Pastry
Frying Pastry Is Baking In A Medium That Conducts
Hot fat transfers heat far faster than air, so fried doughs set their crust in seconds and their internal steam has to do all its lifting immediately.
A doughnut and a bread roll can start from similar dough and finish completely differently. The cooking medium changes the rate at which heat arrives.
Fat carries heat far better than air
Oven air is a poor conductor, so a bake's surface heats gradually and the crust develops over many minutes.
Hot fat is dense and in full contact with the dough, so heat crosses into the surface almost immediately and the crust sets within seconds.
That is why fried items cook in a fraction of the time and why the temperature of the fat is such an unforgiving variable.
Steam escaping is what keeps fat out
Water in the dough turns to steam at the surface and rushes outward, and that outward flow physically blocks fat from entering.
While the dough is producing steam, it absorbs very little fat. Absorption happens mostly at the end, as the item cools and the pressure reverses.
This is why fat that is too cool produces greasy results. Slow heating means weak steam production, and fat enters instead.
The pale band records the float line
A doughnut floats, so part of it sits above the fat and is cooked only by steam and radiant heat from the surface.
That region never reaches browning temperature and stays pale, producing the ring around the middle that marks a well-proofed doughnut.
A thin or absent band usually means the dough was underproofed and dense, so it sat lower in the fat and cooked more evenly and less well.
Interior cooking is limited by depth
Because the crust sets so fast, the centre must cook by conduction through already-cooked dough, which is slow.
Anything too thick browns outside long before the middle is done, which is why fried pastries are small, thin or ring-shaped.
Choux fried as fritters exploits this differently: it is already partly cooked before it enters the fat, so only the setting remains.
Fat degrades as it works
Repeated heating and contact with dough breaks fat down, lowering the temperature at which it smokes and changing its flavour.
Crumbs left in the fat burn and accelerate that breakdown, which is why the fat is strained between batches in any serious operation.
Older fat also browns food faster and less evenly, so a batch cooked at the end of a session behaves differently from the first.
Questions readers ask
Can I make croissants entirely in one day?
You can, but every rest becomes the minimum rather than the comfortable option and the margin for error disappears. Splitting the work across two days is easier and generally gives better results.
Does a laminated dough need a bulk fermentation before lamination?
Recipes differ, and many give the dough only a short rest before chilling, relying on the long cold stages for flavour. A long warm bulk before lamination usually leaves too little fermentation capacity for the final proof.
