Food preservation

Different food preservation methods have different impacts on the quality of the food and food systems. Some traditional methods of preserving food have been shown to have a lower energy input and carbon footprint compared to modern methods.^[3][2] Some methods of food preservation are also known to create carcinogens.

Traditional techniques

Some techniques of food preservation pre-date the dawn of agriculture. Others were discovered more recently.

Boiling

Boiling liquids can kill any existing microbes. Milk and water are often boiled to kill any harmful microbes that may be present in them.

Burial

Burial of food can preserve it due to a variety of factors: lack of light, lack of oxygen, cool temperatures, pH level, or desiccants in the soil. Burial may be combined with other methods such as salting or fermentation. Most foods can be preserved in soil that is very dry and salty (thus a desiccant) such as sand, or soil that is frozen.

Many

Sometimes meat is buried under conditions that cause preservation. If buried on hot coals or ashes, the heat can kill pathogens, the dry ash can desiccate, and the earth can block oxygen and further contamination. If buried where the earth is very cold, the earth acts like a refrigerator, or, in areas of permafrost, a freezer.

In

Butter and similar substances have been preserved as

Canning involves cooking food, sealing it in sterilized cans or jars, and boiling the containers to kill or weaken any remaining bacteria as a form of sterilization. It was invented by the French confectioner Nicolas Appert.^[4] By 1806, this process was used by the French Navy to preserve meat, fruit, vegetables, and even milk. Although Appert had discovered a new way of preservation, it was not understood until 1864 when Louis Pasteur found the relationship between microorganisms, food spoilage, and illness.^[5]

Foods have varying degrees of natural protection against spoilage and may require that the final step occurs in a

Lack of quality control in the canning process may allow ingress of water or micro-organisms. Most such failures are rapidly detected as decomposition within the can cause gas production and the can will swell or burst. However, there have been examples of poor manufacture (underprocessing) and poor hygiene allowing contamination of canned food by the obligate anaerobe Clostridium botulinum, which produces an acute toxin within the food, leading to severe illness or death. This organism produces no gas or obvious taste and remains undetected by taste or smell. Its toxin is denatured by cooking, however. Cooked mushrooms, when handled poorly and then canned, can support the growth of Staphylococcus aureus, which produces a toxin that is not destroyed by canning or subsequent reheating.

Confit

Meat can be preserved by salting it, cooking it at or near 100 °C (212 °F) in some kind of fat (such as lard or tallow), and then storing it immersed in the fat. These preparations were popular in Europe before refrigerators became ubiquitous. They are still popular in France, where the term originates.^[6][7] The preparation will keep longer if stored in a cold cellar or buried in cold ground.

Cooling

Cooling preserves food by slowing down the growth and reproduction of microorganisms and the action of enzymes that causes the food to rot. The introduction of commercial and domestic refrigerators drastically improved the diets of many in the Western world by allowing food such as fresh fruit, salads and dairy products to be stored safely for longer periods, particularly during warm weather.

Before the era of mechanical refrigeration, cooling for food storage occurred in the forms of

The earliest form of curing was dehydration or drying, used as early as 12,000 BC. Smoking and salting techniques improve on the drying process and add antimicrobial agents that aid in preservation. Smoke deposits a number of pyrolysis products onto the food, including the phenols syringol, guaiacol and catechol.^[8] Salt accelerates the drying process using osmosis and also inhibits the growth of several common strains of bacteria. More recently nitrites have been used to cure meat, contributing a characteristic pink colour.^[9]

In 2015, the International Agency for Research on Cancer of the World Health Organization classified processed meat—i.e., meat that has undergone salting, curing, and smoking—as "carcinogenic to humans".^[10][11][12]

Fermentation

Some foods, such as many cheeses, wines, and beers, use specific micro-organisms that combat spoilage from other less-benign organisms. These micro-organisms keep pathogens in check by creating an environment toxic for themselves and other micro-organisms by producing acid or alcohol. Methods of fermentation include, but are not limited to, starter micro-organisms, salt, hops, controlled (usually cool) temperatures and controlled (usually low) levels of oxygen. These methods are used to create the specific controlled conditions that will support the desirable organisms that produce food fit for human consumption.

Fermentation is the microbial conversion of starch and sugars into alcohol. Not only can fermentation produce alcohol, but it can also be a valuable preservation technique. Fermentation can also make foods more nutritious and palatable. For example, drinking water in the Middle Ages was dangerous because it often contained pathogens that could spread disease. When the water is made into beer, the boiling during the brewing process kills any bacteria in the water that could make people sick. Additionally, the water now has the nutrients from the barley and other ingredients, and the microorganisms can also produce vitamins as they ferment.^[5]

Freezing

Freezing is also one of the most commonly used processes, both commercially and domestically, for preserving a very wide range of foods, including prepared foods that would not have required freezing in their unprepared state. For example, potato waffles are stored in the freezer, but potatoes themselves require only a cool dark place to ensure many months' storage. Cold stores provide large-volume, long-term storage for strategic food stocks held in case of national emergency in many countries.

Heating

Heating to temperatures which are sufficient to kill microorganisms inside the food is a method used with perpetual stews.

Jellying

Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include gelatin, agar, maize flour, and arrowroot flour.

Some animal flesh forms a protein gel when cooked.

Jellying is one of the steps in producing traditional pâtés. Many jugged meats (see below) are also jellied.

Another type of jellying is

In rural Afghanistan, grapes are preserved in disc-shaped vessels made of mud and straw, called kangina. The vessels, which can preserve fresh grapes for up to 6 months, passively control their internal environments to restrict gas exchange and water loss, prolonging the lives of late-harvested grapes stored within them.^[13]

Jugging

Meat can be preserved by jugging. Jugging is the process of

Pickling is a method of preserving food in an edible, antimicrobial liquid. Pickling can be broadly classified into two categories: chemical pickling and fermentation pickling.

In chemical pickling, the food is placed in an edible liquid that inhibits or kills bacteria and other microorganisms. Typical pickling agents include brine (high in salt), vinegar, alcohol, and vegetable oil. Many chemical pickling processes also involve heating or boiling so that the food being preserved becomes saturated with the pickling agent. Common chemically pickled foods include cucumbers, peppers, corned beef, herring, and eggs, as well as mixed vegetables such as piccalilli.

In fermentation pickling, bacteria in the liquid produce

The earliest cultures have used

Modern industrial techniques

Techniques of food preservation were developed in research laboratories for commercial applications.

Aseptic processing

Aseptic processing works by placing sterilized food (typically by heat, see

Besides UHT, aseptic processing may be used in conjunction with any of the microbe-reduction technologies listed below. With pasturization and "high pressure pasturization", the food may not be completely sterilized (instead achieving a specified log reduction), but the use of sterile packaging and environments is retained.

Pasteurization

Pasteurization is a process for preservation of liquid food. It was originally applied to combat the souring of young local wines. Today, the process is mainly applied to dairy products. In this method, milk is heated at about 70 °C (158 °F) for 15–30 seconds to kill the bacteria present in it and cooling it quickly to 10 °C (50 °F) to prevent the remaining bacteria from growing. The milk is then stored in sterilized bottles or pouches in cold places. This method was invented by Louis Pasteur, a French chemist, in 1862.

Vacuum packing

Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The vacuum environment strips bacteria of oxygen needed for survival. Vacuum-packing is commonly used for storing nuts to reduce loss of flavor from oxidization. A major drawback to vacuum packaging, at the consumer level, is that vacuum sealing can deform contents and rob certain foods, such as cheese, of its flavor.

Freeze drying

Preservatives

There is also another approach of impregnating packaging materials (plastic films or other) with antioxidants and antimicrobials.[18]^[19]

Irradiation

Irradiation of food

National and international expert bodies have declared food irradiation as "wholesome"; organizations of the United Nations, such as the World Health Organization and Food and Agriculture Organization, endorse food irradiation.^[21][22] Consumers may have a negative view of irradiated food based on the misconception that such food is radioactive;^[23] in fact, irradiated food does not and cannot become radioactive. Activists have also opposed food irradiation for other reasons, for example, arguing that irradiation can be used to sterilize contaminated food without resolving the underlying cause of the contamination.^[24] International legislation on whether food may be irradiated or not varies worldwide from no regulation to a full ban.^[25]

Approximately 500,000 tons of food items are irradiated per year worldwide in over 40 countries. These are mainly spices and condiments, with an increasing segment of fresh fruit irradiated for fruit fly quarantine.^[26][27]

Pulsed electric field electroporation

Pulsed electric field (PEF) electroporation is a method for processing cells by means of brief pulses of a strong electric field. PEF holds potential as a type of low-temperature alternative pasteurization process for sterilizing food products. In PEF processing, a substance is placed between two electrodes, then the pulsed electric field is applied. The electric field enlarges the pores of the cell membranes, which kills the cells and releases their contents. PEF for food processing is a developing technology still being researched. There have been limited industrial applications of PEF processing for the pasteurization of fruit juices. To date, several PEF treated juices are available on the market in Europe. Furthermore, for several years a juice pasteurization application in the US has used PEF. For cell disintegration purposes especially potato processors show great interest in PEF technology as an efficient alternative for their preheaters. Potato applications are already operational in the US and Canada. There are also commercial PEF potato applications in various countries in Europe, as well as in Australia, India, and China.

Modified atmosphere

Modifying atmosphere is a way to preserve food by operating on the atmosphere around it. It is often used to package:

• Fresh fruits and vegetables, especially salds crops, which contain living cells that respire even while refrigerated. Reducing oxygen (O₂) concentration and increasing the carbon dioxide (CO₂) concentration slows down their respiration, conserves stored energy, and therefore increases shelf life.^[28] High humidity is also used to reduce water loss.^[29]
• Red meat, which needs high O₂ to reduce oxidation of myoglobin and maintain an attractive bright red color of the meat.^[30]
• Other meat and fish, which uses higher CO₂ to reduce oxidation and slow down some microbes.^[31]

Nonthermal plasma

This process subjects the surface of food to a "flame" of ionized gas molecules, such as helium or nitrogen. This causes micro-organisms to die off on the surface.^[32]

High-pressure food preservation

Lactic acid bacteria (LAB) have antagonistic properties that make them particularly useful as biopreservatives. When LABs compete for nutrients, their metabolites often include active antimicrobials such as lactic acid, acetic acid, hydrogen peroxide, and peptide bacteriocins. Some LABs produce the antimicrobial nisin, which is a particularly effective preservative.^[37][38]

LAB bacteriocins are used in the present day as an integral part of hurdle technology. Using them in combination with other preservative techniques can effectively control spoilage bacteria and other pathogens, and can inhibit the activities of a wide spectrum of organisms, including inherently resistant Gram-negative bacteria.^[35]

Hurdle technology

Notes

Sources

•  This article incorporates text from a free content work. Licensed under CC BY-SA 3.0 (license statement/permission). Text taken from The State of Food and Agriculture 2019. Moving forward on food loss and waste reduction, In brief​, 24, FAO, FAO.

References

• Riddervold, Astri (1988). Food Conservation. Prospect.
  ISBN 978-0-907325-40-6
  .
• Abakarov, Nunes. "Thermal food processing optimization: algorithms and software" (PDF). Food Engineering. Archived from the original (PDF) on 21 February 2014. Retrieved 22 October 2012.
• Abakarov, Sushkov, Mascheroni. "Multi-criteria optimization and decision-making approach for improving of food engineering processes" (PDF). International Journal of Food Studies. Archived from the original (PDF) on 21 December 2018. Retrieved 9 June 2021.{{cite news}}: CS1 maint: multiple names: authors list (link)

Further reading

• Marx de Salcedo, Anastacia (2015). Combat-ready Kitchen: How the U.S. military shapes the way you eat. New York: Current/Penguin.
  ISBN 9781101601648
  .

External links

Wikimedia Commons has media related to Food preservation.

• A c. 1894 Gustav Hammer & Co. commercial cooking machinery catalogue.
• Preserving foods ~ from the Clemson Extension Home and Garden Information Center
• National Center for Home Food Preservation
• BBC News Online – US army food... just add urine
• Home Economics Archive: Tradition, Research, History (HEARTH)
  An e-book collection of over 1,000 classic books on home economics spanning 1850 to 1950, created by Cornell University's Mann Library.
• Pobojewski, Sally (8 May 1995). "Underwater storage techniques preserved meat for early hunters". The University Record. University of Michigan. Archived from the original on 26 February 2019. Retrieved 28 September 2018.