The Science of Pie – May 19, 2013
Best Tasting Pie
Stephan Phan, Kevin Yang, Amirari Diego (Team Apples to Apples)
Using the technique of spherification, this team applied their knowledge of diffusion and gelation to prepare “reconstituted” apples. They found that optimizing both the calcium chloride concentration and gelation time was key to making a delicious modernist apple pie.
|Calcium promotes the solidification of alginate networks. Alginate is a long, negatively charged molecule called a polysaccharide. Positively charged sodium ions (Na+) dissociate from the alginate when dissolved to create a goopy but liquid solution. Doubly charged calcium ions (Ca2+) can bind two different alginate strands simultaneously, thereby crosslinking and solidifying the solution. Increasing the number of calcium crosslinks by raising the concentration of calcium chloride and/or lengthening the soaking time create a more solid gel.
Deconstructed apple pie with pie crust crumbs and spherified apples
10 g sodium alginate
20 g calcium chloride
1 L 100% organic apple juice*
1 L water**
*Team Apples to Apples recommends using pulp-free organic apple juice. Freshly pressed apple juice tends to have too much pulp, while additives in non-organic apple juice may interfere with the spherification process.
**For the Science of Pie, Team Apples to Apples used 10g of sodium alginate in 1 L of apple juice and 20g of calcium chloride in 1 L of water. This recipe does not require such large volumes, but it is important to maintain these ratios as they affect the gelation time for the apple spheres.
Mix the sodium alginate into the apple juice. We recommend using an immersion blender, but whisking vigorously will also work. Let the solution sit until any foaming subsides; if large amounts of foam formed during mixing, you may also want to skim foam from the surface of the solution. The solution is ready for spherification once it has reached almost an apple sauce viscosity.
Prepare your calcium bath by dissolving the calcium chloride into the water. Mix lightly; the solution is ready once all visible particles have disappeared and the liquid it appears translucent again.
To create each spherified apple, scoop no more than one tablespoon (it becomes increasingly harder with bigger volumes) of apple juice solution using a deep spoon and carefully drop it into the calcium chloride solution. It helps to use a second spoon to scoop the apple solution out of the first spoon. This is mainly technique—you will get the hang of it after a dozen or so attempts!
Let the apple juice solution sit in the calcium chloride solution for approximately 30 seconds. There will not be a noticeable difference if left for an additional 30 seconds, but the apple juice solution will continue to solidify as it sits in the calcium chloride solution and fully solidify after about 10 minutes. Feel free to play around with the timing of this step to achieve the desired spherified apple texture.
To serve, place the spherified apple in an Asian-style soup spoon and garnish with a bed of sugar and graham cracker crust crumbs, a sliver of green apple skin, and a dusting cinnamon.
More information about spherification can be found at Molecular Recipes.