Arrowroot powder or flour is the ground rhizomes of the West Indian M. arundinacea arrowroot plant, a relative of ginger. It is also made from similar tubers. Some of the tubers are poisonous until they are cooked. You can read more about the details here: University of Florida
Per 2 teaspoons arrowroot powder needed use one of these alternatives:
The best Keto substitute for arrowroot thickener in baking is to use Xanthan Gum. The reason for this, as described by Bob's Red Mill, is because "first, it works as an emulsifier, encouraging liquids that usually don't like one another to mix together. Second, it works as a thickener, increasing the viscosity of liquids and batters. Third, it will provide a creamy texture to the mixture.
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Arrowroot is used in cooking as a thickener similar to cornstarch. Choose arrowroot over cornstarch if the product is to be frozen.
Some of the arrowroot you purchase may actually be made from tapioca root. You can buy arrowroot powder in many well-stocked grocery stores or purchase it online at Amazon.com. Walmart sells arrowroot in bulk online via a third party seller. The also sell Namaste brand via local stores.
The true arrowroot plant is the Bermuda Arrowroot and is native to Central America. It is classified as Maranta arundinacea.