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This amuse bouche will consist of 4 'bite' size elements each of which will represent one of the four most recognised and familiar tastes; sweet, sour, salty, bitter. Each element will be coloured differently to represent that taste's colour e.g. salty=white, sweet=red, sour=green, bitter=black. The actual colours used will be based on research by the Cross Modal lab. In case anyone was wondering why other tastes such as fatty, umami etc. are not included, I've limited the course to the four tastes with which people are most familiar with. Reverse spherification is more versatile than basic spherification; it allows you to make spheres with almost any base solution. It is a particularly easy technique for liquids with a high calcium content or alcohol content. The next main advantage of reverse spherification is that the spheres can be stored and consumed later. Unlike with basic spherification the jellification process can be stopped when the sphere is removed from the sodium alginate bath and rinsed with distilled water.

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For the purpose of this recipe we will be making 4 different flavoured spheres using reverse spherification. Given that we are using different ingredients in each of the spheres we will be demonstration 3 variations of reverse spherification. The four flavours are: Sweet=red, in which we will be using cranberry juice and rose compound. Sour=green, in which we will be using lime juice. Bitter=black, in which we will be using a stout beer. Salty=white, in which we will be using yoghurt. The lime and cranberry spheres use the same technique in which we will be adding xanthan gum and calcium to each liquid and 'dropping' the spheres into the alginate bath by hand. The stout spheres will also have xanthan gum and calcium added to it - but in this case the spheres are made by freezing the solution in small 'demi-sphere' moulds, which will be dropped into the alginate bath. Finally there is the yoghurt spheres which (due to its natural thick texture and high calcium content) does not require any additives, and will be 'dropped' into the alginate bath by hand. To begin the most important step is getting your ingredients weighed out. Lime spheres: - 100ml Fresh lime juice - 80ml Water -20ml Stock syrup - Green food colour (add the amount you feel gives your spheres a nice bright colour) - 0.6g Xanthan gum - 4g Calcium gluconate Cranberry spheres: - 195g Cranberry juice - 10g Rose compound (or rose water) - 0.6g Xanthan gum - 4g Calcium gluconate Stout beer spheres: -180g Stout beer - 20g Stock syrup - Black food colouring (add the amount you feel gives your spheres a nice dark colour) - 1g Xanthan gum - 4g Calcium gluconate Yoghurt spheres: - 200g Natural full fat yoghurt - 50g Water - Salt (to taste)

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Now that you have the ingredients weighed out its time to begin incorporating the ingredients for each sphere one at a time. In the case of the cranberry, lime and stout spheres you you need to begin this step at least a day or two ahead of when you want to actually make the spheres (we will explain why in a moment). The yoghurt sphere solution is the only one you can make and pretty much use immediately.

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For the lime or cranberry spheres, add all the ingredients (listed in step 2) together in a bowl and mix with a hand blender. It is important to continue blending the mixture for around a couple of minutes till you can see the solution begin to thicken slightly (this is the xanthan gum hydrating and increasing the viscosity of the liquid).

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Once blended (and slightly thickened) a lot of air will have been incorporated into the solution. This is not desirable as you will end up with air bubbles in your spheres (not the end of the world - but it can take away from the flavour slightly and just doesn't look as good!). So there are two options; either use a vacuum packing machine to remove the air - or leave in the bowl covered loosely with cling film and leave to rest in the fridge for anywhere between 24 to 48 hours. To speed up the process, you can pass the sodium alginate solution through a fine sieve. Let the liquid flow through it on its own without applying pressure. You may have to repeat this process a few times.

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On the right you can see the solution which has just been blended; on the left you can see a solution which has been resting in a fridge for several hours.

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Once the solution is rested you can always skim a little of the bubbles off the top and use the solution below.

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Now you are ready to begin 'dropping' the spheres into the alginate bath using a measuring spoon. The alginate bath is simply sodium alginate and distilled water blended together using a hand blender and left to rest for 12 hours. The ratio of sodium alginate is 0.5% - so in practical terms that equates to 5g of sodium alginate to 1ltr of distilled or low calcium water. Blend the sodium alginate in 1/3 of water with a hand blender until it is completely dissolved. Keep in mind that sodium alginate is hard to disperse and hydrate in water and this process may take up to 10 minutes.

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Start off by dropping one sphere at a time to get an idea on timing. The longer you leave the spheres in the alginate bath, the thicker the gel membrane of your spheres. Ideally you want a thin membrane that gives a good burst in the mouth and leaves very little gel membrane on the palate. However a thin membrane means a much more fragile sphere which can easily burst. Usually we leave the spheres in the bath for between 30 seconds to about 1 minute 30 seconds. Once you have dropped a sphere, gently 'flip' the sphere at intervals to ensure that a uniform membrane is formed all around. An important point to bare in mind once you have several spheres in the bath at one time is to make sure that the spheres don't touch each other for a prolonged period (10-15 seconds) as they will bond to each other.

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Now that you have removed the spheres from the alginate bath its time to rinse them in distilled water (it doesn't have to be distilled water but this just gives a better overall look). Once rinsed; the spheres are ready to eat!! However if you want to store the spheres for over 20 minutes it is best to store the spheres in a liquid which is made of their basic ingredients i.e. we store the cranberry spheres in cranberry juice, lime spheres in lime juice, stout spheres in stout, and yoghurt spheres in a watered down yoghurt solution. We do this as it stops the flavour from diffusing into the water via osmosis.

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The stout spheres are slightly different, but still very easy to execute!

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Blend all the ingredients together and in this case do try to incorporate as much air as possible. With this solution we want to trap in the air bubbles as this gives the stout sphere that creamy texture which gives it body and context.

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Now we take the stout mixture and place it in half sphere moulds. We do this because the amount of air trapped in the solution means that the stout mixture will just float in the alginate bath and will not form the correct shape. By moulding and freezing mix till solid this allows you to drop the frozen half spheres into the alginate bath and continue the process as with the other spheres. Using this frozen spherification method you should make sure the alginate bath is at room temperature so that the frozen mixture forms a gel slightly quicker than if the alginate bath is cold.

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Using this frozen spherification method you should make sure the alginate bath is at room temperature so that the frozen mixture forms a gel slightly quicker than if the alginate bath is cold. Also its important to mention that if you find this frozen spherification method easier to execute than dropping the spheres by hand then you can also follow this process for the lime or cranberry spheres. Just go back to step 7 (once the solution has been rested and released all the trapped air bubbles) and place the solution into the half sphere moulds and freeze.

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The yoghurt spheres are the easiest of all. Mix all the ingredients for the yoghurt spheres specified in step two till you have a homogenous solution. Now jump straight to step 8. Yes it really is that easy!

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Now its time to plate and garnish your spheres! We pair the stout spheres with small crunchy dark chocolate balls.

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Our cranberry and rose spheres are paired with a lychee gel (made by blending lychee juice with 1% of xanthan gum).

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Our lime spheres are paired with cinnamon and coriander.

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Once you get your flavours right its time to have a bit of artistic fun!