Canning
 

Canned food and methods of preservating

 

 

Canning is a method of preserving food products (making canned food) and involves technical processing of food products to inhibit the activity of microorganisms that spoil the food. And also some other ways to increase the shelf life of food products.

In a broad sense, canning refers to any process that significantly extends the preservation of food in a form suitable for human consumption. The main task of canning is to reduce the level of water activity to a minimum level, which deprives harmful microorganisms of a habitat for further development and spoilage of the product.

Methods of canning and preserving food include:

1.
Salting Table salt has long been used to preserve meat and fish products. When salting, in the process of osmosis, the salt 'pulls moisture out of the product'; the product itself is saturated with the salt solution and, due to the decrease in water activity, becomes unsuitable for the development of most bacteria.


Pickles

2. Pickling
Pickling is a combination of biological preservation with acids and pickling. Lactic acid bacteria utilize sugars (carbohydrates) and produce organic acids that prevent the development of mold.


Sauerkraut with cranberries

3.
Marination Marination is carried out with organic acids, which are destructive to bacteria, but suitable for human consumption. Typically, citric, acetic, lactic and other acids are used, creating an acidic environment unfavorable for the development of bacteria.


marinated with acetic or citric acid

4. Canning ( canning fresh fruits in sugar syrup)
With a high concentration of sugar as a result of osmosis, bacteria cannot develop in the product. However, if the acidity of the product is low, the development of various molds is possible. Sugaring occurs when products soaked in a sugar solution (syrup) are dried, and the sugar solution that has soaked the product crystallizes. This is how candied fruits are made.


Candied fruit

5. Use of other preservatives
The addition of preservatives permitted in the food industry improves the safety of products of various types (drinks, canned food, preserves).

6.Methods related to reducing water content These methods include:
- Drying
Drying is the oldest method of canning. During the drying process, moisture is removed from the product, which deprives microorganisms of a habitat for development. Drying can be done either in the open air, in the wind to prevent rotting, or using a vacuum. Salted and dried meat is widespread.

- Gelation
This method also uses the effect of reducing the water activity in the food product. Gelatin, alginates, pectin and starch are used for gelling . The gelled mass of the product is impermeable to most bacteria and mold. The most well-known shelf-stable products in this category are marmalade and stale.


Natural apple marmalade

- Smoking
Smoking combines partial dehydration (sometimes very slight) and chemical preservation. During the smoking process, the product is dried and impregnated with smoke, aromatic hydrocarbons preserve it and give it a special aroma.

- Drying
Drying also combines dehydration of the product and, at the same time, some chemical preservation of it with table salt.


Jerky - thin slices of dried dried meat, which is prepared by dehydration - removing moisture from meat by cooking it in an oven or industrial oven at low temperature with the addition of salt

- Jam, marmalade, jam and marshmallows. Syrups
To obtain canned fruit, they widely use cooking in sugar syrup, or simply evaporating sweet juices without adding sugar.


Plum jam

7. Sealing
- Sealing and vacuum packaging
Sealing is done to prevent microorganisms from entering the processed product from the air. Vacuum packaging leaves aerobic bacteria without oxygen and they die. The bacterium that causes botulism does not produce gases or substances that can be tasted or smelled, and therefore its development in canned food is life-threatening.


Vacuum packaging

- Atmospheric preservation and replacement of gas atmosphere
The oxygen-containing atmosphere in the packaging is replaced by an inert one, thus preserving the product (for example, salad) without disturbing its shape. By replacing oxygen with nitrogen, the insects contained in the products are killed.

8. Temperature treatment and cryopreservation
- Sterilization and pasteurization
Prolonged heating of the product to a temperature of 60-70 degrees C is called pasteurization, named after Louis Pasteur. As a result of this process, the bacteria die, but their spores survive, to prevent the development of which pasteurized products are stored in the cold. The fractional pasteurization method consists in the fact that after pasteurization the product is kept at normal temperature for a time sufficient for the development of spores, after which it is subjected to repeated pasteurization, the process can be repeated several times. For complete sterilization, it may not be enough to boil the product at 100 degrees C - the destruction of heat-resistant bacterial spores requires heating the product to high temperatures at elevated pressure.
Pasteurization is used in cases where long-term storage of canned products is not required, and sterilization is used to obtain shelf-stable products. Typically, products with a sufficiently high acid content are pasteurized, and those with low acidity are sterilized.


Pasteurization of milk by heating to a temperature of 60 degrees C for an hour (or for half an hour at 70-80 degrees C)

- Low temperatures
Cooling products slows down the activity of microorganisms and prevents the development of their embryos; freezing to zero or below completely stops the activity of bacteria. The traditional method is to store food in basements or basements. The combination of low oxygen in the air and low temperature allows for long shelf life.

9. Irradiation (radiation sterilization)
Irradiation of the product with x-rays or gamma radiation is carried out to destroy bacteria and mold.

10. Biological preservation
Such traditional methods of preserving products as their special fermentation - fermentation of perishable substances, with the accompanying formation of preservatives - acids and other microbial metabolites - have been used since time immemorial. These include the already mentioned pickling, fermentation (in the production of wine and vinegar) and others. An example of biological preservation is cheese. The bacteria that formed it prevent the development of other microorganisms in it.


French cheeses from the Loire River Valley