Numerous patents relate to the preservation of egg products. However, these processes either do not truly sterilize the egg products, or the sterilization obtained causes a too significant modification of the liquids, glycides of carbohydrates, and proteins of the eggs.
French Pat. No. 679,991 comprises a process of evaporation in a vacuum, in which sugar is added to the liquid egg product before pasteurization; the effects of the heat are accelerated by evaporation in a vacuum, even at a very low temperature. French Pat. No. 1,271,154 comprises the sterilization of egg products by means other than an elevation of temperature, for example, by a treatment with ultraviolet rays. It is well known that the degradation or deterioration of proteins by heat increases very quickly when heated or even warmed at a reduced pressure. It is also known that a simple pasteurization of egg products for several minutes at atmospheric pressure leads to a significant deterioration of the components of the egg, when the temperature of the treatment attains about 54.degree. C. for egg whites, 60.degree. C. for whole eggs, and 65.degree. C. for egg yolks, being given the conditions of pasteurization.
Swarthout et al, U.S. Pat. No. 2,093,786, treats eggs to a pasteurization process for the conventional purpose of killing bacteria, without recognition that for maximum shelf life, particularly at higher temperatures, it is essential to minimize the oxygen content. White, British Pat. No. 346,031, teaches the placement of an egg product in a container from which the air has been evacuated (page 3, lines 7-19), and teaches the substitution of carbon dioxide (page 3, lines 58-63), which does not, however, remove the gas that is soluble in the treated product (page 3, lines 61-63), and thereafter there is no further heating to remove oxygen. Michaud, French Pat. No. 679,991, discloses (page 2, lines 29-97) air exchange, without any recognition of achieving the critical degree of less than 3 ppm. Van Olphen, U.S. Pat. No. 3,409,446, is directed to pasteurization and evaporation of egg products. A period of 20 minutes is suggested for the pasteurization (column 2, line 18), only for the purpose of killing bacteria and not as a deoxygenation step. Heuser, U.S. Pat. Nos. 1,900,444 and 1,989,359, attempts the removal of air from an egg mixture by subjecting the egg mixture to centrifugal force, which apparently removes some of the oxygen. Fousek, U.S. Pat. No. 1,756,189, discloses the heating of a sugared egg mixture. The applicant's French Pat. No. 2,276,787, also discloses a sugar-salted egg mixture combined, however, with a micro-organism destructing agent.