Vegetarian rennet is a coagulant produced by a microorganism rather than taken from an animal, and for the fresh cheeses most people make at home it works as well as animal rennet does. The rennet in our kits is a microbial one, from Rhizomucor miehei, which means the cheese you make is suitable for vegetarians. Animal rennet, by contrast, is chymosin from the stomach lining of a calf. Both do the same job to the same pan of milk: they turn it from a liquid into curds and whey. Here is what each one is, where the differences genuinely show up, and how to get the best out of the vegetarian sort.
What is vegetarian rennet made from?
The vegetarian rennet used in home cheese making is microbial. A fungus, in our case Rhizomucor miehei, naturally produces an enzyme that behaves on milk protein very much the way calf chymosin does. The enzyme is grown, collected and standardised, and what reaches your kitchen is a coagulant with no animal material in it at all.
That last point is the one that matters to most people asking the question. A cheese made with microbial rennet can be eaten by vegetarians, which is not true of a cheese set with calf rennet, however excellent it may be.
It is worth separating vegetarian rennet from two things it often gets confused with. It is not the same as the plant coagulants sometimes used in traditional cheeses, such as thistle or nettle, which behave quite differently and give their own flavours. Nor is it an acid: citric acid, lemon juice and vinegar also curdle milk, but by lowering the pH rather than by enzyme action, and the curd they give you is a different animal entirely.
How is animal rennet different?
Animal rennet is the original. Chymosin from a calf's stomach is very good at what it does and has several thousand years of cheese behind it, which is why so much traditional European cheese is still made with it.
The differences people talk about show up mainly in cheeses that spend a long time maturing, where the coagulant keeps quietly influencing texture and flavour over months. For a fresh cheese eaten within days, the difference in the result is negligible. Your mozzarella does not know which one set it.
That is precisely why our kits use vegetarian rennet. The kits make fresh cheeses, the outcome is the same, and using a microbial coagulant means nobody has to check before they eat the ricotta.
Does vegetarian rennet work as well?
For the cheeses in the kits, yes. Warm the milk to the temperature the recipe gives, stir the prepared rennet through, and leave it alone. You will get a set, you will get a clean break, and you will get curds that cut and drain properly.
Where people run into trouble, it is nearly always technique rather than the rennet itself. Milk that has been UHT treated or ultra-pasteurised will not set with any coagulant, vegetarian or animal. Milk at the wrong temperature sets badly or not at all. And rennet that has been mixed into chlorinated tap water, or that has sat around for a long time, will be weaker than it should be.
Fix those and microbial rennet is entirely dependable. It is the standard coagulant for an enormous quantity of cheese made commercially, which tells you most of what you need to know about its reliability.
How do you prepare and use it?
Dissolve the rennet in cool, non-chlorinated water. Cooled boiled water or bottled water is ideal, because chlorine from the tap can weaken the enzyme before it ever reaches the milk. Mix it fresh, just before you use it, rather than preparing it in advance.
Then stir it gently but thoroughly through the warm milk. Thoroughly matters because a pocket of milk the rennet never reached will not set; gently matters because thrashing the milk about while it is trying to gel gives you a ragged curd. A slow figure of eight for a few seconds, then stop, then leave the pan completely still.
Check for the clean break before you cut. Dip a clean knife or a finger in at an angle and lift: a curd that splits cleanly, with clear whey filling the gap, is ready. If the split is ragged and the whey looks milky, cover the pan and give it a few more minutes. Cutting too early is the commonest cause of tiny curds and a cloudy whey full of escaped cheese.
Our Cheese Making Kit, Cheeses of the World supplies the vegetarian rennet ready to use with a measuring guide, alongside citric acid, cheese salt, a thermometer, moulds and cheesecloth, so there is no guessing at quantities on your first go.
How should you store it?
Rennet is the one active ingredient in a cheese kit, and it is the reason the best before date on the box is worth paying attention to. Keep the kit somewhere ambient, dry and out of direct sunlight, and use the rennet before the date rather than long after it. The dried ingredients in a cheese kit keep a long time once opened, so you can spread your batches over weeks or months, but an active coagulant is the part that can quietly lose strength.
If you are ever unsure whether your rennet is still lively, the milk will tell you within the hour. A set that is slow, soft and never quite gives a clean break, on fresh whole milk at the right temperature, is a rennet that has had its day.
Vegetarian rennet FAQs
Is vegetarian rennet vegan?
The coagulant itself contains no animal material, but the cheese you make with it is dairy, so it is vegetarian rather than vegan.
Does vegetarian rennet taste different?
Not in a fresh cheese eaten within days. Differences between coagulants show up mainly in cheeses matured over months, which is not what home kits are making.
Can I use lemon juice or vinegar instead of rennet?
For acid-set cheeses such as ricotta and paneer, an acid is the setting agent and works well. For rennet-set cheeses it is not a substitute, because the curd it makes behaves differently.
Why has my rennet stopped setting milk?
Check the milk first, since UHT and ultra-pasteurised milk never set. After that, suspect chlorinated tap water used to dissolve the rennet, the wrong milk temperature, or rennet kept well past its best before date.
How much rennet do I need?
Follow the recipe rather than a general rule, because the quantity depends on the volume of milk and the cheese you are making. Our cheese kits supply the rennet ready to use with a measuring guide.
Ready to set your first curd? Take a look at our cheese making kits.
