SOFT CHEESES 221 
These bacteria grow in the milk previous to the addition of the 
rennet, although the milk is not allowed to become very sour before 
curdling. But they continue to grow during the curdling and for a 
day or two after the cheese is made. If by any chance the lactic 
bacteria fail to develop vigorously, a ruined cheese is sure to result. 
The second step in the ripening is the appearance on the suriace 
of the cheese of a species of mold, which has been named Penzczll- 
ium camemberti (Fig. 43). This mold ap- 
pears in from two to four days and is at 
first of a pure white color; later, when it 
begins to produce spores, it becomes a steel 
gray, but never a deep blue like the common 
mold. It is a species of mold that ap- 
parently does not occur in America, but is 
very common in Europe in those sections 
where Camembert cheese is made. Its 
absence from America is the chief reason 
why this country has been unable to make 
Camembert cheese. Where successful cheese 
of this type has been produced, it has been ons A enol 
by importing and inoculating this type of tipening camembert 
mold into the American cheese factories. cheese (i'hom). 
This white mold grows on the surface of the cheese, but does not 
penetrate below the surface. After about two weeks it reaches 
its limit of growth, forms spores, and dries down to a some- 
what thin crust. The growth of this mold, together with other 
organisms, neutralizes the acid of the curd at the surface of the 
cheese and renders it slightly alkaline. 
In the meantime the mold has secreted an enzyme which has 
the power of digesting the curd. As fast as the acidity of the curd 
is reduced and the enzyme secreted, the latter acts upon the curd, 
changing it from a hard consistency to a soft texture. At first the 
cheese is a hard, solid curd from surface to center; but as this en- 
zyme acts beneath the mold there is formed a thin layer of soit 
