104 THE CREAMERY PATRON'S HANDBOOK. 



of these proteid-converting enzymes, that are extracted from the stomachs 

 of animals. Under proper conditions, certain bacteria have the power 

 of producing various enzymes in a manner similar to the cells of the stom- 

 ach or intestine. This bacterial rennet does not differ materially from 

 rennet of animal origin. Curds precipitated by the action of rennet may 

 be readily distinguished from those produced by acid. As a rule, they 

 are softer, and more gelatinous than acid curds. 



This abnormal milk is produced by a large variety of bacteria which 

 as a class can be characterized as follows: As a rule they are spore bear- 

 ing organisms; therefore, they possess high powers of resistance. It. is 

 for this reason that boiled or heated milks almost always undergo this 

 type of fermentation. If such milk is allowed to stand after it has curdled, 

 another abnormal change usually sets in which is marked by the gradual 

 digestion of the curd and the appearance of a cloudy whey. Such "wheyed 

 off" milks have had the insoluble casein, the leading cheese constituent 

 of the milk, transformed into soluble peptone-like substances. This part 

 of the cheese solids is therefore dissolved or "digested" as it is said. When 

 such a change has occurred, recovery of the casein in the milk is impos- 

 sible. It is for this reason that the cheese yield from tainted milks of this 

 class is lower than from pure sweet milk. The unfairness of the "pound 

 for ten" plan of manufacturing cheese is evident under such circumstances. 

 With such defective milk, it is a physical impossibility for the cheese maker 

 to retain the entire casein in the cheese. 



The organisms producing these quick curdling and digestive fermen- 

 tations are, as ^a rule, bacteria that are associated with fecal matter which 

 finds its way into the milk in a variety of ways. 



SLIMY FERMENTATIONS. 



Not infrequently milk undergoes a marked change in its consistency, 

 becoming so viscous as to even string out in threads to some distance. 

 All gradations of this increased viscosity may be noted, from where the 

 milk is slightly thickened or sticky, through a slimy or slippery stage, to 

 that where it can be pulled out into long strings. A variety of terms have 

 been applied to the different phases of this series of changes to represent 

 the varying conditions that are to be noted. Thus, slimy or viscous milk 

 refers to an increased viscosity; ropy, stringy or thready milk, to where 

 the milk adheres to anything it touches, stringing out in threads often 

 several feet long. 



The causes of these various abnormal fermentations are due to the pres- 

 ence of certain species of bacteria that for the time being gain the ascend- 

 ency over the normal milk bacteria. Several different species have been 

 separated from samples of slimy or ropy milk. 



In some instances the sugar constituent of the milk is changed into 

 a viscous substance by the action of these organisms; in other cases the 

 proteid elements suffer. Ropy or stringy milk besides being unsightly 



