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Methods of storing and preserving food

When storing food, the aim is to ensure that it is protected against dangerous changes in quality resulting from biological and chemical processes and fit for consumption for a significant period of time. There are physical and chemical methods of food preservation. Physical methods include, among others, storage of food at low temperature or use of high temperatures – for example, cooking and pasteurizing, using hermetic packaging and ionizing radiation. Chemical methods of food preservation consist in adding chemical substances to food, e.g. benzoic acid, sorbic acid, sulfur dioxide, nitrate. Unfortunately, the physical and chemical changes that occur in foods as a result of these methods sometimes reduce the biological value of foods and can cause harmful effects.

Preservatives added to food

The first natural agents that protected food against spoilage (preservatives) were salt and sugar, and later the preservative properties of vinegar and other acids, e.g. those produced by microorganisms during fermentation (cabbage, cucumbers), were discovered. These substances change the environment in which microorganisms live, preventing the growth of most of them. Currently, many natural and artificial preservatives are known.

Many substances added to food have undergone extensive studies in terms of their possible effects on the human body. The results of these studies contributed to the collection of detailed information on the properties of food additives. The most widely known list is the classification used in the EU. Substances added to foods have been marked with the E symbol (like Europe) and a number according to the international numeric system – INS (EN International Numbering System). The E numbers on packaging are the manufacturer's declaration that the substances added to food were used in the amount corresponding to the intended use and come from a list approved by the authorities of the European Community and that according to the current state of knowledge they are not harmful to health when used properly. With the list of E additives, a consumer of any nationality will know what is the actual chemical composition of the food product.

Food additives marked with E are the best studied group of compounds that make up its composition. The addition of preservatives increases the safety and quality of the product. Therefore, do not trust labels without E numbers, as it is not known what additives the manufacturer used. It can be assumed that in order to achieve the appropriate shelf‑life of the product, the manufacturer had to use some additives.

Table salt, i.e. sodium chloride

Preservation of meat by using rock salt is one of the oldest and the most popular methods of meat preservation, in addition to drying and smoking. In the 10% rock salt solution, the development of the majority of putrid bacteria is stopped. Rock salt has bacteriostatic effect, which means that it stops the growth of microorganisms, but does not kill them. The disadvantage of this preservation method is the loss of some vitamins and mineral salts. In addition, you have to take into account the loss of moisture and the penetration of sodium chloride into the meat.

Benzoic acid and sorbic acid

Benzoic acid (E 210) and its salts have preservative properties in an acidic medium (pH 2.0 – 4.5). Their action consists mainly in inhibiting yeast development. They inhibit bacterial growth to a lesser extent. The efficacy of their action increases in the presence of sulfur dioxide, carbon dioxide and table salt. In the body, benzoic acid and its salts are rapidly absorbed and metabolized in the liver and then excreted in the urine. Clear symptoms of poisoning, such as vomiting and headaches, are observed only after very high doses, i.e. about 40 g of benzoic acid taken as a single dose. In people with allergy and asthma these substances may trigger allergic reactions.

Sorbic acid (E 200) is found in nature in rowan fruit, but as a food additive it is obtained synthetically. It has a preservative effect, inhibiting the growth of mold and yeast in acidic products with a pH of 3.0 – 6.0, where it works more effectively than benzoic acid. It inhibits the growth of many types of bacteria, with the exception of lactic acid bacteria. As a result, it is particularly useful in the production of fermented vegetables. Sorbic acid is used mainly for preserving vegetable sauces, fermented vegetables, jams, jellies and marmalades. It is one of the safest preservatives, because in the human body it undergoes a process typical for fatty acids, and the final products of its metabolism are usually carbon dioxide and water.

Vitamin C – preservative and antioxidant

Vitamin C, or ascorbic acid (E 300), is a natural component of the diet and a substance that is an additive to food products. It has preservative and antioxidant properties. It is commonly found in many fruits and foods, e.g. citrus, apple, blackcurrant, tomato, pepper, potato, sauerkraut. It is one of the best known and indispensable ingredients of human food. It contributes to the proper function of connective tissue, participates in the processes of biological oxidation and improves the overall immunity of the body. Deficiency of this vitamin (avitaminosis) causes scorbutus (scurvy). The daily requirement of the body for ascorbic acid is approximately 100 mg.

Vitamin C is a colorless or yellowish solid, odorless, slightly acidic, soluble in water and alcohol. On an industrial scale, it is obtained from glucose. In solutions exposed to light and elevated temperature it decomposes (undergoes oxidation) to a biologically inactive chemical compound.

Sulfur dioxide

Sulfur dioxide is one of the oldest chemical preservatives. It was used already in ancient times. It is effective against bacteria and molds, but less so against the growth of yeasts. As a powerful antioxidant, it prevents so‑called food browning. Sulfur dioxide is mainly used for preserving wines, dried vegetables and fruits, and for disinfecting indoor areas and tanks. In products subjected to long‑term heat treatment, this compound causes loss of vitamins. It can cause allergy, therefore it should not be added to food intended for direct consumption.

Task 1

Formulate a research question and hypothesis before watching a video “The ways of preserving food”

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Analysis of the experiment: „The ways of preserving food”. Research question (Uzupełnij). Hypothesis (Uzupełnij).

Analysis of the experiment: „The ways of preserving food”. Research question (Uzupełnij). Hypothesis (Uzupełnij).

Analysis of the experiment: „The ways of preserving food”

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Research question

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Hypothesis

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Film "The ways of preserving food" prezentuje sposoby konserwacji żywności. W pierwszej scenie widzimy plastry mięsa moczone w szklanej misie ze słoną wodą, w drugiej scenie widzimy plastry mięsa suszone w piekarniku, w trzeciej scenie widzimy nabiał przechowywany w lodówce, w czwartej scenie widzimy produkty przechowywane w zamrażarce, w piątej scenie widzimy mleko UHT (Ultra-high temperature processing) nalewane do szklanki, w ostatniej scenie widzimy bekon zapakowany próżniowo.

Film "The ways of preserving food" prezentuje sposoby konserwacji żywności. W pierwszej scenie widzimy plastry mięsa moczone w szklanej misie ze słoną wodą, w drugiej scenie widzimy plastry mięsa suszone w piekarniku, w trzeciej scenie widzimy nabiał przechowywany w lodówce, w czwartej scenie widzimy produkty przechowywane w zamrażarce, w piątej scenie widzimy mleko UHT (Ultra-high temperature processing) nalewane do szklanki, w ostatniej scenie widzimy bekon zapakowany próżniowo.

Film dostępny na portalu epodreczniki.pl

Film "The ways of preserving food" prezentuje sposoby konserwacji żywności. W pierwszej scenie widzimy plastry mięsa moczone w szklanej misie ze słoną wodą, w drugiej scenie widzimy plastry mięsa suszone w piekarniku, w trzeciej scenie widzimy nabiał przechowywany w lodówce, w czwartej scenie widzimy produkty przechowywane w zamrażarce, w piątej scenie widzimy mleko UHT (Ultra-high temperature processing) nalewane do szklanki, w ostatniej scenie widzimy bekon zapakowany próżniowo.

Summary

• Preservatives are substances that prolong food shelf‑life.

• Common preservatives are, for example, table salt, ascorbic acid, benzoic acid, sorbic acid, acetic acid.

• Not only preservatives are used as food additives, but also substances that improve the color, consistency and taste of products are often used for this purpose.

Keywords

preservative, E food additives, colorants

Glossary