Since the beginning of time, humanity has been searching for new ways to preserve food. Some were unreliable and led nowhere, but there were also some that we still use today. There are many methods of food preservation, and we can divide them into natural and chemical. In this article, we'll focus on natural preservation methods; their history, and how they affect food.
What is food preservation?
Preservation as a process boils down to ensuring the shelf life of food over time for as long as possible. It can include food processing methods, but also the way it is stored under the right conditions. Since microorganisms are the main culprits in putrefactive processes, i.e., food spoilage, it is reducing their activity that is of most concern to us. Therefore, all preservation methods essentially boil down to inhibiting their development, rendering them harmless, but also creating the most unfavorable conditions for their growth.
The beginnings of food preservation
Of course, it wasn't always clear what exactly causes food to spoil. Today, practically everyone has a refrigerator at home, which provides a relatively low storage temperature. This is the oldest method used in antiquity. It was discovered that products stored in a cool climate spoil much more slowly than those stored in warm or full-sun conditions. It was also the time when products were buried deep in the earth to maintain the right temperature. This method evolved into earth pits and then transformed into cellars. The breakthrough was the discovery of the preservative properties of salt and then sugar. Then, people experimented with heating food to ensure its shelf life. What exactly was responsible for these negative processes was, of course, not yet entirely clear. This was first explained by Louis Pasteur, who in 1848 hypothesized that bacteria were responsible for food spoilage.
What is the pasteurization process?
The pasteurization process as we know it today was invented by Louis Pasteur in 1864. Interestingly, it was originally used only to remove excess acidity from wine and beer, which was a real nightmare for winemakers and brewers at the time. The process itself is nothing more than heating food to a temperature below 100 degrees Celsius to destroy microorganisms. The most popular types of pasteurization currently in use are flow pasteurization and batch pasteurization. In the first method, the product is heated to a temperature of 72 degrees Celsius for 15 seconds. On the other hand, periodic pasteurization is a much longer process. It takes about 30 minutes, and the desired temperature is 63 degrees Celsius. This temperature is also suitable for slightly altering the flavor of the food. However, it should be noted that both methods do not destroy the spore forms of microorganisms.
It has much in common with pasteurization, but due to the much more aggressive nature of the process, it reduces the nutrient content of the product. It involves heating the product very quickly (2-10 seconds) to a temperature of over 100 degrees Celsius and cooling it just as quickly. The flavor itself remains unchanged, but some proteins, vitamins, sugars, and fats are broken down. This process was originally associated with UHT milk, but is now used to preserve many products, including juices.
Freezing food
Due to the virtually negligible loss of nutritional value, it is one of the most advantageous preservation methods. During this process, the water contained in the food significantly increases in volume, causing cell membranes to rupture. For this reason, once thawed, food should not be refrozen. At such low temperatures, i.e., below -20 degrees Celsius, microbes are killed or enter hibernation. Most importantly, they cannot carry out the metabolic processes responsible for food spoilage.
Dry
Water is a great environment for various chemical reactions, but also for microbes. This is why products with a high content (fruit, vegetables ) spoil much faster than those that naturally contain little of it (flour, sugar). The drying process itself consists of reducing the solvent content in the product. In most cases, this is water. The simplest method is air drying . In addition, drying time is shortened if the ambient temperature is high enough, but good air circulation is also important. For product drying on an industrial scale, special equipment is currently used that ensures appropriate temperature and pressure conditions, which control air circulation to make the process as efficient as possible. Reducing the water content compromises the stability of the finished product, since microorganisms cannot develop freely when the content of this solvent is low.
Freeze-drying – is a highly advanced form of drying that is practically impossible to perform at home. It involves sublimating water from food. More specifically, it involves pre-freezing the product, then subjecting it to a vacuum to remove the frozen water. This process is most commonly used for fruit that is not heat-resistant, or for coffee.
Sugars and salts
Adding sugar and salt to food is a very old practice. For salt, the limit concentration that prevents the growth of microorganisms is 18%, for sugar it is 65%. In both cases, the effect on microorganisms is similar. Such a highly concentrated environment causes them to deodorize through osmosis. This phenomenon consists in the "migration" of water from an area with a lower sugar or salt concentration to an environment with a higher concentration in order to equalize this level. As a result, the water leaves the bacterial cells and causes them to die. This is why honey, jams, and salted fish remain edible for so long. However, consuming large amounts of such products is not particularly recommended precisely because of their high salt or sugar content. They do not have a positive effect on our health and well-being.
Acidification of food
The method of acidifying the environment. Vinegar is most commonly used for this purpose. This changes the pH to acidic, thus inhibiting the growth of microorganisms. Examples include pickled cucumbers or mushrooms. This works similarly to salting and sugaring. You should not consume such products in excess, as acetic acid has adverse effects on the body.
Smoking food
Smoking is a somewhat controversial process due to the toxic compounds that penetrate food. For this reason, smoked meat flavorings are increasingly being used exclusively, although these are not as preservative-effective as the traditional method. This process generally involves exposing the products to heat and the chemicals contained in smoke. The smoke is obtained by burning the appropriate wood and its derivatives. Depending on the temperature used, there are three basic smoking methods: cold, warm, and hot smoking. The penetration of smoke compounds into the product inhibits the development of microorganisms. High temperatures also aid this process, increasing its sterilizing properties. It is also worth mentioning that the food is slightly dried out, especially on the outside. This significantly hinders the penetration of new bacteria into the food.
Summary
Food preservation was a very important achievement of civilization. It allowed our ancestors to colonize new lands and survive times of scarcity. Today, it remains an essential part of our lives. However, it should be remembered that despite the only natural methods of food preservation discussed here, some are healthier than others. The key is to strike the right balance and choose products that are as beneficial to our health as possible. Of course, this doesn't mean that jams, smoked meats, or canned goods should be completely eliminated from the diet. However, you should limit the consumption of pharmaceuticals that may have potential side effects.
