DUCK EGGS AND THEIR NUTRITIVE VATUE

Abstract

From ancient times domestic ducks have served as a source of food and income for people in many parts of the world. Ducks are source of meat, eggs and down-feathers (for making bedding and warm jackets). Ducks are able to subsist and grow to maturity on relatively simple diets, based on locally available feedstuffs. Duck eggs are good dietary sources of high quality protein, energy and several vitamins and minerals. When properly included as part of a well-balanced daily diet, duck eggs can supply a substantial portion of the nutrients required by humans. Duck eggs fetch premium price than chicken eggs. They cost almost double that of chicken eggs. This is mainly due to its size and the preference of people for duck egg over chicken eggs. ln Asian cuisine, duck eggs are sometimes pickled or preserved to make a special product 'Thousand-year-old-eggs. Some people who are allergic to chicken eggs are able to tolerate duck eggs. Consumption of fertilized duck eggs (Balut) is considered a delicacy, highly nutritious and is familiar in the food customs of Chinese, Laotians, Cambodians and Thais. The safted duck egg, another duck egg specialty, salted by traditional Chinese method that is famous for many centuries.

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DUCK EGGS Al{D THEIR ]IUTRITIVE VATUE
Dr. A. Jalaludeenr and Dr. R. R. Churchil2
Centre forAdvanced Studies in Poultry Science
College of Veterinary and Animal Sciences Mannuthy, Thrissur, Kerala
lntroduction
Egger Breeds
High egg producing breeds of duck
such as the Khaki Campbell, Tsaiya or
lndian Runner are used worldwide for egg
production. These breeds are capable of
laying more than 230 eggs, and in some
cases, over 300 eggs per year. These
breeds are usually considerably smaller
in body size than meat-type ducks.
However, notwithstanding to their genetic
potential, these breeds as purebred or as
crosses with local ducks did not have
impressive performance under lndian
conditions. On the other hand, the native
ducks like one in Kerala (Kuttanad ducks)
due to their inherent abilities of egg and
meat production and hardiness received
nationwide popularity in lndia. Kuttanad
ducks now embellish the homesteads of
Assam, Lakshadweep and many other
parts of lndia.l
Advantages of Duckegg over chicken egg
Because the whites of duck eggs
have more protein than those of chicken
eggs, they will whip up higher when
beaten and create more lofts in cakes.
This means higher quantity of lighter
cakes. But since the yolks are so rich,
the cakes may also be richer with duck
1 Director 4 Assistant Professor
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I from ancient times domestic ducks have served as a source of food and I
I income for people in many parts of the world. Ducks are source of meat, eggs and I
I down-feathers (for making bedding and warm jackets). Ducks are able to subsist I
I and grow to maturity on relatively simple diets, based on locally available feedstuffs. I
I or.[ "gg. ,nJ ,"ut are good dietary sources of high quality protein, energy and I
! severatlriamins and minerals. When properly included as part of a well-bafanceO I
I daily diet, duck eggs can supply a substantial portion of tlrc nutrients required by I
I humans. Duck eggs fetch premium price than chicken eggs. They cost almost I
I Oounte that of cnii[en eggs. This is mainly due to its size inO tne preference of I
I peopte for duck "gg. or"iJnicken eggs. ln Asian cuisine, duck eggs are sometimes I
I bi.xr"o or pr"r.riEd to make a speciat product "Thousand-year'bto-rggsJ'Some I
I peopte who are allergic to chickeneggs are able totolerate duck eggs. Consumption I
I of fertilized duck eggs (Balut) is Considered a delicacy, highly nutritious and is I
! familiar in the food customs of Chinese, Laotians, Cambodians and Thais. The !
! safted duck egg, another duck egg specialty, salted by traditional Chinese method I
I ff'ut i. famouJior many centuries. I
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eggs. For these reasons professional
bakers prefer duck eggs because of their
rich yolks and because the baked goods
have better texture and hold their shape
better.
Duck eggs have a slightly higher fat
content and somewhat more cholesterol
than chicken eggs.lt may, in fact, be offset
by the possible health benefits of free-
range nature of duck eggs. Recent
studies have found that the eggs of
foraging free-range ducks are significantly
higher in omega-3 fatty acids than eggs
from birds raised in confinement.
ln addition to its nutritional quality,
though not scientifically proved it is
believed that it has certain inherent
medicinal properties for diseases like
piles. Metabolizable energy production is
less from duck eggs due to the
advantageous ratio between protein and
fat levels and the peculiarity of fatty acid
profile in duck eggs. lt may help in
preventing varicosity of blood vessels/
haemorrhoidal veins in the rectum in
persons having piles.
Appearance and flavor
Fresh free-range duck eggs are similar
to fresh free-range chicken eggs, in both
appearance and flavor. At seven months
old, ducks lay eggs that average in size
between large and extra large chicken
eggs.The yolks are deep orange; the
flavor is rich; and fresh eggs "stand up"
when cracked into a cooking pan.
However, one can notice more variation
in appearance and flavor of free-range
eggs, because all the ducks have not
received a consistent a diet while
scavenging. When the grazing is good or
we supplement the ducks'feed with extra
greens, the yolks of their eggs are deeper
orange; in c.oncentrate feeding they are
paler and yellow. The flavor of duck eggs
is a little different from that of chicken
eggs. Duck eggs have a faint flavor of
duck meat. Duck eggs are rich and
greasy, combined with the higher fat
content; they taste oily with stronger flavor
than that of chicken eggs.
Structure and contents
The shells of duck eggs are thicker
than those of chicken eggs and just a bit
rubbery, which makes them harder to
crack. Duck eggs also have more
albumen (the protein in the white) than
chicken eggs, which gives them more
structure when cooked. For this reason,
many people prefer duck eggs for baking:
the extra protein creates additional loft in
cakes. When fried, duck eggs set up firmer
and firm in texture than chicken eggs
(especially if they are very fresh). The
eggs weigh around 65 to 759 in case of
indigenous breeds like Kuttanad ducks of
Kerala; while, the Khaki Campbell eggs
weigh around 60 g only. With respect to
physical composition of duck eggs,
albumin constitutes 60 %; yolk 30 "h and
shell contribute 1 O'/" of the total weight.
Nutrient Composition of Duck Eggs
Compared to a chicken egg, the
average duck egg is approximately 30%
bigger. lts nutritional value is therefore a
bit higher too. Duck eggs contain all eight
of the amino acids essentialfor a healthy
body and loads of vitamins and minerals.
The duck eggs are slightly high in energy
content due to high fat percentage.
However, the saturated fat content of
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duck eggs that is having adverse health implications is comparable with other avian
species. Though the cholesterol content is higher than chicken eggs, the goodness
of organic nature of duck eggs offsets its ill effects on health.
The nutritive value of 100 g of different types of whole eggs of different species
is compared in the fo table.
o ln spite of their high cholesterol
content, duck eggs offer several
healthy benefits.
o Eggs of duck like that of chicken eggs
are one of the best sources of protein,
vitamins, and minerals. The protein
found in eggs is of a higher quality than
the protein found in meat and fish.
o The high protein white of a duck egg
averages only about 21 calories and
has no fat or cholesterol, making it an
excellent diet food.
. There are nutrients in eggs that are
beneficial in preventing macular
degeneration, which is the leading
cause of blindness in the elderly.
o Eggs are rich in choline, which is
helpful in fetal brain development.
Choline levels in women drop during
pregnancy, so it may be beneficialfor
women to consume eggs during
pregnancy.
Duck Egg Cholesterol
The average duck egg (70 g) has
about 619 mg of cholesterol, which is all
contained within the yolk.There has been
concern that excess cholesterol in the diet
can raise the level or cholesterol in the
blood, causing major health problems
including heart disease. The body needs
cholesterolfor its normal functions and the
body produces the required quantity.
Arteriosclerosis is not only due to the
consumption of cholesterol rich foods but
it depends mainly on the life style and food
habits like intake of saturated versus
unsaturated fatty acids and fibre intake
etc. As a component of duck eggs, high
COMPONENT CHICKENI oulAtL DUCK TURKEY GOOSE
Calories
Total Fat
Saturated Fat
Cholesterol
Carbohydrate
Protein
Vitamin A
Calcium
lron
Sodium
147
9.9 g
3.1 g
423 mg
0.8 g
12.6 g
487 tU
53 mg
1.8 mg
140 mg
158
11.1 g
3.6 g
844m9
0.4 g
13.1 g
543 tU
64 mg
3.6 mg
141 mg
185
13.8 g
3.7 g
884 mg
1.5 g
12.8 g
674IU
64 mg
3.8 mg
146 mg
171
11.9 g
3.6 g
933 mg
1.2 g
13.7 g
554 lU
99 mg
4.'1 mg
151 mg
185
13.3 g
3.6 g
852 mg
1.3 g
13.9 g
650 tu
60 mg
3.6 mg
138 mg
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level of cholesterol is not so harmful
because of rich quantities of choline found
in the phospholipid fraction, which
stabilize the fat content in the liver. As a
result, the absorption rate of cholesterol
is reduced and the absorbed cholesterol
is broken down to smaller f ragmehts. The
accumulation of cholesterol in blood
vessels is thus controlled and hence duck
eggs are comparatively harmless though
it may contain cholesterol level at the rate
of 884 mg/100 g.
Beneficial Fatty acids of Duck Eggs
Unsaturated fatty acids are found
abundantly in duck eggs. Natural food
materials of ducks like snail, crab and
oyster belonging to the family arachinidae
are considered as the major source of
arachidonic acid. Eicosa tetra enoic acid
(ETA) contains 20 carbon atoms and four
double bonds (Arachidonic acid), Eicosa
penta enoic acid (EPA) contains 20
carbon atoms and five double bonds
(Timnodonic acid) and Docosa hexa enoic
acid (DHA)contains 22carbon atoms and
six double bonds (Cervonic acid) are
present in duck eggs.
It is believed that the balanced ratio
between the different fatty acids present
in the duck eggs reduces the chance of
cardiac ailments. Ducks reared under the
foraging system mainly feed on aquatic
foods and those foods contain omega-3
tatty acids mentioned above. Ultimately
these are present in sufficiently large
amounts in duck eggs. lt is reported that
omega -3- fatty acids reduce the
cholesterol level in humans and thereby
reduce the incidence of heart diseases.
The presence of omega-3 fatty acids also
improves the efficiency of heart and
prevents the deposition of fats.
Egg Shell
Duck eggs are white in colour and are
larger in size.The shellthickness is more
and is approximately 0.53 mm. The shell
is very hard and is not broken easily while
handling. This reduces the chances of
breakage while transporting to distant
places. The pore size of the iluck eggs is
more but they are covered by protective
mucus covering which prevents the entry
of microorganisms.
!nternal quality of eggs
Duck eggs are superior to chicken
eggs in their internal quality too. The
albumen is comparatively thicker and egg
yolk is golden yellow in colour and
rounded. The vitelline membrane covering
egg yolk is also very thick.This membrane
can be easily removed from the boiled egg
becauOe of its thickness. Boiled duck
eggs have a pleasant smell.
Preservation of Duck eggs
The industrial preservation of egg is
done by making pasteurized liquid whole
eggs or egg whites or egg yolks. Similarly
converting them into powder or frozen
forms can increase the shelf life of the
eggs.i
Pasteurized shell eggs are heated for
a period of time to destroy any bacteria
that might be present, but the process
does not cook the eggs.They are morg
expensive than unpasteurized eggs, but
are a good alternative for use in raw or
partially cooked egg recipes. The eggs
can be used in egg dishes and for baked
items just like eggs that are not
pasteurized. The shells are stamped to
signify that the eggs have been
pasteurized.l
Liquid Whole Eggs are available as a
pasteurized white and yolk blend and are
packaged small containers. The
pasteurization process destroys any
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harmful bacteria that may be present in
the eggs at the time of processing.
Unopened containers will last as long as
3 months under proper refrigeration.
The pasteu5ized liquid egg white
packaged in pburable containers is also
available. Pasteurized egg yolks that are
already separated from the whites, in
pourable containers are also availble for
cooks who use more egg yolks than
whites.
The liquid egg substitutes are
packaged and sold as refrigerated or fro-
zen food items.The main purpose of egg
substitutes is to cut down or eliminate the
high cholesterol content of eggs. All of the
cholesterol is contained within the yolk,
so most substitutes are produced using
egg whites only, with other ingredients
added as a substitution for the yolks.
Some of these additional ingredients may
include skim milk, starch, and artificialfla-
vorings. Egg substitutes are often used
for scrambling or for preparing omelets.
Powdered whole eggs are another
alternative to fresh eggs and are
convenient to use and store.They can be
used for most types of egg dishes or
recipes requiring eggs. Powdered egg
whites are available containing no other
ingredients while some contain additives
to help build volume and stabilize the foam
when beating egg whites.They also have
a very long shelf life (over one year) and
do not require refrigeration. Powdered Egg
Yolks are blended with water to produce
liquid egg yolks, which makes them
convenient to use. The freeze-dried yolks
have a very long shelf life (over one year)
and do not require refrigeration.
Meringue powder is basically dried
egg whites with the addition of sugar and
gum. [vleringue is created when the
powder is added to water and is then
whipped. Like all other uncooked egg
products, meringue powder is pasteurized
so it is very useful when preparing dishes
requiring uncooked meringues. lt also has
a long shelf life (over one yeafl.
Powdered egg substitutes are
produced using egg whites only, with other
ingredients added as a substitution forthe
yolks. This results in a product that is low
in calories and has no cholesterol or fat.
Some of the ingredients used instead of
the yolks include starch, yeast extract,
gum, and artificial flavorings and color.
Egg substitutes are often used for
scrambling or for preparing omelets. They
are easily prepared by just adding water.
Duck Eggs Products
Duck eggs can be used in the
preparation of allthe egg products, which
can be made out of chicken eggs. ln some
cases the duck egg has a stronger flavor
than a chicken's egg. However,
complemented by onions, peppers,
mushrooms or cheeses, duck eggs are
the best for the preparations like
scrambled eggs or omelets. Cooks
accustomed to using duck eggs use them
much like chicken eggs, taking into
account their larger size. Some cooks
combine duck and chicken eggs to
achieve the consistency they want in
particular dishes. Some of the common
egg products arel
1. Boiled EggS
2. Stuffed eggs or Deviled eggs
3. Coddled Eggs
4. Roasted Eggs
5.Egg Omele!
6. Scrambled Eggs
7. Poached Eggs
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