A black discoloration and a musty flavor in blue cheese were attributed to the growth of Hormodendrum olivaceum, particularly in punch holes and cracks in the surface.

Gas formation is of relatively little importance in blue cheese, presumably because of the open texture, which permits the gas to escape, and the unfavorable conditions in the cheese for growth of the common gas-forming organisms. Trials with a culture of Aerobacter aerogenes recently isolated from gassy cheddar cheese showed that inoculations (of the milk) which resulted in very gassy cheddar cheese caused no gas holes or only insignificant numbers in blue cheese.

A defect of blue cheese in which a portion of the edges became soft appeared to be caused by excessive moisture in the softened parts of the cheese. The defect was readily reproduced by placing cheese near a humidifier where free moisture could strike it. Various conditions encountered in curing rooms favor the accumulation of moisture on the cheese and thus may be involved in the defect.