ae a ig A 
6 BULLETIN 1128, U. S. DEPARTMENT OF AGRICULTURE. 
Cream.—The 150 pounds of 28 per cent cream does not contain more 
fat than is needed; hence the entire amount can be used. 
The amount of 34 per cent cream can be determined by subtracting 
the amount of fat added by the 150 pounds of 28 per cent cream from 
the total amount required and dividing the remainder by 0.34, thus: 
157.5— 42 =115.5. 
115.5+0.34 =340 pounds of 34 per cent cream. 
Skim milk and condensed skim milk.—From these two ingredients 
must come the balance of the constituents (milk solids not fat) of the 
mix. ‘To find the proportions subtract the sum of the milk solids not 
fat in the cream from the total amount required and divide by 927.5, 
the difference between the amount of ingredients already used and 
the total (1,750) pounds required. For instance: 
210— (10+ 20.8) =179.2. 
(179.2 + 927.5) X 100 =19.3 per cent solids. 
This gives the per cent of solids not fat that the additional 927.5 
pounds of mix must contain. To find the proportion of skim milk and 
condensed skim milk necessary, the ‘“‘square method” is used. The 
calculations for the square method ‘ are as follows: 
Skim milk 9/ tet 
19.3 
Condensed milk 27 | 
10.3 
18.0 
927.5+-18=51.53 number of unit portions in total mix. 
51.53 X7.7=396.78 pounds of skim milk in total mix. 
51.53 X10.3=530.75 pounds of condensed skim milk in total mix. 
The aceuracy of the calculation can be ascertained by comparing 
the sum of the figures in each column with the stipulated amounts 
placed at the top of each column. 
When this is done, the ingredients are proportioned by careful 
weighing. The mix is then ready to be pasteurized and homogenized. 
4 The square method, sometimes called the Pearson method, may be used to find the proportion of milk 
and cream necessary in standardizing either the fat or the milk solids not fat in milk and cream. The 
purpose of the square is to separate the three principal factors in making the calculations, and to keep the 
deductions straight after the calculations have been made. For instance, in this poruicular problem, 
which is to find the proportion of skim milk and condensed skim milk necessary in making 927.5 pounds of 
skim milk containing 19.3 per cent milk solids not fat, the three principal factors are: First, the milk solids 
not fat content desired in the mixture; second, the milk solids not fat content of the skim milk; and third, 
the milk solids not fat content of the condensed skim milk. The first factor (19.3 per cent) is placed in the 
center ofthe square; and the other two factors (9 per cent and 27 per cent) are assigned to the corners on the 
left-hand side of the square. When this has been done, two calculations are made and placed as follows: 
(1) The difference between the upper left-hand figure (9) and the center figure (19.3), which is 10.3, is placed 
in the lower right-hand corner of the square, and indicates the number of pounds in a unit portion of the 
condensed skim milk required in the proposed mixture. Similarly the difference between the lower left- 
hand figure (27) and the center figure (19.3) which is 7.7, is placed in the upper right-hand corner of the 
square, and indicates the number of pounds in a unit portion of the skim milk required in the proposed 
mixture. Having ascertained the weight of one unit portion of each of these ingredients, any quantity 
of the desired mixture can easily be made by adding these two together to find the weight of one unit portion 
of the mixture desired, and then multiplying this by the number of unit portions in the total mix, as shown 
in the aboveexample. The same procedure is used in standardizing the fat contents of milk and cream. 
