The vacuum system is food preservation, both raw and cooked in, which involves removing the air from the product bag, especially oxygen, which is the first factor of oxidation and putrefaction of food. For this, different equipment and materials are used, which are the ones we analyze in these lines.
In catering and especially in the kitchens, we must have an endless number of perishable products to be able to supply the entire menu of the establishment, and this system will allow us to prolong its conservation and increase its profitability.
In the cold room, we find a large number of vegetables that the market provides us and more being ours a Mediterranean cuisine in which they intervene new genres of the orchards, as well as fresh aromatic herbs. The conservation of all these vegetables is much more optimal if we apply this conservation system, with or without gas, according to the raw material, and we preserve all its freshness, hardness, and quality. For this, it is essential to buy the products freshly picked from the ground and to treat and prepare them quickly.
Let’s not say if we enter the fish area. These should be purchased as fresh as possible and immediately prepare it for temperate salads, supreme to make in various sauces, ragouts, basques, etc.
The meats, we all know that the excellent manito, in French slang, is the primary basis of good quality. This is a whole system to achieve it because once the pieces are purchased directly from the slaughterhouse, we can proceed to the method of maid or maceration, losing a minimum by drying, depending on the cameras we have, as well as very little serum. With this system, we can give our consistency without the bad tastes or smells that are produced in the chambers where the vacuum is not used, such as flavor to the camera, flavor to other items already cooked, etc.
If we place ourselves in the cooking area, we will have plenty of stir-fry, chopped, ragouts, as well as innumerable garnishes that prepared and made vacuum, with exquisiteness and care, you can get the maximum performance, as long as we have the utmost hygienic considerations and follow the indispensable rules of the vacuum system.
Therefore, observing all the regulations related to vacuum cooking, we can give an excellent restoration with the maximum hygiene and quality, something that interests us so much to the hotel and lodging professionals.
Vacuum packed, In this case, we do nothing but extract the air that surrounds the product we pack. With this, we avoid the oxidant effect (of aging) exerted by the air on food products, in a perfect system in works with a shallow content in water, such as nuts or milk powder.
They are packed with protective gases. This type of packaging, also known as packaging in modified atmosphere, is not satisfied with extracting the air that surrounds the product to be packaged, as in the previous case, but also adds a new atmosphere that offers better qualities, both physical and microbiological than natural air, to increase the duration of the product packaged in optimal conditions.
The kitchens with small productions of discontinuous type and with a great variety of products to be packed usually are used equipment of small dimensions familiarly known as “Bell Machine.”
In general, this type of machine consists, primarily, of the following elements:
- Vacuum pump. To extract the air that surrounds the product.
- A vacuum chamber or “Bell.” Metal container with a transparent methacrylate lid in which the product to be packaged is placed, previously introduced in a bag of suitable dimensions and a film with high gas impermeability.
- Gas inlet pipes inside the vacuum chamber.
- Metal strip with built-in electrical resistance. Its mission is to weld the open edges of the packaging bag in the final part of the operation to ensure its subsequent sealing.
To understand the operation of this type of equipment, it is necessary to know the physical concept of atmospheric pressure. On a typical day, the pressure of the air that surrounds us is in what we call an atmosphere, which is eliminated by making a vacuum.
Closely related to the above is the observable fact that a product is “cramped” inside a bag, or, conversely, that the bag is “swollen.” As a general rule, we will say that a pack will be flat if the pressure inside it is lower than the outside pressure, and the more significant this difference, the more chaos it will be, and a bag will be swollen when the pressure inside it is greater than the pressure on the outside of it.
- Empty. Place the product in a suitable bag and place it in the vacuum chamber, putting the open end on the welding strip and one or several gas pipes slightly inserted in the bag, and close the transparent lid of the room.
- The vacuum pump automatically starts sucking the air inside the entire Vacuum Chamber. In this phase of the process, it is usual to notice an “inflation” of the bag that is completely normal since the welding strip presses the bag, and the aspiration of the air inside is carried out at a slower rate.
- They are filling the protective gas. Once the previously regulated vacuum has been reached, which depends on the product to be packed, the vacuum pump stops sucking.
- After this operation, the machine begins to blow gas into the Vacuum Chamber through the pipes, so that the bag swells again because it has more pressure than the rest of the chamber.
The regulation system of all the parameters varies a bit according to the different machines, but in all of them, it is straightforward.
- Welding of the bag. Once the pre-established amount of gas has been introduced into the chamber, the open end of the bag is sealed by the electrical resistance of the Solder Strip.
- Cooling of the seam. It usually takes a few seconds for the solder to cool, and the closure of the bag is fully affirmed.
Air inlet in the rest of the vacuum chamber. This is the final phase of the process, in which the outside air is allowed to enter the chamber again. At this moment, there is the apparent paradox that the bag, hitherto “swollen,” is “chaff” to a greater or lesser extent. This is because the air from outside has not entered it when it is sealed, and the pressure of the protective gas inside it is much lower than atmospheric.
They are an essential part of the assurance of the quality of the packaging since its physical characteristics depend on the effective conservation of the modified atmosphere that we have introduced inside the bags that are used in this type of packaging.
These films must have particular characteristics consisting of:
- Protection of the packaged product against external mechanical aggressions, stretching, perforation, sunlight, etc.
- Impermeability to all gases or according to what gases.
- Good welding properties by temperature.
Since all these characteristics are very different from each other and are sometimes against each other, it is not possible to use only one type of plastic.
Thus, multilayer films are used that collect together these characteristics; in this way, the structure type of a packaging film in a modified atmosphere could be:
- The external layer of plastic with high melting temperature and mechanical strength.
- The intermediate layer of low or selective gas permeability (es).
- The internal layer of plastic of low melting temperature, to facilitate the welding of the bag and which, at the same time, is the least aggressive possible against the product that is packaged inside, if it is in contact directly with said plastic.
There is a high number of possible combinations of plastics that meet these characteristics.
Characteristics of gases for a modified atmosphere
It is an inert gas that carries out a primary effect of eliminating the oxygen present, which makes the growth of aerobic microorganisms present in the environment impossible, but not that of the so-called anaerobes.
It also displaces oxygen from the air with the same effect as nitrogen. It also dissolves in the water, resulting in a slight reduction of the pH of the medium. It is also bacteriostatic and fungistatic, which allows slowing the growth of all microorganisms, whether aerobic or anaerobic.
In the cold, it dissolves better with what still increases its effects. It can cause an extra “vacuum” due to its dissolution in the product.
This gas is only used when it is essential since its presence is what shortens the shelf life of the various products to be packed. Its use is usually restricted to the preservation of the color of red meats, and the conservation of fresh vegetables is used in these cases in small concentrations.