I've eaten both and except for the fact that sometimes polenta is a little bit more firm, they taste the same...Any southerners out there that can help?
Some people say it's just preparation and the base is the same ground corn / corn meal, some people say for grits you need (more coarsely) ground hominy (which is corn that has been soaked in lye or lime).
Polenta can be found loose and really solid: grits are generally loose.
Corn type may also differ, as may the dish's 'typical cultural trappings' (fat cheddar and bacon vs. leaner stuff)
True southern grits are made with ground hominy whereas polenta is simply ground cornmeal. The proper name for them is actually hominy grits. You can make "grits" out of untreated corn, but these are corn grits and not really found in southern US cuisine. Grits are typically a much coarser grind than polenta.
Hominy is corn that has been nixtamalized, which means soaked and cooked in an alkali solution, typically lye or limewater. This process converts the niacin present in corn into a form more soluble in the human body. Early European importers of corn from the USA dismissed this process as unnecessary, and as corn became a subsequent staple a pretty nasty disease called pellagra took hold caused by niacin deficiency.
Reading the definition of grits ("a dish of coarsely ground corn kernels boiled with water or milk"), the only difference I see with polenta (living in an Italian region where it's largely used) is that polenta is not made with milk.
Other differences could be:
- The coarse grade of the ground corn kernels.
- The type of corn kernels used; we use also buckwheat to make polenta.
- The other ingredients used to make grits; In Lombardy, there is a polenta called taragna that is made using buckwheat flour, and adding cheese.