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Little Known Uses for Eggs
For centuries the egg was known as a perfectly packaged, portion controlled,
highly nutritious food providing the most complete, and therefore the
highest quality proteins, all necessary vitamins except vitamin C, and
minerals. In the 1970s, however, it was identified that serum cholesterol
in humans was one of the many causes of cardiovascular disease. Eggs contain
dietary cholesterol, and although there has never been any scientific
evidence to link egg consumption with heart disease, that link was suggested
and accepted by many commentators, some doctors, and by a large percentage
of the population.
This perception, exacerbated by changing lifestyle factors and a greater
choice of food products, led to a decline in egg consumption. To counteract
this, the egg industry invested millions of dollars in research to investigate
the real relationship between cholesterol and eggs and heart disease.
Recent research has confirmed what had been known for years, that egg
is nature's perfect food and beneficial to consumers' health.
This intensive research program, prompted by falling consumption, led
to further research into the effects of feeding programs on egg composition.
Differentiated diets for laying hens can be utilized to enhance the levels
of certain beneficial compounds like vitamins. In addition, studies into
compounds which could be extracted from eggs for use in food sciences,
nutrition, dietetics, analytical chemistry, phytochemistry, pharmacology,
toxicology, biotechnology and clinical sciences also escalated.
The egg, therefore, has been re-born not only as a "Functional Food" i.e.
one which by virtue of the presence of physiologically active components
is efficacious in the prevention and/or treatment of disease and the promotion
of optimal health, but as a food containing a treasure chest of products
which can be utilized in many areas.
With adjustments to the diets of the laying hen, the profile of fatty
acids, fat-soluble vitamins and minerals such as iodine, fluorine, manganese
and B vitamins can be changed.
Using a flax-based diet (although others such as rapeseed, and fish oils
have been used), eggs can be enriched with omega-3 and omega-6 fatty
acids. Omega-3 fatty acids have been shown to reduce plasmatriglyceride
levels, and have been associated with a reduced risk of heart attacks
and recurrence of myocardial infarction. They also prevent heart disease
by decreasing the clotting activity of platelets in the blood. Research
has also shown that omega-3 fatty acids in the human diet are essential
to brain function and visual acuity and are critical nutrients in neonatal
development.
Vitamin E in eggs can also be enriched. In Japan, the iodine
level can be enhanced, and in Korea eggs are fortified with ginseng.
There is some indication that conjugated linoleic acids (CLA) have
anitcarcinogenic properties (3), and research has been done enriching
eggs with CLAs.
The use of egg shells as a dietary source of calcium for humans
has been investigated. A powdered, purified product has been tested in
fortification of breads and confectioneries, fruit drinks, crackers, condiments.
Egg shell calcium has been tested as an oral phosphate binder for
use in low phosphate diets for e.g. patients suffering from renal failure.
The protein from egg membranes adheres to and grows human skin
fibroblasts and increases their production of type III collagen which
is rich in the skin of infants, presumably softening the skin. This egg
membrane protein is being used as an ingredient in many cosmetics.
Lecithin from egg yolks is a rich source of phosphatidylcholine
(PC) which is a major phospholipid component of the cellular membrane.
PC also serves as a precursor of acetylcholine, a neurotransmitter. Egg
PC in conjunction with vitamin B may slow the progress of, or even prevent
Alzheimer's disease. (5)
Choline is a vitamin which research indicates plays an essential
role in the development of brain function and memory. Lactating mothers
are recommended to increase their dietary choline intake to reduce the
severity of memory defects later in life.
Lutein and zeaxanthin are found in egg yolks - their levels depending
on the diet of the layers. Research has suggested that these two carotenoids
reduce the risk of cataracts and age-related muscular degeneration - the
leading cause of vision loss in the U.S.A. Studies also show that the
bodies' anility to utilize these compounds from egg yolks is better than
from green leafy vegetables.
Egg Yolk Phospholipids (EYPLs) have been defined as a natural
cell membrane-refreshing nutrient. They have recently been registered
in the European Community as a Novel Food. (15)
Sialic acid derivatives from egg yolk are known to be involved
in brain (neuron) functions and are also important in protecting infants
from various diseases. These and sialyloligosaccharides attract attention
from pharmacalogical and food chemical industries because of their potential
biological functions.
Sialyloligosaccharides have been shown to be very high in mothers'
milk at the time of parturition, suggesting that they play a significant
role in the defence mechanisms against diseases such as pneumonia, diarrhoea,
gastritis and ulcers. Sialyloligosaccharides can be extracted from egg
yolk. One commercially available product containing sialyloligosaccharides
is Sunsial. (5)
Antigen specific immunoglobulins (IgY) By challenging the
hen with a specific antigen (e.g. Escherichia coli), the hen will utilize
her natural system to create antibodies which will not only protect her
but will be passed on to the eggs she lays. Humans or other monogastric
animals that eat these antibody enhanced eggs will then have an increase
in this particular antibody and an increased ability to counteract the
effects of the original antigen: a very effective method of administering
vaccine to a population. This is known as passive immunity and it can
provide immediate but short lived protection against specific diseases.
This is in contrast to active immunity which primes the body to make its
own antibodies and confers life-long immunity.
Sim, et al (13) states: ‘This new IgY technology opens new potential
market applications in medicine, public health, veterinary medicine and
food safety. A broader use of IgY technology could be applied as a biological
or diagnostic tool, nutraceutical or functional food development, oral-supplementation
for prophylaxis, and as pathogen-specific antimicrobial agents for infectious
disease control.......This concept could serve as an alternative agent
to replace the use of antibiotics, since today, more and more antibiotics
are less effective in the treatment of infections, due to the emergence
of drug-resistant bacteria.'
Successful results have been obtained by feeding piglets (and rabbits)
egg yolk powder containing anti-E. coli antibodies. This serves
as a protection against the pathogenic effects of E. coli which
causes usually fatal diarrhoea in early weaned piglets.
IgYs from eggs have been used in foods e.g. passive immunization by oral
administration of IgY has been effective in preventing dental caries and
rotaviral diarrhoea. Some food products e.g. candies, chocolates and gums
containing anti-Streptococcus mutans (a cause of tooth decay)
have been used in Japan for oral care.
Egg antibodies have also been successfully tested to provide immunity
against snake venom in humans, mastitis in cows, Pseudomonas aeruginosa
in cystic fibrosis patients and Edwardsia tarda infection of
Japanese eel.
Tests indicate that IgYs can be used to counteract some Salmonella
spp.
Egg antibodies have also been extracted and used in diagnostics and affinity
chromatography applications e.g. antibodies directed against ochratoxin
- a mycotoxin widespread in foods and feeds - can be used to detect the
presence of ochratoxins. (16)
Work is underway to genetically alter chickens so that they produce eggs
containing a large quantity of human serum albumin (HSA),
a protein used in saline drips in hospitals. Currently the protein is
taken from human blood plasma, but this is very costly. It is estimated
that a flock of 100,00 layers could produce 5% of the world's demand for
HSA.
Using transgenic chicken, research is also being done in collaboration
with a number of companies and research establishments to produce egg
antibodies which will fight hepatitis, melanoma and other cancers.
Proteins from egg albumen are being researched in the preparation of
biological polymer films for use in food packaging. (6)
Cystatin found and isolated in egg white is an inhibitor of sulphydryl
proteinases which are involved in muscle activity. Research indicates
that cystatin is effective as an antimicrobial, and antiviral agent, and
in the prevention of cerebral haemorrhage and cancer cell metastasis.
(4)
Avidin is a protein of egg white. When bound with the vitamin biotin
it forms an avidin-biotin system which has been extensively used in biotechnological
applications, particularly in medical diagnostics. By the1990s, egg white
Avidin had been all but replaced by the bacterial protein Streptavidin
(extracted from Streptomyces), but recently a modified egg white
Avidin has been created (and manufactured as NeutraLite AvidinTM) which provides a greatly
improved product for applied and commercial usage. (1, 10)
Lysozyme is a naturally occurring enzyme which was discovered and characterized
in the 1920s as having antibacterial activity against gram-positive bacteria.
It attacks the cell wall of gram-positive
bacteria leading to cell lysis and death. It is present in many secretions
and tissues such as human tears, saliva and mother's milk, as well as
viruses, bacteria, phage, plants, birds, eggs, insects, birds, reptiles
and other mammalian fluids. The most readily available source is the white
of hen's eggs. Lysozyme is effective against a number of bacteria responsible
for infections of the human body and for the spoilage of various foods.
One of the most important commercial uses of Lysozyme is in the ripening
of certain European-type cheeses. Lysozyme inhibits the growth of Clostridium
tyrobutyricum - a bacterium which can be present as a contaminant
in milk. The presence of Clostridium tyrobutyricum in the developing
cheese has the effect of producing butyric acid which causes an "off-flavour",
and excess hydrogen and carbon dioxide which causes internal pressures
leading to slits and cracks. Lysozyme has been used for over a decade
in many European countries and has received GRAS (Generally Recognized
As Safe) status from the Food and Drug Administration of the USA.
A more recent use of lysozyme is in wine preparation as a substitute for
sulfites. The lysozyme inhibits lactic acid bacteria and development of
malo-lactic fermentation can be controlled. This leads to better organoleptic
(color and taste) properties and a better tolerance by those consumers
who are sensitive to sulfites.
Lysozyme can also form synergies with other antimicrobial compounds such
as nisin and the resultant compound will attack gram-negative
food spoilage bacteria.
A standardized and refined preparation of Lysozyme is manufactured in
Canada under the trade name Inovapure. This is marketed for use in selected
processed foods to extend the shelf life by inhibiting or destroying spore
forming and non spore-forming spoilage organisms.
(2, 10)
Ovotransferrin or Conalbumin is another protein of egg white
which has been used as an antimicrobial agent in food applications. More
recently research has been in the treatment of HIV and in preventing periodontal
disease. Lagarde reports that in Japan, immobilized ovotransferin has
been used to remove iron from drinking water, as well as water for brewing,
and a company in the Netherlands has filed a patent for a nutraceutical
drink containing ovotransferin. (10)
Ovalbumin is the predominant protein in egg white and is utilized
in cell culture systems and in the diagnostic industry where enzymes and
hormones require stability to maintain their functional integrity. It
acts as a stabilizer, binding protein, transport protein and growth media
supplement.
For more than forty years, hatching eggs have been used as a culture
medium for influenza virus to produce vaccines - particularly influenza
vaccines. A small quantity of the influenza virus is injected into the
developing embryo. For three days the virus multiplies in the protein-rich
medium. The egg is then broken, the fluid extracted and the virus purified
and split. This dead virus is used as vaccine.
Listed are some of the non-food products which can be obtained from eggs.
Many of these are still being researched. Many are already in production.
This is a growth area which will result in the discovery and production
of increasing numbers of non-food products from eggs. These will provide
new and improved products in many sectors, particularly in pharmaceuticals.
Some of these products can be extracted from eggs without altering its
fundamental structure, but many utilize the whole egg. In the coming years
we can expect to see an increased demand for eggs to provide for non-food
products.
- Sim, J.S. and S. Nakai, editors - Egg Uses and Processing Technologies
- New Developments, CAB International, UK 1994, pp 158-176
- Sim, J.S. and S. Nakai, editors - Egg Uses and Processing Technologies
- New Developments, CAB International, UK 1994, pp 177-191
- Sim, J.S., S. Nakai, and W. Guenter, editors - Egg Nutrition and
Biotechnology, CABI Publishing, UK 2000 pp 181-195
- Sim, J.S., S. Nakai, and W. Guenter, editors - Egg Nutrition and
Biotechnology, CABI Publishing, UK 2000 pp 205-217
- Sim, J.S., S. Nakai, and W. Guenter, editors - Egg Nutrition and
Biotechnology, CABI Publishing, UK 2000 pp 219-232
- Sim, J.S., S. Nakai, and W. Guenter, editors - Egg Nutrition and
Biotechnology, CABI Publishing, UK 2000 pp 253-267
- Sim, J.S., S. Nakai, and W. Guenter, editors - Egg Nutrition and
Biotechnology, CABI Publishing, UK 2000 pp 289-299
- Sim, J.S., S. Nakai, and W. Guenter, editors - Egg Nutrition and
Biotechnology, CABI Publishing, UK 2000 pp 351-370
- Sim, J.S., S. Nakai, and W. Guenter, editors - Egg Nutrition and
Biotechnology, CABI Publishing, UK 2000 pp 371-374
- Lagarde, G. Development of added value applications for lysozyme
and other proteins extracted from eggs, Canadian Inovatech, Abbotsford,
C.C.
- Canadian Inovatech Inc. http://www.inovatech.ca/news/news4.htm
- Sim J.S., E.N. Lee, H.H. Sunwoo and K. Manninen - IgY technology:
egg antibodies for food production. World Poultry Congress 2000
- Naidu, A.S., editor, CRC Pr, 2000 - Natural Food Antimicrobial
Systems pp 227-252
- Cunnane, S.C. and L. U. Thompson, editors - Flaxseed in Human
Nutrition, AOCS Press, Champaign, 1995 pp 315-333
- De Meester, F., J. Lignian, L. Philippin et al - Egg yolk phospholipids
as a balanced dietary source of vitamin F. World Poultry Congress 2000
- Sim, J.S. and S. Nakai, editors - Egg Uses and Processing Technologies
- New Developments, CAB International, UK 1994, pp 207-212
- Sim, J.S. and S. Nakai, editors - Egg Uses and Processing Technologies
- New Developments, CAB International, UK 1994, pp 349-361
- Sim, J.S. and S. Nakai, editors - Egg Uses and Processing Technologies
- New Developments, CAB International, UK 1994, pp 362-373
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