Food preservation methods

Can you imagine the modern world without preserved food? Us neither. Thanks to the time saved by having food preserved and always at hand, we can spend more hours working, living and dedicating ourselves to day-to-day activities.

Have you ever thought about the importance of preserving food in our lives?  We invite you to learn about the most used food preservation methods in the food industry and kitchens around the world. Let’s get started!

History of food preservation

Food plays a fundamental role in the genetic makeup and brain development of today’s human beings. For this reason, human evolution has a close relationship with food and, consequently, with its conservation. In this way, the development of conservation methods goes hand in hand with the great steps of humanity. Without a doubt, it is exciting to follow the trail of ancient food preservation methods:

How food was preserved in prehistory

• In the Paleolithic, the first hunters consumed food right after hunting it.
• Desiccation arises as a result of human needs. This technique uses the air and the sun as principles. It is still practiced today.
• At the end of the Paleolithic (upper) or beginning of the Mesolithic, the first clay pot is created in Japan (Jimson period), the first container for conservation.
• In the Neolithic, humans leave their nomadic life, agriculture and livestock arise. At the time, they build the first barns, to protect their food from animals. Caves and pits dug into the ground are used for this mission.
• During the Iron Age, northern Europe experimented with dehydration. The first ovens to dry freshly harvested wheat appear.

Food preservation in ancient times

• The first salting and smoking techniques arise, thanks to the Egyptians.
• The Greeks create two forms of fruit preservation, one with virgin wax and the other with honey.
• The Romans preserve wine for decades, packing it in hermetically sealed amphorae.
• The Visigoths prepare jams with honey and apples, keeping them in wineskins.
• A revolutionary preservative emerges in New Guinea: sugar. It then travels to India, China, and other parts of the East, Persia, and finally Europe in the fourth century.

Refrigerators to preserve food in the middle Ages

• Sometime after the discovery of America, the Spanish took the cane to Santo Domingo, Cuba and Mexico to cultivate it and import it throughout Europe.
• In the North of Europe, deposits excavated in the stone are created, where they keep a large amount of snow and blocks of ice, which they call refrigerators.

Modern Age: new conservation techniques

• In the 16th and 17th centuries, recipes for different types of food preservation are recorded: brined and salted vegetables, meats preserved in lard (these techniques are still practiced today).
• In the 17th century, the production and consumption of sugar are widespread throughout the world.
• In 1795, Nicolas Apart, a French cook, discovered that by boiling food inside a closed container (glass bottles with corks in this case); they are preserved in perfect condition for a long time.
• The same year, the first artificial food dehydrator, called the hot water room, is invented in France.

Food preservation methods of the Contemporary Age

• In 1801 the first beet sugar factory was built. However, it is not until 1811 that jams gain popularity, a culinary method that until then was reserved for the upper class.
• In 1810, Peter Durand patented the first cans, made with wrought iron and vacuum sealed.
• In 1858, Charles Teller created the first ice machine. Thus, the transport and conservation of feed become much easier.
• Louis Pasteur discovers pasteurization in 1864, one of the most widely used preservation methods today.
• As of 1879, the refrigerator reaches many homes, becoming an appliance for domestic use.
• At the beginning of the 20th century, vacuum freeze-drying or freeze-drying was created.
• Thanks to technological advances, in the 20th century machinery is becoming more sophisticated every day and is designed to prevent contamination by microorganisms.
• In the second half of the 20th century, substances that preserve food for decades are discovered: preservatives.
• At the end of the 20th century, more aseptic containers were designed, such as the tartaric, as well as biodegradable plastic polymers.
• At the end of the 20th century and the beginning of the 21st, the revolutionary techniques of food irradiation and biotechnological manipulation open the spectrum of food preservation to unimaginable limits.

Types of conservation

Virtually everything we consume today has previously gone through a conservation process. For this reason, there is much that we can learn from the various forms of conservation that exist, as well as the advantages they bring to each food. Food preservation techniques are divided into two main blocks: according to the performance of microorganisms and according to the type of technique applied. The first block distinguishes the types of conservation as follows:

• Methods that destroy germs or inactivate them: sterilization, pasteurization, radiation, high pressure, among others.
• Methods that prevent the development and proliferation of microorganisms: refrigeration, freezing, dehydration, smoking, addition of chemical substances, among others.
• Methods that avoid re-contamination: aseptic processing, packaging, hygienic storage, among others.

On the other hand, the first type of conservation according to the kind of technique applied is the conservation by variation of the temperature of the food. This is divided into cold storage and heat storage or thermal storage.

Cold storage

This uses low temperatures (around 0 ºC) to extend the freshness of food. Cold slows down chemical reactions and decreases the activity of microorganisms. However, it does not kill them, so when the food is heated, they begin to multiply again. Cold preservation methods are divided into:

• Refrigeration
• Freezing
• Deep freezing

Heat preservation or thermal preservation

For its part, thermal preservation uses heat to slow down chemical reactions, as it inactivates enzymes in a process called denaturation. In this technique, the variables of temperature and time play an essential role in the durability of the product. The higher the temperature, the greater the durability. The different methods that apply this technique are:

• Pasteurization
• Sterilization
• Cooking (blanching), used to preserve and freeze foods such as broccoli

There are other conservation techniques that use variables other than temperature. Some of them are:

Preservation by humidity reduction

This process is based on the control of the humidity contained in the food. Since microorganisms and bacteria reproduce through water, if humidity is controlled, the probability of contamination decreases. That is, less water, less reaction capacity of enzymes and development of microorganisms. The methods that apply this technique are:

• Desiccation
• Dehydration
• Evaporation
• Lyophilization
• Concentration

Chemical preservation or by addition of substances

Chemical preservation prolongs the resistance and shelf life of foods through the addition of substances that chemically modify the product. This method is widely used in the food industry, as it is a very effective method for industrial production, thanks to the fact that it considerably increases the durability of food. Within chemical conservation, we can find organoleptic conservation, in which the sensory properties of food are modified, such as:

• Alcohol addition
• Addition of fats
• Addition of sugars (jam, grace ado, grajeado)
• Addition of salts (salting, curing)
• Acidification (marinating, various forms of marinade, pickles and marinades)
• Fermentation (alcoholic, acetic, butyric)

On the other hand, we can also find various food preservation methods that use the addition of other chemical substances or food additives of industrial origin, such as:

• Dyes
• Preservatives
• Antioxidants
• Stabilizers

If you want to know what food additives are and what their advantages and disadvantages are for food production and health, do not hesitate to click on the link and visit our article.

Non-thermal or emergent methods

The growing interest in organic food (without additives or preservatives) has drawn the attention of the technology industry. Currently, the new forms of conservation are very sophisticated, considerably increasing the quality of the products and their durability. The most relevant new food preservation methods are those that are achieved with:

• High pressures
• Electric fields
• Light pulses
• Radiation
• Irradiation (ionizing)
• Non-ionizing method (microwave)
• Surface treatment and edible coatings
• Encapsulation and controlled release
• Vacuum packed
• Modified atmosphere
• Ultrafiltration
• Sterilizing filtration

Food preservation techniques

Although supplying ourselves with food is as simple as visiting the supermarket and storing food at home, there is a great mechanism behind it that depends a lot on the conservation of these products. In many cases, foods do not use a single preservation method, but several combined to improve their quality and durability.

It is interesting to mention that although the elementary principles of conservation are applicable to most foods, not all microorganisms react the same way to a method (they can be inhibited or die). Therefore, there are better methods than others depending on the characteristics of the food and the microorganisms that can be activated in it.

Below, we’ll take a look at some of the top food preservation techniques out there, including ones you can use at home.

Refrigeration

Refrigeration or positive cold consists of keeping a food at a stable and cold temperature, close to 0 °C, to avoid piling and hygrometric value. Consequently, the proliferation of microorganisms is controlled.

The most suitable domestic refrigeration temperature is 0-8 °C, while the industrial one is between 0-5 °C. In refrigeration, food can last a few days maximum.

Freezing

Freezing or negative cold consists of preserving a food for a long time, at temperatures below 0 °C, in such a way that the water in the food freezes. Remember, the cold chain must be respected; otherwise the microbes will reproduce again.

Deep freeze

Deep freezing is based on lowering the temperature of a food to -40 ºC. This can be achieved through various processes that can use the use of plates, immersion in liquids, cold air, among others. This type of rapid freezing occurs in less than 2 hours.

Lyophilization

Lyophilization consists of freezing a food (at a temperature below -30 ºC) in order to extract its water under vacuum, transforming the ice into water vapor. This method preserves almost all the nutritional value of the food. However, its use is expensive, which is why it is applied in products such as coffee (normal or decaffeinated soluble), infant milk and some other foods.

Pasteurization

Through this technique, heat is applied to the food for a certain time (the time varies depending on it), at temperatures between 80-100 ºC. Immediately afterwards, the food must be cooled rapidly. This treatment regulates and destroys pathogenic microorganisms in the food, but does not inactivate their spores. For this reason, the product must be kept cold after opening.

Sterilization

It is the process that is applied to a food or object in order to eliminate germs and spores.  When sterilizing a product, it is exposed to temperatures around 115 ºC. This treatment affects the organoleptic qualities of the food and causes it to lose some nutrients. In the dairy industry, one of the most used sterilization treatments is pasteurization.

Dehydration

Dehydration is a procedure by which food loses water, thus inhibiting the development of bacteria. This practice can be carried out by exposing the food to the sun or using a dehydrating oven. It applies to many food products such as grains, cereals, fruits, vegetables, among others. With dehydrated foods you can obtain dehydrated soups, powdered coffee, dehydrated eggs, cereals, among other products.

Desiccation (or drying)

This thermal technique is used prior to freezing food, with the intention of destroying the enzymes that affect the color, flavor and vitamin content of the product. It also softens the food.

Salting

This preservation technique consists of dehydrating a food by adding common salt  (sodium chloride), either by immersing the product in a saline solution or by direct diffusion of the salt on its surface. This procedure inhibits the growth of microorganisms, the degradation of enzyme systems and, consequently, slows down chemical reactions.

Cured

It is the process prior to smoking and has several objectives: to provide more flavors, better texture and prolong the duration of the food. Simple curing can be done with homemade ingredients; however, industrial curing is done with common salt, curing salts, nitrites and nitrates (potassium and sodium).

Smoked

This procedure is a combination of drying and salting. In smoking, the smoke obtained from the combustion of certain substances is used with the intention of giving the food a sterilizing and antioxidant effect. In addition, it gives the product a peculiar aroma and an excellent texture. Beef, fish, and pork are generally smoked. Some recipes with smoked meats include smoked salmon, smoked chicken, and smoked chops.

Acidification

This technique is based on lowering the pH of the food through the addition of acidic substances (such as vinegar). In this way, the development of microorganisms is prevented.

Pickled

This procedure uses a mixture of salt and vinegar to preserve food. Vinegar provides its qualities as a preservative, while salt dehydrates the food. In its beginnings, this technique was used as a preservation method, but today it is used in gastronomy to highlight the texture of food and provide it with a very characteristic flavor. Some pickled recipes include pickled mussels or pickled chicken.

Fermentation

This preservation technique takes advantage of the microorganisms present in the food to enhance its organoleptic qualities and optimize its nutritional quality. This process is usually applied in dairy products.

Irradiation

This method consists of exposing food to controlled radiation, with the main intention of preventing the reproduction of microorganisms (bacteria or fungi). Food irradiation (cold pasteurization or ionization) preserves the organoleptic properties of the product and a large part of its nutrients.

Vacuum packed

The vacuum packaging system is based on the extraction of a large part of the oxygen that surrounds the food (cooked or in its natural state) to later pack it in plastic bags. This method stops food oxidation and putrefaction, extending its expiration date for more than 30 days and even up to a year.

Food additives of industrial origin

Additives are substances that are added to foods in order to recover, maintain, enhance their organoleptic qualities (flavor, color, texture and volume) or prolong their storage times (stopping the proliferation of microorganisms).