Sterilization, pasteurization, canning and preserving
Preserves and canned products
Sterilization, pasteurization, canned food, preserved food, temperature, heat
STERILIZATION, PASTEURIZATION, CANNING AND PRESERVING
The application of high temperatures is one of the most used methods to preserve food.
Sterilization is a thermal treatment developed in the 19th century that consists of exposing the food and/or the container to high temperatures for a certain period of time. The main objective is to inactivate pathogenic microorganisms and other biological agents that can deteriorate food and cause harm to our health.
The sterilization technique can be applied both to containers that will later receive food, as well as to food itself and it maintains most of the nutritional and organoleptic characteristics of the food product.
Sterilized food can be stored at room temperature for a long period of time. The success of sterilization depends on the combination of time and temperature, according to the rate of heat penetration into the food. The environment around the food product, its size and shape, the material of the container, the type of handling and the thermal resistance of the microorganisms are factors to be taken into account.
Pasteurization, named after Louis Pasteur, is also a heat treatment which objective is to maximize the destruction of pathogenic microorganisms and minimize chemical changes in the food, increasing its shelf life. Since living organisms capable of development may persist in this process, pasteurization may have to be combined with other preservation methods, such as refrigeration (eg yogurt).
Pasteurization is a technique carried out industrially. The most used is UHT (Ultra High Temperature), through the injection of steam between 130 and 150 Co. for 3 to 5 seconds, followed by rapid cooling in vacuum. Other more recent techniques, such as pasteurization through the application of high pressure, are being developed, namely at the University of Aveiro, in Portugal.
Preserved and canned products are the result of conservation techniques that involve a thermal processing of the food, storing it in appropriate, sterilized and hermetically sealed containers, preferably made out of glass or metal. Food products are processed according to their typology and final shape for consumption (peeled, chopped, sliced, cooked). The main objective is to extend the shelf life of the food and enable a versatile use and consumption throughout the year.
As with pasteurization, the technique of canning food is essentially carried out in an industrial environment, where food placed inside cans is subject to high temperatures for a very short period of time, maintaining its nutritional value almost intact.
In the domestic preparation of preserves, the containers, usually made of glass, must be sterilized by placing them in boiling water for a few minutes. The food to be preserved is then inserted, together with other ingredients suitable for natural preservation (lemon, oil, herbs, vinegar, sugar, salt) and the container undergoes a second sterilization process from 15 to 20 minutes.
The main benefit of thermal sterilization, pasteurization, preserving and canning processes is to increase the shelf life of the food, which can be extended for several years, essentially maintaining its organoleptic characteristics (texture, appearance, nutrients) and ensuring safety, if all good practices in terms of food processing and container sanitation are followed.
These preservation processes offer great advantages for the consumer: diversity of flavors, aromas and presentation, versatility, possibility of consuming the food immediately or at any time of year, durability, saving time and money, easy storage and transportation.
Moreover, food products subject to these processes keep their nutritional value almost unchanged. Canned fish, for example, can be a very interesting option, given its protein, vitamin and mineral content.
Likewise, the use of liquid or sauce involving a preserved or canned food can often be used for other complementary purposes (for example, water resulting from cooking chickpeas can be used to prepare a vegan mayonnaise).
The thermal processes of food preservation also contribute to reduce food waste.
Milk and dairy products (yoghurt, cheese, soft cheese);
Fish and seafood (tuna, mackerel, sardines, squid, octopus, cuttlefish, cod, shrimp, shellfish, eels);
Processed meat (pâtés);
Fruit in jelly or jam (peach, apple, pear, fig, pineapple, cherry, plum, blueberry, quince, pumpkin, olive, capers);
Vegetables (tomatoes, asparagus, cabbage, carrots, onions, garlic, cucumbers, peppers, artichokes);
Legumes (chickpeas, beans, lentils, lupines, peas, broad beans);
Ensuring the safety of sterilization, pasteurization, preserving and canning processes is mandatory, complying with food safety standards, including the quality of raw materials.
Therefore, we should:
- sanitize and properly prepare food (for example, slicing or dividing into equal portions);
- check the good conditions of the container, discarding packages that have a broken or deformed appearance, as they can deteriorate or even compromise the quality and safety of the food;
- completely fill the container where the preserved or canned food is placed to minimize the presence of oxygen;
- store preserves and canned food in cool and airy places;
- after opening a canned food, consume it as soon as possible; if there are remains, they should not be stored in a metal container;
- after opening a jar with a preserved food, we must always use clean utensils at each use;
- read the labels carefully and comply with the recommendations, taking into account that, depending on the ingredients used for preserving the food, its durability may vary.