Where does all the milk go?

In late 2024 I was shopping for milk when I started wondering how many cows -- or how many days -- it would take to produce my 1.5L bottle. I looked it up and found that the most productive dairy cows can yield fifty litres per day at their peak. Which means my bottle took roughly 43 minutes to produce. 43 minutes!!

My first reaction was that milk must be absurdly overpriced. If one cow can produce fifty litres a day, how is supply ever a problem? But that question quickly got overtaken by a different one. I was standing in the dairy aisle looking at the yoghurt, the cheese, the butter, the cream, the condensed milk, the powder, the ghee.. and it hit me -- hold on. This is all from milk? ALL of it? The same white liquid? How?

So I spent a few weekends Googling, and the answer was way more complicated than I expected. This post is me documenting that rabbit hole.

Why don't we just drink it straight from the cow?

People drank raw milk for thousands of years. Why can't we just.. do that?

Short answer: raw milk can carry salmonella, E. coli, and listeria, among other things. Before pasteurisation was widespread, diseases spread through raw milk were a genuine public health crisis. So yeah, we process it. But the processing is where things get interesting.

The journey from cow to carton

Once milk comes out of the cow, it's cooled immediately to slow bacteria, tested for pathogens, then clarified -- basically filtered to get rid of dirt and debris. Clarified milk is technically the first product -- clean, raw milk ready for processing. Standard stuff so far.

Dairy Production Process Tap any step for details Raw Milk Processing 🐄 Milking Raw Milk product Cooling Testing / QC Clarification Clarified Milk product Hover any step for details Milking Raw Milk Cooling Testing / QC Clarification Clarified Milk 🐄 Simple enough so far. Five steps from cow to clarified milk.

Then comes the first surprise. Milk isn't just one thing -- it's a complex mix of fats, proteins, vitamins, and minerals all suspended in water. The next step, separation, spins the milk in a centrifuge and splits it into two streams: skim milk and cream -- the first of many divergences in the dairy production process.

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