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Spherification Potluck

There are times when gourmet edges more towards the laboratory than the kitchen; spherification is one of those times. In this culinary technique, liquids are transformed into globular semisolid gels thanks to a hydrocolloid gum extracted from seaweed. When these gel-encased balls are broken, the liquid contents gush out, akin to biting down on mochi or a Gushers candy. In theory, almost any liquid can be spherified, so the possibilities are endless. Ever wanted to eat plum juice caviar, spherical crème brûlée, or mojito spheres? With food-grade sodium alginate, calcium solution, and some creativity, it’s possible.

At the Spherification Potluck last month, graduate students Liz Roth-Johnson and Kendra Nyberg delved into the process on the molecular level. Gelation is made possible through the interaction between alginate and calcium ions. Alginate is a long, negatively charged, noodle-like molecule. When mixed into a liquid, alginate floats about freely, its elongated structure creating a thick, jelly-like consistency. Calcium ions are single calcium atoms with two positive charges, enabling each ion to link together two alginate molecules. Many calcium-linked alginate molecules gives rise to a more solid structure—the gel skin that encases a gooey center.

SpherificationLecture

Liz (left) and Kendra (right) explain the nuts and bolts of spherification.

Spherification - Options

Students brought a variety of beverages, sauces, and condiments to the potluck.

Attendees at the student event opted for items found in kitchen pantries and grocery store shelves, such as pomegranate molasses, rose water, coffee drinks, milk tea, sodas, guava nectar, and hot sauce.

In the first attempt at spherification, coffee was mixed with the sodium alginate to produce a rather thick goop. Plopping globs of this dense solution into the calcium chloride baths gave comical results, as the mixture adamantly refused to form any shape remotely resembling a sphere. Some blobs even broke upon removal from the calcium chloride baths.

CoffeeSpherification

Students prepare an alginate solution (left) and attempt to create spherified coffee (right)

Milk tea and Jarritos orange soda gave the best results in terms of shape and stability. Initially, the center of the milk tea spheres was thicker than expected, yielding a much chewier texture than bargained for. Minimizing incubation time in the calcium chloride solution managed to fix this halfway, somewhat decreasing the thickness of the gel casing. A quick search also revealed that our recipe used twice the sodium alginate other spherification recipes called for. If less alginate was added to the milk tea or orange soda, the spheres would have definitely been gooier.

Spherification - Jarritos sphere

A student shows off a fairly successful attempt at spherified orange soda.

The most difficult to work with was Tapatio, and not just because of the spicy fumes that emanated from the mixing bowl. Hot sauce is acidic, meaning it is full of positively charged hydrogen ions. Mixing it with alginate neutralizes the negative charges, hampering the interaction between alginate and calcium. No alginate-calcium interaction, no cross-link formation, no gel. Dropping the Tapatio-alginate mixture into calcium chloride resulted in nothing more than dissolved Tapatio swirling around in solution.

Spherification encompasses a high degree of flexibility. Besides the gamut of foods that can be used, there are also technical alterations—the ratio of liquid to sodium alginate in the pre-sphere goop; the concentration of the calcium chloride solution; the amount of time the spheres are left sitting in the calcium solution. And this is only the direct method. Other variations on this technique include reverse and frozen reverse spherification. With spherification kits readily available online, why not try spherifying your own recipe? Share your spherification adventures with us in the comments below!

Deconstructed Apple Pie

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.

TeamApplestoApples

photos courtesy of Patrick Tran

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.

The Recipe
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.