A raw dough ball is soft, stretchy and would collapse if you pressed it. A few minutes in the oven later, its bubbles are fixed in place and it can be sliced. Starch does much of that work. This page explains what happens to it, using Modernist Pizza (2021) by Nathan Myhrvold and Francisco Migoya, and what it means for a gummy center or a stale slice.
Starch in flour
Modernist Pizza puts starch at 63 to 72% of flour’s weight. It’s made of two sugar polymers, amylose and amylopectin, packed into tiny, partially crystalline granules that don’t dissolve in water.
Milling cracks some of those granules. The book explains that damaged starch matters in two ways:
- It absorbs more water than intact starch, which is part of why flours from hard wheat need more water than soft-wheat flours. Too much damage and the dough takes up excess water and flattens; too little and it absorbs less and is harder to handle.
- It feeds the yeast. The flour’s amylase breaks damaged starch, not intact granules, into the sugars yeast eat, and that later brown the crust.
Millers aim for a set level: typically 8 to 12% damaged starch for hard wheats and below 4% for soft. Modernist Pizza credits Caputo’s Naples mill with running its grain through 32 rollers, milling in many small stages to avoid starch damage. For the browning side, see the Maillard reaction.
What gelatinization is
Modernist Pizza defines it carefully. Gelatinization is what happens when starch granules are heated with water: the bonds holding their ordered, crystalline structure break down, so the granule loses its order and can absorb water and swell. (Scientists see this as a loss of birefringence, the double refraction of light by the crystalline granules.) Gelation is a separate step: the swollen starch forming a cross-linked network as it cools.
The result is a clear gel. The crumb of a pizza looks white, the book explains, only because many thin, transparent sheets of gel overlap, the same way clouds of clear droplets look white.
When it happens in the oven
Modernist Pizza describes this in a few places, with overlapping temperatures for related processes, so read them as approximate descriptions rather than switches that flip at a set point.
In one passage, starch granules heated with water degrade, leak amylose and stick together into a gel at about 131 to 149°F (55 to 65°C), and this gelled starch is what holds the bubbles together. In another, starch gelatinizes and the proteins unravel and coagulate together at about 140 to 176°F (60 to 80°C): the dough loses most of its stretch and oven spring comes to a halt, and as the crumb passes about 158°F (70°C) it changes from a foam to a set gel, its bubbles locking in place, then bursting and connecting so that steam can carry heat quickly into the center. Elsewhere the book says most granules have gelatinized by about 185°F (85°C), when the dough is “pasted,” or cooked out, with the starch drawing water from the gluten as it sets. None of these is an internal temperature that proves a pizza is baked.
Gelatinization needs water, and pizza dough has plenty. Modernist Pizza also notes that, in general, the higher the hydration, the more open the crumb and the greater the volume, which is part of why the hydration you choose changes the texture.
The gummy layer under the sauce
Cut a slice and look from the side, and you may see a white, gummy line between the crust and the sauce. Modernist Pizza calls it the gel layer and describes it as undercooked starch gel. Steam rising through the crust condenses against the cooler sauce, very little heat gets through from the top, and the dough touching the sauce is the last part to cook. When the pizza comes out, the tiny bubbles at that interface collapse into a translucent, partly cooked layer.
The book’s authors measured it across 120 test pizzas with different thicknesses, temperatures and toppings, and found only one complete fix: prebaking the dough. New York square and al taglio pizzas, which are prebaked by design, aren’t prone to it. The Pizza Planner’s Detroit and Sicilian-style pan pizzas follow King Arthur Baking’s two-stage bake, baking the crust untopped before adding the toppings. For other pizzas, Modernist Pizza suggests:
- Cheese first, then sauce. That gives a much smaller gel layer than sauce applied straight onto the dough.
- Moderate toppings. The bigger the topping load, the harder it is to avoid.
If the whole underside is pale and the middle doughy, not just a thin line under the sauce, check the heat from below first: the Pizza Doctor’s first question for that symptom is whether the baking surface was fully preheated. See also how to fix a soggy pizza bottom.
Why leftover pizza goes stale
As a baked crust cools, water vapor escapes and the gelatinized starch begins to recrystallize. Modernist Pizza calls this retrogradation, “a technical term for staling.” Some crusts, such as Neapolitan, keep some of their initial softness; others don’t. Sugar and other ingredients that hold water slow it, by keeping moisture in the crumb.
Temperature changes the pace. The UK’s Quadram Institute, writing about bread, says it stales faster at 3 to 5°C (37 to 41°F), fridge temperature, than in the freezer or at room temperature. That doesn’t make the counter a better place for leftover pizza. The FDA’s two-hour rule says leftovers and other food that needs refrigeration shouldn’t sit out for more than 2 hours, or 1 hour when the air is above 90°F (32°C), as it can be at an outdoor meal; refrigerate or freeze it promptly, and freeze it for longer storage. Heat reverses much of the staling: Modernist Pizza notes that retrograded starch softens again when it’s reheated. How to reheat pizza covers the methods and the food-safety limits.
Frequently Asked Questions
- At what temperature does starch gelatinize in pizza dough?
- Modernist Pizza puts the gelling of starch at about 131 to 149°F (55 to 65°C), describes starch gelatinizing and proteins coagulating together between about 140 and 176°F (60 and 80°C), and says most granules have gelatinized by about 185°F (85°C). They're overlapping, approximate figures, not a doneness test.
- What is the white, gummy layer under the sauce?
- Modernist Pizza calls it the gel layer: undercooked starch where the dough meets the sauce, which stays too cool to cook through. In 120 test pizzas, the only complete fix was prebaking the dough; putting cheese on before the sauce and keeping toppings moderate both help.
- What is damaged starch?
- Starch granules cracked during milling. They absorb more water than intact granules, and flour's amylase breaks them into the sugars yeast feed on. Modernist Pizza gives typical levels of 8 to 12% for hard wheats and under 4% for soft wheats.
- Why does pizza go stale in the fridge?
- As it cools, the gelatinized starch recrystallizes, which Modernist Pizza calls retrogradation. The Quadram Institute says bread stales faster at fridge temperature than in the freezer or at room temperature, but leftovers still belong in the fridge within 2 hours, or 1 hour above 90°F (32°C), for safety; reheating softens the starch again.
Sources
- Nathan Myhrvold and Francisco Migoya, Modernist Pizza (2021), volume 1, printed pages 274–275 (starch, gelatinization and gelation, damaged starch, enzymes, retrogradation), 279 (Caputo’s milling), 288 (hydration and crumb), 328 (staling after baking), 337 (retrograded starch softening when reheated), 348 (the starch gel, its temperatures and its white look), 362–365 (the crumb setting and the heat pipe effect) and 370–371 (the gel layer).
- Quadram Institute: “What is the best way to store bread?” (2022). Checked October 14, 2026.
- US Food and Drug Administration: “Are You Storing Food Safely?” (the two-hour rule, one hour above 90°F, refrigerating or freezing perishables). Checked October 14, 2026.
- King Arthur Baking: Weeknight Detroit Pizza and Sicilian-Style Pizza (two-stage bakes), as used by the Pizza Planner. Checked October 14, 2026.