How Is Cheese Made?
By the BrainSnail editorial team. How these articles are written and checked, and how to tell us when one is wrong.
Cheese-making is at heart a way of concentrating milk so it keeps. Milk is mostly water, and cheese is what happens when you separate out the solids and control what grows in them. Every cheese in the world comes from variations on the same four basic steps.
The process, step by step
The process is remarkably consistent across styles. Milk is acidified with bacteria, then set with an enzyme so it forms a gel. That gel is cut, the liquid whey drains away, and what remains is salted, shaped and often aged.
Everything that distinguishes one cheese from another is a choice within those steps: which milk, which bacteria, how finely the curd is cut, how much moisture is removed, how long it ages and what is encouraged to grow on it.
Curds and whey
Milk contains casein proteins that normally float apart. Adding rennet, an enzyme traditionally from calf stomachs and now often produced by fermentation, clips off part of the protein so the casein molecules link into a network that traps fat and water.
Cutting that gel releases whey. The size of the cut is critical: small pieces lose more moisture and give hard cheeses like parmesan, while large gentle cuts retain moisture and give soft cheeses like brie. Heating and stirring drive out more whey again.
What the bacteria do
Starter cultures convert lactose, the sugar in milk, into lactic acid. This lowers the pH, which helps the curd set properly and makes the cheese hostile to spoilage organisms.
Different bacteria then shape the character. Some produce carbon dioxide, which is where the holes in Swiss style cheese come from. Others break down proteins and fats slowly during ageing, producing the compounds responsible for sharp, nutty or savoury flavours.
Why cheeses differ so much
A few variables account for most of the world's cheese styles:
- •Milk source, since sheep, goat and cow milk differ in fat and protein
- •Moisture, which separates fresh, soft, semi hard and hard styles
- •Surface treatment, such as washing the rind or introducing mould
- •Ageing time, from days for mozzarella to years for aged gouda
Mould on purpose
Blue cheeses are inoculated with a mould, usually Penicillium roqueforti, and then pierced with needles so air can reach the interior. The mould needs oxygen to grow, which is why the blue veins follow the channels.
Brie and camembert use a different mould applied to the surface, forming the white rind. It works inwards over time, breaking down the interior into that soft, oozing texture. In both cases the mould is deliberately chosen and controlled, which is why it is safe to eat while random fridge mould is not.
Why lactose intolerant people can often eat cheese
Lactose is the sugar in milk, and it is water soluble, so most of it leaves with the whey during draining. What remains is then consumed by the bacteria during ageing.
This is why hard aged cheeses such as parmesan, cheddar and gouda contain almost no lactose and are usually tolerated well, while fresh cheeses like ricotta and cottage cheese retain considerably more. It is a good illustration of how a preservation process incidentally changes the nutritional profile of a food.
The takeaway
Cheese is made by acidifying milk, setting it with rennet, cutting and draining the curd, then salting and ageing it, and every difference between cheeses comes down to choices made within those same four steps.