The first thing your teeth sink into, as you chew your way through a juicy burger is the bun. As we all know, bread is made from wheat and yeast, the classic GCSE microbe. The leavening process starts with the yeast respiring anaerobically off the sugars present in the flour, which then releases carbon dioxide. Naturally, these form gas bubbles, which let the bread take up more volume. The purpose of kneading the dough is to mix two proteins found in the dough – gliadin and glutenin – into gluten, which most of us love (and celiacs hate). The meshes of gluten then further trap the carbon dioxide formed, which causes the bread to expand more. The alcohol released during the respiration then contributes to the flavour and the texture of the bread.
The burger patty is simply beef brisket or short rib which has been freshly butchered. However, the meat is slightly preserved at the butchers and left to age for a couple of days, as fresh meat often undergoes rigor mortis, making it tough and less juicy. Some people also enjoy bacon on their burger, which is a form of pork, usually cut from the belly or the back. The belly has more fat and tends to be made into what is known as ‘streaky bacon’, whilst back bacon is ‘back bacon’. Although bacon seems relatively easy to procure, given it is sold en masse in supermarkets, the curing process is very important. First, the meat is cut into large chunks by type. Then, there are two main ways of curing: brining or salting. In brining, salt is introduced in the form of a solution, in which the meat is dunked for a sufficient period of time, ranging from weeks to months. Salting is a lot simpler, with the meat just being left in the open after having been thoroughly covered in sodium chloride or sodium nitrite. These processes serve the purpose of removing water from the bacon, drying it, and making sure that no microbes can grow on it. Furthermore, they ensure that the pork keeps its colour. Dead meat usually turns grey after a short period as a result of the oxidation of the haemoglobin in the muscle tissue. For the gastronomically cultured, some may use smoked bacon, which involves slowly burning fuel under the meat, often wood such as hickory or oak. This not only adds flavour, but also prevents the breakdown of fat, as the naturally forming formaldehydes coat the meat.
Cheese is formed from milk, and its production involves coagulating the fats and separating the curds formed from the whey. The majority of the process is done through the use of bacteria. First, the milk needs to be acidified, so that the curds and whey separate and so unwanted microbes do not appear. Second, rennet is added, which contains the enzyme chymosin, which allows for curdling at lower pHs and speeds up the bulking together of the proteins. Once the two substances have been properly removed, the whey is used in other products such as whey butter or dietary supplements. However, the curds are what we are interested in. These are shaped nicely and left to ripen, after being coated in bacteria and fungi, which break down large protein molecules, giving cheese its soft and sometimes runny texture.
Once the various ingredients have made their way into your kitchen, it is time to prepare them, and where better to start than toasting the buns? There are many types of bread, and their textures, tastes and makeups vastly differ. Some are mostly consumed on their own, with spreads; others are often slotted into one specific use. For burgers, however, the idea is that the buns are toasted lighlt on top of the pan you use to grill the patties. A light toast is not only healthier, as it reduces fat intake and lower glycemic index, which is better for diabetics and people on diets, but also helps with diarrhea. Most importantly, it scientifically tastes better. There are two aspects of the process that makes this true. The Maillard reaction happens between amino acids and reducing sugars, irreversibly changing their texture and chemical composition. This gives the bread, as well as any other ‘browned’ foods (steak, fried dumplings, lamb chops, etc.) its distinctive flavour. Caramelisation is the oxidation of sugars in the bread, which adds a nutty flavour and sweetness. These two processes give the bread a brown crust. However, if you toast the bread too long, it burns and the black that you see is carbon, which happens from incomplete combustion.
The burger patty also involves the Maillard reaction and caramelisation, giving the same desired effects in the meat. Naturally, we have to start at the classic, no-fuss fresh patty grilled on a cast-iron pan. Apart from the Maillard reaction creating browning on the outside, the meat on the outside is well-done, giving it a bit of a grey colour, which contrasts with the medium-rare, pink inside. This is due to the myoglobin, another protein, inside of the meat changing shape and permanently denaturing. For the adventurous, there are many ways to cook the patty. One interesting way is to deep fry the patty, which ensures that the heat transfer from oil to meat is even, giving it a full, uniform crust. The cooking process is quite similar for the bacon, except for the fact that you do not have to use cooking oil. Fats play an important role in providing conduction so that the heat can pass quickly to the food, stimulating the Maillard reaction, and preventing the result of this reaction from sticking to the pan instead of to the burger.
The last crucial part of any good burger is the melted cheese, which drips off. You will have noticed that once you melt cheese, it will still be cheese, but never regain its original texture or size. Furthermore, some cheeses are significantly better at melting than others. This occurs because of the way that cheeses react to heat. The solid fat liquefies, and is brought to the surface of the cheese, while the bonds holding the casein proteins together break, which makes the cheese less rigid. The water content of the cheese also decreases, as the moisture is evaporated off. Processed cheeses are specially designed and mixed with emulsifiers and acids, for the express purpose of melting, while still having the firm texture at room temperature, which makes them ideal for grilling over a burger.
The role of science in food is often overlooked, and its impact on our day-to-day life is surprisingly related to what is taught at school. In a generic sense, a simple, mundane task such as making a burger includes scientific reactions and decades-old research, which while seeming irrelevant, can have a great impact on the quality of the dish. Is anybody hungry?