EXPERIMENT STATION BULLETINS. 635 



In 1918 Biishuell (0) experimented on the influence of cold sliock on 

 the sterilization of foods, working with both glass jars and test tnbes. 

 He found that cold shock did not promote the keeping qualities of 

 canned food. Exclusion of air, however, prevented aerobic organisms 

 from developing when their spores were present. 



Minna Denton (14) investigated various factors which influence tlie 

 length of time required for heat penetration in mason jars. Ordi- 

 nary mercury thermometers inserted through the can cover were used 

 in these experiments, in Avhich carrots only were employed. It was 

 determined that increasing the vegetable mass by about two and con- 

 sequentl}' decreasing tlie amount of water added to the jar, almost 

 doubled the time required for heat penetration to the center of the jar. 

 Miss Denton makes a point of the fact that in the more solid pack 

 there was an interval of 115 minutes when the temperature remained 

 above SO degrees C; later, however, she suggests that various strains 

 of B. hotuUnus may have higher thermal death points than Van Ermen- 

 genr's strain Avhose spoies were destroyed at this temjjerature. An- 

 other point brought out is that two women using the same material and 

 following each step with equal care and intelligence may often obtain 

 very different results since the time for the interior of the can to reach 

 a temperature near the boiling point may vary from 30 to 100 minutes 

 and easily could vary more widely. The statement is made that "with 

 any given period of processing, the longer the time required to heat 

 through to the center of the mass, the shorter the time remaining for 

 the accomplishment of sterilization." 



Cheyney (11) examined bacteriologically "seven hundred and twenty- 

 five cans of merchantable foods in prime condition" and found fifty- 

 eight or eight per cent to contain living micro-organisms. Fruits showed 

 living microbes in a uniform average of three per cent of the cans ex- 

 amined, with vegetables the percentage was eight, and' with meat and 

 fish it varied from ten to twenty per cent of all cans. The organisms 

 isolated from peas were B. valgatus (Fliigge), B. mesentericiis (Fliigge- 

 Migula), and B. suhtilis (Cohn). B. viilgatus is perhaps the most fre- 

 quent type found in canned foods containing viable organisms because 

 such cans are very frequently "leaks." Of the forty-nine cans of fruits, 

 vegetables, etc., found leaky, thirty-seven per cent contained living organ- 

 isms. Six cans of peas which were found to be sterile may have been 

 leaks. B. mesentericus "is typical of apparently perfect cans which re- 

 tain bacteria in spite of standard processing." The cans (No. 2) of peas 

 containing, these organisms were processed from 30 minutes at 235 de- 

 grees F. to 45 minutes at 240 degrees F. in different factories. 



J. Weinzirl (31) in his thesis entitled, "The Bacteriology of Canned 

 Foods" gives his results from investigation of one thousand and eighteen 

 samples of canned goods. Besides molds and yeasts, he isolated three 

 hundred and ninety-two bacteria, representing thirty-eight species. The 

 most prevalent organisms found were B. mesentericus, B. suhtilis, B. 

 thermoindiffercns, B. vulgatus and B. cereus. 



He concludes that spores may be present in apparently unspoiled can- 

 ned goods as found on the market. These may be unable to grow due 

 to lack of oxygen. Vacuum is essential for the preservation of foods 

 under the present methods of processing. Food poisoning organisms, 

 B. totuUnus and B. enterit'idis are not found in commercially canned 

 foods. 



