Ravioli without borders: Liquid pea ravioli

(This post was our first venture into the world of spheres, but not our last.  To learn about liquid mango ravioli, click here)

I can't believe I did it, and on my own, too.

In a career chock full of signature creations, there may be no dish more identified with Ferran Adria and El Bulli than liquid pea ravioli, and no molecular gastronomy preparation generates more amazement and discussion.  It is kitchen alchemy, really, and it captivates me.

Liquid ravioli derive their name and their mystery from the fact that the entire raviolo is, well, the filling, and a liquid filling at that.  The ravioli I made, for example, are made from nothing but peas, mint, water, and two very special ingredients.  There's no pasta, no shell of any kind; it's just filling.

I still remember the first time I saw liquid ravioli (cue the dreamy music).  I was watching a documentary about Adria hosted by Anthony Bourdain, Decoding Ferran Adria.  There is a moment in El Bulli's workshop early in the show where, after much debate, the production crew is allowed to tape the kitchen team making mango liquid ravioli, though no ingredients or technique are revealed.

Subsequently, two people are shown preparing pea liquid ravioli.  The viewer sees one person take a spoonful of pea soup, drop it gently into what appears to be nothing more than water, and have it turn instantly, magically, into a yolk-shaped raviolo (to view the clip, click the image of the pea ravioli here).  Serve on a Chinese soup spoon sprinkled with a little sea salt, and, voila, the pure taste of pea in a way never imagined.  Jaw dropping!

From the moment I saw it, I didn't just want to taste it, I wanted to make it.  Actually, that's not entirely true.  More than anything, I wanted to know how to make it. Therein lies the problem, because this recipe seemed to be the most closely guarded secret in gastronomy, unless you include how they get the caramel inside the Caramilk bar.

My big break came from an episode of Chef At Large, a Canadian-produced programme on Food Network Canada.  This particular episode featured the husband and wife team of DC Duby, Vancouver-based molecular patissiers and chocolatiers (view a post about their Science Kit here, or about their chocolates here and here) who also happen to make liquid ravioli.  The show revealed that the two agents responsible for liquid ravioli are (drumroll, please)...

... calcium chloride and sodium alginate.

Mmmm... sodium alginate.

Once I knew that, all it took was a Google search to reveal all.

So, how does it work?

Sodium alginate, which is derived from seaweed, is a common emulsifier and thickener in the food industry.  If you've ever wondered how a McDonald's apple pie maintains its jam-like consistency, wonder no more.  When sodium alginate meets calcium chloride, the sodium ions in the alginate are replaced by calcium ions, thus creating a polymer skin that holds everything inside (read more here).

The first obstacle is knowledge, but the second obstacle is almost as challenging: finding food grade sodium alginate and calcium chloride.  There are many, many companies in China willing to sell a couple of tonnes of either, but it was damn near impossible to find companies that would sell in quantities suitable for the home cook.  The best thing to come of all this was finding an online supplier who will soon be selling both ingredients, especially since this company already sells virtually all the molecular gastronomy ingredients I need .  As soon as I receive word that both ingredients are available, I will post a link to the supplier.

The supplier, L'Epicerie, now has calcium chloride and sodium alginate for sale.  Check out this post for details.

Sodium alginate and calcium chloride in hand, I decided to experiment with instant coffee before taking the big green plunge. Aside from the fact that there are few things more vile than instant coffee, the experiment was a success -- I ended up with slightly misshapen ravioli that tasted exactly like the loathsome instant coffee with which I made them.

It was time to make pea ravioli.  My first decision was what to put in the pea mixture.  I found a recipe for pea soup in El Bulli: 1998-2002, and decided that was my best bet.  El Bulli's pea soup is made from only three ingredients -- peas, mint, and water -- so my mixture was too.  After a little fussing and a lot of worry, it was time for the big test.  I scooped up a little of the now pea and sodium alginate mixture, and slowly tilted it into the calcium chloride and water bath.  The shape was ugly, but it gelled properly.  I had ravioli. After a little fussing, I even managed to get the shape right too.  The ravioli were excellent -- they taste like peas -- though I'd like to play with the recipe to see if I could intensify the flavours, perhaps by using less water.

I still have a lot of learning to do.  The problem with the mixture is that the ravioli must be eaten as soon as possible, because the reaction between the calcium chloride and sodium alginate does not stop.  This means that, left alone, the ravioli will in fact turn into solid balls.  My Spanish is poor, but I believe this site says the El Bulli team solved this problem by reversing the use of the critical ingredients: putting the calcium chloride in the food mixture instead, and then immersing it in a sodium alginate bath.  I've also learned through my research that this does not work with highly acidic bases like orange juice, unless something is added to neutralize the acidity.

Who knew studying chemistry could be so fun?

Rob's liquid pea ravioli

For the pea mixture:
260 grams frozen peas
325 grams water
5 large mint leaves
3 grams food grade sodium alginate (approx. 1 tsp)

For the bath:
1500 grams cold water
10 grams food grade calcium chloride (approx. 2 tsp)

1. In a 23 cm x 23 cm x 5 cm (9 x 9 x 2) baking dish, combine water and calcium chloride.  Whisk until calcium chloride is dissolved, then store in the fridge.

2. Meanwhile, cook frozen peas in a small amount of water for four minutes, adding mint leaves for the last five seconds of cooking. Drain, then shock immediately in a cold water bath for three minutes.

3. Combine water and sodium alginate, and blend with an immersion blender until the sodium alginate has dissolved into the water.  The water will thicken considerably.  Bring to a boil over high heat, stirring constantly.  Remove from heat and allow to cool to room temperature.  When cooled, blend with pea mixture using an immersion blender until the mixture is smooth.

4. Remove chilled calcium chloride mixture from fridge.  Scoop pea mixture into a tablespoon measure in the shape of a half-sphere. Set the bottom of the tablespoon measure against the surface of the calcium chloride mixture, then pour the mixture in with a gentle turn of the wrist (to view a video of this being done, click the image of the pea ravioli here).  Leave ravioli in the calcium chloride mixture for two minutes.

5. Gently remove the ravioli from the calcium chloride bath using fingers or a slotted spoon. Place in another 23 cm x 23 cm x 5 cm (9 x 9 x 2) baking dish filled with cold water or rinse gently under running water.

6. Top with a couple of grains of sea salt and serve immediately.

Comments

[rob]

Helen, thank you and I hope you buy the ingredients (the post is coming soon, I promise) and try to make liquid ravioli yourself.

Sam and Bron, I'm somewhat speechless. It's heartening to know that so many people are interested in this little effort.

Owen, thanks for the compliment, but more importantly, thanks for the advice. Chemistry is not my forte (let's hear it for history degrees!), so I'm a little... challenged in that regard.

Luther, I actually bought my sodium alginate at naturalhealthsupply.com and was pretty darn unhappy with the service. I had no idea calcium chloride is available homebrew and cheesemaking shops. Do you know how it's used in those processes?

yes indeed the site in spanish says that
nice work

[Digijam]

Hey Rob - great results!

For working with more acidic ingredients El Bulli uses sodium citrate rather than bicarb. I guess the amount needed depends on the ph of the ingredient, but for mango ravioli they use 1.3g alongside 1.8g of alginate and 250 g of water, boiling and cooling then adding 250g of juice.

[JMG]

I'm surprised that the reaction continues; isn't that the reason for putting it in a cold water bath or rinsing under cold water at the end? Have you tried a brief immersion in an ice bath to stop the reaction?

[Tyler]

Wow, this is unlike anything I have seen. I too am very impressed with your investigation and execution of this one. Now I just have to find a way to convince Amanda to try to make it ;)

[rob]

Anon, thanks for confirming my hunch about the Spanish site.

Digijam, thank you for the compliment and thank you very, very much for the tip about the sodium citrate. I've also seen a recipe for apple caviar that uses baking soda. I assume this is also to lower acidity, but I'm not sure. Any idea what the differences are between the two?

JMG, I don't know enough about chemistry to explain it properly, but unfortunately the reaction cannot be stopped so simply. The Spanish website I mention in the post, states that the chefs at El Bulli were confronted by the same problem and overcame it by adding the calcium chloride to the food mixture, and then adding that to a sodium alginate bath. Problem is, I'd have to start really playing around with the chemical proportions to make that work.

Thanks, Tyler, I hope you and Amanda give this a try. It's always fun to go out on a limb in the kitchen.

[Tom Mikkelsen]

So, anybody find a commercial source for the Calcium chloride?

Thanks TM

[Chubby Hubby]

Wow. This is amazing. And to think I was congratulating myself form making foam. Sigh...

[David]

that's just wacky!

[JMG]

Rob, I realized the error in my thinking shortly after I posted that. It makes sense that the reaction would continue regardless of temperature.

I've got my alginate and calcium chloride in the mail from Room 4 Dessert in New York, and I can't wait to give this a shot!

[Digijam]

As far as I can tell, Sodium Citrate reduces acidity, yet is sour (and salty) and so less prone to spoiling the flavour. Sodium bicarb on the other hand, is alkaline, so could easily add a bitter taste. Which is presumably why jello manufacturers work with Citrate rather than bicarb. If only I'd paid more attention in chemistry class...

[Brett]

Rob, in case you don't already know, the book with all the recipes and techniques for the 2005 season at El Bulli has been released (approx. 75 Euros). The book for the 2003-04 season was released last year. Both, however, are in Spanish. Please apologize to your wife that I gave you this info;-) Keep up the great work! So much fun to read.

[teri]

That is one of the sexiest green food things i've ever seen! i wish you had an "Email this page to a friend" thing going on.

teri

[loukoum°°°]

Thanks a lot! I discovered the liquid pea ravioli here and manage to make some with your receip!

[David]

Frankly I am beyond words!

I saw this episode (Decoding) last year and was enthralled. I would LOVE to try and make this at home.

Never been to your site before but will be returning soon.

The saying may date me...but you RULE!!

[in2food]

Hi Rob-
Love the blog. Im writing a magazine story on molecular cusine, and I wonder if you would be willing to talk with me?

Thanks in advance

[rob]

in2food, I would happily assist you, but you've left no contact info. You can email me using the "Email me" link on this page.

[Doti]

Yup..Bourdain was also my first gate to Adria, but I'm just on the way on making it..wish me luck!

Love your site, a lot! xD

Doti - Indonesia

[Stefan]

Rob, thank you for sharing so much great insight. I just made the ravioli tonight and was surprised to see it worked exactly as advertised, even with my hackneyed proportions (grams? Lets see thats two kings-finger's right..) As it turned out mine were very much fried-egg-yolk-shape, and I was wishing I could make them more spherical (pop up) like yours (are those flat on the back?); I suppose the pea is always greener on the other spoon. I was having a bit of trouble with the mix sticking to the spoon and I found swishing the 'dipping' spoon with a little cal carb mix before dosing helped. I also finished with a touch of cinnamon which people seemed to like.
Thanks again for sharing so much knowledge.

Stefan

[Nadia]

We don´t have much info about molecular gastronomy in Brazil, but I visited your site and loved your recipe. I intend to try it on the first opportunity. I will be in NY next week and will buy the chemicals... tell you later about the results. Thank you!

[PATRICK]

I like to try to make foie gras caviar any idea?

[st]

the idea does sound interesting. til i found out how it was made:P omg i didn't know that calcium chloride and sodium alginate are actually edible! i played with those duringmy science practical. ewww.

[Kraig]

I want to try linguini shaped ground shrimp

[pixen]

thank you so much for the info! I can't wait to try it ot...somehow :-D

[Mr.Q]

Hi! your article was very informative but I wanted to know what you meant by "...does not work with highly acidic bases like orange juice..." do you just mean it won't work with highly acidic and basic substances?