Have you ever peeled back the glorious cheese layer on a french onion soup to uncover soup that is as hot as the surface of the sun? Or removed a pizza from the oven and been so excited and hungry that you took a bite only to instantly blister the roof of your mouth with nuclear sauce just beneath the cheese?
There are certain foods that get us every time, and while I'm sure actual scientists have some type of scale based on conductivity, density and water content for this phenomenon... I don't know about it, so Bart and I created our own scale. The HEAT RETENTION FACTOR or HRF scale. This scale describe the property a food has to retain heat after cooking, the ability to heat to temperatures that will burn your gingival tissues, and the stickiness of that food to said tissues (worsening the burn results).
Our love of frozen pizzas led us to discuss this problem many years ago and since we created the scale we have made a number of observations in HRF.
1. HRF is variable for each food depending on the preparation. Sometimes microwaving a food creates higher HRF than baking.
2. HRF differs for the same food item in different preparations. Marinara sauce baked in a ziti with no mozzarella cheese covering has less HRF than the cheesed version.
3. Certain foods are HRF multipliers, some exponentially. Because cheese traps steam below it in foods like pizza and french onion soup, it protects the extreme heat pocket, dramatically increasing HRF values.
4. The time component of HRF can be subjective. Some foods never reveal their potential HRF because they are cooled before eating or because they take longer to reach the table (like delivery pizza)
We base our rating on the following scale:
10 - most likely to cause serious burns on the tongue and roof of mouth: this rating is given to french onion soup for the extreme heat of the liquid, ability to retain large amounts of heat for a period of time, and stickiness of the cheese topping. The soup burns your tongue, the cheese takes the roof of the mouth. Plus it usually smells and looks so appetizing that consumers are unable to wait the 20 minutes it would take to cool.
5 - medium risk HRF foods: given the right circumstances, when eaten with haste will inflict burns on the eater. Foods like reheated mashed potatoes and cheese whiz belong near this rating.
1 - foods that lose heat at an alarming rate, pose no risk of burns and become less appetizing quickly after cooking: steamed asparagus and broccoli have the least HRF because they lose heat immediately after cooking and have no stickiness.
Why am I sharing my HRF scale with you? Because its so annoying to burn your mouth. Your tastebuds lose their ability to communicate the glorious food you're eating, it's painful, and if it blisters - impossible to stop yourself from running your tongue over the burn like a weird-tasting ocd tic. As I type, I'm licking my wounds - literally - from last night's pizza incident in which I tried a new oven configuration thanks to an article from the food lab over at Serious Eats. The pizza was cooked perfectly, but I prematurely bit (forgetting the HRF) and roasted my palate.
Other high-HRF foods that always need extra time to cool: steam-baked potatoes [HRF 8](wrapped in foil and baked or microwaved), baked macaroni and cheese [HRF 7] and microwaved soup [HRF 8+].
So if you do any cooking at home, which is where most HRF-related burns occur, consider potential HRF based on temperature, timing and stickiness before excitedly trying your dish. Your mouth will thank you.