Can deep frying oil be too hot? Some days ago I made some "eggplant meatballs" (no meat inside - not sure how you would call them in English).

The recipe was quite simple: bake the eggplants for 45 mins to soften the pulp, put it in a bowl with a spoon, add some seasoning, grated cheese and egg, make same small "meatballs" as balls about 3cm in diameter, soak in whisked egg, roll in grated bread, deep fry.

We used a proper frying oil, heated it in a small saucepan and fried about four balls at a time.

We were using an induction stovetop and I am no expert of it at all, so this might have contributed.

The point is that the oil was probably too hot. I did not have a thermometer but of course it did not reach the smoke point, I just waited a bit and tried it with a breadcrumb. When I put the balls in the oil it immediatly started to boil, so it definitely was not too cold. Problem is that in something like 20s the outside of the balls turned golden brown but unfortunately the inside was just warm.

We ate them and they were delicious and not raw at all, but I started to wonder if too hot oil when deep frying is a thing or not since I've never heard of it. I was surprised also because the balls were very small, anything human made can't be that smaller and of course bigger chunks of food would soffer much more the "too hot oil syndrome".

The question then is: can oil be too hot when used for deep frying?
Yes, certainly. Deep frying only works well in a very narrow temperature range. The optimal temperature is different for every food, but it's in the 180 to 210 Celsius range. 

The needed temperature is determined by the starch type and the amount of wetness on the outside, and is chosen such that it crisps immediately (not allowing the inside to get soggy with oil) without burning immediately. The inside doneness is not controlled by changing the temperature. If you get underdone or overdone insides at the correct frying temperature, you need to change some other variable, such as the thickness of the food, the degree of parcooking, or the food temperature at the moment it hits the pan. 

Because a good result is so dependent on temperature, I can strongly suggest both the use of an oil thermometer (a barbeque probe does it too, if it's rated for the temperature) and controlling the initial temeprature of the food (room temp, out of the fridge, or frozen). A good recipe will tell you the proper parameters for both.