Fig. 84.—A battery of horizontal rectangular steam chests in actual use in a canning factory.
Fig. 85.—A battery of cylindrical process kettles in actual use in a canning factory.
A process closely akin to sterilization by heat is pasteurization. This means the heating of material at a temperature and for a time which will destroy the actively growing bacteria but not the spores. The methods for doing this vary but are essentially two in principle. 1. The material in small quantities in suitable containers (bottles) is placed in the apparatus; the temperature is raised to 60° to 65° and maintained for twenty to thirty minutes and then the whole is cooled (beer, wine, grape juice, bottled milk) ([Figs. 92], [93] and [94]).
Fig. 86.—A steam chamber used in government disinfection work. Size, 4 feet 4 inches × 5 feet 4 inches × 9 feet.
Fig. 87.—Circular steam chamber used in government disinfection work, 54 inches in diameter.
