224 UNSWEETENED CONDENSED MILK DEFECTS 



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. It indicates that these cans received relatively little 

 heat in the sterilizer, otherwise the curd would have a darker 

 color. This defect usually 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 variety of species of 

 bacteria, yeast and torula that are capable of producing a bitter 

 curd, either direct, or through the secretion of casein-curdling 

 enzymes, and while these different species of micro-organisms 

 come from a variety of sources, the most common sources are, 

 the soil, pasture, water and the udder itself. It is a noteworthy 

 fact that this defect is most commonly found in milk and milk 

 products when the cows are on pasture. It is, therefore, probable 

 that, in most cases, this troublesome germ is carried into the milk 

 on the farm. 



Again, in summer, at a time when this defect generally 

 occurs, the effect on the cows of the summer heat and flies, and 

 the tendency toward high acid in milk, render the milk most 

 sensitive to the sterilizing heat. The operator finds it difficult 

 to avoid the formation of a disastrous curd in the sterilizer. In 

 order to guard against this trouble he is tempted to either lower 

 the temperature, or shorten the duration of the sterilizing process. 

 This tends towards incomplete sterilization. A very frequent 

 result of this incomplete sterilization in the early summer 

 months, is the formation of a bitter curd. When the processor 

 returns to the proper sterilizing process, the occurrence of bitter 

 curd in the cans disappears and the product is normal. 



A further safeguard against the recurrence of this trouble 

 lies in providing for uniform distribution of heat in the sterilizer. 

 If the cans have to be stacked in deep tiers, which is un- 

 desirable and should be avoided, slats should be placed over 

 the top of every second row of cans. This will make possible 

 the free access of steam to at least one end of each can. If the 

 circulation of steam in the sterilizer is poor, the uniform distribu- 



