Curds and whey: how cheese is made

The only ingredients in artisan cheese (except those with added flavourings such as spices or alcohol) are milk, salt, rennet and a starter culture. The milk can come from cows, goats, ewes, buffalos (and even camels). The majority of British artisan cheeses are made from cow’s milk, but ewe and goat cheeses have become much more popular over the last few decades. It goes without saying that a high quality cheese can only be made using the best milk available, which is why many artisan producers use their own herds or buy from local farmers – it takes roughly ten kilograms of milk to produce just one kilogram of cheese, so it’s important to ensure it is rich, full-flavoured and creamy.

Milk is either pasteurised or left ‘raw’, depending on the cheesemaker’s preference. It is then heated up to no more than 40°C and a strain of bacteria known as a starter culture is added. These are often kept secret by producers and passed down over generations of cheesemakers, or can be bought from specialist companies. Starter cultures work as an acidifier, thickening the milk, increasing the amount of good bacteria in the liquid and adding unique flavours. For some fresh cheeses, lemon juice or vinegar is used instead.

Once the cultures have done their job, a coagulant is added to separate the cheese into solids (curds) and liquids (whey). In cheesemaking, this is known as rennet. Traditional rennet is an enzyme found in the stomachs of young mammals known as ruminants (a family of animals which cows, goats and sheep all belong to). This makes the cheese unsuitable for vegetarians, however, so many modern cheesemakers use vegetarian rennet, made from certain plants, instead.

Once the milk has separated, cheesemakers are only concerned with the curds – the whey is drained away and can be used to make different products such as whey butter or ricotta, used in baking or turned into plant fertiliser. How the whey is drained and the remaining curds are handled makes all the difference to the final texture of the cheese. Fresh cheeses are generally left uncut and are ready to eat at this point.

For soft cheeses, curds are often gently ladled out of the liquid and left to drip-drain in moulds. For harder cheeses, however, there are several methods producers use to get rid of any leftover whey. The curds are cut (the smaller the pieces, the more whey is removed), stacked on top of each other (the pressure squeezes out extra whey), cooked and pressed. All these different methods result in different textures.

It’s at this point that the curds need to be salted. As well as enhancing the flavour of cheese, salt helps to preserve the curds and stops unwanted bacteria forming in the curds and helps form a rind on the surface. Salt is added at different stages depending on the cheesemaker – some even soak the curds in brine.

Apart from fresh varieties, cheeses need time to develop, be it for a few weeks or several years. This allows them to form a rind whilst in their moulds and take on new flavours. Traditionally, caves were a popular place to age cheeses as they had a stable temperature and humidity, but these days environmentally-controlled rooms are used to ripen cheese in a safe and consistent way.

There are all sorts of methods used by cheesemakers during maturation – blue cheeses are sprayed with penicillium roqueforti then pierced using steel needles to promote mould growth; soft bloomy cheeses are inoculated with another type of bacteria to achieve the perfect rind. Large wheels of cheese such as Stilton are turned daily to ensure an even distribution of moisture, while washed-rind cheeses are covered in alcohol such as cider, brandy or beer to further enhance the flavour. Some are even smoked or blended with other ingredients such as spices or leaves. All these artisan techniques result in wildly different flavours and textures in the final product, which is what makes cheese one of the most interesting – and loved – foods in the UK today.