It is not uncommon to see the terms flour and starch used interchangeably when describing different gluten-free flours such as tapioca, corn and potato.
In some instances, this doesn’t really matter as they are used by different people to describe the same ingredient (for example, what the Americans refer to as corn starch, we refer to as cornflour and they are the same thing…the white, starchy flour that is commonly used to thicken soups and sauces – among its many other uses!)
When it comes to the potato, however, it really does matter as gluten-free potato starch and gluten-free potato flour are two totally different beasts and you will get wildly different results from your baking if you use one in your recipe when the other is called for!
The starch and the flour share two things in common – that they are both derived from potatoes and that they are both naturally gluten-free. But that’s where their commonalities end.
Potato flour is made from whole, cooked, dehydrated potatoes ground to a fine powder – or flour. Potato flour is a source of fibre and protein as well as imparting a slightly ‘potato-y’ flavour.
Potato starch, on the other hand, is made by extracting and refining the starch from raw, peeled potatoes to form a fine powder – or starch. It is tasteless and almost nutritionally void.
To illustrate my point, here is a picture of potato starch and potato flour – not even remotely similar looking!
Potato starch looks, feels and performs pretty much the same as cornflour (corn starch) and can be used interchangeably in gluten-free baking. It is great for adding lightness to your bakes.
Potato flour is more dense, absorbs more liquid and should really be used in small quantities along with other gluten-free flours. It works well in gluten-free breads (in small amounts) to help retain moisture and stop the bread staling as quickly. It also adds a binding element – always handy to stop gluten-free breads from falling apart!