cutting through the joint, cut into
two pieces.
4. Cut the breast section (after the wing has been removed) into three
equal pieces.
5. Remove leg, by pulling back and cutting through the joint, cut into
3 equal pieces.
6. Cut the thigh section (after the leg has been removed) into 3 equal
pieces.
7. Repeat with second side. The chicken should now be cut into
twenty-two pieces.
8. The Chinese cut the chicken in this manner for two reasons:
8.1 The chicken is cut into small pieces, which allows it to be
eaten with chop sticks.
8.2. The chicken can be re-assembled into chicken shape on the serving
platter.
22.13 Boning a whole
chicken breast
See diagram 22.23: Boning a chicken breast
Lay chicken breast skin side down on a wooden board. Using a sharp,
short-bladed knife, cut into flesh close to outer edge of central
breast bone, carefully easing it away from the bone, without cutting
through the skin. With the left hand, take a firm grip on outer end of
breast bone, holding remaining breast with right hand. Bend bone firmly
until it snaps at the joint and carefully pull it out, working from
joint end. Remove remaining bones using one of the following methods:
1. Using the knife, and working from top to bottom, carefully cut away
flesh from rib bones. Insert point of knife into flesh at base of
wishbone, cutting along either side of the bone until It can easily be
removed. Repeat with remaining bones.
2. Holding the breast with left hand, use the fingers of the right hand
to ease ribs gently away from the flesh.
3. The remaining bones, except
the wishbone, can easily be removed with the fingers by pulling
on each bone with one hand and pushing the flesh away with the other.
Use a knife if the bone is difficult to remove at the joint end.
4. Cut along both sides of the wishbone, push flesh away to base,
twist firmly and pull out.
22.14 Carving a chicken
Remove the legs by pressing them outwards and downwards and cutting
them off. Remove the wings by cutting down through the joints together
with a portion of breast. Cut the breast into several thin slices
lengthways, leaving a piece of skin attached to each slice. Divide
a smaller bird into 4 pieces, the two legs and the halved breast
and wings, without the back.
22.15 Enjoy eggs every
day!
1. Eggs have a high nutrient density because they provide top quality
protein and small to significant amounts of a wide range of vitamins
and minerals in proportion to their calorie count. One large egg, 50
g,
contains 310 kJ / 75 Kcal.
2. Egg protein quality is so high that scientists often use eggs as the
standard by which they measure the protein quality of other foods. Eggs
add protein to the diet, as well as various other nutrients. Eggs
supply all
essential amino acids for humans, besides vitamins and
minerals, including vitamin A, riboflavin, folic acid, vitamin B6,
vitamin B12, choline, iron, calcium, phosphorus and potassium. Eggs are
one
of the few foods that contain Vitamin D. A large egg yolk
contains about 250 kJ. The egg white
contains about 60 kJ. A large yolk contains more
than two-thirds of the recommended daily intake of 300 mg of
cholesterol. Aout 33% of
the liquid weight of the egg is the yolk that contains all of the fat,
about half the protein, and most of the other nutrients. The yolk
contains choline, about half the recommended daily intake.
3. One egg equals one ounce of lean meat, fish or poultry.
4. Besides protein, eggs also contain small to significant amounts of
13 vitamins and 13 minerals. Eggs do not contain vitamin C, but serving
eggs with orange juice, tomatoes or broccoli easily remedies this.
5. For most healthy people, an egg yolk a day is okay and will not
increase risk of heart disease. Researchers recently concluded that
there was no difference in relative heart disease risk between those
who ate less than one egg a week and those who ate more than one egg a
day.
6. Research has found that dietary fat, especially saturated fat, is
the real culprit in raising blood cholesterol levels. However, the
ratio of an egg's fat content equates closely with the recommended
ratio of a dietary fat intake, i.e. 2 /3 monounsaturated and
polyunsaturated fats and 1 / 3 third saturated fats.
For a 50 g large egg yolk,
1.5 g (37.5%) = saturated fat
1.9 g (46%) = monounsaturated fats
0.68 g (16.5%) = polyunsaturated fats
7. All of the fat and cholesterol of an egg are found in the yolk,
including all of the egg's vitamins A, D and E; almost all of the
vitamins B3 and B12, choline and folic acid, 93% of the vitamin B6, 90%
of the thiamin, 76% of the biotin, 73% of the inositol, 50% of the
niacin, 42% of the riboflavin, 44% of the. protein and substantial
portions of the mineral content of the egg.
8. Eggs are one of the most versatile foods. They can be used to make a
souffle rise and a custard set. Also, they can be scrambled, fried,
pickled, hard-boiled, soft-boiled, poached, cooked in the shell, baked
and refrigerated. The proteins in egg white allow it to form foams and
aerated dishes, e.g. meringues, angel food cakes. Egg yolks are an
emulsifyer and are used to enrich cakes,
emulsify creamy sauces and thicken pie fillings. Eggs can be eaten raw,
as in Japanese sukiyaki dishes and the "Prairie Oyster" (one raw egg +
Worchestershire sauce + pepper sauce), a supposed hangiver cure.
However, raw eggs are not a suitable food for old people or pregnant
women because of the danger of Salmonella infection. In general, raw
eggs should be avoided as a food.
9. Egg yolks are one of the few foods that contain vitamin D, which
enhances the work that calcium performs.
10. Egg yolks can provide about 6% of our daily requirement of folate.
11. Lutein and zeaxanthin, found in egg yolks and plant sources such as
carrots and spinach, have been shown to protect against a serious
age-related eye disease, macular degeneration. Carotenoids may be
better absorbed through egg yolks than through vegetables due to the
fats present in egg yolks.
12. Egg shell color is caused by pigment deposition during egg
formation in
the oviduct and can vary according to species and breed, from the more
common white or brown to pink or speckled blue-green. Chicken breeds
with white ear lobes lay white eggs. Chickens
with red ear lobes lay brown eggs. There is no link between shell color
and nutritional value. In the United States, chicken eggs are usually
white. In the United Kingdom, chicken eggs are usually light-brown. In
other countries other colours of eggs may be preferred.
13. Cephalosporin resistance in humans may be caused by the use of the
drug n poultry production.
22.16 Genetically
modified organisms (GMOs) and chicken feed
Some raw materials that are incorporated into stock feed may have been
derived from genetically modified plants or microbes.
These raw materials are indistinguishable from equivalent products
which have come from plants or organisms that have not been genetically
modified, and they do not affect the composition of the end product in
any way.
Stock feed ingredients that may have been derived from genetically
modified plants or microbes that could currently be in use are:
1. Soybean meal and maize, imported from the USA
2. Cottonseed and cottonseed meal imported from the USA
3. Possibly some amino acids
4. Some feed enzymes
5. Vitamins
In the not too distant future, canola and canola meal can probably be
added to this list of GMO-derived stockfeed ingredients.
In considering the GMO foods issue as a whole, it is important to
recognise the difference between primary and secondary ingestion of GMO
foods by humans.
Primary human ingestion occurs via direct. consumption of GMO-foods,
for example GMO-derived soybeans or processed foods such as tofu which
are manufactured from GMO-derived soybeans. Secondary human ingestion
occurs via consumption of animal food products such as meat, eggs and
milk from animals fed rations containing GMO-derived stockfeed
ingredients.
To date, community discussion and debate regarding consumption and
labelling of GMO-foods has centred largely around primary human
ingestion. Currently the regulatory arrangements that apply to
genetically modified organisms in Australia do not extend to secondary
ingestion via food products from animals that may be fed stockfeed
rations which include one or more ingredients derived from genetically
modified organisms.
Animals ingest millions of genes every day from all the food that they
eat but these genes are not incorporated in their own genetic make up.
For an interpretation of the fate of genes consumed by animals please
see the attached "The metabolic fate of genes eaten by animals".
Based on information from the Australian Chicken Meat Federation Inc
22.17 Egg
grades
1. The US Department of Agriculture egg grading uses the interior
quality
of the egg and the appearance and condition of the egg shell. So eggs
of any quality grade may differ in weight or size.
Grade AA and Grade A eggs are used for frying and poaching where
appearance is important.
U.S. Grade AA eggs have thick and firm whites, high and round yolks,
almost free from defects, clean, unbroken shells.
U.S. Grade A eggs are the same as Grade AA eggs but the whites are
"reasonably" firm. This is the usual quality sold in shops.
U.S. Grade B eggs have thinner whites and wider or flatter yolks.
Shells must be unbroken, but may show stains. This quality is used to
make liquid, frozen, and dried egg products and other products
containing eggs.
2. The Haugh unit, HU, describes egg freshness, based on the thickness
of the albumen, (Raymond Haugh, 1937). Note
the temperature, weigh the egg and break the egg onto a flat plate. Use
a M-shaped tripod micrometer to measure the height of the albumen
midway between the yolk and the edge of the albumen. Compare the
height with the weight of the egg to give a whole number score between
20 and 100. Scores above 90 for excellent, 70 for
acceptable, and reject eggs below 60. In United States egg grades, AA
grade eggs score 72 HU or higher, A grade, 60 – 72 HU, and B grade,
lower than 60 HU.
The Haugh unit is a correlation between egg weight and the height of
the thick albumen. The cumbersome calculation is weighted for a
56.7g large size egg.
HU = 100 log(h-.01*5.6745(30w^.37-100) + 1.9)
h = observed height of the albumen in millimeters
w = weight of egg in grams
3. In other countries, eggs can also be graded as coming from free
range
hens, hens in barns and hens in battery cages.
22.18 Egg
sizes
USA
Extra Large (XL) > 64 g, 56 mL
Large (L) > 57 g, 46 mL
Medium (M) > 50 g, 43 mL
Small (S) > 43 g
Europe
Very Large 73 g and over
Large 63-73 g
Medium 53-63 g
Small 53 g and under
Australia
Jumbo 68 g
Extra-Large 60 g
Large 52 g
Medium 43 g
22.19 Boiled
eggs
If boiled eggs that are difficult to peel are usually too fresh. Fresh
eggs have a lower pH, and this does not allow the shell to separate
easily from the underlying albumen. If overcooked, a greenish ring may
appear around
egg yolk from the iron and sulfur compounds in
the egg or when there is excess iron in the water. Although the green
ring does not affect the taste of the egg, overcooking may harm the
quality of the food protein. If you chillthe
egg for a few minutes in cold water until the egg is completely cooled
the greenish ring does not form on the surface of the yolk.
22.20
Nutritional value
One large egg is 50 g.
Chicken egg, whole, hard-boiled Nutritional value per 100 g
Energy 150 kcal 650 kJ
Carbohydrates 1.12 g
Fat 10.6 g
Protein 12.6 g
Tryptophan 0.153 g
Threonine 0.604 g
Isoleucine 0.686 g
Leucine 1.075 g
Lysine 0.904 g
Methionine 0.392 g
Cystine 0.292 g
Phenylalanine 0.668 g
Tyrosine 0.513 g
Valine 0.767 g
Arginine 0.755 g
Histidine 0.298 g
Alanine 0.700 g
Aspartic acid 1.264 g
Glutamic acid 1.644 g
Glycine 0.423 g
Proline 0.501 g
Serine 0.936 g
Water 75 g
Vitamin A equiv. 140 μg 16%
Thiamine (Vit. B1) 0.066 mg 5%
Riboflavin (Vit. B2) 0.5 mg 33%
Pantothenic acid (B5) 1.4 mg 28%
Folate (Vit. B9) 44 μg 11%
Calcium 50 mg 5%
Iron 1.2 mg 10%
Magnesium 10 mg 3%
Phosphorus 172 mg 25%
Potassium 126 mg 3%
Zinc 1.0 mg 10%
Choline 225 mg
Cholesterol 424 mg
For edible portion only.
Shell: 12%
Source: USDA Nutrient database
22.21
Cholesterol and fat in eggs
People on a low-cholesterol diet may need to reduce egg
consumption.However,recent research showed no correlation between egg
consumption of 6 eggs per week and cardiovascular disease or strokes
except
in diabetic patients.
22.22
Contamination by bacteria
Pathogenic
bacteria, e.g. Salmonella enteritidis, can contaminate eggs as they
pass through the cloaca of the hen. So the egg shell shiould not be
contaminated with chicken faeces byut be washed with a sanitizing
solution as soon as possible. Although Salmonella infection is rarely
caused by eating eggs infections by Salmonella enteritidis and
Salmonella
typhimurium may occur if egg shells are broken by careless handling or
if
laid by unhealthy chickens.
22.23 Egg
allergy
Infants may have an egg food allergy usually against egg whites rather
than egg yolks, but they usually grow out of it. Adults
may experience a food intolerance to egg whites.
22.24 Food
labels
Foods containing eggs should have an allergen alert on the labels, e.g,
for the wine indusry in Australia:"PRODUCED WITH THE AID OF EGG AND
MILK PRODUCTS AND TRACES MAY REMAIN"