4 MASS. EXPERIMENT STATION BULLETIN 434 



An analysis of the ash of fresh mushrooms gave the following results: 



Calcium .. 0.0024 percent 



Phosphorus 0.15 



Potassium 0.50 



Total iron _ 19.50 p. p.m. 



Available iron 5.95 p. p.m. 



Copper 1.35 p. p.m. 



Protein 



The protein present in mushrooms has long been a subject of much discussion- 

 The controversy has ranged from the extreme of calling mushrooms the "vege- 

 table beefsteak" to the opposite extreme when Chatfield and Adams (4) assigned 

 a value of zero for the percentage of protein in mushrooms. 



Saltet (21) employed human beings to test the digestibility of mushroom nitro- 

 gen and reported that 69 percent of the total nitrogen of Agaricus campestris 

 existed in the form of protein. He concluded further that 50 percent of the total 

 nitrogen was in the form of a digestible protein. Mendel (14) and Konig (12) 

 indicated that the protein content of mushrooms was approximately 5 percent, 

 and expressed the opinion that mushrooms would be a good source of protein. 



Skinner, Peterson and Steenbock (23) investigated the digestibility of the 

 protein of Agaricus campestris with albino rats and found it to be 71 percent, in 

 fairly close agreement with the findings of Saltet (21). However, these data 

 were not in agreement with those of Morner (16) who reported that only 50 per- 

 cent of the total nitrogen of mushrooms was capable of being digested in vitro. 



Recently Fitzpatrick, Esselen and Weir (7) have reported the results of an 

 extensive investigation on the composition and nutritive value of mushroom 

 {Agaricus campestris) protein. Several rat-feeding experiments were carried out 

 according to the paired-feeding method of Mitchell and Beadles (15). Assigning 

 an arbitrary value of 100 to purified casein, the relative quality of mushroom 

 protein was 32.6 when they were fed at an 8 percent protein level. When the 

 level of protein was increased to 15 percent, the relative quality of mushroom 

 protein increased to 56.6 percent. The data indicated that the mushroom protein 

 contained all of the amino acids essential for the rat. The fact that the rats on 

 the mushroom diets did not gain as much weight as those on the control diet 

 indicated that the essential aminoacids, although present, were probably in low 

 concentrations in the case of certain individual acids. As is discussed later the 

 tryptophane content of mushroom protein was found to be particularly low. 



Studies on the mushroom protein itself showed that total nitrogen content of 

 Agaricus campestris was approximately 0.5 percent of which 63 percent was in 

 the form of protein. Purified mushroom protein was found to have a nitrogen 

 content of 11.79 percent. 



By means of qualitative chemical tests the mushroom protein was found to 

 contain the following essential amino acids: phenylalamine, histidine, leucine, 

 lysine, arginine, tryptophane, and threonine. The essential amino acids which 

 failed to give positive tests were: valine, isoleucine, and methionine. However, 

 that these three essential amino acids were also present was borne out by the 

 animal feeding trials. 



The microbiological technique was employed in making a quantitative de- 

 termination of certain of the amino acids in mushrooms. The dried mushrooms 

 were hydrolyzed, prior to assay, in a manner similar to that described b}' Schwei- 

 gert, Mclntire, Elvehjem, and Strong (22). The microbiological method of 



