A considerable amount of cheddar cheese of poor quality is manufactured in the Western states, especiaIly during the m~mmer months, since proper care is not given to the milk by the pro- ducers; consequently, the supply is not Hnlform throughout the year, and usually varies during a season. Cheese is the only dairy product which can be manufactured in California from mi|lr produced from herds infected with tuberculosis without pasteurization of the milk. Due to these conditions experiments were started at the California Experiment Station at Davis in October, 1925, in order to determine l~he advisability of flash pasteurization at different temperatttres in the oheddar cheese process. The process is not new, since there are several references in the literature. Sammis and Bmlhn (1) in 1912 reported the success- ful manufacture of cheddar cheese from milk flash pasteurized at 160 ° to 165°F. for an instant. They added hydrochloric acid to the milk in order to aid the coagulation by rennet. This method evidently has not been used to any extent in commercial manufacture during recent years. Stevenson in 1920 (2) and in 1923 (3) discussed the methods used in New Zealand, where approximately two-thirds of all cheddar cheese m~nufactured is from mi|ir pasteurized by the flash method. Regenerative flash pasteurization was used, heating the milk to 160 ° to 165°F., and cooling to the setting temperature. Temperatures below 160°F. allowed a deterioration in the flavor of the cheese, and if above 165°F., the body and tex-