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2.6. Food preservation and hygiene

Food preservation and hygiene

Citizens have the right to know that we are safe when consuming any type of food.

If the food is not going to be consumed immediately, it is necessary to subject it to some preservation techniques to avoid its deterioration, since microorganisms can develop that alter its properties and produce toxic substances for people.

Food handling

To avoid contamination of food, people who handle it both in the food industry and at home, have to follow a series of basic recommendations:

  • Take maximum care of personal hygiene (washed hands, hair tied, do not touch the nose, ...).     
  • Wear suitable and clean clothing, gloves if necessary.
  • Monitor the hygiene of work instruments (knives, containers, etc.).

Types of food contamination

In the process of handling food, different types of contamination can occur:

  • Biological contamination, due to the growth of microorganisms in food, such as bacteria and fungi. For example, salmonella, the cause of 65% of food poisoning. 
  • Chemical contamination, due to the presence of chemical substances in food, which can be harmful or toxic in the short, medium or long term.
  • Physical contamination is the presence of any material in the food that should not be there, such as plastics, stones, bones, etc. that can cause harm to the person who consumes it.

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Food preservation techniques

There are many techniques that allow you to preserve and extend the life of food:

Dehydrating products

Water is necessary so that microorganisms can proliferate in the food. By removing the water from the food or replacing it, the food will last longer. Some examples are:

  • Salting: It consists of adding salt ( sodium chloride ) to the food and letting it dry, since microorganisms cannot live in places with a high concentration of salt (cod, ham, etc.).           
  • Sugar: When sugar is in high concentration, it allows the preservation of food (syrup, jams, etc.).  
  • Vinegar: Acetic acid acidifies the environment favoring conservation (pickles, onions, pickles, etc.).       
  • Smoking: The smoke from certain firewoods is used to preserve food (salmon, bacon, etc.).   
  • Alcohol: Good preservative when food is allowed to marinate for a certain time (fruits).

Preservation by drying or dehydration

By removing water from food, the proliferation of microorganisms is prevented. The food can be left to dry in the sun (fish, fruits) or in specialized ovens (powdered milk, condensed milk).  

Vacuum packed

With vacuum packaging, water and air are removed from the food packaging, creating conditions in which microorganisms cannot grow.


The irradiation of food consists of exposing the food to the action of ionizing radiation for a certain time so that microorganisms cannot develop. It is used in condiments and spices.

Conservation by heat

Microorganisms can also be killed by applying a high temperature to food. Later it will be necessary to pack it hermetically to avoid new contaminations. Some examples of heat preservation are:

  • Bain marie. It is a method of indirect cooking of food, hermetically closed in a container, which allows it to cook in a smooth, uniform and constant way.
  • Pasteurization: It consists of subjecting the food to an approximate temperature of 80ºC for a short period of time followed by rapid cooling. It allows to extend the useful life of the food for a few days. It is widely used in milk. It is carried out with the aim of eliminating microorganisms without altering the composition and qualities of the liquid.
  • Sterilization: It allows a longer duration of the food than in pasteurization. The food is heated at temperatures between 115 and 127 ºC for a time. At these temperatures, some vitamins can be lost and the characteristics of some products may change.

Cold storage

Low temperatures also prevent the proliferation of microorganisms, which is why cold storage is the most used for perishable foods. They are distinguished:

  • The cooling: the temperature is kept above 0°C, typically at 4°  and 6°C, allowing the conservation of food for several days without alteration.
  • The freezing: temperature is below 0°C, typically between -12 and -24°C. Food is preserved for a long time, since microorganisms cannot grow at these temperatures.

Food Additives

food additive is that substance that, without constituting a food by itself or possessing nutritional value, is intentionally added to food and beverages in minimal quantities with the aim of modifying their organoleptic characteristics (texture, flavor, color) or facilitating or improving their elaboration or conservation process. Authorized additives are identified by the letter E followed by three digits. We distinguish:

  • Colors (E-100): They provide color to food (sweets, yogurts).
  • Preservatives (E-200): They allow food to last longer and not spoil by the action of microorganisms.
  • Antioxidants (E-300): They prevent food from going rancid when oxidized in contact with air (cold cuts, precooked).        
  • Emulsifiers, stabilizers, thickeners and gelling agents (E-400): They ensure that the food has the desired consistency and texture (creams, mayonnaise).          
  • Aromas and flavor enhancers (E-600): They provide extra flavor to food, stimulating taste receptors (for example, yogurts).
  • Sweeteners (E-420): They accentuate the sweet taste of food (cakes).


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