It’s happened to all of us: Just as you go to turn out the perfect upside-down cake to impress your dinner guests, it sticks to the dish and crumbles into pieces over the serving plate, leaving you frustrated and not knowing what to serve instead—and knowing you’ll have to deal with scrubbing the mess out of the pan later.
But why does food stick? Well, food sticks to cookware for the same reason that a wine label sticks to a bottle. It might sound strange, but in both cases, there’s glue. Most glues (whether manufactured or homemade) contain long molecules that bond well with certain surfaces. Think of them as ropes tightly knotted to two objects, keeping them firmly fixed together. And in the case of food sticking to pans, the glue is usually protein. During cooking, proteins in food can react to the surface of the pan, and these reactions literally glue the food to the dish.
Proteins as glues
Proteins have been used as glues since ancient times; the glues used in fine furniture were prepared from the proteins in animal bones and cartilage, while milk proteins were used to make paper glues. Many modern glues differ only slightly from the protein glues of old.
Airplanes are increasingly glued together, rather than riveted, so glues can make very strong bonds. This simple experiment shows just how strong protein glues can be: Take two pennies. Clean them with vinegar or lemon juice. Spread a thin layer of egg white on one penny and then place the second one on top. Now hold with tongs over a hot burner for a minute, or bake in the oven at 270°F for 10 minutes. Let them cool and then try to separate the two coins. You can’t. They have become glued together. The same will happen, more or less, with any protein (eggs are just easily accessible).
Proteins make good glues because they’re long molecules (strings of amino acids, really) that become chemically reactive when heated to 240°F (116°C) or hotter. When cooked, proteins change in structure and consistency, creating new flavors and textures in food. In the process, proteins form strong bonds with one another, as happens when we cook eggs, and also with metal, as happens when food gets stuck to the pan.
This doesn’t just happen when you’re using a metal pan. There are many metal atoms in the surfaces of glazed ceramics and even in glass, so nearly all traditional cookware is potentially prone to problems of food sticking.
Most food is susceptible to sticking—not only high-protein foods like meat, fish, and eggs. Even foods that we think of as being starches, such as flour and rice, contain enough protein to make them stick.
Ways to prevent sticking
Now that we know the main cause of food sticking to pans (proteins in the food reacting with metal on the pan surface), the way to prevent sticking is clear: just make sure the proteins never come into direct contact with the pan’s surface. Indeed, this is how all the traditional methods for preventing sticking actually work.
Stir the pot. People often find that thickened sauces such as gravy and béchamel sauce stick to the pan unless they’re continually stirred. As long as you keep stirring the sauce, you keep the temperature uniform, and it will not get much hotter than the boiling point of water 212°F (100°C), even at the bottom surface. If you stop stirring, however, then water can boil away from the bottom, and the temperature can rise well above 212°F, allowing reactions between proteins and metal atoms to happen more quickly and more frequently.
Buy a nonstick pan. These days, many cookware manufacturers offer pots and pans with a “nonstick” finish. The coating is a layer of inert material bonded to the underlying metal. Most manufacturers use polytetrafluoroethylene or PTFE, which has a number of trade names including Teflon. PTFE simply will not react with the proteins no matter how hot the pan gets so food never sticks to the pan.
Nonstick pans work well, but if the PTFE layer is bonded to the pan’s surface, it can gradually wear away as you wash the pan, and once any metal is exposed, food will stick. Or, if you scratch the PTFE off the surface, then you may expose the metal underneath, converting it from a nonstick to a sticky pan. Recently some manufacturers have managed to incorporate PTFE particles inside the metal in an attempt to avoid this problem.
What to do if a cake sticks
If you’ve greased and floured properly, a cake should release from the pan when you invert it onto a plate. If it doesn’t, the best thing to do is to turn the tin and plate right way up and leave the cake to cool completely. The cake will be stronger when cool so there’s less risk of it breaking when you try to extract it. To get the cooled cake out, gently slide a thin knife around the sides of the pan to free it. This, we hope, will be enough.
If the cake has stuck to the bottom of the pan, you’ll have to try something more drastic. If you have time, freeze the cake in the pan overnight, so that the cake becomes hard (and quite strong). Then put the base of the pan in hot water for a minute or so to soften a thin layer at the bottom. Now invert the pan onto a plate and firmly strike the bottom with your hand, or if it’s that sort of day, any available blunt instrument. This should release the bottom so the frozen cake can come out in a single piece.
Make your own nonstick pans
You can always turn a sticky pan into a nonstick pan. The method depends on the type of pan and how it’s used.
For baking…If you bake, you already know how to make cake and muffin pans nonstick by greasing the surface with butter and applying a dusting of flour or confectioners’ sugar. The proteins from the eggs in the batter get trapped in the layer of flour or sugar and never get to the surface, so the cake never sticks. (If you just use butter with no flour, the butter will melt away, leaving the bare surface of the pan exposed, so there’s still a chance the cake will stick.) This step is always worth the trouble when baking—even with pans that you consider nonstick, just in case there’s a scratch you haven’t seen.
For cooking…The patina that builds up on carbon-steel woks and cast-iron skillets over years of use is another kind of nonstick finish you can make yourself. You can make a similar patina on stainless-steel or copper pans (but not tin-lined ones), but it’s easiest and works best on iron and carbon-steel pans (the sort that rust easily and that you can pick up cheaply at restaurantsupply stores) because their surface is rough and porous, allowing the patina to form a bit thicker and adhere better.
There are a few ways to create a patina in a metal pan. With all of them, the goal is to get cooking fat to undergo a chemical reaction that creates a nonstick layer on the surface of the pan. When you heat cooking oil on a metal surface, it forms a film that’s very similar to PTFE and, like PTFE, will not react with proteins.
Here’s my preferred method: Heat the pan on the stove with a little light cooking oil in it until the oil starts to smoke. Reduce the heat to very low and let the pan sit for 5 minutes, keeping a watchful eye on it the whole time. Be careful as you do this, as the pan and oil are very hot. After letting the pan cool, wipe off the excess oil with a paper towel. Repeat two or three times to build up a nonstick layer, or patina, at the surface.
Some people recommend other methods, usually involving lower temperatures and longer times, but I prefer my method for its speed and also because the patina layer tends to be stronger.
The patina layer, however it’s made, is vulnerable to detergents. So once you’ve created a patina, you might not want to wash these pans. After using mine, I just wipe the pan clean with a paper towel; and, occasionally, I heat oil in the pan to refresh the patina. All my favorite pans are coated in this way, and it gives a double advantage: I never have problems with food sticking. And I never have to wash the pans.