254 BIOLOGICAL ACTIVITIES OF MOLDS 



G. candidum {Oidium lactis, Oospora lactis) is a very common 

 and widespread mold, said to be extraordinarily resistant to heat and 

 antiseptics. It grows everywhere where lactic acid is present — on 

 sour milk, cheeses, butter, sauerkraut, silage, and pickles. It is 

 said to oxidize lactic acid completely to carbon dioxide and water, 

 thus reducing the acidity of the medium in which it is growing. 

 This, however, has not been satisfactorily proved, for it is also 

 actively proteolytic and the reduction of acidity of sour milk may 

 well be due to neutralization of the acid by the ammonia produced, 

 rather than to the oxidation of lactic acid. 



G. candidum is of practical importance in the dairy industries 

 for, because of its proteolysis, it may in some cases cause spoilage 

 and off flavors. However, in others it must take part in causing 

 the proteolysis which is necessary for the manufacture of certain 

 kinds of cheese. We have invariably found this mold in all samples 

 of domestic or foreign Brie or Camembert cheese which we have 

 examined. It is especially troublesome in butter and cottage cheese. 

 It is ordinarily only found in the presence of lactic acid. The pres- 

 ence of this organism in any abundance in most dairy products is a 

 good indication of uncleanliness, since it gives evidence that vessels 

 have been used without proper cleansing or sterilizing after milk 

 has stood in them long enough to sour. 



The Mucors are also found, very frequently in stale, moist breads 

 and are often called bread molds on this account. These organisms 

 are capable of hydrolyzing starch to sugar. N. sitophila is another 

 important cause of trouble in bakeries, giving rise occasionally to 

 "epidemics" of infected bread. The spores apparently come from 

 the flour. 



S. brevicaulis is a common species of some importance in food 

 spoilage. The spores are yellowish brown. It is important as a cause 

 of spoilage of various substances. Growing more slowly than many 

 other molds, it takes part in the final disintegration of the product. 

 It is very active in proteolysis, producing ammonia abundantly from 

 organic nitrogen compounds. In the presence of sugars, it produces, 

 from arsenical compounds, diethylarsine which has a very character- 

 istic garlic-like odor. This reaction has been used as a test for 

 arsenic, the reaction being said to be more delicate than the usual 

 chemical tests. Only arsenious acid or its salts of the alkaline metals 

 may be detected readily, salts of the heavy metals not so surely, 

 and arsenic sulphide not at all. Disagreeable odors may be pro- 

 duced on other substrates, described as ammoniacal, like turnips or 

 cabbages. According to Thom it is an important secondary invader 



