That page has some half truths and incomplete info. Yes, raw milk does contain lipase, but that page seems to say that all lipases are somehow equal. For example, "Lipase (pronounced lie-paze) is one of at least 60 enzymes living in real milk. " This is not technically true. It's true that you can call an enzyme that degrades fats a lipase, but there is only one lipase in milk that has any really significant lipolytic activity. It's called a lipoprotein lipase. The rest of the lipases have such little ability to break down fats that they hardly register when doing a tributyrin assay.
Lipases also have distinct preferences of what they cleave on the glycerol substrate. If you look at the first pic, it illustrates that lipases will cleave all three positions. This is absolutely not true for all lipases. Some lipases may cleave all of them, but there is a huge difference among milks of the structure of fat globules, and there is a difference among calf, lamb, and kid lipases in terms of their cleaving preference. Calf lipase, for example, will not preferentially cleave the last position in the triglyceride, whereas kid lipase will. That's why you get more sharp flavor when using kid lipase.
What causes lipolysis in milk is as the page says, first, damage to the milkfat globule membrane starts the process of lipolysis. And second, the lipoprotein lipase can act on the globules, so can lipases that bacteria excrete, and of course, if you add pre-gastric esterase, it will act as a lipase on the fat.
The mechanism of fat membrane globule degradation is not well known yet, but it seems to be triggered by some sort of balance of the natural enzyme levels in the milk and temperature.
Agitation will ruin milk for cheesemaking. That's why those cheap little pumps are a problem - the impellers really increase acid formation.
