If you are looking for a thickener with a neutral taste and that can provide your dish with a nice shiny surface and smooth texture, tapioca is arguably your best option. It is easy to find and works in both savory and sweet dishes. If you miscalculated and it turns out that there is none in your cabinet, you will need to find an equally effective replacement. Maybe you have one of the tapioca starch substitutes below on hand.
Your best bet: Arrowroot
Arrowroot is another root starch that has similar qualities to those of tapioca. It is derived from plants in the Marantaceae family as well as from other tubers. In some cases, tapioca is actually one of the tubers sold as arrowroot. Not only is arrowroot a neutral-tasting thickener, the liquids thickened with it remain clear and have a glossy surface just as they do when you use tapioca. In addition to having a similar effect, arrowroot also has similar qualities in that it is gluten-free and therefore an ideal substitute if you are on a gluten-free diet.
Arrowroot actually has a couple of advantages over tapioca starch in that it can stand up to acidic liquids without losing its properties and also has a greater nutritional value.
One of the characteristics of root starches like arrowroot is that they cannot be subjected to heat for long periods or they will simply break down and thin out. Add it to your dish at the last minute, just before you remove it from the stove. You should also avoid using arrowroot to thicken dairy as it can give the dairy product a slimy texture.
Use about half as much arrowroot as your recipe requires for tapioca starch. Mix with cold water to make a slurry and add that to your dish.
A decent second choice: Potato starch
Like both tapioca starch and arrowroot, potato starch is derived from a root. It consists of starch extracted from potatoes. It differs from potato flour in that it has a neutral flavor and works in exactly the same way as tapioca starch. It also provides the same glossy surface and transparent appearance as the other root starches. Potato starch also contains more nutrients than tapioca and is a resistant starch, which means that it does not get digested in the stomach or small intestine like other starches. This makes it important for blood sugar management.
Use half as much potato starch as your recipe requires for tapioca starch and use the slurry method when adding it to your dish.
In a pinch: Corn starch
Corn starch is a widely used thickener, so much so that most serious home cooks have a box or two of it in the kitchen. Corn starch is a grain starch that comes from the endosperm of the corn kernel. This gives it a few different benefits along with some drawbacks when compared to root starches. The main benefit is that it does not break down when subjected to long cooking. All that will happen is that the water in the dish will evaporate and it will become even thicker. The big drawback is that corn starch does not deal with high concentrations of acids or sugar very well. It can lose its thickening power and leave dishes thin and with a chalky texture.
Bear in mind that liquids thickened with corn starch do not have the same transparent appearance that comes with root starches. They tend to be slightly cloudy in comparison.
Use half as much corn starch as your recipe requires for tapioca starch.
Heavy cream can be an effective thickener for many dishes. Its high fat content is what does the thickening and it can be as effective as starches while also adding a distinct richness.
Pectin is the starch used for making jams and jellies solidify. It can be used in some dessert items in place of a root- or grain-based thickener.