Jan. IS, 1915 Moldiness in Butter 303 



In at least one sample, contributed by Dr. G. P. Clinton, of the Con- 

 necticut Agricultural Experiment Station, and again in a sample of fat 

 studied by Dr. C. N. McBryde, of the Bureau of Animal Industry, a 

 fungus producing abundant orange to red mycelium and red blotches 

 upon the butter was obtained. In butter and in the culture media 

 used no spores have thus far been obtained. This organism grows under 

 the same conditions as Altemaria. 



2. Green-mold type. — Green molds were found more or less frequently 

 upon all the samples tabulated except Nos. 3546a and 3546c. Cultures 

 of these molds proved to be species of Penicillium. Three common 

 species were often found. These were P. roqueforli, a variety or strain 

 of P. expansion, and P. chrysogenum. Several other forms difficult to 

 identify were occasionally obtained. Aside from P. roqueforti, these are 

 identifiable only by careful culture and comparison. These molds form 

 green patches on the surface and follow seams or cracks into the mass. 

 In one tub (No. 3515), where extensive moldy areas were found in cracks 

 and seams, the presence of P. roqueforti was suggested by a strong odor 

 and flavor resembling that of Roquefort cheese. Marked physical 

 changes in the fat itself were noticeable. Culture confirmed the identi- 

 fication of the organism. So far as observed, no such extensive changes 

 were produced by the other species. The storage of butter in tubs is 

 accompanied by low percentages of free oxygen* in the butter sug- 

 gestive of the conditions in Roquefort cheese (Thom and Currie, 1913). 

 Mold is found upon the liners, upon the inside of the tub itself, and in 

 the cracks of the butter. In all these places interchange of gases is very 

 slow, thus favoring the dominance of Roquefort mold, which is more 

 tolerant of such conditions than other species. 



3. OiDiuM Type. — The third form produces various shades of orange- 

 yellow discoloration, with little or no surface growth. Culture and 

 microscopic examination show that these areas are produced by Oidium 

 lactis. This organism grows to the depth of several miUimeters within 

 the mass of butter as a complex mycelium with hyphae varying in diam- 

 eter with the size of the spaces between the masses of fat. Some spores 

 are fonned and at times surface-fruiting areas. Bacterial activity is 

 commonly associated with the presence of this mold. 



Black molds, or mucors. — Where butter has been moist enough for 

 loose masses of surface mycelium to grow, mucors are sometimes seen. 

 These molds are found by culture to be present in many other samples 

 in which no visible colonies are produced. 



EXPERIMENTAL WORK 



To study the conditions favorable to mold- growth in butter special 

 samples of butter were prepared, some low in water content and some 

 high in water content, some thoroughly washed to reduce the curd con- 



^ Unpublished results of Dr. D. C. Dyer, of Uic Dairy Division. 



