Science Buddies: "Ask an Expert"

In conducting this experiment, Coca-Cola and Tomato Juice formed spherical balls. However, Cranberry Juice did not. I kept adding more and more sodium citrate, but the solution would simply dissolve immediately upon being dropped into the calcium chloride bath. I noticed that the Cranberry Juice contains 10% Calcium. Could that be the problem?

12moocow,

Welcome to the forum and thank you for your question. You may be right that the calcium content of the juice is thwarting your attempt at spherification. Foods that contain calcium require a technique called "reverse spherification".

Instead of blending your food/drink with Sodium Alginate into a solution and dripping that into a Calcium Chloride solution to get the spherification reaction, you turn that procedure around by dripping your food/drink that contains calcium into a solution of sodium alginate and water (I don't know ideal ratios here). If your food/drink doesn't contain (or contain enough) calcium to cause the reaction, you can blend it with Calcium Lactate or Calcium Lactate Gluconate to create an ideal solution (again, I don't know proper ratios) and drip that into your Sodium Alginate solution.

Of course you are performing a science experiment. In order to conduct a fair test of spherification of cranberry juice against your other food/drinks, you can't switch up the procedure in the middle of the test. A fair test is one where only a single independent variable is changed and the dependent variable(s) are measured for a quantifiable effect.

If it truly is the calcium in your juice causing the failure, I'd find another food to test that you know doesn't contain calcium and should work with the spherification process. Else, you can change to the "reverse spherification" process and add calcium to your non-calcium containing food/drinks. As long as they ALL undergo the same procedure.