612 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



was done on the morphology and cultural characteristics of different 

 species of bacteria isolated from home-canned vegetables. Prelimi- 

 nary experiments were carried out on the effect of hydrogen-ion 

 concentration of culture media on the growth and thermal death 

 points of bacteria in canned vegetables. The results of these inves- 

 tigations indicate clearly that the spoilage of home-canned vegeta- 

 bles in the majority of cases is caused by germination in the cans 

 of spores of gas-forming butyric acid bacteria. The successful can- 

 ning of vegetables depends on the sterilization of the contents of 

 the can during processing, or the exclusion of anaerobic spore- 

 forming bacteria by careful selection, preparation, and packing of 

 the vegetables, or on the failure of spores or anaerobes to develop 

 in the can during storage. The latter undoubtedly happens in some 

 cases, since these spore-forming anaerobes have been isolated in a 

 few instances from canned vegetables in good condition. 



The studies begun last year on the digestibility of various raw 

 starchy food materials with women as subjects were completed. 

 Tests were made with the following nine materials: Separated 

 corn, wheat, and potato starches, wheat flour, wheat farina, graham 

 flour, corn flour, fine hominy, and ground so-called soft corn or 

 waxy maize. The wheat and corn starches eaten as such were com- 

 pletely digested, and a high coefficient of digestibility was noted 

 with the wheat and corn products rich in starch. It was found 

 that the carbohydrate which constitutes the major portion of waxy 

 maize was almost completely digested. A bulletin summarizing the 

 results of these experiments was prepared for publication. 



Eespiration calorimeter studies on energy expenditure in house- 

 hold tasks, particularly sweeping and ironing, were continued. The 

 average energy expenditure per hour for sweeping a bare floor was 

 found to be 57.5 calories as compared with 61 calories in case of a 

 pile carpet. In ironing clothes the expenditure ranged from 24.9 

 calories per hour when the working surface was 82 centimeters 

 (32.28 inches) high, to 30.1 calories when the working surface was 

 67 centimeters (26.37 inches) high, and to 29.7 when it was 89 cen- 

 timeters (35.03 inches) high. Such studies showed that the height 

 of the working surface influences the expenditure of energy in house- 

 hold tasks, being less when the equipment is adjusted to a comfort- 

 able height. A paper reporting the results of previous studies of 

 the energy expenditure in sewing and some other household tasks 

 was presented at the annual meeting of the American Home Eco- 

 nomics Association. 



In the special calorimeter designed for investigation work on fruits, 

 vegetables, and other foodstuffs, further tests were made with ba- 

 nanas to determine the gaseous exchange and heat elimination dur- 

 ing the ripening period and to observe the effect of humidity and car- 

 bon dioxid on the ripening of the fruit. A study was also made of 

 the shrinkage in a quarter of beef under conditions comparable with 

 the cool-storage room in a retail market. The beef kept in the respira- 

 tion calorimeter for 13 days was in the condition termed " hotel 

 ripe " when removed, and the shrinkage was 2 per cent. 



Considerable progress was made on the egg calorimeter that is 

 being constructed in cooperation with the Bureau of Animal In- 

 dustry. 



