ANNUAL REPORT, 1946-47 51 



influence on the viability of the final product are the seed yeast, the nutritive 

 factors during yeast production, and the method of drying, including temperature 

 and time. 



The storage factors were studied after a suitable fermentmeter had been con- 

 structed which permitted the recording of gas pressure produced by a mixture of 

 yeast, flour, and water. Dried yeast was then packed in various gas atmospheres 

 such as carbon dioxide, nitrogen, ox^'gen, and air; and stored at various tem- 

 peratures, including —5°, 40°, 70°, and 100°F. Various containers were also 

 used, in order to determine the effect of light during storage. Temperature 

 appears to be the most important factor of all. In 18 days, dried yeast stored at 

 100°F. was no longer suitable for baking bread, regardless of the container or the 

 gas atmosphere used. 



Vitamin D Bioassay Research. (C. R. Fellers and L. R. Parkinson.) As yet, 

 no physical or chemical methods have been devised that are accurate for the de- 

 termination of vitamin D in food. A literature survey has been made of likely 

 procedures, and research will be carried out to check new laboratory methods 

 against the standard rat bioassay. An enormous saving of time and cost will 

 result if chemical or physical procedures can be perfected. 



Of the 72 samples of vitamin D milk assayed during the year, two were seriously 

 deficient and three slightly deficient in vitamin D. 



Fish Investigations. (C. R. Fellers and A. Lopez-Matas.) Studies on fresh, 

 frozen, canned, and smoked swordfish have been completed, and three scientific 

 papers prepared for publication. The study covers both technological and 

 nutritional aspects. 



Rapid Estimation of Added Aluminum in Foods. (C. R. Fellers and R. Barton.) 

 A nephelometric method has been perfected which is accurate for inorganic 

 aluminum to ± 10 parts per million. The brine or pickle is cleared with phos- 

 photungstic acid, the pH adjusted, and the aluminum hydroxide precipitated 

 with ammonia. The density of the suspended aluminum hydroxide is read in a 

 specially constructed nephelometer. A description of the procedure is being 

 prepared for publication. 



DEPARTMENT OF HOME ECONOMICS NUTRITION 

 Julia O. Holmes in Charge 



Losses of Iron in the Menses of Women. (A. \\. Wertz, B. V. McKey, and 

 J. O. Holmes.) Because of the loss of blood in the menses it is customary to 

 recommend a higher level of iron for women than for men. As a part of the study 

 on the metabolism of iron in women, conducted last year, a collection was made 

 of the menses throughout the 115-day experimental period. Because of its 

 significance in determining the requirement of iron by women the results of the 

 analyses of the material are presented here. The losses of iron by these four 

 women varied markedly, although the loss of an individual woman was fairly 

 constant from period to period. The subjects ranged in age from 24 to 37 years; 

 none had had any children. The range in iron excreted per menstrual period was 

 as follows: Subject A, age 28 years, 1.98-2.49 mg.; Subject B, age 29 years, 

 2.6-8.13 mg.; Subject C, age 24 years, 15.13-33.9 mg.; Subject D, age 37 years. 



