28 CONTROL BULLETIN NO. 148 



The Quality of Soy Bean Oil Meal 



Experimental work has established that properly cooked soy bean oil meal has 

 greater nutritive value than either undercooked or overcooked meal. Apparently 

 the heat required to produce a meal of high nutritive value will also render in- 

 active the enzyme urease that is present in raw soy beans and in uncooked soy 

 bean oil meal. Therefore, there is good correlation between the nutritive value 

 and the urease activity of soy bean oil meal. 



This fact has been used as the basis in the development of several methods for 

 determining whether or not a particular meal has been cooked adequately. 

 Strictly speaking, these methods measure the urease activity of the soy bean 

 oil meals. 



It has been found that soy bean oil meal having a high urease activity, indi- 

 cating undercooking, also usually contains a relatively high percentage of water- 

 soluble protein. In cases of very high urease activity about 60 percent of the 

 total protein was found to be in the water soluble form. In properly cooked 

 meals usually less than 10 percent of the total protein is water-soluble. 



Foiu-teen samples of soy bean oQ meal were examined by the Massachusetts 

 Control Service during the past season. The urease activity was determined in 

 all cases. The water-soluble protein was determined in several samples that 

 showed some urease activity. 



Work done in other laboratories shows that tests resulting in an increment 

 of less than 1.0 in the pH value indicate that the meal has been cooked adequately. 



On this basis and on the basis of the percentage of the water-soluble protein 

 found, it is indicated that all the fourteen samples reported in the following table 

 had been properly cooked. 



