16 MASS. EXPERIMENT STATION BULLETIN 426 



In California many technical studies have been made regarding botulism. 

 This subject is of particular interest in that State because of the many outbreaks 

 which have occurred there. The following recommendations were made in 1943 

 regarding the destruction of toxin in home-canned foods. 



1. The California Department of Public Health (1943) advised that: 



Although the botulinus toxin is extremely poisonous, it is fairly readily 

 destroyed by heat. The amount of heat required varies according to the 

 food in question. To be on the safe side, home canned vegetables, meat or 

 fish, should always be brought to a boil and kept boiling at least 15 minutes 

 before being used. To ensure that all parts of the food are heated sufifi- 

 cienth' the food should be thoroughly stirred frequently during the heatitig 

 period. It should never be tasted before being heated, and should never 

 be used cold in salads without first being boiled. With some products, 

 particularly string beans, it is often very difficult to detect signs of spoilage 

 when the jar is opened. On heating, however, the odor of decomposition 

 is more apparent. Sometimes a very potent toxin may be present and yet 

 the brine may be clear and there may be no off odor. 



2. The California Extension Service (1943b) has advised the following heat 

 treatments of home-canned foods in order to prevent botulism: 



a. If a non-acid food such as vegetables, meat, poultry, or fish has 

 been processed in a pressure cooker with an accurate gauge or thermometer 

 and if the method, pressure or temperature, and time prescribed have 

 been followed, it should be unnecessary to reboil the canned product before 

 using it. However, always boil string beans for 10 minutes before using 

 them, even for salads. 



b. Boil before tasting or using, any such non-acid food canned without a 

 pressure cooker or in a cooker with an untested gauge or thermometer, 

 or if the prescribed processing or any part of the recommended method 

 has not been followed. 



To boil, empty the food into a pan and place directly over the heat. 

 Either cover the pan, or stir the food or break up clumps. Count time 

 after boiling has begun. Boil steadily for at least 10 minutes. Spinach and 

 creamed corn mast be boiled for at least 20 minutes. 



c. Never taste any canned food having a disagreeable odor or showing 

 gas pressure in the can, jar or bottle. A sour, rancid or putrid odor is a 

 warning but may not be always present. The odor is intensified by boiling. 



Effect of Acid 



It has been reported that botulinum toxin is very resistant to acids (pH 4.0) 

 but that it is less resistant to alkali. Bronfenbrenner and Schlesinger (1920) 

 have reported that the toxicity of a crude filtrate or cultures of CI. botulinum may 

 be greatly increased by acidification (approximately pH. 4.0). Geiger (1923) 

 pointed out that inasmuch as outbreaks of botulism have occurred following the 

 consumption of vegetables, such as string beans and beets, served in the form of 

 salads and containing vinegar, the definite knowledge of any increase in toxicity 

 due to the addition of an acid might become of practical importance. However, 

 in experimental work he found that the potency of the toxins of four strains of 

 the organism was not increased by acidification. Bengtson (1924) reported a 

 definite increase in toxicity upon acidification to pH 4.0. However, this increase 

 in toxicity was not as great as that reported bv Bronfenbrenner and Schlesinger 

 (1920). 



