Sodium Alginate and Reverse Spherification

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Introduction to Sodium Alginate and basic ‘Reverse Spherification’


In this post I’m going to focus on using sodium alginate in a process know as ‘Reverse Spherification’ to create orbs about the size of an egg yolk, which hold their shape but burst into liquid in the mouth. This fantastic technique can be both really enjoyable to experiment with and give you some delicious results with a novel texture/eating experience. And when creatively and intelligently applied Spherification, and the principles behind it, can open up a world of new culinary possibilities and help us create extraordinary dishes.

So I’m going to try and give you a little bit of basic information and advice on how to use this ingredient and technique and then provide a simple recipe that’s easy to try at home that uses this technique. That way wish any luck you can get comfortable enough with the basics that you can go on to do more complex preparations and be creative in your own way.

First off it’s worth briefly making a quick distinction between the two basic forms of spherification, ‘Regular’ and ‘Reverse’.

‘Regular’ spherification involves adding sodium alginate to a liquid, for example a fruit juice, and then ‘dropping’ this liquid (via a pipette, syringe, squeezy bottle, ‘dropping spoon’ etc etc) into a calcium bath.

Generally, for best effect, Regular Spherification into a calcium bath needs to be done too service, just before the spheres are to be consumed as the orbs very quickly solidify all the way through, (this isn’t the case with ‘Reverse’ Spherification, but I’ll go into the science of why this is in more detail elsewhere).
I’ll create separate posts soon on ‘Regular’ spherification (using a calcium bath) and also on making smaller ‘caviars’. However, as I mentioned, for the moment here I want to focus on ‘Reverse’ spherification.
So in ‘Reverse Spherification’ flavourful calcium rich liquid (either naturally calcium rich or spiked with something like calcium lactate) is dropped into a sodium alginate solution (thus the ‘reverse’ of dropping a mixture containing sodium alginate into a calcium bath). The calcium rich liquid reacts with the sodium alginate and a thin film is formed around it, giving you ‘Spheres’ or orbs that are liquid on the inside.
So first off I’ll give you a bit of basic information on Sodium Alginate which is the vital ingredient you will need for this technique, and in the UK you can buy from www.Modernist-Chef.com (Note it the El Bulli ‘texturas’ range its called‘Algin’).

Ok, so basically Sodium Alginate is derived from brown seaweed, its not some scary chemical concocted in a lab so don’t let that be a n excuse to not have a go using ingredients of this type.

It’s a hydrocolloid, which means it can form a gel or act as a thickener when hydrated. But particular to sodium alginate is that it rapidly forms a gel when it comes into contact with calcium. These gels are heat stable (they won’t melt) to above 150C. This allows us to heat up orbs made using spherification, so they can be served hot, as I did in a recipe you can see
here.

It was largely Ferran Adrià who made the use of sodium alginate popular amongst chefs through pioneering the spherification technique for haute cuisine at his famous restaurant ‘El Bulli’.
Now, for simplicity in this first post I’m just going to focus on making spheres from naturally calcium rich liquids. This means you don’t have to add calcium to the liquid you want to make orbs from. But once you master this basic technique you’ll find it’s really easy to add calcium to almost anything from fruit juices and sauces to … well pretty much any liquid you want to make orbs from (by blending calcium lactate into it for example), and just following the same basic steps.

Preparing a sodium alginate bath.

So first you’ll need to prepare a sodium alginate solution by blending 5g of sodium alginate into one litre of cold water. My preferred way of doing this is with an immersion blender (hand blender) in a plastic rectangular tub where the liquid will sit about 10cm deep (but you could blend in a food processor or similar).

Sprinkle the sodium alginate into the water and moving the blender around blend for about 2 minuits until you have a nice smooth solution. Let this solution settle in the fridge for at least 30 minuits to allow air to escape from the solution (it will appear clearer when settled).

Dropping Technique

Here I’m focusing on the preparation of larger spheres, but I will deal with making smaller ‘caviar’ balls in another post.

So there are two ways that I’ll talk about here of making your orbs, dropping using a spoon and freezing as a hemisphere prior to dropping.

A lot of the time my preference is to use the ‘Dropping Spoon’ technique, but for this to work best the liquid you want to make spheres from needs to have a certain viscosity, about the thickness of yogurt, this can of course be achieved my thickening the liquid prior to dropping (i.e. with xanthan gum) if its too thin.

So to create orbs this way you take a small spoonful of your calcium rich liquid in either a specially designed ‘dropping spoon’ (which can be bought here) or a small measuring spoon, lower the spoon to the alginate bath and gently tip the spoonful of liquid into the bath so that it forms a small orb (they don’t have to be absolutely perfect as once out of the bath they will naturally sit in an egg yolk like shape under their own weight).

Leave the orbs in the alginate bath for 30 seconds to a minute. A very fine film will form on the outside of the spheres, which will hold their shape but most importantly give the effect that they burst into liquid in your mouth when eaten.

Remove the spheres from the Alginate bath with a slotted spoon and place in a bowl of fresh cold water to refresh them. Remove them from the fresh water with a slotted spoon when you’re ready to use them.

The other technique for forming spheres that is very successful is to freeze your liquid in hemisphere moulds and then simply pop the frozen hemispheres into the sodium alginate bath to react. The time left to react with this technique can be variable as can the temperature of the sodium alginate bath (you could use a heated bath to speed up the thaw of the hemispheres). Making the orbs this way will give you nice uniform sized and shaped spheres but it does take longer (freezing time) and might not be best for all applications. Again refresh spheres in fresh water after the alginate bath.

In some cases it may be obvious which way to go out of the two techniques, or it might come down to time constraints, which way you find easier, or even just personal preference. Have an experiment to get the feel for it and find out what best suits you and your recipe.

So now, here’s a quick simple recipe that uses the technique of ‘Reverse spherification’ into a sodium alginate bath.

It’s a simplified version on an amuse bouche that I do, which you can see
here

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Hopefully it can serve as a good introduction to using the technique and show you what can be achieved very simply.

Recipe -
Spheres of Yoghurt, Honey, Black Pepper and Poppy Seeds. With Crushed Walnut and Strawberry Puree


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So first prepare a sodium alginate solution as above by blending 5g of sodium alginate into one litre of cold water. Leave this to settle in the fridge for thirty minutes before using.

For the Yoghurt mixture - in a bowl mix together 200g natural Greek yoghurt, 60g Honey, One Teaspoon cracked black pepper and three teaspoons of poppy seeds and stir well.
Now carefully drop spoonfuls (as described above) of the yoghurt mix into the Sodium Alginate solution and leave the small orbs that form for 30 seconds to a minute to react. Refresh the spheres in cold water and remove them with a slotted spoon when ready to serve.

Serve with crushed walnuts and a simple strawberry puree made by blending fresh strawberries with a little icing sugar and a squeeze of lemon juice to taste. I sometimes thicken purees like this with xanthan gum (which I will right a post on soon) to get the consistency however I want it, but for a first go at this technique a very simple puree will do, or even just some chopped fresh strawberry.

I hope this is useful

Enjoy yourselves xx

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