This is not so much a recipe post as it is one about how different cooking methods work, and why some are better than others for specific items. Before we continue, let us stipulate that the definition of cooking that we shall use has to do with adding heat to foods to change their physical, chemical, and other properties. Under this definition, things like making a salad do not count.
We are concerned this evening about the different ways that heat can be introduced into food. There are really only a few, and all of them have their merits and demerits, depending what is being cooked.
Before we get started, we much review the three ways that heat can be added to anything. Those are the Big Three of conduction, convection, and radiation. Conduction is when heat is transferred from a hot object to a cold one by means of physical contact, like cracking an egg onto a hot griddle. Convection is unique to fluids or semifluids and has to do with heat moving from one place to another because, in general, hotter materials are less dense than cooler ones. Thus, in a pan of water on the stove the water heated by the bottom of the pan (via conduction) rises towards the top because is is less dense. Convection requires gravity, by the way, or there is no driving force for less dense materials to rise. Radiation (classically, infrared radiation) heats things by causing their molecules to undergo vibrations, and this motion in turn makes them hot. Think of the broiler. In cooking, there is another radiative heating mechanism, microwaves. These are lower in energy than infrared and work by causing water molecules to undergo rotations when exposed to microwaves. This motion heats up the other molecules in the food.
Basically, we cook using all three (four, if you, as I, make a distinction betwixt infrared and microwave radiation) methods. In reality, convection does not really do to much to cook food, but is mostly a method of getting the high temperature media to the food, when conduction takes over. But since convection is a term that is highly misused, I thought it important to include it. Here is how it is misused:
A convection oven is really a misnomer. A better name would be a forced circulation oven. All conventional ovens are convection ovens, in that the air near the electric element or gas fixture is heated and rises towards the top of the oven. As it cools when it heats up the top of the oven, it becomes cooler and sinks, displacing the hotter air at the bottom. The cycle repeats until the oven is deactivated.
What is called a convection oven uses fans to circulate the air artificially, so that the natural, fairly slow convection cycle is replaced with a much faster forced circulation that is more efficient in bringing hot air to cool (relatively) food, making it cook faster. But it not really convection, is is just forced circulation.
OK, that leaves us with conduction and radiation for the most part if we accept that convection is just a way of moving heat around and that conduction is really the active agent. There are several ways to cook by conduction. The most common ones use some sort of a fluid medium to transfer the heat in the medium to the food. That fluid medium is most often either air, water, or some sort of oil (aka fat).
In roasting (baking for breads and oddly for poultry, but the process is identical), hot air from an oven transfers heat to the food to be cooked. Roasting is very inefficient as far as heat transfer goes, but gives results not possible with other methods. For one thing, there is no upper limit to how hot air can get, since it is so inert. Ovens can range from barely on to 500 degrees F or more. There is not any danger of the air catching on fire! However, it is possible for grease cooking out of the food to contact the electric element and become alit. That is more probable with toaster ovens.
Roasting is a dry method of cooking, meaning that no water is used as a heat transfer medium. Since air is around 1000 times less dense than, say, water, it transfers heat quite slowly. Here is a thought experiment for you to try. In you mind, preheat your oven to 212 degrees F. Now put your hand inside of it, and by magick close the door so the oven stays at that temperature. I suspect that you can keep your hand inside for a LONG time before it gets painful. Now, for the second part of the thought experiment, take a large pot of water and bring it to the boil, the same 212 degrees F, and put your hand in it. See what I mean? Within one second you would not only feel horrible pain, but you would be seriously injured. That is what I mean when I talk about roasting being inefficient insofar as heat transfer is concerned.
Sometimes inefficiency is a good thing. For example, the moisture that evaporates from a nice roast keeps the outside from getting overdone before the centre cooks through. Yes, I have reverted to UK spelling! Also, since air can get really, really hot, Maillard browning reactions can occur that give bread and some wonderful meats a flavour spectrum not possible otherwise. That is sort of characteristic of dry cooking methods.
Roasting is best used for meats that are inherently tender, because this method does little to tenderize things. Poultry, being tender, roasts well, as do tender cuts of beef and pork. Tougher cuts do not do well when roasted, because the heat balance is all wrong. Of course, breads do well roasted (baked) because they are designed to be tender in the first place. In general, dry methods are good for tender meats and vegetables and wet methods for tougher cuts of meat and vegetables that tend to be either dry or tough, like beans.
There are a couple of other dry cooking methods, and, as odd as it sounds, they involve putting a liquid on them. Those include the variations of frying. In frying food, some sort of fat is used as the heat transfer medium. Since liquids are, as I said earlier, around 1000 times more dense than gases, this method of transferring heat is much more efficient than is using air as the heat transfer medium, and the browning reactions are evident in fried foods.
There are several variations in frying, including stir frying, sauteing, pan frying, and deep frying. The major difference in these methods is the amount of fat that is used and the temperature.
Stir frying, for reasons to be given presently, is mostly a professional activity. In stir frying, extremely high temperatures and just a little fat are used to cook relatively small pieces of food quickly. Browning reactions can take place if the food is in contact with the hot surface long enough, but generally the contact time is so short that they are minimized. The reason that is mostly a professional activity is that the heat input required for proper stir frying is so great that most home ranges just can not keep up with it. There is a reason for that.
All food, except for dried or dehydrated food, is mainly water. The heat capacity of water (the amount of energy to raise water by one degree C) is 4.2 kJ kg-1K-1, higher than almost any other substance. That means that it takes a LOT of energy to make the temperature of water rise compared to just about everything else. It also has an extremely high latent heat of vaporization (the amount of heat to change from liquid to vapour) of 40.g kJ mol-1, so it takes LOTS of energy to heat up food containing water, and almost ten times more to drive it off as steam. Remember this, because it is important later as well.
That means, at least for stir frying, it is almost impossible without some huge energy input (think turkey fryer burner) to perform stir frying properly except for very small quantities of food, because the range just can not pump enough energy in for more than one or two servings. What we usually do rather than stir fry is to saute. It IS possible to stir fry at home, but on a normal range this involves something like heavy cast iron heated really, really hot, some oil put in at the last second, and only enough food to cover the bottom added. Generally, stir frying takes only a few minutes. By the way, it is not possible to stir fry properly in woks heated on a kitchen range, at least in the thin sheet metal ones, because it is not possible to store enough heat in such a flimsy vessel.
Sauteing is similar to stir frying in that only a small amount of fat is used, but the temperatures are significantly lower than for stir frying. This has some important ramifications. The first is that water is not driven off fast enough to prevent it from making the food wet, so in many cases the food boils for a while. That is not necessarily a bad thing, such as in sauteed onions. However, for things like broccoli, for example, the boiling softens the vegetable and mutes the color. That is the chief difference betwixt the two methods.
Pan frying involved cooking food in enough fat to come up just over halfway on the food being fried. Lesser amounts of oil is more like sauteing, and it is possible to cook somethings successfully that way. Generally pan fried foods are breaded (except for French fries) to provide a carbohydrate rich surface for browning reactions and to insulate the interior of the food somewhat from too much heat. In most cases the outside of the food gets overdone before the centre is cooked through if it is not breaded. Here is how I cook pan fried chicken.
I cut up and wash the chicken and dry it a LITTLE. Then I roll it in seasoned flour (salt, black pepper, usually thyme, and sometimes a little garlic powder) and add it to a cast iron skillet containing enough oil that is preheated until a drop of water dances on it. I use medium to medium low heat and cover the pan, so that the chicken both steams and fries. Before the bottom is golden, I turn the pieces and cook the other side. Then I uncover it and crank up the heat to medium high to finish browning one side then turn it to brown the other side. Then I use tongs to remove it from the fat, let it drip a few seconds, and then put of absorbent paper and serve right away. The only delay is in a low oven, on a rack, whilst I make the gravy.
Deep frying is cooking food in enough fat that it is completely immersed. Lot of food can be deep fried or pan fried, but the results are somewhat different. Because of the large amount of oil, it is hard to change the temperature quickly like one can do with pan frying. Thus, in many cases there is a compromise betwixt nice browning and getting the food too done unless the pieces are thin, like fish fillets or French fries. Here is my method for perfect French fries.
Cut potatoes in as uniform strips as possible. I just scrub and cut, but you may pare them if you prefer. Keep them covered with salted water until ready to cook to prevent darkening. When ready to cook add them to a deep fryer of oil at around 350 degrees F and cook until JUST STARTING to brown. Then take them out of the fat and chill them in the refrigerator for an hour or longer. The oil coating will prevent them from darkening from air contact. Now crank your oil up to around 380 degrees F and add back the potatoes. Cook until brown enough to suit you. Drain on absorbent paper, salt them (the McDonald's really fine salt in the little red packs is perfect), and serve them immediately. Speaking of McDonald's, one of the secrets to their wonderful French fries is that they precook them just like I said and them cook them frozen at about the temperature that I just specified. Do not try to cook French fries in only one step or they just do not turn out as well as with two cookings. I prefer red potatoes, but French fry experts like russets because the interior is fluffier. You can do like McDonald's and precook French fries and freeze them for later use. NEVER freeze raw potatoes because they will spite you.
Here is a little known fact about frying, in particular deep frying bare foods like French fries. Perfectly fresh oil does not make them brown very well. The oil has to be broken in with a previous batch of food to brown properly. There is some science behind that. It turns out that very fresh fat does not interact with polar materials very well, and thus does not bind as tightly to the food in the pan. After oil has been used, there are some degradation products in it that can wet the surface of food better, and better wetting means better heat transfer. Thus, when you get ready to change oil in your deep fryer, keep about 5 to 10 per cent of it and add it to the new fat.
Fried foods are not inherently bad for you, at least when fried properly and in "good" fats. However, they have a high calorie value and are best eaten sparingly. By proper frying I mean frying in such a way that excess fat is not absorbed, just enough for good mouth feel and taste. That is why frying at the proper temperature to discourage excess fat absorption, allowing fat to drip off for a few seconds, and using the absorbent paper. A rack is essential if you store the cooked food for more than a couple of minutes because moisture coming from the interior will rapidly make the coating soggy if it can not breathe.
So far, all of the dry cooking methods that we have discussed involve conduction of heat, either by air or by fat. There are three other dry methods (two are actually just variations of a theme for the most part) that cause the Maillard reactions and improve the flavour of food.
The first is grilling, which may be our very first cooking method. In grilling, food is placed over hot coals (or hot lava rocks if using a gas grill) and infrared radiation cooks the food. There may be a bit of hot air contributing, but for the most part it is the IR that does the work. The real difference betwixt grilling and broiling is that in grilling the food cooks from the bottom, whilst in broiling it cooks from the top. There are some ramifications of that fact.
In grilling, drips of fat and water often fall onto the hot coals. Those drips are vaporized and a significant fraction is redeposited on the surface of the food. In broiling, we use a catch pan to keep the drips from the bottom of the oven, and only a very small amount of them are vaporized and redeposited. That makes quite a taste difference. It also may make a health difference, because when fats in particular hit hot coals they are pyrolyzed (literally, "changed by heat") and some of the pyrolysis products are carcinogenic. When grilling, try to avoid letting the grill flame up to reduce the amount of these products. Even without flaming up, grilled foods high in fat should be eaten in moderation.
Both of these processes are quite efficient, but work only on the very outer surface of the food. Grilling and broiling are very fast in searing the outside, but slow conduction is what cooks the interior. Thus, unless you are very careful, it is easy to incinerate the outside of the steak or chop whilst the inside is not done.
However, with a little experience both broiling and grilling are excellent methods for cooking tender cuts of meat and also slices of vegetables like summer squash or whole, narrow, tender vegetables like asparagus. Grilling tends to be a bit faster because in broiling the oven door is usually left open so the moisture can escape. In grilling, the top of the grill is often closed to regulate the fire, so there is some cooking with hot air as well.
The other method is pan broiling, and it is a misnomer. It is closer to stir frying or sauteing, but yet different a little. In pan broiling, a griddle or skillet is heated hot and a piece of (generally) meat is added usually after a tiny amount of oil has been added. It it turned once, and that distinguishes this method from stir frying and sauteing since those methods generally involve lots of agitation of small pieces of food. "Frying" an egg is really more like pan broiling, since a very small amount of fat is used and it is turned only once.
There is another cooking method that involves radiation, and that is microwave cooking. Microwaves work by imparting rotational energy into water molecules (or a few other molecules such as fat), whilst infrared involves stretching and bending of molecular bonds. Actually microwaves contain less energy per einstein of photons than even infrared, so "nucking" is a poor term indeed for microwave cooking. In no way can microwaves cause food to become radioactive!
Since it is almost always water that is being heated in microwave cooking, there is little chance for the Maillard reactions to occur. Notable exceptions are foods that are extremely high in fat, like bacon. Fat also is influenced by microwaves, so microwave oven bacon can be just as crisp and nicely browned as roasted or pan fried bacon. I actually prefer cooking bacon by that method because I have a microwave bacon pan with little ridges that allows the fat to fall from the bacon, producing a less soggy product. By the way, I greedily keep all of the fat the cooks from the bacon to use as seasoning. Yes, I am a son of the south.
Microwave cooking is extremely efficient of power because only the food is heated (unless you are using a microwave dense container to get some browning). However, it is inferior to some other methods for many things, but where the microwave oven works well, it has no peer. Want a single cup of tea? Just heat your cup of water in the microwave oven and add you tea bag when it is hot. By the way, be sure and use containers that have imperfect interior surfaces when boiling water in the microwave oven. Some folks think that this is urban legend, but I have personal (well, I was in the kitchen at the time).
Years ago, the former Mrs. Translator was heating water in a new container. After it had been heating for the amount of time that she estimated was about right, she reached to get the container and as soon as she touched it it erupted, spewing a geyser of boiling water. She had fast reactions and was able to move her hand before she got a serious burn, but she still got burnt a little. This happens because of the phenomenon of superheating. When liquids are heated to the boil, they, well, boil. Except when they do not. It is possible to heat a liquid past its boiling point if the container is very smooth on the inside. It turns out that water (and other liquids) require nucleation sites to boil smoothly. In older containers, the daily routine of use and cleaning produces tiny surface defects that serve as nucleation sites.
For brand new containers, that is not always the case. Those of you who have had high school or college chemistry laboratory probably remember boiling chips, those little alumina or PTFE chips that you put in a test tube to prevent bumping, which is just superheating. You can do the same thing at home. The next time you break a stoneware plate or bowl, save a few pieces to use as boiling chips. Obviously you can not put them in a stew or anything, but if you are merely trying to boil water, add two or three to the container and just pour the water off of them after it comes to the boil.
The microwave oven is great for heating up leftovers, and I have eaten microwaved "baked" potatoes that were OK, but without Maillard browning to crisp up the skin, I do not really care for them because I scrub my baked potatoes and eat the skin. There are lots of prepared foods that are designed for the microwave oven, and some of them are OK. One thing I hit on independently is that asparagus can be cooked in the microwave oven with excellent results. Here is what I do.
Remember the bacon cooker that I mentioned a while ago? The ridges designed to keep the bacon off of the bottom are great for allowing one to separate asparagus spears in the low part of the pan betwixt the ridges. Then just add a little water and sprinkle with salt (not too much, because there is little water), and add a little butter to each spear. Cook just until barely done. The color is excellent because you are really steaming more than boiling, and since so little water is used, the sugars in the asparagus are mostly retained. I find this a superior method for asparagus.
For tougher cuts of meat and tougher vegetables, wet methods work well. They can also be used for more tender items if care is taken. Wet methods involve cooking in water, sometimes just the water that is contained in the food but usually with water added.
There are several variations of wet methods, which include boiling, simmering, braising, and steaming. Wet methods not only allow foods to become tender, they also add moisture to them and are extremely efficient. Remember the Geeky stuff about heat capacity and latent heat of vaporization that we talked about earlier? For those very reasons water transfers heat very readily.
Boiling actually has little use in the kitchen. It has its places, but those places are actually few and far betwixt. Making jellies and blanching vegetables for freezing are two of the few that come to mind, along with cooking pasta. Boiling involves a lot of motion and can sort of make mush of things, and it is way too hot for most foods. Remember, heat transfer is extremely efficient in wet methods, and it is very easy to overdo it.
What many call boiling is actually simmering. In simmering, the water is kept at around 180 to 190 degrees F. Since there are not big bubbles to cause turbulence, the food is not damaged as much. For pasta the turbulence is a good thing, because it keeps the pieces separated and so they do not stick together. For other things, not so much. The primary use of boiling other than the ones just mentioned is to reduce stocks because you want to drive the water off in your lifetime, and a rolling boil is the most efficient way to do that.
For example, eggs that are actually boiled are awful. They have green rings around the yolks, are tough and dry, often have cracked shells, and have a strong odour. The better way to "boil" eggs is to simmer them. For example, to cook hard cooked eggs, take the eggs and cover them with cold water. Be generous with the water. Bring it to simmering (for those of you without a thermometer, just before continuous bubbles are forming). Leave the lid on the pot whilst you do that. Then turn off the heat and wait 12 to 15 minutes. Drain the hot water and thrown in ice and cold water and let the eggs sit for about ten minutes.
This does several things. First, at only around 180 degrees F, the harsh flavors, broken shells, and green yolk rings are largely avoided. Second, by adding ice and cold water cooking is stopped at the outside of the egg, helping to prevent it from being overcooked whilst the centre still is finishing. Third, the ice and cold water shock makes them easier to peel. Another hint is to use not perfectly fresh eggs for hard cooked ones. Really fresh eggs almost always are hard to peel without damaging the albumen. If you know that you will be cooking simmered eggs and have only really fresh ones, leave them out of refrigeration for a day or two.
Simmering is used a LOT in cooking, and it is a component part of braising. Braising is cooking food (think pot roast) in its own juices, sometimes with additional water or stock or tomato juice, very slowly and for a long time. It is the ideal method for cooking relatively tough cuts of meat, because the extended treatment of the tough collagen in the tough cuts transforms it to tender gelatin, tenderizing the entire piece. But please do not just throw the chuck roast into the Dutch oven and get it going. It will be lacking flavour if you do that. The same thing goes for stewing, which is just another form of braising.
First, coat the meat with seasoned flour, salt and pepper of course, and whatever else your heart desires. Then saute it with a little fat on a hot skillet or griddle to brown the surfaces. For stew, make sure that the meat is only a single layer and keep turning the pieces until they are browned on the surface all over. For a pot roast, brown one side nicely and then the other. This step is quite important, because the Maillard browning reactions provide lots of flavour depth. Then put it in a little water in a heavy pan and either cook it on the surface just below the simmer (around 170 degrees F) or in a slow (300 degrees F or so) oven. Do not put the lid completely on the pan, but leave it ajar a bit. Here is why.
If the lid is left on, there is essentially no water evaporation, and that allows it to reach the boil, thus overheating the meat. Leaving it ajar helps keep the braise from overheating. The evapourative cooling is important to keep things from overheating. The secret for a successful braise to tender up the meat is to have several hours at around 170 to 180 degrees F. Obviously, you may have to add a bit a water from time to time. If you want to have vegetables cooked in the stock, add them around an hour before you want to serve the meal. You might want to put on the lid and increase the temperature a bit to make sure that they cook through at serving time, or quarter potatoes and onions, and cut celery and carrots to about three inch lengths.
Steaming is interesting because it uses the latent heat of vaporization in a reverse fashion. When a relatively cold food, say broccoli, is added to the basket of a steamer that is already preheated and at the boil, the water vapor condenses on the cold food. There is a lot of heat released when that happens, remember the 40.g kJ mol-1 for the latent heat of vapourization of water? Well, that energy is deposited into the food immediately. As the food heats, less and less water is deposited on it, so steaming is most useful for small pieces or ones that have lots of surface area, like broccoli. Even though a wet method, properly steamed food cooks very quickly and that preserves the bright colors in green vegetables.
The most extreme method of wet cooking is pressure cooking. In this method, a closed and sealed pan is charged with food and some water and is taken to extreme temperatures (for a wet method). We are talking around 240 to 250 degrees F. Things happen rapidly at those temperatures, and not all of them are good. Meat becomes stringy and the high temperatures degrage collagen, leaving the broth thin and with poor mouth feel.
However, pressure cooking is great for some things. Dried beans cook in a fraction of the time that is required in a regular pan, and are not damaged too much by the high temperatures. Just be sure to have enough water in the pressure cooker! I do not like to use it for potatoes because they are too easy to overcook anyhow.
Pressure cooking is necessary for home canning of meats and low acid vegetables because of the possibility of spores of Clostridium botulinum being present in the food. Normal boiling temperatures at not high enough to kill the spores, and if they survive in a low acid medium they form the botulism toxin, one of the deadliest toxins known. Interestingly, the name derives from the Latin botulus, meaning sausage. Sausage cured without nitrite is indeed a hazard, but nitrite seems to prevent the spores from reproducing and prevents the formation of the toxin.
That about does it for tonight. Since I am writing this of Friday, I have no idea what I will have for dinner tonight, but I shall provide a menu in the comments. I appreciate being able to contribute to this series. It has been a long time.
Warmest regards,
Doc, aka Dr. David W. Smith