170 SCIENCE AND PRACTICE OF CHEESE-MAKING 



milk containing- more than 4.5 per cent of fat, the ratio 

 of casein to fat is frequently less than in milk con- 

 taining less than 4.5 per cent of fat. Starting with 

 milk containing an average of 3 per cent of fat and 

 a casein content of 2.1 per cent, milk with 4 per cent 

 of fat was found to contain about 2.5 per cent of 

 casein on an average. 



RULE FOR CALCULATING AMOUNT OF 



CASEIN IN MILK 



On the basis of the observed general relations stated 

 above, the following formula was worked out for cal- 

 culating the percentage of casein in milk when the per 

 cent of fat is known : 



(F — 3) Xo.4+2.i=per cent of casein. 



F equals the number representing the per cent of fat 

 in milk. Expressed as a rule, we have the following: 

 From the number representing the per cent of fat 

 in milk subtract 3 ; multiply the result by 0.4 and 

 then add 2.1. The formula is apt to give results 

 not quite up to the actual in case of milk produced 

 nfter the eighth or ninth month of lactation period, 

 when the casein is usually a little greater in rela- 

 tion to fat than during the previous stage of the 

 lactation period. Applied separately to the milk 

 of 50 herds of cows during the factory season, the 

 average results for the season are summarized as 

 follows : ( I ) In 4 cases, the results found by chemi- 

 cal determination were identical with those given 

 by calculation; (2) in ^6 cases, the results by cal- 

 culation were within o.i per cent of those obtained 

 by the chemical method; (3) in 8 cases the chemi- 

 cal method gave o.i to 0.2 per cent less than the 



