GB1020447A - Obtaining a commercially useful product from egg-shells - Google Patents

Abstract

Calcium carbonate is obtained from freshly broken egg-shells by washing the shells to remove egg-white and yolk therefrom, germicidally treating the shells, then washing to remove any germicidal odour therefrom optionally drying, then immersing the shells in a hot alkaline solution to effect solution of the membrane, removing the solution, washing the shells (the washing including treatment with acid) to remove all traces of alkali therefrom, and finally drying the shells quickly to prevent bacteriological and enzymatic changes therein. The removal of the egg white and yolk may be achieved by centrifugal washing and drying coupled with an intermediate treatment with a suitable germicide such as sodium hypochlorite or hydrogen peroxide. The shell is rapidly dried at preferably 180 DEG F. to 210 DEG F., preferably for 15 to 30 minutes. The dry sterile egg-shell is immersed in a hot solution of a weak alkali and/or alkaline salts, e.g. NaOH, to effect complete removal of any remaining trace of egg-white and solution of the egg-shell membrane. Any entrained alkali is removed by water washing and the use of a low concentration of a mild acid such as acetic acid, and a final removal of occluded odours may be effected by using a mild oxidizing agent such as sodium hypochlorite or hydrogen peroxide. The treated egg-shells may be stored, or finely ground. Grinding may be either by wet grinding in the presence of a low concentration of a mildly acetic substance, e.g. acetic acid, or of a low concentration of an oxidizing agent, e.g. sodium hypochlorite, or by dry grinding to achieve particle sizes of mostly below 20 microns. A combination of both types of grinding may be used. The powder product may be used to replace creta-preparata as a nutritional supplement of calcium in flour as used for bread-making and other food purposes. In admixture with various powdered forms of calcium carbonate in suitable proportions, the powder confers "free-running" properties not possessed by other powder forms of calcium carbonate by themselves. Such free-running mixtures may be used as a nutritional supplement in flour, and also in the preparation of toothpastes and powders, and cosmetics. The powder may also be used as lubricants and as fillers. Reference has been directed by the Comptroller to Specification 790,073.ALSO:Calcium carbonate from waste egg-shells (see Division C1) may be mixed with various powdered forms of calcium carbonate to confer "free-running" properties not possessed by the powder forms of calcium carbonate by themselves and the mixture may be used in the preparation of toothpastes powders, and cosmetics. Reference has been directed by the Comptroller to Specification 790,073.