An overloading of the gel with a soluble protein creates a semicircular band of this protein (e. g. in the marker lane of the image at 66 KDa), allowing other proteins with similar molecular weights to be covered.
Like arrowroot, tapioca also comes from the root of a plant, however, in this case it is the root of the Cassava plant. It is ground into powdered form and is often referred to as tapioca flour.
So, if you're making something that you plan to freeze, arrowroot is an excellent thickener to use. If you don't see arrowroot powder shelved with the other thickeners at your grocery store, check the natural foods section. You can also order it online. Buy Arrowroot Powder on Amazon