EXPERIMENT STATION BULLETINS. 



PREVENTION. 



Effect of Heat on B. botulinus Spores. — A very false sense of security is 

 given by various text books due to the fact that van Ermengen's statements 

 with regard to the low thermal death point of the spores of B. botulinus have 

 l^een copied without proper qualifications. These statements are to the 

 effect that the spores of B. botulinus are easily killed by heating at 80 °C. 

 (176°F.) for 60 minutes. 



Ordinary Canning Methods Not Effective. — If these statements were 

 true of all strains of this organism, the amount of heat applied in any one 

 of the four well recognized methods of canning would be sufficient to de- 

 stroy the spores: (1) hot pack or open kettle; (2) cold pack, hot water bath 

 or steam; (3) intermittent sterilization; (4) pressure canning. Experiments 

 by various investigators in different parts of the United States, however, shoiv 

 that the spores of most all strains will resis'. much higher temperatures than 

 80°C. for a considerable length of time. Burke of California (1918) found that 

 spores of certain strains of B. botulinus would withstand 100°C. (212°F.) 

 for 2,}/2 hours, and in the foam which gathers on the side of the kettle they 

 may live for a much longer period. One period of heating in boiling water 

 for five hours or less will not sterilize the contents of jars if they are contam- 

 inated with the more resistant spores of this bacillus. She found that be- 

 cause of the much delayed germination of spores due to heat injury, fractional 

 or intermittent sterilization on three successive days is of doubtful value since 

 the spores do not develop before the third heating period. Even pressure 

 canning cannot be considered safe if a pressure of 5, 10 or 15 pounds is applied 

 for only 10 minutes. A comparatively long sterilization period must be used. 



Effect of Protein, Acid and Sugar on Spores. — Experiments were also 

 performed at the University of California (1919) which showed (1) that the 

 spores of B. botulinus when mixed with animal or vegetable protein are much 

 more resistant to heat than has been believed. (2) When lemon juice (5 to 

 7 oz. per gallon of vegetable) is added, the thermal death point (killing tem- 

 perature) is markedly lowered when heat is applied. (3) Cane sugar in con- 

 centrations up to 64 per cent does not prevent the growth or toxin produc- 

 tion of B. botulinus although both are inhibited to a certain extent, and (4) 

 in connection with this, the particular fruits tested which had been canned 

 in sugar syrup were suitable as a food for this organism. (5) Certain technic 

 of the canning method of commercial as well as of home canners may be 

 inefficient if the raw material happens to be contaminated with the spores of 

 B. botulinus, for example, the degree of heat used in processing may not be 

 applied suflaciently long to reach the center of the cans at all, or for an effec- 

 tive period. 



Why We Fail to Prevent Botulism. — It is very evident that it would be 

 quite impractical to think of preserving poultry or stock-foods in the man- 

 ner used for human foods. The solution of prevention of botuhsm in both 

 types of food then apparently lies in preventing the original contamination. 

 Our knowledge, however, of the habitat of B. botulinus in nature is so lim- 

 ited that the preventive measures we take are not sufficiently exhaustive. 

 If B. botidinus could be wholly prevented from gaining entrance to or de- 

 veloping upon food, botulism would not occur. Thus it is seen that lack 

 of wide human knowledge, combined with human failings where knowledge 

 is present, are responsible for many of the outbreaks of botulism. 

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