Determination of pyoverdine, the fluorescent pigment of pseudomonads, in frozen whole egg.

The Federal Food, Drug, and Cosmetic Act of 1938 defines as adulterated any food that is composed in whole or in part of a filthy or decomposed substance. Objective laboratory and field tests for detection of decomposed products are always advisable to supplement organoleptic examinations. In any product where organoleptic tests fail because decomposition is masked by any means, objective tests are an essential part of the enforcement program. Spoilage of shell eggs by pseudomonads usually cannot be detected by white-light candling devices except when the eggs are in the latter stages of decomposition. Most of these organisms, however, produce in the albumen a pigment that is fluorescent in black light. The term "pyoverdine" is recalled from the work of Turfreijer (1941) as the first definitive name for this pigment. A candling device employing black light was developed in the California egg industry and was first described by Lorenz (1950) as an effective tool in the detection of pyoverdine in eggs spoiled by pseudomonads. Black-light candlers were shown by Elliott (1954) to detect both incipient and obvious spoilage by pseudomonads. An automatic candler for detection of fluorescent eggs has been developed by Norris (1955). This candler was shown by Mercuri et al. (1957) to be effective in keeping eggs with a high bacterial count out of liquid egg packs. Trussell (1955) found that fluorescent eggs usually contained other organisms as well as the pseudomonads causing fluorescence. However, Florian and Trussell (1957) reported that pseudomonads predominated among isolates from infected eggs from four sources. The normal egg yolk contains products that are fluorescent under black light. These materials do not interfere with the shell-egg candling technique; but when they are mixed intimately with the albumen, as in the case of whole egg pulp, they mask the presence of pyoverdine completely. A means of detecting fluorescent eggs in frozen whole egg pulp therefore would be of value. Canadian workers have developed a "fluorescence value" applied to extracts of dried egg (Pearce and Thistle, 1942) and of liquid and frozen egg (Reid, 1946). Whereas fluorescence value measures general quality, it is not sufficiently specific to be used for detection of pyoverdine. In fact, Brooks (1954) and Brooks and Hale (1954) found the fluorescence value of musty eggs infected with pseudomonads to be the same as that of normal eggs. They found, however, that the addition of a measured amount of sodium hydrosulfite to the egg extract resulted in a roughly measurable increase of fluorescence in the case of the musty eggs. This increase did not occur with the normal eggs. Chemical and physical characteristics of pyoverdine which might be of use in separating it from and determining it in frozen whole egg have been described in a preceding report (Elliott, 1958). The present paper is concerned with description of a method of analysis based on this information, and with limited experience in its use.