of shell eggs
In order to preserve eggs they has to be
produced of good quality. Therefore any method of preservation starts from the
point of production itself. The following practices are recommended as routine
for the production of quality eggs on the farm.
Collection of eggs at least 3 times daily.
Using a clean receptacle with ventilated
sides and bottom, preferably filler flats.
Careful handling of eggs during collection
and while keeping in filler flats etc.
Cooling the eggs quickly to 50oF
or less at 75-85% relative humidity.
Marketing the eggs at least twice weekly.
There are several methods of egg preservation of which
some are explained below
Eggs are kept in an earthen pot with clean
dry packing material and the pot is buried in wet sand.
Immersion in liquids
This is one of old method and it primarily
prevents the evaporation of moisture from the egg. Depending on the liquid used
it may also inhibit bacterial decomposition by chemicals action or by physical
means such as occlusion of air passages/pores.
Lime water is prepared by mixing about 0.5kg
of quick lime (calcium oxide) in about 1 litre of boiling water. After settling
the mixture clean supernatant liquid is poured out into a jar to which sodium
chloride of 112 grams/litre may also be added to increase the specific gravity
of water and will minimize the chance of breakage of eggs. In this solution,
2.5 liters of cold water is added and filtered through muslin cloth. Keep the
eggs in a glass jar or earthen pot and pour the lime solution over the eggs to
immerse. Keep the eggs in solution for 24 hours. After 24 hours taken out the
eggs, dry and arrange in filler flats. Eggs can be persevered for 2-3 months in
a good edible condition at normal ambient temperature.
A 10% solution of sodium silicate is prepared
in hot water and allowed to cool. The cooled solution is poured into a jar
containing the eggs till they are immersed completely. The jar is covered and
kept in a cool place where the temperature should not exceed above 700F.
Eggs preserved by this method are usually punctured before boiling to avoid the
breakage of shell while boiling and it also helps for easy peeling of
Shell – Sealing treatments
1. Coating with oil Or Wax
The rate of CO2 escape is
considerably reduced. This is a fairly successful method of rendering the egg
less permeable. It can be done by simply dipping the egg in a bowl of
tasteless, odorless, colourless edible oil, having a specific gravity of about
0.855 to 0.870 at 150C; viscosity should not be more than 70 to 90
and having a high boiling point so that at lower temperature it remains in the
liquid form. If oil treatment is to be effective it should be done preferably
at the point of production the day after the egg is laid. Oiling is not a
substitute for refrigeration. These eggs must be held at a low temperature.
Cotton seed, linseed and groundnut oil are good sealing agents but mineral oils
are preferable since they are less subject to oxidative changes during storage.
Oil immersed eggs and these eggs are not likely to absorb foreign odours. The
oil treatment can also be done by spraying using a hand or electric sprayer.
The commercial egg treatment with oils are
Heavy paraffin oil (Central Food Technology Research Institute
Myvacet 9-40 (developed at CFTRI – Mysore)
Carboxyl methyl cellulose
Technical white oil.
This method is good for fertile eggs since it
kills the embryos and therefore is also known as ‘defertilization’ method. It
essentially consists of immersing shell eggs in hot water at 130oF
for 30 minutes which tend to coagulate the albumin and then the egg is cooled
under tap water. Treated eggs remain edible for 3 to 4 weeks even during summer
months. Though this method has many advantages such as stabilizing of the
albumin and sterilization of the egg shell, the egg looses the property of
foaming to a remarkable extent. Moreover, embryonic development in fertile eggs
is completely arrested.
Over wrapping of eggs is commercially done by
using polyethylene, cellophane, polyvinylidene and other transparent, thin but
sufficiently strong, films are used. These films should be impervious to gases
and moisture. Over wrapping of eggs in different atmosphere like carbon
dioxide, vacuum etc. have been tried.
This is the best and most efficient method
for commercial storage. Eggs for cold storage must be clean, unbroken, and free
from fungus and other infections. A temperature of 0oC or 30-32oF
and relative humidity of 85-90% is recommended for cold storage of eggs to
preserve them for 5 to 8 months. For short period of preservation of 2 to 3
months, eggs can be stored at 10-12oC or 50-55oF with a
relative humidity of 60-70%. Intact eggs are held at the lowest possible
temperature that will avoid freezing and bursting of the shells. It has been
observed that intact eggs do not freeze at temperature between -1.5oC
and -2oC and the relative humidity must not go beyond 90%.
Dried and frozen eggs
This is another method of preserving egg
contents or edible eggs. Egg products of commercial utility are prepared by
drying or freezing eggs. Albumin flakes, yolk and egg white powder can be
produced by drying process. Frozen yolk or frozen egg white can be produced by
freezing. For egg white powder production the best known method is spray drying
and for albumin flakes, pan or cabinet drying method is mostly adopted.
It’s a new method of preserving eggs at room temperature.
Also called as the “plastification” in situ of the shell, using a
liquid synthetic polyvinyl chloride acetate plastic. The plastified eggs can be
stored at 220 C for periods longer than 135 days.