Researchers are recommending frying with olive oil whenever possible and adhering to the 350-degree frying temperature recommended by the International Olive Oil Council.
The researchers focused on emissions of volatile pollutants, particularly the chemical compounds acetaldehyde and acrolein --both the subject of pollution studies by the EPA.
The EPA has declared acetaldehyde a "probable human carcinogen" and acrolein "extremely toxic to humans"
and "a possible human carcinogen." (From the "National Air Toxics Program: The Integrated Urban Strategy Report to Congress," 2000.) They cooked the oils for 15 hours at 180 degrees Celsius (or 356 F), and for seven hours at 240 degrees Celsius (or 464 F).
At 180 C, canola oil released twice the amount of acetaldehyde as extra virgin olive oil and as much as four times the levels of acetaldehyde emitted from regular olive oil. Acrolein levels emitted at this temperature were five and one-half times higher than from either of the olive oils.
At 240 C, canola oil released two and one-half times the amount of acetaldehyde as extra virgin olive oil and as much as five times the levels of acetaldehyde emitted from regular olive oil. Acrolein levels emitted at this temperature were as much as nine times higher than from either of the olive oils.
"Those are significant differences, especially at the higher temperature," Carbonell said. "A lot of people fry at the higher temperature, especially when they stir fry. What's important about this research is that we're not talking about toxins being absorbed into the body by ingestion but by breathing them. So they can be harmful to the person who is cooking and others nearby.These studies were carried out at high temp and over prolonged periods of time2.
And this answer is quite simple
the sauce coagulates (thickens) as it cools,
if you apply a warm sauce to a pizza base it will be thin and runny and not give you the same coverage.
Cold thickened sauce gives a good base for applying the grated Mozarella cheese and topping, without them sliding about the crust.
Hope that helps, when I wrote this recipe years ago, most chefs said,
keep the Extra virgin Olive oil for dressings and keep the other (lighter) oils for frying.
Looks good Just a couple of questions: 1), what toxins are released with extra virgin oil? I've never heard of that before. And 2) why "MUST" it cool overnight before use?