When swapping standard flour with GF flour, should it be measured in cups or by weight?

Question

Sometimes I use a recipe that is not gluten free (GF) and make it GF by using GF flour instead of normal flour, but GF flour does not weigh the same as normal flour. It is significantly lighter. I use a standard GF flour blend from the supermarket, such as Coles or Woolworths brand.

If I find a recipe that lists cup measurements, let’s say 2 cups for example, should I measure out 2 cups of GF flour and use that amount? If the recipe has measurements in grams, should I weigh out the same number of grams as it lists for the non-GF flour?

I like to work by weight rather than cups and have made a lot of things GF over the years but have never really been quite sure about this. I have usually tended to measure out the weight of GF flour, so in the example I would use the weight of 2 cups of GF flour, rather than what the weight of 2 cups of normal flour would be. Sometimes I use about halfway between what the two weights would be, because occasionally it seems like maybe not quite enough flour for some things.

I understand that for ideal outcomes, it is always better to use recipes that were originally designed to be GF, but nonetheless it would be good to have clarity on this issue.

Answer 1

There is no general answer to this question. You have to follow the manufacturer's instructions.

You say that you use "a standard GF flour blend", but there is nothing standard about such blends. GF flour is never a perfect substitute for wheat flour, and while the manufacturers do their best to get it to work well, they take different approaches and accept different tradeoffs. So one mix is never the same as another mix. Also, different recipes "react" differently to the substitution, and the same mix is never optimal for all possible recipes.

This is compounded by the problem of people loving to use volume measurements, especially in the US. In a simple world, measuring by weight gives better, more consistent results, at least when you follow the original recipe. So, if you have a recipe that is designed for weight, and you're using a substitution mix that's designed to be used by weight, that would give the best results. But! The manufacturers know the density of their product. And if they assume that their customers will measure by volume, they will adjust the properties of their mix to give the best results when substituted by volume. And if you start using such a mix but substitute by weight, you're almost sure to overcorrect and end up with worse results.

So, the best thing you can do is to read the package and see what it suggests. If no suggestion is printed, but it suggests a sample recipe, you can try to infer from that (is the recipe given by volume or by weight? does it correspond to a standard ratio?). Or, you can call the manufacturer customer service and ask for the intended usage of that exact product.

If you can't get (or can't be bothered to get) that information, I would probably use weight when the original recipe is designed for weight, and volume when the original is designed for volume. It might need a few rounds of tweaking until it starts working, but that's not so rare with GF substitutions anyway, and frequently the reason is not even the small difference in density, but the difference in binding power.