A mesophilic culture is a blend of bacteria that works at moderate temperatures, added to milk to acidify it slowly and build flavour as a cheese ripens and ages. You do not need one to make cheese at home, and you do not need one for any recipe in our kits. Our recipes are either acid-set, using citric acid, or set with fresh rennet, and they produce fresh cheeses that are eaten within days rather than matured for months. Cultures belong to the next stage of the hobby, and if you get there you will buy them separately and choose the strain to suit the cheese.
What does a culture actually do?
A starter culture is live bacteria. Stirred into warm milk and left for a while, it converts lactose, the sugar in milk, into lactic acid. That does three things at once: it lowers the pH, which helps the milk set and the curd expel whey; it changes the texture as the cheese matures; and, over weeks and months, it produces the flavour compounds that make an aged cheese taste of more than milk.
The word mesophilic means medium-loving. These bacteria are happiest at moderate temperatures, roughly kitchen-to-lukewarm, and they are the starters behind cheeses that are not cooked hot during making.
Thermophilic cultures are the heat-loving counterpart. They tolerate and prefer higher temperatures and are used where the curd is cooked warm during the make. Both are bought as sachets of freeze-dried bacteria, and both are chosen to suit a particular style rather than used interchangeably.
So why do the kit recipes not need one?
Because acidification and flavour are being handled another way, and because nothing is being aged.
In an acid-set cheese, citric acid does directly and in minutes what a culture would do slowly over hours: it lowers the pH of the warm milk until the proteins clump into curds. Ricotta, paneer and queso blanco work this way. The quick mozzarella method uses citric acid alongside rennet, which is what makes a stretched, glossy ball possible in about an hour instead of overnight.
In a fresh rennet-set cheese, the rennet coagulates the milk on its own and the cheese is eaten while it is young. There is no ripening period for a culture to work through, so adding one would change very little and add a long wait.
It is worth saying this plainly, because a great deal of cheese making writing treats cultures as a compulsory shopping item and leaves beginners convinced their kit is missing something. It is not. The kits make fresh cheeses, which is the right place to start, and fresh cheeses are exactly the ones that do not need a starter.
What can you make without cultures?
More than most people expect. Our Grand Cheese Making Kit runs to forty recipes, from ricotta, cream cheese and paneer through to mozzarella, burrata and pressed, brined and flavoured cheeses such as herb halloumi, with seven seasonings alongside the vegetarian rennet, citric acid and cheese salt. Everything in it is acid-set or set with fresh rennet.
The range comes from technique rather than from ingredients. Drain a curd lightly and you have something soft and spoonable; press the same curd under a weight and you have something you can slice and fry. Brine it and you have a halloumi. Stretch it warm and you have mozzarella. Wrap a mozzarella shell around curds and cream and you have burrata. That is a genuinely wide repertoire, and none of it waits on bacteria.
When would you actually buy a mesophilic culture?
When you decide to make cheeses that are ripened or aged: the hard, pressed, matured styles, the blues, the bloomy-rinded soft cheeses that develop over weeks. Those need a starter, often a specific one named in the recipe, and they need somewhere with a steady cool temperature and humidity to sit while they mature.
At that point you are buying cultures separately, by strain, and probably a few other things as well. That is a perfectly good place for the hobby to go, and the groundwork you laid making fresh cheeses is exactly what you need: reading a curd, hitting a temperature, judging a clean break, draining to a texture rather than to a clock.
What you should not do is buy a culture in the hope of improving a kit recipe. The recipe was not written around one, the acid or rennet is doing the setting, and adding bacteria to a cheese you plan to eat on Thursday will not give you cheddar.
Are cultures the same as the rennet in a kit?
No, and the two get muddled constantly. Rennet is an enzyme that coagulates milk directly; a culture is live bacteria that acidify it over time. A cheese can use one, the other, or both.
The rennet in our kits is a vegetarian one, a microbial coagulant from Rhizomucor miehei, so it is suitable for vegetarians. It is also the one active ingredient in a cheese kit, which is why it is worth using before the best before date on the box rather than long after. Dissolve it in cool, non-chlorinated water just before use, since chlorine from the tap and simple old age both weaken it.
Citric acid and cheese salt, by contrast, are stable and undemanding. Keep the kit somewhere dry and out of direct sunlight, reseal anything you open, and the ingredients will happily wait while you work down the recipe list over weeks or months.
Cheese culture FAQs
What is the difference between mesophilic and thermophilic cultures?
Mesophilic cultures work at moderate temperatures and thermophilic cultures prefer higher ones. Which you use depends on the cheese, and in particular on how warm the curd gets during the make.
Can I use yoghurt as a starter culture?
Live yoghurt does contain bacteria, but it is not a substitute for a named cheese culture in a recipe written around one. For the fresh cheeses in our kits no starter is needed at all.
Do I need a culture to make mozzarella?
Not for the quick method, which uses citric acid and rennet and takes about an hour. Traditional long-fermented mozzarella is a different process and does use a culture.
Does the cheese kit include cultures?
No, because the recipes do not need them. The Grand Cheese Making Kit includes vegetarian rennet, citric acid and cheese salt, which is what its forty recipes call for.
Can I age a cheese made from a kit?
These are fresh cheeses, made to be eaten within a few days to a week from the fridge, not built for ageing. Moving on to aged cheeses means cultures and controlled storage.
Want forty recipes and nothing to age? Have a look at our cheese making kits.
