There’s a better way: German flour types. They’re specifying mineral content, e.g. standard “white flour” is Type 405, meaning that when you pyrolyse 100g of flour, 405mg of ashes will be left. As the minerals were all in carbon solution before, and temperatures are low enough to not melt them into slag, you’re essentially left with single atoms. Close enough at least for an assumption. If you disagree I shall hand you a mortar.

Of course, that doesn’t specify everything. I suggest also measuring the released energy, then jot both numbers down on the complex plane. So you have joule-moles of flour.