The De Longhi Cool-zone deep fryer underneath the heating element means that food particles do not burn, if they drop into the bottom. The oil therefore remains cleaner for longer. The deep fryer has a “cool zone” at the bottom of the fry bowl. This is where larger food particles sink and the lower temperature keeps them from burning and tainting the oil. A tube-style fry pot has a large cool zone because the tubes are slightly above the bottom of the vat, leaving generous space for cooler oil and crumbs. In this way the oil will be clean for longer.