128
Indigenous Methods of Egg Preservation
refrigerator or other cold storage either impossible
or uneconomic, the real problem in India demand-
ing urgent attention is the evolving of a cheap
and efficient method for the lengthening of the
useful life of fresh eggs during the hot weather.
The village producers usually put the eggs laid
by their birds into baskets and keep them in the
coolest part of the house till the egg collector
arrives or they are sent to the town markets.
These conditions are not conducive to the conserv-
ing of egg quality, especially during the hot
weather; consequently the average market egg
at this period is of poor quality. Occasionally a
few indigenous materials are used as preservatives
in different parts of the country. The materials
generally employed are such things as green neem
and shisham leaves, rice husks or bran, dry salt,
dry charcoal powder and moist sand [Marketing
Report, 1938]. Little is known about the effi-
ciency of these preservatives in conserving egg
quality.
Recently, however, the writer has carried out a
series of tests as to the efficiency of some of the
above substances for the preservation of eggs
during the hot and moist months of July and
August. The following materials were studied :—
1. Green neem (Melia azadirachta) leaves
2. Green shisham (Dalbergia sissoo) leaves
3. Rice husk
4. Dry salt
5. Dry wood charcoal powder
6. Raw linseed oil
Though preservation with linseed oil may not
be strictly classed among indigenous methods,
yet as it is one which was largely used before the
development of modern cold storage processes and,
as the material is abundant and inexpensive, its
efficiency was also investigated.
METHOD
Day-old eggs produced at the Institute's poultry
farm were employed for the experiments detailed
below. Eggs for preservation were placed in
unglazed earthern pots and completely surrounded
with the material under study. In the case of
linseed oil, the eggs were coated with the raw oil
by means of a rag and, after draining off the excess
oil, were stored in an earthen pot. Control eggs
for each of the tests were put into similar vessels
without any preservative. The vessels were
covered and kept in the laboratory under ordinary
room conditions. The experiments were not all
conducted simultaneously but were spread over
the months of July and August, 1940.
Except in the experiment with linseed oil, 30
eggs were used for each test. Of these, six were
broken out on the starting day and the initia
interior quality was determined. The remaining
eggs were divided into two equal groups, one kept
as control and the other preserved in the selected
material. At the end of five days, six eggs each
from the control and preserved groups were
removed and opened, and their interior quality
was measured. Again at the end of ten days the
balance of six eggs in each of the two groups were
removed and measurements made for quality.
In the linseed oil test 66 eggs were used, six eggs
being used for the determination of initial quality.
The experiment was conducted over a period of
five weeks, six eggs being examined for their
quality at weekly intervals from the control and
preserved lots.
The interior quality of eggs was judged by mea-
suring the yolk index. This term is applied to
the height : diameter ratio of the yolk. In a
fresh egg of good quality, since the yolk stands up
well-rounded, the height of the yolk is at about
its maximum and the diameter about its minimum.
The yolk index of a fresh egg is generally about
0.4. With deterioration in quality, the vitelline
membrane weakens and the yolk begins to flatten
out, resulting in a decrease in height and an
increase in diameter. Hence, the ratio of these
measurements, the yolk index, decreases progres-
sively with the increasing loss of quality, the index
serving as a measure of interior quality.
In the original method of Sharp and Powell
[1930], the yolk is separated from the albumen
and the index of the separated yolk is determined.
In this procedure the frail vitelline membrane is
subjected to stresses and strains during the separa-
tion of the yolk from the albumen which affect its
elasticity and consequently also the accuracy of the
yolk index. Moreover, when the yolk index is 0'2
or below, the handling of the yolk during its separa-
tion from the albumen, without breaking it, is
extremely difficult. Hence, the measurement of
yolk index on poor quality eggs by this method is
often impossible owing to the rupture of the
vitelline membrane. To avoid these handicaps
the modification suggested by Parsons and Mink
[1937] was adopted. In this method the yolk is
not separated from the albumen and the measure-
ments for the determination of yolk index are
made on the unseparated yolk of the broken egg.
The procedure adopted is as follows: The egg is
broken out on to a levelled glass plate and allowed
to stand for two minutes to attain equilibrium.
The height of the yolk is measured at the apex of
the top curvature by means of a spherometer
(Plate X, fig. 1) and the diameter by sliding
callipers (Plate X, fig. 2). By this modification
errors due to handling of the yolk are avoided and
at the same time the range in quality over which