Clean arrowroot tubers and peel off skin. Chop into 1/2 inch cubes.

Place chopped tubers in bowl of water mixed with lemon juice to prevent browning.

Working in batches, blend tubers into a pulpy mash. Add just enough acidified water to blend.

Pour mash into a fine mesh strainer over a bowl. Press out starchy water. Discard pulp.

Let starchy water settle 2-3 hours. Carefully pour off water.

Wash starch 2-3 more times by mixing with water, settling, and pouring off water.

Spread wet starch on dehydrator trays or baking sheets. Dehydrate at 115°F for 12-24 hours until fully dried.

Mill dried starch into a fine powder using a blender or food processor. Sift to remove any fibrous bits.

Store powder in an airtight container in a cool, dry place. Keeps 1-2 years when stored properly.