Copy of May 2011 - Lazyfish Technology

May 2011 Kangaroo Valley Voice www.kangaroovalley.nsw.au Page 31
Oölogy—the study of eggs
I never thought that teaching ‘Egg
Quality and Bird Handling’ to first year
Veterinary Science university students
would be so much of a learning
experience for me as well.
When cracking eggs onto the glass plate, I
posed three questions: would you rather a
white or brown shelled egg; would you prefer
yellow or orange yolk; and is there any
difference
I usually got standard answers of “brown”,
“orange” and “yes, the others are bad”.
My short answer to them - not true, they are all
the same when you eat them and here is why.
First, the shell. There are many different
colours of egg shells around the world, yet in
different countries we have created preferences
for a particular type.
In fact, the New York Times reported about
egg colour preferences during the First World
War! In Australia and the United Kingdom, we
have preferences for brown shelled eggs.
In the United States of America, they prefer
white shells. It really doesn’t matter which
colour it is as it has absolutely no bearing on the
quality, taste or nutritional value of the egg.
All eggs are white by default being the colour of
the calcium carbonate of which they are made.
As the egg travels through the reproductive
system, the lining of the oviduct adds pigments
to the eggs, which vary in colour depending on
the breed of chicken.
This is a trait controlled by the female bird,
meaning that the breed of the rooster has no
effect on egg colour. Some examples of egg
colours and the breeds which produce them are:
dark brown speckled egg (Speckledy or Maran),
a pure white (White Star or White Leghorn), a
pinkish-brown (Rhode Island Red), a creamy
white (Ancona or Vorwerk), a mid-brown (ISA
Brown, Black Rock or Barnevelder), and a bluish
-green (Araucana or Cream Legbar).
Secondly, the yolk. Same as for shell colour, the
colour of the yolk does little to give us an
indication of quality, taste or nutritional value.
Yolk colour is directly related to the amount of
yellow/orange pigments (called Xanthophylls) in
the diet.
These pigments are found in common feedstuffs
such as corn and marigolds. Adding more of
these types of feed in the diet of the layer will
increase the orange colour of the yolk.
So if we can’t use either of these to assess
quality, then what are we really looking for in an
egg It is not easy to outwardly assess the taste
“Fresh from the Paddock”
or quality of an egg.
Obviously we don’t
want those with thin
shells that will break
easily in transitwhich
will occur as
the bird increases in
age and has less calcium in her bones to utilise
for the shell.
The main indicator of quality is the ability of
the albumin (the egg white) to hold together
when cracked. The older the egg, the more the
proteins that
hold the egg
white
together will
have lost
their ability
to do just
this.
The result is
that when we
crack the
egg, the
white tends
be thin and
run. In order
to maintain the best quality of the eggs, keep
them in the fridge.
This will slow the protein degrading process
down and can keep them fresh for more than
six weeks.
Remember, we can’t always judge a chook by
its cover!
Kiri Broad
Moss Vale Road (near Dan the pharmacist)