First, as the milk leaves its healthy environment it enters a much harsher environment of possible contamination. It is here that the milk producer has the ability to control the quality of milk by preparing and keeping a clean milking area and practicing a proper sanitation routine.
Next, in commercial milking, the milk moves through the tubes, pipes, and pumps into the refrigerated tanks, where more physical changes begin to take place:
1. During handling, fat globules can be damaged, releasing enzymes that may cause problems in ripening.
2. During cold storage, some of the calcium can go into solution, resulting in weakened curds.
3. Also, during cold storage, undesirable bacteria that grow well at these cold temperatures can increase to very large populations.
As the milk is transported and then cold stored again, the above problems begin to accelerate. Since the lactose in milk is a good food supply for many types of microbes, all of the above conditions translate into a deteriorating milk quality. So, to safely preserve this milk for the public, something has to be done...