[Opinión] Barros Luco Day

On June 9, one of the emblems of the national culinary tradition is celebrated in our country: El Barros Luco. Marraqueta, meat and cheese, three ingredients that are enough for something close to perfection. And although each one, like everything in the kitchen, has the science of it, today we will reflect on the physics behind melted cheese.

First, to have melted cheese… you have to have cheese. Its origins lie far back in time, before historical records existed, and it is suspected that cheese must have been discovered by accident around 8,000 BC, which is when sheep were domesticated. Since it is known that ancient people used animal entrails to preserve different foods, It is possible that when storing milk in the stomach of an animal, our ancestors would have noticed that the milk turned into a mixture of solid curds and liquid whey.. From then on, it was a matter of refining the procedure by trial and error, since curds are, essentially, cheese.

Separation that is possible because milk is not a simple liquid, but composed of various molecules, such as water, oils and fats. Normally, these substances do not mix, as we can see by putting a drop of oil in a container of water. Which is a problem every time we have to wash dishes: How do we remove grease from a dish, using only water? It is difficult, but fortunately there are other substances that reduce the barriers between water and grease or oil, such as detergent or soap, allowing them to mix and, ultimately, the grease to leave that dish and go with the water.

They are emulsifying substances, and in milk there is one, and it is very abundant: a protein called casein, which forms almost 80% of the proteins in cow’s milk.. It is so abundant, in fact, that cheese and casein come from the same Latin word. Thus, casein is responsible for mixing fats, oils and water in what we call milk.

But everything that can be joined together should be able to be separated, and that is what curdling is all about, which is achieved by adding some type of suitable substance to the milk. It can be an acid (lemon juice, vinegar) or a bacteria, which interact with the casein and destroy its emulsifying property, leaving on the one hand a substance with a more solid consistency (the future cheese) and another liquid (the whey). Finally, it is a game of repulsions and electrical attractions that turn a food into something relatively inedible: The milk has fermented.

However, human ingenuity, surely combined with the need not to waste food, found a way to take advantage of the result. Perhaps adding salts, saving it to dry, trying other substances, until you find the right combination to achieve a result that is once again edible and, even better, that can be stored for much longer than milk, without spoiling. And the different solutions to convert curd into cheese give rise to the enormous variety of cheeses that we can enjoy, starting with the 42 mentioned in the sketch about Monty Python’s cheese shop.

Varieties that are distinguished by their different levels of salt, hardness, acidity, etc., which make them more suitable for some uses than others. A cheese that is left to mature for a long time will progressively lose its moisture through evaporation., so this type of cheese will be more rigid, ideal for grating, like Parmesan, for example. The acids, for their part, will cause the casein molecules to attract and adhere to each other, forming more or less rigid structures. Thus, cheeses to which acid is added, or in which the bacteria involved produce a higher level of acid, may be softer, but not melt well. Like the Greek classic, feta, which is fantastic either as cubes in a salad, or tasty grilled, without losing its shape.

And by the way, We have those perfect cheeses to melt. Younger cheeses, which still retain high levels of moisture, in which the electrical attraction between the casein molecules is overcome by the absorbed heat, separating them and allowing them to flow, giving rise to a more liquid texture. In this group we have mozzarella, cheddar, and the classics traditionally used for the sandwich that motivates this article: gouda, chanco or other buttery cheeses.

Legend has it that President Ramón Barros Luco used to go to Confitería Torres, in the center of Santiago, to order this mixture of bread, meat and cheese prepared especially for him. And like most good ideas, it was replicated over and over again until it became one of our most popular dishes, and deserving of a day in his honor, June 9, Mr. Barros Luco’s birthday. A sandwich that is a delicious tradition, and that also has its science.