Gluten-free sourdough pizza dough: a calculator that models the gel and the culture at the same time

The short answer

A gluten-free starter is the same community as a wheat starter, wild yeasts and lactic acid bacteria, fed on brown rice, sorghum or buckwheat rather than wheat. It raises a gluten-free dough the same way, with the same sub-linear inoculation law and the same sensitivity to temperature. What changes is what holds the gas: a psyllium gel (2 to 4 % of the flours' weight), sometimes helped by xanthan, in a dough that drinks 87 to 120 % water. And what changes in failure: a wheat dough pushed too far tears, a gluten-free dough pushed too far collapses, because nothing elastic is holding it.

Three rules follow. The starter must be kept on a flour that is part of the blend, and its flour is subtracted from it. The inoculation is computed for the schedule, as with wheat. And you bake at the peak, never after, judging by volume, not by the clock.

A gluten-free starter, from scratch

Brown rice is the most reliable starting flour: it carries enough sugars, minerals and surface microorganisms for the culture to get going, and it stays neutral in taste. Buckwheat starts fast but marks the flavour; sorghum is a good compromise. Pure starches (tapioca, potato starch, cornstarch) do not feed a culture: a "tapioca starter" does not exist.

1. Day 1. In a clean jar, 50 g of brown rice flour and 50 g of water at 28 °C. Cover loosely, keep at 24–26 °C. The mix is looser than a wheat starter: that is normal.
2. Day 2. Stir, add nothing.
3. Days 3 to 6. Every day, keep 50 g, discard the rest, add 50 g of flour and 50 g of water. The bubbles are finer and quieter than on wheat; the smell goes from frankly sour to yoghurt and fruit.
4. Day 7. If it doubles in 6 to 8 hours at 24 °C after a feeding, it is ready. If not, carry on two or three more days.

A gluten-free starter is kept at 100 % hydration, like a wheat starter, and lives in the fridge between uses with a feeding the day before. It does not climb as high in the jar: without gluten there is no film to hold the bubbles. Judge it by smell, by the bubbles on the surface and by the spoon test (it must be airy, not dense).

The starter's flour is one of the blend's flours

It is the most common arithmetic mistake in sourdough recipes, and it costs more gluten-free than on wheat. Twenty percent starter at 100 % hydration is 10 % of the total flour and 10 % of the total water already in the jar. If you add them on top of a formula at 104 % water, your dough is at 114 %, and a gluten-free dough at 114 % is a pancake batter.

Fornello takes the starter's flour out of the blend flour it is kept on. If your blend holds 25 % sorghum and your starter is on sorghum, the weigh-out tells you to add less sorghum, by exactly the amount already in the starter. If your starter is kept on a flour that is not in the blend, it is taken out pro rata from every flour, and the composition stays that of the whole formula. Hydration, gel and structure are computed on the whole, because the whole is what bakes.

Example computed by the engine on the "classic" blend (50 % white rice, 25 % tapioca, 25 % sorghum) with 5 % psyllium. Ten points of hydration is the difference between a dough that shapes and a dough that runs.

The gel, the rise, and why order matters

In a wheat dough, the gluten network builds during mixing and strengthens during fermentation. In a gluten-free dough, the psyllium gel forms within minutes on contact with water and does not strengthen with time. It holds the gas, it gives extensibility, but it has no spring-back, and it does not tolerate over-fermentation: when the gas exceeds what the gel can hold, the dough sinks and does not come back. Xanthan (0 to 2 %) adds a little elasticity for rolled or fast-set styles, never in a pan.

The starter adds something yeast does not: acid, which rises with time. Gluten-free, the acid weakens no network, and the pH matters mostly for taste. Fornello estimates the pH trajectory and the expected character (sharp, balanced, mild) from the temperature and the starter's hydration, and flags a crust that will be frankly sour (pH below 4.5) as a choice of taste, not a structural error.

Sugar stays in the formula (3 to 5 % in the published formulations): without wheat amylases to free sugars, the culture needs that help, and so does the crust, to colour.

The schedule: at the peak, not after

The rule of gluten-free sourdough fits in one sentence, and the calculator repeats it at every calculation: judge by volume, bake at the peak. A wheat dough forgives an hour too many; a gluten-free dough does not. Short, warm schedules are therefore safer than long, cold ones, and the fridge serves to gain flavour on an already shaped dough, not to make it rise.

Rates computed with the Fornello 0.24 engine for a 400 g dough, at confidence C: the inoculation law has not yet been refitted on gluten-free starters. Your bake journal is made for that.

Shape early. A gluten-free dough is neither balled nor stretched: it is spread with a wet spatula or pressed into the pan, then does its final rise in place. The stay in the fridge therefore happens already shaped, on the sheet, covered.

In the calculator

The calculator below opens on the gluten-free 48-hour New York, in sourdough mode. You can switch formulation (Neapolitan, Detroit, buckwheat…) in the menu. The inoculation dial replaces the yeast. The starter card shows the starter's flour (chosen among the whole-grain flours of your blend), its flour and water in grams, the suggested inoculation for your schedule, the expected pH and the feeding to do the day before. The weigh-out shows the flours to add once the starter is deducted, and the water to add, not the total water.