Canned food for pregnant women: only harm?

First, let's try to figure out what canned foods are. Canned food (from lat. conservo - “preserve”) is food products of plant or animal origin, specially processed and suitable for long-term storage. The main effect of preservation is protection against spoilage, which is caused mainly by the vital activity of microorganisms, as well as by the undesirable activity of certain enzymes that make up the products themselves. All methods of preservation are reduced to the destruction of microbes and the destruction of enzymes, or to the creation of unfavorable conditions for their activity.

What are the canned goods?

Food products sealed in sealed containers, subjected to heat or other treatment that ensures the microbiological safety of the product during storage and sale under normal (outside the refrigerator) conditions, are classified as full canned food.

Another group of semi-preserves, or the so-called preserves, is also distinguished - these are food products sealed in sealed containers, subjected to heat (up to 100 ° C) or other treatment (for example, using food additives), which ensures the death of most of the microflora. At the same time, the microbiological stability and safety of the product can be ensured for a limited shelf life at a temperature of 6 °C and below (for example, when stored in a refrigerator). Consider the main methods of canning.

∗ Heat sterilization. This is the processing of a hermetically sealed product at a temperature above 100 ° C (most often up to 120 ° C under conditions of increased pressure) for a certain time. When sterilizing, it is important to strictly maintain not only the temperature, but also the time regime. For example, for meat, the sterilization time ranges from 60 to 120 minutes (depending on the feedstock and production technology), for fish - 40-100 minutes, for vegetables 25-60 minutes.

With this method of preservation, the complete destruction of microorganisms and their spores in the processed product occurs. Such products can be stored from several months to two years. However, sterilization reduces the taste and nutritional value of the product and destroys most of the vitamins. And in sterilized milk, useful enzymes and immunobiological compounds are additionally destroyed. In addition, canned fish and meat contains a large amount of purines and uric acid, which burdens the work of the kidneys and is contraindicated in gout and urolithiasis. Therefore, it is better for pregnant women to exclude such canned food from their menu.

∗ Sterilization currents of ultrahigh frequency (UHF) and ultrahigh frequency (UHF). It is carried out in a hermetically sealed container by placing it in an alternating current electromagnetic field. The temperature rise of the product reaches 100 °C.

With such heating, the heat is evenly distributed throughout the product and provides a higher bactericidal effect, and the processing time is reduced by 10–20 times. At the same time, vitamins and original taste are well preserved, and such preservation can be recommended for pregnant women. However, you will not find an inscription on the package that will talk about sterilization using microwave or UHF (it will simply indicate that the product has been sterilized, but you can only guess how).

* Pasteurization. This is the processing of a product for a certain time with a temperature of less than 100 ° C (usually 65–85 ° C). With this sparing method of preservation, the nutritional value of the product almost does not change, vitamins, minerals and biologically active useful substances are preserved. However, pasteurized canned food is unsuitable for long-term storage, as the vegetative forms of microbes die, while the spores remain viable. For milk, the ultra-pasteurization (or over-pasteurization) method can be used, in which raw milk of the highest quality undergoes instant (3-4 seconds) processing at a temperature of 135-137 ° C and is quickly cooled. At the same time, microflora and bacterial spores are killed in milk, and natural beneficial properties are preserved with minimal losses. Often such milk is packaged under sterile conditions (aseptic filling). All this allows you to extend the shelf life of milk without the use of preservatives.

Extending the shelf life of products can be achieved with multiple (fractional) pasteurization (2-4 times) with an interval between pasteurization sessions of 24 hours. This process is called tendalization. However, in this case, a more intensive destruction of vitamins and other biologically active substances occurs.

Pasteurization and its varieties (ultra-pasteurization, tendalization) are mainly used to protect milk and juices from spoilage.

For a pregnant woman, pasteurized milk is more preferable than sterilized (almost all useful substances are stored there). But as for juices, then, of course, freshly squeezed juices are a more complete product for an expectant mother than thermally processed ones - there is a guarantee of preserving all vitamins and microelements.

∗ Freezing. Freezing is one of the useful methods of preservation, which is achieved by lowering the temperature from -18 to -25 ° C.

During freezing, the vital activity of microorganisms and the action of enzymes that cause food spoilage are practically stopped, and at the same time, the taste, color, smell and nutritional value of the products are preserved to the greatest extent. To maintain the high quality of frozen products, it is important that they are packaged so that they do not come into direct contact with the chamber air during storage. With such contact, not only oxidative processes occur, leading to loss of taste, but also large weight losses due to evaporation (freezing) of ice.

Currently, industrial freezing of meat and meat products is practiced. Of particular importance is the freezing of berries, fruits and vegetables (except for radishes, lettuce), since with any other method of preservation it is impossible to preserve the main quality indicators to such a high degree: taste, smell, appearance, texture, as well as unstable vitamins, in particular vitamin C, the main source of which in the human diet are vegetables and fruits.

Frozen vegetables and vegetable mixtures at temperatures not higher than -18 ° C (fruits and berries not higher than -12 ° C) are stored for up to 12 months (depending on the type of product).

In winter, when there is a clear shortage of fresh fruits, frozen vegetables and fruits for a pregnant woman will be an indispensable source of vitamins and minerals.

* Drying. During drying, water is removed from the products, as a result of which the reproduction of microorganisms leading to product spoilage becomes impossible. Drying is a universal method of preservation, it is applicable to most products (vegetables, fruits, milk, eggs, fish, meat, juices). A variety of natural drying is drying (drying in the open air) of fish and meat.

The old method of artificially drying with hot air in an oven leads to significant losses of water-soluble vitamins due to prolonged exposure to high temperatures. More gentle is drying in special dryers with controlled temperature.

Freeze-drying (freeze-drying) is recognized as the most perfect type of canning under industrial conditions. During this process, water is removed from the frozen product by evaporation using high frequency currents in a low vapor pressure chamber. This mode ensures maximum preservation of the nutritional value of the product. Most often this is done with milk powder.

For a pregnant woman, dried preserves at any time of the year will be of great help, excluding, of course, dried fish and meat, which are not only poorly digested, but also a source of unnecessary excess salt for the expectant mother's body.

* Salting. This canning method is carried out by adding high concentrations of table salt to the product (in meat - up to 10-12%, fish - up to 14%, canned vegetables up to 10%). The introduction of table salt increases the osmotic pressure in the product, which disrupts the metabolic processes in the microbial cell and causes its death. Most pathogenic and opportunistic microorganisms die at a concentration of table salt of about 10%, and salmonella and staphylococci - at a concentration of 15-20%. It is important to understand that excess salt retains water in the body, which can lead to edema and become a risk factor for the development of preeclampsia. Therefore, salty preservation for a pregnant woman in her menu should be limited.

* Sweet preservation. Preservation with sugar at high concentrations (at least 60-65% depending on the type of food) also creates a significant osmotic pressure in the solution. At the same time, microbial cells are destroyed as a result of severe dehydration, and the product does not deteriorate. This method is used for preserving fruits (making jam, jam, marmalade, jelly, etc.).

Sweet preserves for a pregnant woman must be consumed in reasonable quantities so as not to burden the pancreas and not gain excess weight.

* Souring and urinating. During fermentation, urination, lactic acid microorganisms ferment sugars that are part of vegetables and fruits with the formation of lactic acid from them, which at concentrations of 0.7% and above has a preservative effect and inhibits or stops the vital activity of microorganisms. Most often, fermentation occurs naturally due to the microflora contained on the fruits or vegetables themselves. The preservative effect during fermentation is complemented by a small amount of table salt (1.5–3%).

A pregnant woman is not forbidden to eat pickled vegetables, but before eating it is better to rinse them under running cold water so that less salt remains on them.

∗ Pickling. This is canning with acetic acid, which has a preservative effect on fruits and vegetables at concentrations of 1.2–1.8%. They also marinate fish and sometimes meat. At this concentration of acetic acid, microorganisms do not die, but only stop their development. Pickled, as well as salted, pregnant women should be limited as much as possible in their diet due to the irritating effect of vinegar on the stomach.

∗ Smoking. Smoking is a combined preservation under the antiseptic effect of substances formed in the smoke during the combustion of wood (phenols, formaldehyde, acetic acid). They mainly smoke meat and fish, which are usually pre-salted. There are cold and hot smoking, differing in the temperature of the smoking medium and the amount of table salt introduced. As chemicals that replace direct smoke smoking, various smoking liquids are used in which the product is soaked.

Smoking (especially cold) certainly cannot be classified as a useful method of preservation due to the formation of carcinogenic substances in the product (for example, benzo (a) pyrene). Obviously, such products should not fall on the table of pregnant women.

∗ Preservation. Preserves - canned food is non-sterile, not subject to long-term storage, so it is not worth stocking them for future use. They are preserved by pouring marinade or spicy salting. The composition of the filling for preserves will include a preservative - sodium benzoate. By the way, a frequent violation in the production of preserves is the addition of an increased concentration of this preservative.

Most often, salted fish (herring, capelin, mackerel, pink salmon, etc.), which are packed in plastic containers, are preserved in this way. It is better for a pregnant woman not to use such canned food.

* Canning with food additives. The use of preservatives and antioxidants allows several times to extend the shelf life of ready-to-eat products.

The most commonly used preservative is benzoic acid and its salts (E 210 - E 219). The antimicrobial effect of benzoic acid is associated with its effect on the enzyme system of microorganisms. However, the abuse of products (as a rule, these are sweet carbonated soft drinks, fish preserves), which contain artificial benzoic acid, can adversely affect the health of the pregnant woman and the child. The fact is that benzoic acid has a significant sensitizing potential (it causes allergic reactions in the body, such as hives, asthma, and even anaphylactic shock). Therefore, while waiting for the baby, we include such products in the black list.

What canned food should be discarded?

In a tin with rust and discoloration on the inside of the lid. The contact of a metal container with the contents often leads to undesirable chemical interactions - corrosion (rust) on the surface of tin and tin. These phenomena are more pronounced in canned foods with high acidity (marinades, vegetables, etc.).

In jars with canned food from products containing a lot of protein substances (meat, fish, peas, etc.), the so-called marbling, or sulfide corrosion, is usually formed when tin and tin iron interact with the sulfur components of protein products. This sulfide bluish-brown film has not been proven to be harmful to health, but it impairs the appearance and taste of the product and expectant mothers should definitely not eat canned food with such defects.

To prevent corrosion and marbling, cans are made from pre-lacquered metal (tin, aluminum), and sometimes finished cans are varnished from the inside with food varnishes. However, you can find out what is hidden inside the tin and whether the product can be eaten only after you open it.

Bloated banks. This is the so-called bombing - swelling of the lids and bottoms due to gas formation as a result of the vital activity of microorganisms with insufficient sterilization (biological bombing) or when the acids of the product interact with the metal in unlacquered cans (chemical bombing). Such canned food can be dangerous due to the likelihood of developing botulism or chemical intoxication.

Top 5 healthy preserves

1. Frozen fruits, vegetables, berries.
2. Pasteurized milk.
3. Sterilized meat, fish, vegetable, fruit canned food for children.
4. Dried fruits.
5. Canned peas and corn.

Top 5 Unwanted Canned Foods

1. Dried fish and meat.
2. Salted vegetables, meat, fish.
3. Pickled cucumbers, tomatoes, peppers.
4. Smoked products and preserves.
5. Canned foods with food additives.

Promising direction

Currently, aseptic preservation is one of the promising and safe preservation methods, in which the product is first sterilized in special apparatus at high temperatures for a very short time (1–2 minutes), then cooled and packaged in a pre-sterilized sealed container. The quality of products obtained with aseptic preservation is much higher than with conventional sterilization, and such preservations (juices, fruit purees, etc.) can be recommended for pregnant women.

In conclusion, I would like to note that in the conditions of a long winter, reasonably selected canned foods for a pregnant woman and her family can be a useful help in diversifying their diet.