8 MASS. EXPERIMENT STATION BULLETIN 374 



original weight. Very few products contain less than 5 percent of dry- 

 matter, while products that ripen slowly, or those that are exposed to 

 drying as they are stored or shipped, contain more than 20 percent. 



Analytical Methods for Nutrient Constituents 



Moisture was determined by drying the product to constant weight in 

 a vacuum oven at 50° C; protein (Nx6.25) by the Kjeldahl-Gunning 

 method; fat by extraction with anhydrous ethyl ether; fiber by the Official 

 Method for Grains and Stock Feeds; and ash by incineration in an electric 

 muffle furnace at a temperature below visible redness (about 510° C). 

 The crude ash was resolved by acid extraction into two carbon-free por- 

 tions, one soluble and the other insoluble. 



Determination of Minerals 



Numerous determinations of the more prominent inorganic elements 

 in plant products have been reported in the literature during the past few 

 decades. The results were obtained largely by gravimetric methods then 

 in vogue. More recently, with the introduction of microchemical colori- 

 metric methods, the determination of mineral elements has received con- 

 siderable impetus. The results shown in the table were obtained by col- 

 orimetric methods based on visual readings with a Duboscq comparator. 

 In the preparation of solutions, wet combustion was found to be more 

 serviceable, more rapid, less subject to contamination, and of wider applica- 

 tion than dry combustion, when many samples were involved. Iron was de- 

 termined by the thiocyanate reaction; copper by sodium-diethyl-dithio- 

 carbamate reagent and extraction with carbon tetrachloride; manganese 

 by periodate oxidation; and phosphorus as molybdenum blue. 



Results of Analysis 

 The results of the proximate analyses for nutrient constituents, as well 

 as the analyses for minerals, are shown in the accompanying table. For 

 comparative purposes, the samples were grouped according to the nature 

 of the products and their use as food, as follows: 



Major fruits— large fruits such as apples and peaches 



Minor fruits — berries 



Garden fruits — pumpkins, squash, melons 



String beans 



Shell beans and peas 



Leaf and stem vegetables — spinach, lettuce, celery, cabbage, 



onions, asparagus, cauliflower 

 Cereals, low fiber — without hulls, or with hulls removed 

 Cereals, high fiber — with hulls, as oats 

 Nuts 



Processed human foods — breakfast foods 

 Cattle feeds, low protein — hay 

 Cattle feeds, high protein — grains 

 Roughage 



After water was eliminated, most fresh and processed foods contained 

 about 50 percent of soluble and easily digested carbohydrates (sugars and 

 starch), and some contained up to 90 percent. Appreciable amounts of 

 protein were found in some members of most of the group. Fat was a 



