Spherification is a technique used for encapsulating liquids within a jelly-like outer shell, made famous by Ferrara Adria (El Bulli).  It has since found its way into common use in modern cuisine and is great for adding a nice twist to any dish.   Caviar (or salmon roe), is probably the best comparable in sensation- a slightly chewy sphere that explodes flavor and liquid.

The chemistry that makes spherification possible is pretty straightforward: when a solution containing sodium alginate comes into contact with a solution containing calcium a layer of calcium alginate immediately begins to form.  This membrane is water insoluble and effectively traps liquid within.

One way to create “spheres” is to add drops of liquid containing sodium alginate into a calcium-based bath, which will result in caviar-sized spheres.  Larger spheres can be created by immersing spoonfuls of liquid.  The reverse is also possible- creating spheres of liquid containingcalcium in a sodium alginate bath.  This is often used if the liquid already contains some calcium (milk, yogurt etc…), and hence known as reverse spherification.  The other key difference is in normal spherification the spheres will continue to “cook” even when taken out of the calcium bath and will quickly become solid.  Reverse spherification doesn’t have this issue, but the calcium salt may add a slight off-putting flavor to your liquid.

My calcium salt of choice is calcium lactate, which unlike calcium chloride, does not make your spheres taste like a swimming pool.  In addition,  xanthan (a thickening agent) and sodium citrate (for adjusting pH) are also useful to have around.  You will need a digital scale that can weigh in tenths of grams.  To test out a simple reaction, I recommend starting with a reverse spherification using cream/milk thickened with xanthan.

Since this post is getting long, I’ll post a part 2 in a few days on my little experiment with yogurt drinks and Vitagen.  In the meantime, if you’re curious about spherification and other molecular techniques, check out these handy resources:

• blog.khymos.org – probably the best blog on molecular cuisine.  Also publishes an open hydrocolloid recipe collection with enough recipes to get you jumpstarted.
• WillPowder – chemicals and ingredients for your molecular gastronomy needs from Chef Will Goldfarb.  I found his chemicals a) worked and b) much cheaper than the Texturas offerings (hooray Amazon!).