Physic cooking tips

Barbecue times are coming. It reminds me of the observations I made a few times when seeing different people cooking raw cow steaks using frying pans. Basically it can be summed up as : "most people have no ideas of the physics of cooking" . They have no clue regarding how to control the fire. They have no clue regarding the flipping of the steak. And what's even more frightening, is that often this results in risks for your health. So let me show you how to improve.

Why are we cooking things ? The first reason is a sanatory one. Cooking kills bacterias. To kill bacterias by cooking, you need to have the temperature inside the bacteria maintained over a temperature for a certain time. Sterilisation time-temperature charts varies with bacterias, but you can consider that  if the raw meat cell is cooked, bacterias are dead. For cow steaks, dangerous bacterias are only on surface of the raw steak. This mean that if your steak is raw you can cook only the sides, but if your steak is grounded, you need to cook the inside (because bacteria that were on the sides are now everywhere). Depending on the type of meat you are cooking you may or may not cook only the surface. For exemple chicken, pork and most fishes should be cooked to the heart. The second reason for cooking is to ease digestion. Cooking chemichal reactions are somehow similar to reactions that will occur in your stomach. Stomachs used only to cooked food, may need some time to adapt to rawer food.

Now that we know  how it can be cooked, we need to know how to cook it the right way. Cooking is all about controling the "temperature over time" inside the meat. So you need to understand the heat diffusion inside the meat. The rule is that heat transferts are slow, and the speed of heat transfert depend on the local difference (gradient) of temperature. This mean for example that if the temperature on the side is very high, the heat will not have time to propagate inside the meat, and only the exterior will be cooked very rapidly. If the temperature on the side is lower, then heat will have time to be diffused inside the meat, and the meat will be cooked to the heart. The thickier the steak, the more time it takes to heat the heart. Flipping a steak, allow to bring quickly down the temperature of a side.

Now we need to know how to precisely set the temperature of one side. This is usually done using grease. This provide an accurate mean of setting the temperature, because we have a nice physic property which states that at a given pressure, vaporisation occurs at a constant temperature. (Around 200 Celsius depending on the oil). This mean that if you use some grease, as long as the grease is bubbling, the temperature is precisely known. No matter how strong the grease is bubbling, it will be at the same temperature, but if it bubbles strongly, the grease will evaporate and disappear more quickly while forming lots of fumes. Once the thin layer of grease between the pan and the steak has evaporated, temperatures will skyrocket and your steak will get carbonised on the outsides, grease fumes might get carbonated which is cancerigenic. So the way to regulate the fire is to set it as low as possible while preserving a bubbling greese, ideally when the fire is perfect, only the greese below and near the steak should bubble, and fumes should be quasi inexistent.

When flipping a steak be sure to maintain a thin layer of greese between the steak and the pan.

Now the last thing you need to know is that "cooking" is in fact modifying the internal structure of the meat. "Cooking" are chemical reactions that occur inside the meat. There are plenty of various reactions, but each of these reactions occurs at different speed, speed of which depends both on the reaction, and the temperature. By controlling the temperature precisely inside the meat, you can favor certain chemical reactions, and limit negative ones (like carbonization). 

An other factor that you can modify is the inner pH by cooking with some acids.

Hopefully, you now have a physically correct model, of the cooking process, which will allow you if you use a chronometer (up to seconds (once cooked remove from the pan to slow down the cooking process) ), to cook consistently. This model will help you understand what you are doing, which will make more easy to cook safely according to your tastes. 

A corrolary of this model you can use to cook salmon steak with a frying pan :  put a thin layer of water, make it boil, put the fish in the frying pan, skin side down, cover the frying pan to keep the vapor inside. As long as there is liquid water in the pan, the steam will stay 100 Celsius. Cook to the heart, find the time needed depending on the thickness. Because we only heat with less than 100 Celsius, the inside won't go higher than 100 Celsius, therefore the fish will retain its water and savor.