Science & Tech

You may have used aluminium foil to fry vegetables, cook fish or keep meat juicy in the oven and you may have worried that this metal may leak into your food. However, before doing this, it is useful to consider where aluminium is found other than in foils, to what extent it is taken into the body, how much of it is absorbed in the body and what effects it may have on health.

Aluminium is the third most abundant element in the earth's crust. The atoms of this metal bond with ions such as phosphate and sulphate and many other elements and are frequently encountered in nature in the form of various compounds. For this reason, aluminium is naturally found in soil, water resources and many natural foods we consume. Food additives such as colorants, thickeners and preservatives used in the food industry also contain aluminium. This metal, which is cheap and easily processed because it is abundant, is also used in the production of pots, pans and some serving utensils.

Cooking utensils containing aluminium easily oxidize as they are used. This creates a low chemical activity (inert) layer on the cooking surface. This layer prevents aluminium from leaking into the food. However, if these utensils are cleaned harshly after cooking, the inert layer may wear off and cause aluminium to leak into the food in subsequent uses. The inert layer can be renewed by boiling water to mattify the surface of these utensils.

Since aluminium foils are disposable, it is not possible to create an inert layer on their surfaces. This leaves food vulnerable to aluminium migration. Especially when acidic foods such as lemon and tomato juice are cooked in foil, the possibility of the aluminium on the surface interacting with acids and being released and leaking into the food increases. The increase in the density of spices added to the food further increases the possibility of aluminium leakage.

According to a study conducted on this subject, cooking acidic and spicy foods in aluminium foil triggers the passage of aluminium into the food in higher amounts than the safe limit determined by the World Health Organization. Another study found that the amount of aluminium in red meat cooked in foil can increase by 89 to 378 percent.

While experts say that wrapping cold foods in foil is safe, they also add that contact with aluminium should not be prolonged depending on the intensity of the spice or acid content in the food.

On the other hand, some researchers say that only a portion of the aluminium taken into the body remains in the body, the rest is excreted from the body through excretion, and that there is not yet enough evidence to directly link aluminium left in the body to health problems.

 ***

WHY ARE METALS SHINY?

Photons, which enable us to see our surroundings, reach our eyes by coming directly from a light source or by reflecting from surfaces. When it comes to reflecting visible light, the first examples that come to mind are usually the surfaces of substances in the metal class. What gives metals their dazzling shine are the elementary particles, namely electrons, that wander away from the atomic nuclei.

The electrons in the outermost layer of a metal atom are weakly connected to the atomic nucleus. These elementary particles, also called valence electrons, can move freely between the atoms and around the pile when metal atoms come together in a pile. These free electrons form the negatively charged, moving structure called the "electron sea" that flows around the positively charged nuclei.

The electron sea gives metals some of their basic properties. For example, during a received impact, these electrons move and compensate for the displacement of the atomic nuclei, allowing metals to change their shape without breaking or cracking. Metals also owe their superior electrical conductivity to the electron sea.

The electron sea is also the reason why metals appear shiny. When a light wave hits an electron sea, the electrons absorb the energy of the wave and their energy increases. The electrons release this extra energy they gain back into the environment by producing a new light wave. We perceive this collective occurrence as the metal shining.

The reason why metals shine differently is that the number of free electrons and the properties of the electron sea vary depending on the type of metal. Most metals appear metallic gray because they can reflect a significant portion of visible light.

Some metals, such as copper and gold, cannot reflect wavelengths corresponding to the blue tones of visible light. Therefore, they shine in shades of red or yellow. Some metals, on the other hand, may not be able to reflect higher energy waves such as ultraviolet and X-rays even though they reflect visible light very well. High-energy waves penetrating these metals may be absorbed or pass through the metal, depending on the type and thickness of the metal. Silver, which is used in mirror manufacturing, can be an example of such metals because it can reflect visible light almost perfectly.

Some metals, such as tin and aluminum, are used in roofing because they reflect ultraviolet rays at a high rate. On the other hand, lead can reflect even high-energy X-rays, which can pass through most metals. Because of this feature, it is used in medicine to protect against X-rays.