a. Oil Processing. All military procurements of shell eggs for oversea
shipments and many domestic shipments are oil-treated to seal the pores. This
prevents contamination, absorption of offensive odors and flavors, and loss of moisture.
(1) Treatment. For oil treatment to be effective, the egg must be dipped or
sprayed as soon as possible after the egg is laid. Mineral oil that is tasteless, odorless,
and colorless must be used for the processing. Heavy mineral oils are more effective
than those with low viscosity, but they must be heated to a temperature higher than the
temperature of the egg to flow easily. Vegetable oils are not acceptable because of the
oxidation that occurs during storage.
(2) Method. Federal specifications state that, when eggs are oil-processed,
the oil must be applied by immersion or by spraying, a substantial amount of the shell
covered, and the area surrounding the air cell completely covered. The method of
application varies from hand-dipped and drained to the complicated wheel arrangement
and spraying used to treat large quantities. The spray method has advantages over
immersion since it:
Reduces the number of Check eggs.
(b) Eliminates eggs being broken in the processing oil.
Is more sanitary.
(d) Requires less labor, thus is less expensive.
b. Thermostabilization. Thermostabilization is also used to preserve shell
eggs. At a temperature of approximately 40oF (4oC), shell eggs are placed on a
movable metal belt and conveyed under a continuous stream of oil at a temperature of
132o to 134oF (56o to 57oC) for approximately 15 minutes. This permits a thin layer of
albumen to coagulate immediately adjacent to the shell membranes. The treated, warm
shell eggs, which then have an internal temperature of approximately 120oF (49oC), are
packed and placed in a cooler at 30o to 35oF (-2o to 2oC) until shipment.
Thermostabilization is helpful because it:
Seals the pores, supplementing the cuticle.
Helps prevent absorption of foreign odors.
Helps prevent dehydration.
Helps prevent loss of gaseous carbon dioxide.
Destroys the fertile germ cell.