MAIN FOOD PRESERVATION METHODS - CULTURE VOCABULARY - 2025

Food preservation methods are a set of processes that seek to control the factors that cause its alteration. There are two major causes of food spoilage. On the one hand there are the biological ones; that is, the action of microorganisms and their own enzymes.

On the other hand, the chemical causes stand out, the most important being the rancidity of fats and non-enzymatic browning, also known as the Maillard reaction. Conservation methods consist of the application of various techniques that can minimize these causes.

These methods include using high temperatures (pasteurization, sterilization), handling low temperatures (refrigeration, freezing), reducing the available water (dehydration and drying, salting, freeze-drying, smoking, confit), fermentation, the use of chemical preservatives, ionizing radiation, and others.

Packaging and storage conditions are very important to guarantee the desired stability once the food has been preserved.

Main methods of food preservation

As in many areas, the human being first developed and learned the processes that made it possible to achieve the proposed objective - in this case, increasing the useful life of food - and later science explained the fundamentals of the processes.

In the first place, to preserve a food it is necessary to maintain its physical integrity and keep it sheltered from attack by insects and rodents. The procedures that are applied for its conservation seek:

- Avoid or delay microbial action.

- Destroy or inactivate enzymes.

- Prevent or delay chemical reactions.

Procedures based on handling high temperatures

These methods are based on the fact that heat destroys microorganisms: it coagulates their proteins and inactivates the enzymes necessary for their metabolism. The main preservation methods that use high temperatures are:

Scalding

Short-term heat treatment (a few minutes) and moderate temperature (95-100 ° C). It is not a preservation system in itself, it is an important previous operation in sterilization, freezing and dehydration.

Pasteurization

Term used in homage to Louis Pasteur, who in the mid-nineteenth century conducted studies on the lethal effect of heat on microorganisms.

Pasteurization achieves the destruction of all the pathogenic microorganisms, the maximum (not total) destruction of non-pathogenic microorganisms (in order to achieve conservation under refrigeration) and the microbial and enzymatic destruction, for the purpose of reigniting to produce fermented products under special conditions.

This process is accompanied by other methods, such as refrigeration (as can be seen in milk, other dairy products and ham), packaging the product in a closed container, creating anaerobic conditions, adding high concentrations of sugars or salt, or the addition of other chemical preservatives.

Commercial sterilization

It is a procedure that requires the application of heat to reach higher temperatures than in pasteurization. The purpose is to achieve the destruction of all pathogenic and toxin-generating microorganisms, as well as all other types of microbes that, if present, could grow in the product and break it down.

Procedures based on the management of low temperatures

These are based on ensuring the temporary stabilization of food by delaying or inhibiting chemical reactions, microbial growth or enzymatic activity, which would produce undesirable alterations if the food were kept at room temperature.

In refrigeration, the storage temperature is of the order of 3 to 4 ˚C or even lower, as long as it does not allow the water present in them to freeze. In freezing the temperature is below -18 ˚C.

Decrease in available water

Without water, microbial development is very difficult. The more moisture a food contains, the shorter its useful life, as it is more perishable. The reduction of water is achieved by physical means such as drying or dehydration, evaporation or centrifugation.

It is also achieved by adding solutes that decrease the availability of water, as a solvent and as a reagent. Among these solutes we have salt and sugar; There are many examples of this type of food: jams, sweets, sausages, among others.

Freeze-drying, also called cryo-drying, is a preservation process in which a severe decrease in food moisture is achieved. Freeze-dried products have excellent and easy rehydration, long shelf life and retain their aromas and nutrients.

This expensive technique is mostly used in the pharmaceutical industry to preserve vaccines and antibiotics. The method consists of freezing the water present and, by managing temperatures and pressure, making the water sublime; that is, it passes from the solid state to the gaseous state without going through the liquid state.

Fermentation

It is a very old conservation method that uses microorganisms to carry out transformations to organic matter.

It consists of the breakdown of carbohydrates, both under aerobic and anaerobic conditions. However, strictly speaking, the process is anaerobic.

By controlling the process conditions, it is possible to obtain final products such as acids and alcohols, which are inhibitors of the pathogens that may be present in food.

Furthermore, fermented foods have different characteristics - many of these desirable - from their non-fermented counterparts. During fermentation, microorganisms synthesize vitamins and other compounds, release nutrients, and break down substances such as hemicellulose.

There are countless examples of fermented products: wine, beer, yogurt, various types of matured cheeses such as cabrales or roquefort, kumis, kefir, sauerkraut, fermented or cured sausages, pickles, among others.

Use of preservative additives

They are characterized because they inhibit or retard the growth of microorganisms and the deterioration they cause. With the use of these substances - in the doses established as safe - the inhibition of the development of eventually present pathogenic microorganisms (Salmonella, Clostridium, Staphylococci, molds, among others) and the production of their toxins is achieved.

The organoleptic stability resulting from stopping the presence of disturbing microorganisms is also guaranteed. Antimicrobial additives are not bactericidal but bacteriostatic; that is, they seek only to conserve, not to improve. Among the main preservatives of mineral origin most frequently used, the following stand out:

- Chlorides (NaCl).

- Nitrates and nitrites of sodium and potassium NaNO ₃, KNO ₃, NaNO ₂, KNO _3.

- Carbonic anhydride (CO ₂).

- Sulfur dioxide and sulphites SO _2, Na ₂ SO ₃, NaHSO ₃, Na ₂ S ₂ O _5.

Organic preservatives include the following:

- Saturated fatty acids and derivatives (formic acid, formate, acetic acid, acetates, propionic acid, propionates, caprylic acid).

- Sorbic acid and sorbates.

- Benzoic acid and benzoates.

- Other organic acids.

- Phenolic antioxidants.

- Antibiotics.

Methods based on a combination of the above principles are often used. The purpose is not only to increase the shelf life, but also to maintain the organoleptic and nutritional characteristics as close as possible to those of the original food.

For example, today it is common to find products packaged in oxygen-poor atmospheres (vacuum packed, with inert gases). In addition, emerging technologies based on non-thermal processing are being developed that attempt to use less energy.

References

1. Casp Vanaclocha, A. and Abril Requena, J. (2003). Food preservation processes. Madrid: A. Madrid Vicente.
2. Cheftel, J., Cheftel, H., Besançon, P., & Desnuelle, P. (1986). I ntroduction to biochimie et à la technologie des alimentants. Paris: Technique et Documentation
3. Conservation des aliments (2018) Retrieved on March 19, 2018, from fr.wikipedia
4. Coultate, T. (1986). Foods. Zaragoza: Acribia.
5. Gaman, P., & Sherrington, K. (1990). The science of food. Oxford, Eng.: Pergamon.