Who has never eaten or prepared foods in oil? Keep the vegetables in oil protects them from oxygen, creating a real barrier, isolating them and slowing down its deterioration. Oxygen in fact, indispensable for life, however it represents an enemy for the conservation of food, since it accelerates its oxidation, altering color, taste And nutritional values. Furthermore, air exposure promotes the proliferation of bacteria and aerobic molds. However, an oxygen -free environment can encourage the development of those bacteria that do not need oxygen to survive, such as the Clostridium botulinumwhich produces a very dangerous toxin, botulinum toxin. Signals like swollen lids O superficial patinas can indicate its presence in our preserves. To avoid risks, the guidelines of the Istituto Superiore di Sanità (ISS) provide clear rules to guarantee food safety even at home: it is fundamental blaze vegetables in water and vinegar to lower the pH, clean and sterilize Accurately the containers, seal and pasteurize them. The jars must then be kept in a cool and dry place.
Oxygen: from ally for life to enemy of conservation
It is since we are small that they teach us the importance of oxygen. If it is true that without this element we could not live, it is also true that, when it comes to food, oxygen becomes one of the main responsible for deterioration. In contact with the air, the foods begin to oxidize: this means that molecular oxygen (or2) present in the air begins to react with various molecules present in foods, fundamental nutrients such as fatty acids, carbohydrates and some proteins. These chemical reactions lead to a series of side effects: color change, loss of aromaalteration of taste and, in some cases, decrease in nutritional value. In a nutshell, in contact with oxygen, the food “ages” faster.
Contact with the outside also allows the contamination by bacteria or mold. Most of these microorganisms are aerobicThat is, they need oxygen to live and replicate. Once contaminated, if the food remains exposed to the air (and therefore to oxygen), these organisms can increase, proliferate and accelerate the deterioration of food.
This explains why aubergines or mushrooms are preserved well if immersed in a jar of oil: it is not so much the oil itself that has preservative properties, as the fact that it acts as a real physical insulator. It is as if the oil enveloped the vegetables in a film that protects them from the outside world, preventing the air (and therefore to oxygen and unwanted contaminants) to get in touch with food. As insects imprisoned in amber, the vegetables immersed in the oil remain suspended Over time: protected, isolated and destined to age more slowly.
When the absence of oxygen becomes a risk
However, it is necessary to consider the downside: If an environment without oxygen, on the one hand, prevents the proliferation of mold and aerobic bacteria, on the other it can lead to the development of microorganisms anaerobicthat is, capable of surviving and reproducing In the absence of oxygen. The best known is certainly the Clostridium botulinum, A bacterium present in the soil and vegetables. In favorable conditions, such as the lack of oxygen, it is able to produce the botulinum toxinone of the most powerful in nature: it acts on the nervous system, blocking the transmission of signals to the muscles and causing paralysis. In the most serious cases, it can also affect respiratory muscles, with potentially fatal consequences.
In some cases, suspicious clues can be observed, such as swelling of the jar cover or the presence of superficial patinassigns that indicate the metabolic activity of bacteria engaged in fermentation processes.
The rules of science for safe preserves
To avoid any risk linked to botulinum toxin, therefore it is not enough to “cover the vegetables of oil”. There are some fundamental rules, confirmed by the guidelines of theISS (Higher Institute of Health), which guarantee security also in home preparations.
The first is the blancing vegetables, useful for reducing the initial microbial charge. This procedure must be made in a solution of water and vinegar in equal parts. Acetic acid is in fact useful for acidify Foods: the Clostridium botulinum It does not develop in acid environments, with a pH less than 4.6.
The jars and covers must also be well cleaned and better if sterilizedmaking them boil in the water. Once filled with vegetables and oil, they must be sealed and, after one pasteurization performed in a bain-marie, the jars should be preserved in a cool and dry place (like the pantry of the house) and it is advisable to consume them 2-3 months after the preparation to be able to better appreciate its taste.
