Baking – How long should I bake a hamburger meatloaf, and at what oven temperature

If we had a magical (or 4d) oven that could heat up the inside of the food all at once and uniformly, the baking rule would be simple:

• bake batters and doughs at 100°C / 212°F until dough expands and dries, and
• then increase to 150°C / 302°F to brown.

Any recipe that followed it would take way longer (several hours) than regular recipes, but the timings would be forgiving. The rule works because baking consists of growing the dough bubbles with water vapor and after that browning for flavor. Without a magical 4d oven and without hours to bake a dish, recipe authors have to experiment.

In ovens at higher temperatures the water near the surface of the dough or batter will first evaporate, keeping that region at 100°C. Once the surface dries its temperature starts to rise and eventually browns. While it browns, the region below goes into bubble growing mode and the process repeats. To get the whole dish cooked and browned at the same time requires an impossible balancing act because of how the bubble region moves depends on the dough's shape, its water content, its initial temperature, air flows in the oven ... There are many solutions to the balancing act and therefore many possible baking temperatures.

The exact details of all this are still the subject of research, as a recent paper exemplifies.

I'd reheat it at 375 again, covered, and add maybe 1/2 cup liquid to start. It will probably take about 30-40 minutes to come back to temperature. If you have an instant-read thermometer, it is at a servable temperature at 160, though you may want to go a fair amount higher if it will sit long before being eaten.