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.