Topics Food and drink

How is cheese made?

Cheese is made by separating milk into solid curds and liquid whey, then shaping, salting and often aging the curds. Bacteria turn milk sugar into acid, and an enzyme mix called rennet helps the milk proteins link together into a gel. That gel is cut, warmed, drained and pressed into the cheese you recognize.

What makes it interesting is how little the starting ingredients change from one cheese to the next. Cheddar, mozzarella, brie and parmesan all begin with milk, microbes and salt. The differences come from small choices: how much acid, how finely the curd is cut, how hot it gets, how much whey is pressed out, and how long and in what conditions it ages. Molds, bacteria and time do much of the final work.

An episode on this would walk through the process in order, from milk to the aging room, and explain why a soft fresh cheese and a hard aged one are cousins. The hosts at bre are AI, so they can make mistakes, and you can press Talk to ask about any step, like why cheese melts or what rennet is.

What a bre episode would cover

An outline of the episode bre would make for this question. Every episode is written fresh when you ask, so yours will differ.

  1. Milk and what is in itCheese begins with milk's proteins, fat and sugar. Cows, goats, sheep and buffalo all give milk that can be made into cheese, with different results.
  2. Starter bacteria and acidBacteria eat lactose and make lactic acid. That acid changes the milk and sets the flavor foundation for the cheese.
  3. Rennet and the curdRennet contains enzymes that cause the main milk protein, casein, to clump into a gel. Some cheeses use mostly acid instead.
  4. Cutting, cooking and drainingCutting the curd lets whey escape. Smaller pieces and more heat generally mean a drier, firmer cheese.
  5. Salting, pressing and shapingSalt adds flavor, slows unwanted microbes and draws out moisture. Pressing and molds give the cheese its form.
  6. Aging and rindsDuring aging, enzymes and microbes slowly break down proteins and fats. Molds and washed rinds shape flavor, and what happens inside is still partly a craft.
  7. Why cheeses differFresh, soft, semi-hard and hard cheeses come from the same basic steps with different choices along the way.

How the episode might open

A sample exchange between two of bre’s AI hosts, bre and Tess. Both are AI; this is written by AI, as every bre episode is.

  1. breAI host

    Okay, I want to start with a glass of milk. It's liquid, it pours, and somehow people turn it into a block you can slice. What actually happens in between?

  2. TessAI host

    Short version: you make the milk curdle on purpose. Bacteria sour it a bit, and rennet makes the proteins grab onto each other. Suddenly your milk is more like a wobbly gel.

  3. breAI host

    A wobbly gel, that's the first picture. Then someone cuts it into little cubes and the liquid starts leaking out.

  4. TessAI host

    Right, that liquid is whey. And the solid bits are curds. Most of cheesemaking is deciding how much whey to get rid of.

  5. breAI host

    So the cheese in my fridge is basically a decision about water.

  6. TessAI host

    Pretty much. Wetter curd stays soft and fresh. Drier, pressed curd can sit around for months. Same milk, totally different cheese.

  7. breAI host

    And I'm guessing aging is where it gets weird, because I've seen cheese with mold on purpose.

  8. TessAI host

    Oh, it gets weird. Okay, but real talk: some of the best flavors come from microbes doing slow work in a cool room. Let's go through it step by step.

Questions people also ask

What are the basic steps of making cheese?
Most cheese follows the same outline: warm the milk, add bacteria and rennet, let it set into curd, cut the curd and drain the whey, salt it, press or shape it, then age it if it is that kind of cheese. Fresh cheeses skip the aging.
What is rennet?
Rennet is a mix of enzymes that causes casein, the main protein in milk, to clump into a gel. It traditionally comes from the stomachs of young calves, but similar enzymes are also made by microbes and some plants.
What is whey?
Whey is the watery liquid left behind when milk curdles and the curds are drained off. It contains water, some proteins and milk sugar. It is used in other foods, and some cheeses, like ricotta, are made from it.
Why does cheese have holes or mold?
Some cheeses have holes because gas-producing bacteria release gas as they age, as in Swiss-style cheeses. Molds are added or encouraged on purpose in cheeses like brie and blue cheese, where they change texture and flavor.

Related topics

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bre’s hosts are AI, and every episode is generated, so they can be wrong: check anything that matters. This page outlines what an episode would cover. It is for interest and learning, not medical, financial or legal advice.