UNSWEETENED CONDENSED MILK DEFECTS 263 
A careful examination of the cans of sour, curdled evaporated 
milk usually shows faulty cans or faulty seals. 
Bitter Curd. 
General Description.—\\Vhen the cans are opened the con- 
tents present a solid coagulum, eenerally noticeably white im 
color and very bitter to the taste, similar to the bitterness of 
dandelions. here is a:separation of practically clear whey, the 
curd does not break down readily upon shaking and the acid 
saction of the mixture of curd and whey is about .35 to 49 per 
cent, which is normal for evaporated milk. 
Causes and Prevention.—\icroscapic examinations under 
high magnification of cultures in sterile milk show the presence 
of very small bacilli, The milk forms a firm coagulum in five to 
seven days and when over one week old the curd has the same 
strong, bitter taste as that in the cans. The bitterness increases 
with age. These bacilli grow best at CO degrees F. They are 
facultative anaerobes, developing both, in aerobic and anaerobic 
media, but prefer anaerobic conditions. 
In the cases under observation no spores were detected and 
exposure for fifteen minutes to 212 degrees I. destroyed these 
germs. ‘The above findings do not exclude the possibility of spore 
formation under conditions very unfaverable to growth and life. 
The presence of this species of bitter curd organisms sug- 
eests incomplete ea of the evaporated milk. The strik- 
ing whiteness of the curd in all cases that have come to the 
writer's attention, is further proof of the correctness of this de- 
duction. Tt indicates that these cans received relatively little 
heat in the sterilizer, otherwise the curd weuld have a darker 
color. This defect ust acu does not show up in all the cans of 
one and the same batch, but only in a limited portion of each 
batch. This fact suggests that the distribution of heat in the 
sterilizer is not uniform, some cans getting less heat than others. 
This defect occurs generally in summer, a fact which may be 
due to one or both of the following conditions: 
\While it is well known that there is a group of species of 
bacteria, yeast and torula that are capable of producing a bitter 
curd. either direct, or through the seeretion of casein-curdling 
