June 15,1914 
Ripening of Cheddar Cheese 
207 
longed standing takes place in a meat extract such as Liebig's. In the 
curing of cheese the disappearance of active lactic acid, as well as the pro¬ 
duction of racemic lactic acid, takes place rapidly. The early stages 
of these phenomena were next investigated. 
Whey drawn from the vat during the process of cheese making and 
subjected to analysis for lactic acid gave the results shown in Table XV: 
Table) XV .—A nalysis of whey , showing quantity of lactic acid as zinc lactate 
Fraction No. 
Crystals of zinc 
lactate. 
Water of crys¬ 
tallization. 1 
I. 
Grams. 
2. 45 8 7 
. 7902 
Per cent . 
13 * 07 
12. 27 
1 The theoretical percentage for water of crystallization in active zinc lactate is 12. 89. 
Fresh curd from which the above whey was drawn was kept at 35° C. 
for 3 days and gave the following results (Table XVI): 
Table) XVI .—Analysis of fresh curd, 3 days old , showing quantity of lactic acid as zinc 
lactate 
Fraction No. 
Crystals of zinc 
lactate. 
Water of crys¬ 
tallization. 1 
I. 
Grams. 
2. 0837 
• 1652 
Per cent. 
z 7 * 99 
17-43 
2. 
1 The theoretical percentage for water of crystallization in racemic zinc lactate is 18.18. 
It is seen that whey contained active lactic acid, while curd or cheese 
only 3 days old and kept at 35 0 C. contained nearly all its lactic acid in 
the racemic form. It is probable that a second group of organisms fol¬ 
lows the early action of the predominating active lactic-acid producers 
in the cheese during the first 3 days. There is also a possibility that a 
somewhat different sequence of bacterial life occurs in the whey from 
that which takes place in the curd, with the result that active acid is 
produced in whey and the racemic variety in the curd. To settle this 
point, whey and curd were investigated for the forms of lactic acid 
occurring in them. The results are given in Table XVII: 
Table XVII .—Analysis of whey and curd , showing the quantity of lactic acid as zinc 
lactate 
Whey when drawn. | Curd at hooping time. 
Fraction No. 
Crystals of 
zinc lactate. 
Water of 
crystallization. 
Crystals of 
zinc lactate. 
Water of 
crystallization. 
I. 
Grams. 
O. 4570 
I. 6520 
Per cent. 
13-65 
12.50 
Grams. 
O. 1974 
Per cent. 
12. 36 
