pineapple spheres

Molecular Gastronomy – Spherification

On my blog I write about food science a lot, discussing chemistry, physics and microbiology and applying all of that to the food I make in our kitchen. Just today I realized I haven’t really used the term molecular gastronomy yet. This despite the fact that most of what I’ve been doing could be called molecular gastronomy. Therefore today will be about molecular gastronomy, focussing on one of its branches: spherification.

Molecular Gastronomy

Molecular gastronomy as a term is several decades old. At the time, food science was all about industrial food production: scaling up food processing, preservation of products, etc. However, studying the science of regular home cooking, wasn’t part of food science at the time! This is how molecular gastronomy came to be, it isn’t a separate science within food science, but a different way of applying food science. So it started applying physics, chemistry and microbiology in home cooking!

In my opinion, most of my blog is all about molecular gastronomy since I write about the science of cooking. Understanding why jam is made the way it is, why a roux becomes brown, how enzymes work or why leafy vegetables shrink during cooking could all be considered molecular gastronomy.

I prefer not using the term molecular gastronomy for this though. Most people will think of fancy new technologies and ingredients when it comes to molecular gastronomy and I do not want to confuse people.

But today will be different, today will be about fancy new technologies. Not because I use them in my kitchen regularly (not at all really), but because I recently followed a workshop on this topic and simply because it involves science and food and that’s what this blog is all about!

Today we”ll start with spherification.

New techniques

As mentioned above, molecular gastronomy isn’t new, nor are the techniques I’ll be discussing below. But they are new compared to the traditional cooking techniques which have been used for centuries. Even though the equipment used is new (think food processor), it still isn’t more than cutting up food. The techniques we’ll be discussing today are newer and haven’t necessarily been used that long.

Spherification

Spherification is probably one of the most hyped techniques when it comes to molecular gastronomy. It is a great technique to cause a surprise. It’s a new way to present known flavours and a perfect way to confuse people’s sense.

In spherification spheres (= balls) are made of just about any type of liquid. When making a small balls the entire ball might be solid, gel-like. However, when making larger spheres (think the size of an olive) the outside tends to be set, whereas the inside is still liquid. This is part of the surprise when eating: the sphere bursts open inside your mouth

Some surprising examples: make a dark coloured pineapple juice and into the shape of a olive. It will look like an olive, but taste like pineapple! Or make a ravioli that tastes like peas.

Alginate & calcium ions – two component glue

One of the most common ways to make these spectacular spheres is by using alginate and calcium. Calcium is an ion (Ca2+), alginate is a complex longer molecule and is harvested from seaweeds. There are various types of alginates, not all work as well as for spherification.

For a sphere to be formed a firm enough outer layer has to be made, a gel. When making a gel a large complex molecule generally tends to form a large network, which holds the liquid together.

Alginate is this large molecule. Alginates are large polysaccharides made up of a long chain of two different molecules (mannuronic & guluronic acid). This long chain of molecules by itself cannot form a gel though, it needs something to structure them in such a way that it holds on to the liquid.

This is where the calcium-ions come in. These calcium ions can sit in between two chains of alginate molecules, stabilizing them, see image below.

spherification, alginate and calcium egg box network
A schematic representation of how alginate and calcium ions can form a stable gel.

The working mechanism of alginate and calcium is very similar to that of 2-component glue. Only when the two components meet will the glue work. As long as they are separate, nothing happens.

 

Bringing the two together

We now know that we need two components to form our spheres. The trick is to keep them separate until we need them to come together. This is done by dissolving both of the components in a watery phase. One of the two will be dissolved in the product of which you want to make a sphere (e.g. the pineapple juice), the other is dissolved in water, making a water bath.

By dripping balls of the liquid that has to be made into a sphere into the water bath, spheres are formed. The alginate or calcium-ions sitting in the outer layer of the liquid will interact with those present in the water bath. This will cause them to form a layer/gel around your sphere.

Here’s a video demonstrating this technique:

Basic & reverse spherification

You might have wondered which component to dissolve in the water bath and which one to add to the product of which you’d like to make a sphere. Actually, both are possible and it depends on the desired structure of your sphere as well as on the material of which you’d like to make a sphere.

As mentioned, for this technique to work, the alginate and calcium shouldn’t ‘meet’ before actually making the spheres. So, if you have a product rich in calcium (e.g. milk), you will not want to add alginate to your mixture, this will start the spherification process. Instead, you’ll make a bath of alginate.

Apart from interactions with ingredients already present in your food, you should also consider the type of spheres you’re looking for. Since the alginate is the molecule that forms the gel layer, the phase which contains the alginate will make a gel. This means that if the alginate is dissolved in the water bath, the gel layer will form around the ingredients. This is called reverse spherification.

If, on the other hand, the alginate sits in your product (e.g. the pineapple juice), it will form a gel within the pineapple juice. There will be no layer around the juice. Generally, adding the alginate to the ingredients and making a calcium water bath gives a more delicate sphere. This version is called spherification.

Concentration

When making spheres you would want spheres with a delicate outside and a juicy inside. It is important that the outer layer is thick enough to support the liquid, but thin enough to allow it to break open easily. Concentration is key here.

If there isn’t enough calcium to sit in between two alginate strands or not enough alginate to form a gel, nothing happens. Some structures might be formed, but if there aren’t enough, it simply won’t be strong enough to hold on to the liquid.

If there is too much of both on the other hand, a gel will be formed throughout the entire product. All the calcium ions and alginate will meet, forming gels everywhere. This can create a very gelly thick structure, whereas you might only want a thin layer on the outside.

Texturas

Wondering where on earth to get these ingredients? Luckily, a very famous chef: Ferran Adria has developed a line of these products. Ferran Adria has run the highly succesful restaurant El Bulli in which he used a lot of new techniques, one of which was spherification.

Since these ingredients cannot be found in supermarkets easily a special range has been developed, called: Texturas. Within this line of products the Algin and Gluco are the alginate and calcium-ions you will need for spherification.

 

If you give spherification a try, let me know how it went!

 

2 comments

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  • Very nicely written. How long does it last? If I made some spheres out of balsamic vinegar could I mail them to someone?

    • Hi Brendan,

      Glad to hear you found the article useful and a good question you asked.

      I must admit that I haven’t tested out how long the spheres would last. It certainly depends on what you use to make the spheres. If you made them from balsamic vinegar they are definitely more stable than let’s say some you made from fruit puree, so that helps for you.
      I think the spheres hold up for a few days, I wouldn’t see why they would break down.

      What my advice would be to make some spheres and simply leave them on your counter for a few days in a closed container to see how they hold. Do they keep their shape and is there any sign of spoilage? That should give you an indication of how long they can be kept. Also try shaking them once in a while to see how sturdy they are for any transport.
      When mailing any food keep in mind that the temperature might fluctuate quite a bit during the journey and it might jostle around.

      I hope these tips help you to figure out your best next steps. As with any food, shipping really depends on the exact composition.

      Good luck!