De Vries[219] has described a blue condition that is found in Edam cheese. It appears first as a small blue spot on the inside, increasing rapidly in size until the whole mass is affected. This defect he was able to show was produced by a pigment-forming organism, B. cyaneo-fuscus. By the use of slimy whey (lange wei) this abnormal change was controlled.
Moldy cheese. With many varieties of cheese, especially some of the foreign types, the presence of mold on the exterior is not regarded as detrimental; in fact a limited development is much desired. In hard rennet cheese as cheddar or Swiss, the market demands a product free from mold, although it should be said that this condition is imposed by the desire to secure a good-looking cheese rather than any injury in flavor that the mold causes. Mold spores are so widely distributed that, if proper temperature and moisture conditions prevail, these spores will always develop. At temperatures in the neighborhood of 40° F. and below, mold growth is exceedingly slow, and often fructification does not occur, the only evidence of the mold being the white, felt-like covering that is made up of the vegetating filaments. The use of paraffin has been suggested as a means of overcoming this growth, the cheese being dipped at an early stage into melted paraffin. Recent experiments have shown that "off" flavors sometimes develop where cheese are paraffined directly from the press. If paraffin is too hard, it has a tendency to crack and separate from the rind, thus allowing molds to develop beneath the paraffin coat, where the conditions are ideal as to moisture, for evaporation is excluded and the air consequently saturated. The use of formalin (2% solution) has been suggested as a wash for the outside of the cheese. This substance or sulfur is also applied in a gaseous form. Double bandaging is also resorted to as a means of making the cheese more presentable through the removal of the outer bandage.
The nature of these molds has not been thoroughly studied as yet. The ordinary blue-green bread mold, Penicillium glaucum, is most frequently found, but there are numerous other forms that appear, especially at low temperatures.
Poisonous cheese. Cases of acute poisoning arising from the ingestion of cheese are reported from time to time. Vaughan has succeeded in showing that this condition is due to the formation of a highly poisonous alkaloid which he has isolated, and which he calls tyrotoxicon.[220] This poisonous ptomaine has also been demonstrated in milk and other milk products, and is undoubtedly due to the development of various putrefactive bacteria that find their way into the milk. It seems quite probable that the development of these toxic organisms can also go on in the cheese after it is taken from the press.
Prevention or cheese defects. The defective conditions previously referred to can rarely be overcome in cheese so as to improve the affected product, for they only become manifest in most cases during the later stages of the curing process. The only remedy against future loss is to recognize the conditions that are apt to prevail during the occurrence of an outbreak and see that the cheese are handled in such a way as to prevent a recurrence of the difficulty.
Many abnormal and undesirable results are incident to the manufacture of the product, such as "sour" or "mealy" cheese, conditions due to the development of too much acid in the milk or too high a "cook." These are under the direct control of the maker and for them he alone is responsible. The development of taints due to the growth of unwelcome bacteria that have gained access to the milk while it is yet on the farm are generally beyond the control of the cheese maker, unless they are so pronounced as to appear during the handling of the curds. If this does occur he is sometimes able, through the intervention of a starter or by varying some detail in making, to handle the milk in such a way as to minimize the trouble, but rarely is he able to eliminate it entirely.
One of the most strenuous duties which the maker must perform at all times is to point out to his patrons the absolute necessity of their handling the milk in such a way as to prevent the introduction of organisms of a baleful type.
FOOTNOTES:
[178] Russell, 13 Rept. Wis. Expt. Stat., 1896, p. 112; Campbell, Trans. High. & Agr. Soc. Scotland, 5 ser., 1898, 10:181.
[179] Winkler, Milch Zeit. (Hildesheim), Nov. 24, 1900.