MINERALS IN NUTRITION 



TOTAL NUTRIENTS AND MINERALS IN HUMAN 

 AND CATTLE FOODS 



By Walter S. Ritchie and E. B. Holland, 

 Department of Chemistry 



Foods have been subject to investigation by the Massachusetts Experi- 

 ment Station since its organization, and experiments have embraced a 

 wide range of products. Recently attention has been directed to min- 

 erals because of their importance in human and animal nutrition. Those 

 given particular attention are iron, copper, manganese, and iodine. In the 

 report here presented, fruits and vegetables from different sources have 

 been analyzed for nutrients, including nitrogen and sulfur, and for iron, 

 copper, manganese, and phosphorus. 



Collection and Preparation of Samples 



Samples of fruits and vegetables were obtained from the State College 

 and vicinity, and vegetables from the Waltham Field Station and from 

 gardens in the eastern part of the State. Similar samples were obtained 

 from other sections of the country for comparison. Cereals, nuts, proc- 

 essed human foods, and cattle feeds were also included in the survey. 

 All fruits and vegetables were expected to be mature and marketable, and 

 in prime condition for use. Both immature and overripe products will 

 vary appreciably in proximate analyses, but to a less extent in minerals. 

 The variety of the fruit or vegetable and the rapidity of growth are also 

 factors causing variation. 



The samples were culled as they would be for household use. They 

 were washed if necessary, ground, and then dried in a current of warm 

 air at about 50° C. Under such treatment, the tissue sets quickly with a 

 minimum deterioration in fat and carbohydrates. In the earlier part of 

 the work, the fruits and vegetables were pared or scraped, but the prac- 

 tice was discontinued later. After the samples had been dried, they were 

 ground to pass through a 1-mm. sieve, and then were kept in closed glass 

 containers until they were analyzed. Analyses of products were repeated 

 in successive years for the purpose of comparison. This procedure assisted 

 in leveling variations in plant constituents traceable to seasonal differences 

 in temperature and rainfall. 



Basis of Analysis 



Most fruits and vegetables as they come from the field contain from 

 80 to 96 percent of water at maturity, but lose moisture rapidly after 

 they are liarvested and particularly during storage. Fruits and garden 

 vegetables are marketed fresh, frozen, canned, or dried. On the other 

 hand, cereals, navy beans, nuts, and industrial by-products such as oil 

 meals are substantially air-dried when they are marketed. In considera- 

 tion of such a range of moisture content, dry weight seemed to be the 

 only logical basis for comparison. Consequently, in the table, proximate 

 constituents are recorded as percentages and minerals as parts per mil- 

 lion (p. p.m.) of the dry weight of the products. 



The amount of moisture lost by fruits and vegetables varies with the 

 nature of the product and with the way in which it is handled after it is 

 liarvested. Generally the dry weight ranges from 5 to 20 percent of the 



