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Bactericidal Action of Radiant Energy from Special Types of Lamps on Organisms Found on Dairy Utensils and Equipment

New Jersey Agricultural Experiment Station, New Brunswick, N. J.

ABSTRACT

The bactericidal action of two lamps, both of which emit radiations mainly in a narrow band centered around the wave length of 2,537 Ångstrom units, has been studied. No attempt was made to compare the action of the two lamps.

The data show that the radiant energy from the lamps resulted in a logarithmic order of death of microörganisms only after the early part of the exposure period had passed.

The bactericidal rate decreased as the distance of the lamp from the organisms increased, but the relationship did not follow the law which says that the concentration of radiant energy per unit area varies inversely as the square of the distance.

Increasing the angle of incidence of radiant energy to the exposed surface did not greatly affect the bactericidal rate until the angle became greater than 50°.

Low temperatures had no appreciable effect on the bactericidal rate, provided that the lamp remained at room temperature. When the lamp was operated at low temperatures, however, a decided decrease in bactericidal rate occurred.

Films of water, 5 and 10 millimeters deep, over growing organisms did not decrease the bactericidal rate, but opaque substances such as milk and agar decidedly decreased the destructive power of the radiations. It is apparent that organisms must lie on or near the surface if they are to be destroyed by radiations from the lamps.

Increasing the concentration of organisms per unit area decreased the bactericidal rate. The formation of clumps of organisms probably would have a similar effect.

Unclean, rough, cracked, and shaded surfaces were not readily sterilized.

Organisms growing on the surfaces of such equipment as milk bottles, tinned dippers, cans, and pasteurizing vats were completely destroyed or greatly reduced in numbers in comparatively short times by the radiant energy of the lamps used in these studies.

^* Now with the armed forces of the Nation.