Experiments with Cardoon Rennet

Caseous Cardoons

The boss, Guy, has been growing a pic-1-a-harvestingvegetable called a cardoon on the farm for the last few years. It is a giant thistle from the same family as the artichoke; to prepare it the leaves are stripped back and the celery-like leaf ribs are braised and cooked. They are quite bitter but are much loved by the Italians and we have been making progress selling them in the boxes. The harvest is pretty much over by the end of June but we leave the plants to carry on into flower. They produce a stunning thistle head which we have used to decorate the restaurant or give out as free gifts in our veg boxes. I heard rumour a few years ago that cardoons could be used to make a vegetarian rennet for cheese making, but it had worked its way slowly down the to-do list. This year, heartened by a good crop, a good summer and a few rows of flowering plants, I have decided to give it a go.

The Benchmark
There is often a worry that culinary disaster see-saws opposite to experimentation in the kitchen; sometimes the fact that you can do something doesn’t necessarily mean that you should, especially with fringe methods. I could find plenty of reference to cardoon rennet cheeses in Italy and Portugal, but were these a tradition driven by thrift and circumstance rather than flavour? The setting enzyme from thistles are certainly rumoured to affect the texture; oddly the resulting cheeses seem to get runnier as they age and are often eaten by removing the top and scooping and dipping like a room temperature fondue. The taste too is said to be affected; a slight bitterness is transferred, which is characteristic of the thistle family as a whole. The one strict rule was that any cheese must be made from sheep or goat’s milk only, as the reaction with cow’s milk renders the whole thing unpalatably bitter. That rules out the milk from our dairy herd.Pic-2-Cardo-cheese

In the UK all paths led very swiftly to a lady called Mary Holbrook in Somerset. She produces a seasonal batch of washed rind goat’s cheese called Cardo.

Chef Craig from our restaurant the Riverford Field Kitchen stopped into Neal’s Yard Dairy in London while visiting our pub, The Duke of Cambridge, and managed to bring me back half a round of it to deepest, darkest Devon. It was, by any standard, a great cheese. Any concerns about taste and texture were soon put to rest and the faint bitterness balanced well with the briny pong from the rind. As a benchmark it is quite a thing to aim at, but at least I now know that it is worth the effort.

A Lunchtime Well-Spent
Toward the end of August, the flowers are almost all in bloom. The tightly armoured thistle heads have burst open into a splay of bright purple two-inch stamens. There is something a little punkish about them, like a field of gently nodding mohawks. Feelers have been put out to a few of our cheese suppliers and a sample has been promised to Gary Jungheim of the nearby Country Cheeses shop to have a play with.

I have made somepic-3-harvesting-flower-heads progress in trying to track down the elusive Mary Holbrook, too. I’ve decided to harvest about 300 flower heads, enough to get a decent yield but not so much that I affect the harvest of flower heads destined as a free gift in the veg boxes. To be honest an angry farm manager is the least of my worries; it seems that cardoon flowers are the place to be seen for the local bee population. Open, accessible and brazen in their flourishing, each flower contains at least one happily grazing bee. Deciding to spread the threat, I managed to cajole a handful of volunteers into giving up a lunchtime to weave in and out of the triffid-like plants and brave the bees. A blessedly sting-free 30 mins later and we have our harvest.

At Home with the Onions

pic-4-removing-the-stamensArmed with a sharp serrated knife I’ve set aside a few hours early on a Friday to scalp my cardoons. I’ve managed to recently get hold of Mary Holbrook and she kindly gave me all the help and encouragement I could have hoped for. She confirmed that it was indeed the bright purple stamen that I needed to collect and dry. They can then be crushed to a powder in a pestle and steeped in warm water to make a rennet.

Jason from our maintenance team let me pinch a few metres of fine mesh netting from our new poly tunnel and between us we rigged a simple hammock structure in the roof of our onion drying store. The stamen cut away pic-5-removing-the-stamenswith ease, but the bees refuse to abate, so as I created a cardoon pollen mother-lode I choose to adopt a stoical trance, amidst a growing swarm, as I work. The stamen are spread evenly in their mesh hammocks and left to dry in our onion store, where the hot air created by our store fridges is harnessed to hasten drying.

The Wait

I check the cardoon stamen after the weekend and am amazed to find that they feel pretty much dry already. I gently rake and turn them to make sure they are evenly spread and decide to leave them for at least two weeks just to be sure.
I use the intervening time to gather as much info as I can on how to use the stamen to the best effect, and also to muse as to what end this experiment may lead. I thought at the least it could be an interesting experiment but am wondering if it may lead to the possibility of producing a small run of sheep’s cheese each pic-6---drying-and-turning-the-stamenssummer when the cardoons flower. Guy has been getting some good media for his cardoons and the word is starting to spread.
As with his artichokes, he tends to grow them for the love rather than the money so I’m sure they’ll be a long term fixture on the farm. It would be a nice cycle to in effect harvest the same crop twice before ploughing the remains back into the field; botanical thrift.

Bag and tag
The stamen are bone dry and have an audible dry rustle to them. I try pressing some firmly between a sheet of soft paper and there is no liquid blotting at all. Once gathered and weighed it seems that I have just over 5kg of dried stamen. They have faded in colour but there is still a purple tinge to them, the scent is still strong and almost a little overpowering when gathered in one place. Our recipe box packing team kindly offer to try vac-packing them for me but they are so light and delicate that the machine keeps sucking them from the bag as the air is purged. We opt for a tightly hand-sealed bag instead. I drop some in to Country Cheeses in Totnes, save a few bags for myself and send the rest to our suppliers High weald farm and Wootton Dairy, who both supply us with wonderful sheep’s cheese in various forms. The die has been cast, now to see if we can roll a few sixes.



Bob Andrew,
Riverford Chef

11 responses to “Experiments with Cardoon Rennet

  1. What a great idea. Good luck!

  2. Good luck, I hope it turns out really well, fingers crossed

  3. Hope the price won’t be to exclusive. Really fascinated to see good use of the crop.

  4. Great blog Sir!

  5. Bless you for try this hope it is successful. Look forward to hearing how you get on.

  6. Loving the gung ho, derring-do attitude!

  7. That’s really interesting. A truly vegetarian rennet!
    Brilliant 🙂

  8. Fascinating! You say that—if it works at all, it will be with sheep or goat’s milk I wonder if it would work with soya or almond milk.

  9. Hi I would really like to get hold of some dried cardoon stamens. I wonder if anyone can help🤞
    Many thanks

  10. Hiya!

    I’m looking for dried cardoon stamens as well. 🙂 🙂 🙂
    Could you please help us?

    Ps: portuguese chap here. … cardoon is what my granny used for her cheese 🙂
    Together with goat’s milk, pure or mixed with cow’s milk.

  11. Great article, I been making cheese with my mother ever since I can remember here in Toronto, Canada. In fact, just made 8L worth using cardoon as my rennet source. We pick the cardoon thistle tops in the fields where it grows wildly around my family’s property in Portugal and bring it back home with us . We make fresh soft cheese using cow’s milk 2% or 3% ready to eat the next day. It’s easy to make and delicious. You can find many videos on YouTube on how to make this cheese by searching “how to make Portuguese cheese.

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