MILK AND MILK PRODUCTS 7 



five days after calving, and contains not less than 12 per cent, 

 of total solids, not less than 8.5 per cent, of solids not fat, and 

 not less than 3.25 per cent, of nailk fat. 



Blended milk is milk modified in its composition so as to 

 have a definite and stated percentage of one or more of its 

 constituents. 



Skim milk is milk from which a part or all of the cream has 

 been removed and contains not less than 9.25 per cent, of milk 

 solids. 



Analytic Processes. 



As already noted, the specific gravity of milk rises gradually 

 for some time after it has been drawn, and the determination 

 is to be made only after this action has ceased. This will re- 

 quire about 5 hours after the milk is drawn, if it has been 

 kept below 15°, but at a higher temperature it will be necessary 

 to allow at least 12 hours. For all other determinations the 

 milk must be analyzed as soon as possible. The following 

 figures, published by Bevan, show that a considerable loss in 

 total solids may occur in 24 hours: 



Total Solids. Loss. 



Evaporated immediately, ii-73 



Evaporated after 24 hours, iO'79 °-94 



Evaporated after 48 hours, 10.38 i .35 



Evaporated after 120 hours, 9.42 2.31 



The decomposition is very irregular, and it is not possible 

 to determine, by estimation of the lactic acid or other products, 

 the original composition of the milk. The pipet used for taking 

 a portion for analysis should have a wide opening, that no cream 

 may be retained when the pipet is discharged. 



When rigid accuracy is not essential, it will suffice to measure 

 the portions of milk taken for the determinations. Vieth uses 

 a pipet graduated to deliver 5 grams, and finds that, working 

 with whole and skimmed milk, under the ordinary variations 

 of temperature, the error will not exceed o.i on the total solids 

 and is less on the fat. 



