Autor: Julio Cesar Tafforelli | Publicado: 2015-08-06T03:21:00-07:00


Food preservation


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Food preservation&nbsp;usually involves preventing the growth of&nbsp;bacteria,&nbsp;fungi&nbsp;(such as&nbsp;yeasts), or other&nbsp;micro-organisms&nbsp;(although some methods work by introducing benign&nbsp;bacteria&nbsp;or&nbsp;fungi&nbsp;to the food), as well as retarding the&nbsp;oxidation&nbsp;of&nbsp;fats&nbsp;that cause&nbsp;rancidity. Food preservation may also include processes that inhibit visual deterioration, such as the&nbsp;enzymatic browning&nbsp;reaction in apples after they are cut during food preparation.

Many processes designed to preserve food will involve a number of food preservation methods. Preserving fruit by turning it into jam, for example, involves boiling (to reduce the fruit’s moisture content and to kill bacteria, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination). Some traditional methods of preserving food have been shown to have a lower&nbsp;energy input&nbsp;and&nbsp;carbon footprint, when compared to modern methods.[1]

Maintaining or creating nutritional value,&nbsp;texture&nbsp;and&nbsp;flavor&nbsp;is an important aspect of food preservation, although, historically, some methods drastically altered the character of the food being preserved. In many cases these changes have come to be seen as desirable qualities – cheese, yogurt and pickled onions being common examples.





Contents
&nbsp;&nbsp;[hide]&nbsp;

1&nbsp;Traditional techniques
1.1&nbsp;Drying
1.2&nbsp;Cooling
1.3&nbsp;Freezing
1.4&nbsp;Heating
1.5&nbsp;Salt
1.6&nbsp;Sugar
1.7&nbsp;Smoking
1.8&nbsp;Pickling
1.9&nbsp;Lye
1.10&nbsp;Canning
1.11&nbsp;Jellying
1.12&nbsp;Jugging
1.13&nbsp;Burial


2&nbsp;Curing
2.1&nbsp;Fermentation


3&nbsp;Industrial/modern techniques
3.1&nbsp;Pasteurization
3.2&nbsp;Vacuum packing
3.3&nbsp;Artificial food additives
3.4&nbsp;Irradiation
3.5&nbsp;Pulsed electric field electroporation
3.6&nbsp;Modified atmosphere
3.7&nbsp;Nonthermal plasma
3.8&nbsp;High-pressure food preservation
3.9&nbsp;Biopreservation
3.10&nbsp;Hurdle technology


4&nbsp;See also
5&nbsp;Notes
6&nbsp;References
7&nbsp;External links





Traditional techniques[edit]

New techniques of food preservation became available to the home chef from the dawn of&nbsp;agriculture&nbsp;until the&nbsp;Industrial Revolution.

Drying[edit]

Main article:&nbsp;Drying (food)

Drying is one of the oldest techniques used to hamper the decomposition of food products. As early as 12,000 B.C., Middle Eastern and Oriental cultures were drying foods using the power of the sun. Vegetables and fruit are naturally dried by the sun and wind, but in the Middle Ages, "still houses" were built in areas that did not have enough sunlight to dry things. A fire would be built inside the building to provide the heat to dry the various fruits, vegetables, and herbs.[2]

Cooling[edit]

Main article:&nbsp;Refrigeration

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

Freezing[edit]





Pictorial guide inside a freezer door



Main article:&nbsp;Frozen food

Freezing&nbsp;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[edit]

Heating to temperatures which are sufficient to kill microorganisms is a method used with&nbsp;perpetual stews. Milk is also boiled before storing to kill many microorganisms.

Salt[edit]





Bag of Prague powder #1, also known as "curing salt" or "pink salt." It is typically a combination of salt and sodium nitrite, with the pink color added to distinguish it from ordinary salt.



Main article:&nbsp;Curing (food preservation)

Salting or curing draws moisture from the meat through a process of osmosis. Meat is&nbsp;cured&nbsp;with salt or sugar, or a combination of the two. Nitrates and nitrites are also often used to cure meat and contribute the characteristic pink color, as well as inhibition of&nbsp;Clostridium botulinum. It was a main method of preservation in medieval times and around the 1700s.

Sugar[edit]

Main article:&nbsp;Sugaring

The earliest cultures have used sugar as a preservative, and it was commonplace to store fruit in honey. Similar to pickled foods, sugar cane was brought to Europe through the trade routes. In northern climates without sufficient sun to dry foods, preserves are made by heating the fruit with sugar.[2]&nbsp;"Sugar tends to draw water from the microbes (plasmolysis). This process leaves the microbial cells dehydrated, thus killing them. In this way, the food will remain safe from microbial spoilage."[3]&nbsp;Sugar is used to preserve fruits, either in an&nbsp;anti-microbial&nbsp;syrup with fruit such as&nbsp;apples,&nbsp;pears,&nbsp;peaches,apricots&nbsp;and&nbsp;plums, or in crystallized form where the preserved material is cooked in sugar to the point of crystallization and the resultant product is then stored dry. This method is used for the skins of&nbsp;citrus&nbsp;fruit (candied peel),&nbsp;angelica&nbsp;and&nbsp;ginger.

Smoking[edit]

Main article:&nbsp;Smoking (cooking)

See also:&nbsp;List of smoked foods





Smoked&nbsp;ham&nbsp;in a&nbsp;smokehouse&nbsp;inSchleswig-Holstein,&nbsp;Germany



Smoking is used to lengthen the&nbsp;shelf life&nbsp;of&nbsp;perishable&nbsp;food items. This effect is achieved by exposing the food tosmoke&nbsp;from burning plant materials such as&nbsp;wood. Smoke deposits a number of pyrolysis products onto the food, including the&nbsp;phenols&nbsp;syringol,&nbsp;guaiacol&nbsp;and&nbsp;catechol.[3]&nbsp;These compounds aid in the drying and preservation of meats and other foods. Most commonly subjected to this method of food preservation are&nbsp;meats&nbsp;and&nbsp;fish&nbsp;that have undergone&nbsp;curing.&nbsp;Fruits&nbsp;and&nbsp;vegetables&nbsp;like&nbsp;paprika,&nbsp;cheeses,&nbsp;spices, and ingredients for making&nbsp;drinks&nbsp;such asmalt&nbsp;and&nbsp;tea&nbsp;leaves are also smoked, but mainly for&nbsp;cooking&nbsp;or&nbsp;flavoring&nbsp;them. It is one of the oldest food preservation methods, which probably arose after the development of&nbsp;cooking&nbsp;with&nbsp;fire.

Pickling[edit]

Main article:&nbsp;Pickling

Pickling is a method of preserving food in an edible&nbsp;anti-microbial&nbsp;liquid. Pickling can be broadly categorized 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 micro-organisms. Typical pickling agents include&nbsp;brine&nbsp;(high in&nbsp;salt),&nbsp;vinegar,&nbsp;alcohol, and&nbsp;vegetable oil, especially&nbsp;olive oil&nbsp;but also many other oils. 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&nbsp;cucumbers,&nbsp;peppers,&nbsp;corned beef,herring, and&nbsp;eggs, as well as mixed vegetables such as&nbsp;piccalilli.

In fermentation pickling, the food itself produces the preservation agent, typically by a process that produces&nbsp;lactic acid. Fermented pickles includesauerkraut,&nbsp;nukazuke,&nbsp;kimchi,&nbsp;surströmming, and&nbsp;curtido. Some pickled cucumbers are also fermented.

Lye[edit]

Sodium hydroxide&nbsp;(lye) makes food too&nbsp;alkaline&nbsp;for bacterial growth. Lye will&nbsp;saponify&nbsp;fats in the food, which will change its flavor and texture.&nbsp;Lutefisk&nbsp;uses lye in its preparation, as do some olive recipes. Modern recipes for&nbsp;century eggs&nbsp;also call for lye.

Canning[edit]





Preserved food



Main article:&nbsp;Canning

See also:&nbsp;Home canning

Canning&nbsp;involves cooking food, sealing it in sterile cans or jars, and&nbsp;boiling&nbsp;the containers to kill or weaken any remaining bacteria as a form of&nbsp;sterilization. It was invented by the French confectioner&nbsp;Nicolas Appert.[4]&nbsp;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 wasn't understood until 1864 when Louis Pasteur found the relationship between microorganisms, food spoilage, and illness.[2]

Foods have varying degrees of natural protection against spoilage and may require that the final step occur in apressure cooker. High-acid fruits like&nbsp;strawberries&nbsp;require no preservatives to can and only a short boiling cycle, whereas marginal vegetables such as&nbsp;carrots&nbsp;require longer boiling and addition of other acidic elements. Low-acid foods, such as vegetables and meats, require pressure canning. Food preserved by canning or bottling is at immediate risk of spoilage once the can or bottle has been opened.

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 causes gas production and the can will swell or burst. However, there have been examples of poor manufacture (underprocessing) and poor&nbsp;hygiene&nbsp;allowing contamination of canned food by the obligate&nbsp;anaerobe&nbsp;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, handled poorly and then canned, can support the growth of&nbsp;Staphylococcus aureus, which produces a toxin that is not destroyed by canning or subsequent reheating.

Jellying[edit]

Main article:&nbsp;Aspic

Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include&nbsp;gelatin,&nbsp;agar,&nbsp;maize&nbsp;flour, and&nbsp;arrowroot&nbsp;flour. Some foods naturally form a&nbsp;protein&nbsp;gel when cooked, such as&nbsp;eels and elvers, and&nbsp;sipunculid&nbsp;worms, which are a delicacy in&nbsp;Xiamen, in the Fujian province of the&nbsp;People's Republic of China.&nbsp;Jellied eels&nbsp;are a delicacy in the East End of&nbsp;London, where they are eaten with mashed potatoes. Potted meats in&nbsp;aspic&nbsp;(a gel made from gelatine and clarified meat broth) were a common way of serving meat off-cuts in the UK until the 1950s. Many jugged meats are also jellied.

See also:&nbsp;Potted shrimps

A traditional British way of preserving meat (particularly&nbsp;shrimp) is by setting it in a pot and sealing it with a layer of fat. Also common is potted chicken liver; compare&nbsp;pâté.

See also:&nbsp;Confit

Jugging[edit]

Main article:&nbsp;Jugging

Meat can be preserved by jugging. Jugging is the process of&nbsp;stewing&nbsp;the meat (commonly&nbsp;game&nbsp;or&nbsp;fish) in a covered&nbsp;earthenware&nbsp;jug or&nbsp;casserole. The animal to be jugged is usually cut into pieces, placed into a tightly-sealed jug with brine or&nbsp;gravy, and stewed.&nbsp;Red wine&nbsp;and/or the animal's own blood is sometimes added to the cooking liquid. Jugging was a popular method of preserving meat up until the middle of the 20th century.

Burial[edit]

Burial of food can preserve it due to a variety of factors: lack of light, lack of oxygen, cool temperatures, pH level, or&nbsp;desiccants&nbsp;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 root vegetables are very resistant to spoilage and require no other preservation than storage in cool dark conditions, for example by burial in the ground, such as in a&nbsp;storage clamp.&nbsp;Century eggs&nbsp;are created by placing eggs in alkaline mud (or other alkaline substance), resulting in their "inorganic" fermentation through raised pH instead of spoiling. The fermentation preserves them and breaks down some of the complex, less flavorful proteins and fats into simpler, more flavorful ones.&nbsp;Cabbage&nbsp;was traditionally buried in the fall in northern farms in the USA for preservation. Some methods keep it crispy while other methods produce&nbsp;sauerkraut[citation needed]. A similar process is used in the traditional production of&nbsp;kimchi. 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.

In&nbsp;Orissa, India, it is practical to store rice by burying it underground. This method helps to store for three to six months during the dry season.

Curing[edit]

The earliest form of curing was dehydration. To accelerate this process, salt is usually added. In the culinary world, it was common to choose raw salts from various sources (rock salt, sea salt, etc.).[2]&nbsp;More modern "examples of salts that are used as preservatives include sodium chloride (NaCl), sodium nitrate (NaNO3) and sodium nitrite (NaNO2). Even at mild concentrations (up to 2%), sodium chloride, found in many food products, is capable of neutralizing the antimicrobial character of natural compounds."[3]

Fermentation[edit]

See also:&nbsp;Fermentation (food)

Some foods, such as many&nbsp;cheeses,&nbsp;wines, and&nbsp;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 resulting alcohol 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.[2]

Industrial/modern techniques[edit]

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

Pasteurization[edit]

Main article:&nbsp;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&nbsp;°C for 15 to 30 seconds to kill the bacteria present in it and cooling it quickly to 10&nbsp;°C 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&nbsp;Louis Pasteur, a&nbsp;French&nbsp;chemist, in 1862.

Vacuum packing[edit]

Main article:&nbsp;Vacuum packing

Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The&nbsp;vacuum&nbsp;environment strips bacteria of oxygen needed for survival. Vacuum-packing is commonly used for storing&nbsp;nuts&nbsp;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. Vacuum sealing is not very versatile, with a wide range of products for home use. Equipment and single-use bags are expensive and clog landfills.

Artificial food additives[edit]

Main article:&nbsp;Preservatives

Preservative food additives can be&nbsp;antimicrobial, which inhibit the growth of&nbsp;bacteria&nbsp;or&nbsp;fungi, including&nbsp;mold, or&nbsp;antioxidant, such as&nbsp;oxygen absorbers, which inhibit the&nbsp;oxidation&nbsp;of food constituents. Common antimicrobial preservatives include&nbsp;calcium propionate,&nbsp;sodium nitrate,&nbsp;sodium nitrite,&nbsp;sulfites&nbsp;(sulfur dioxide,&nbsp;sodium bisulfite,&nbsp;potassium hydrogen sulfite, etc.) and&nbsp;disodium EDTA.&nbsp;Antioxidants&nbsp;include&nbsp;BHA&nbsp;and&nbsp;BHT. Other preservatives includeformaldehyde&nbsp;(usually in solution),&nbsp;glutaraldehyde&nbsp;(kills insects),&nbsp;ethanol, and&nbsp;methylchloroisothiazolinone.

Irradiation[edit]

Main article:&nbsp;Food irradiation

Irradiation of food[5]&nbsp;is the exposure of food to&nbsp;ionizing radiation. The two types of ionizing radiation used are&nbsp;beta particles&nbsp;(high-energy&nbsp;electrons) andgamma rays&nbsp;(emitted from radioactive sources as&nbsp;cobalt-60&nbsp;or&nbsp;cesium-137). Treatment effects include killing bacteria, molds, and insect pests, reducing the ripening and spoiling of fruits, and at higher doses inducing sterility. The technology may be compared to&nbsp;pasteurization; it is sometimes called "cold pasteurization", as the product is not heated.

The irradiation process is not directly related to&nbsp;nuclear energy, but does use radioactive isotopes produced in&nbsp;nuclear reactors. Cobalt-60, for example does not occur naturally and can only be produced through neutron bombardment of&nbsp;cobalt-59. Ionizing radiation at high energy levels is hazardous to life (hence its usefulness in sterilisation); for this reason, irradiation facilities have a heavily shielded irradiation room where the process takes place. Radiation safety procedures are used to ensure that neither the workers in such facilities nor the environment receives any radiation dose above administrative limits. Irradiated food does not and cannot become radioactive, and national and international expert bodies have declared food irradiation as wholesome.[6][7]However, the wholesomeness of consuming such food is disputed by opponents[8]&nbsp;and consumer organizations.[9]&nbsp;National and international expert bodies have declared food irradiation as "wholesome"; organizations of the&nbsp;United Nations, such as the&nbsp;World Health Organization&nbsp;and&nbsp;Food and Agriculture Organization, endorse food irradiation. International legislation on whether food may be irradiated or not varies worldwide from no regulation to full banning.[10]&nbsp;Irradiation may allow lower-quality or contaminated foods to be rendered marketable.

Approximately 500,000 tons of food items are irradiated per year worldwide in over 40 countries. These are mainly&nbsp;spices&nbsp;and&nbsp;condiments&nbsp;with an increasing segment of fresh fruit irradiated for&nbsp;fruit fly&nbsp;quarantine.[11][12]

Pulsed electric field electroporation[edit]

Main article:&nbsp;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[edit]

Main article:&nbsp;Modified atmosphere

Modifying atmosphere is a way to preserve food by operating on the atmosphere around it. Salad crops that are notoriously difficult to preserve are now being packaged in sealed bags with an atmosphere modified to reduce the oxygen (O2) concentration and increase the&nbsp;carbon dioxide&nbsp;(CO2) concentration. There is concern that, although salad vegetables retain their appearance and texture in such conditions, this method of preservation may not retain nutrients, especially&nbsp;vitamins. There are two methods for preserving grains with carbon dioxide. One method is placing a block of&nbsp;dry ice&nbsp;in the bottom and filling the can with the grain. Another method is purging the container from the bottom by gaseous carbon dioxide from a cylinder or bulk supply vessel.

Carbon dioxide&nbsp;prevents insects and, depending on concentration,&nbsp;mold&nbsp;and&nbsp;oxidation&nbsp;from damaging the grain. Grain stored in this way can remain edible for approximately five years.[citation needed]

Nitrogen&nbsp;gas (N2) at concentrations of 98% or higher is also used effectively to kill insects in the grain through&nbsp;hypoxia.[13]&nbsp;However, carbon dioxide has an advantage in this respect, as it kills organisms through&nbsp;hypercarbia&nbsp;and hypoxia (depending on concentration), but it requires concentrations of above 35%,[14]&nbsp;or so. This makes carbon dioxide preferable for fumigation in situations where a&nbsp;hermetic seal&nbsp;cannot be maintained.

Controlled Atmospheric Storage (CA): "CA storage is a non-chemical process. Oxygen levels in the sealed rooms are reduced, usually by the infusion of nitrogen gas, from the approximate 21 percent in the air we breathe to 1 percent or 2 percent. Temperatures are kept at a constant 0 to 2&nbsp;°C (32 to 36&nbsp;°F). Humidity is maintained at 95 percent and carbon dioxide levels are also controlled. Exact conditions in the rooms are set according to the apple variety. Researchers develop specific regimens for each variety to achieve the best quality. Computers help keep conditions constant." "Eastern Washington, where most of Washington’s apples are grown, has enough warehouse storage for 181 million boxes of fruit, according to a report done in 1997 by managers for the Washington State Department of Agriculture Plant Services Division. The storage capacity study shows that 67 percent of that space —enough for 121,008,000 boxes of apples — is CA storage."&nbsp;[15]

Air-tight storage of grains (sometimes called hermetic storage) relies on the respiration of grain, insects, and fungi that can modify the enclosed atmosphere sufficiently to control insect pests. This is a method of great antiquity,[16]&nbsp;as well as having modern equivalents. The success of the method relies on having the correct mix of sealing, grain moisture, and temperature.[17]

A patented process uses&nbsp;fuel cells&nbsp;to exhaust and automatically maintain the exhaustion of&nbsp;oxygen&nbsp;in a shipping container, containing, for example, fresh fish.[18]

Nonthermal plasma[edit]

Main article:&nbsp;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.[19]

High-pressure food preservation[edit]

Main article:&nbsp;Pascalization

High-pressure food preservation or pascalization refers to the use of a food preservation technique that makes use of&nbsp;high pressure. "Pressed inside a vessel exerting 70,000 pounds per square inch (480&nbsp;MPa) or more, food can be processed so that it retains its fresh appearance, flavor, texture and nutrients while disabling harmful microorganisms and slowing spoilage." By 2005, the process was being used for products ranging from&nbsp;orange juice&nbsp;toguacamole&nbsp;to&nbsp;deli meats&nbsp;and widely sold.[20]

Biopreservation[edit]





3D stick model of&nbsp;nisin. Somelactic acid bacteria&nbsp;manufacture nisin. It is a particularly effective preservative.



Main article:&nbsp;Biopreservation

Biopreservation&nbsp;is the use of natural or controlled&nbsp;microbiota&nbsp;or&nbsp;antimicrobials&nbsp;as a way of preserving food and extending its&nbsp;shelf life.[21]&nbsp;Beneficial bacteria or the&nbsp;fermentation&nbsp;products produced by these bacteria are used in biopreservation to control&nbsp;spoilage&nbsp;and render&nbsp;pathogens&nbsp;inactive in food.[22]&nbsp;It is a benign ecological approach which is gaining increasing attention.[21]

Of special interest are&nbsp;lactic acid bacteria&nbsp;(LAB). Lactic acid bacteria have antagonistic properties that make them particularly useful as biopreservatives. When LABs compete for nutrients, their&nbsp;metabolites&nbsp;often include active antimicrobials such as lactic acid, acetic acid, hydrogen peroxide, and&nbsp;peptide&nbsp;bacteriocins. Some LABs produce the antimicrobial&nbsp;nisin, which is a particularly effective preservative.[23][24]

These days, LAB bacteriocins are used as an integral part of&nbsp;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&nbsp;Gram-negative bacteria.[21]

Hurdle technology[edit]

Main article:&nbsp;Hurdle technology

Hurdle technology&nbsp;is a method of ensuring that&nbsp;pathogens&nbsp;in&nbsp;food products&nbsp;can be eliminated or controlled by combining more than one approach. These approaches can be thought of as "hurdles" the pathogen has to overcome if it is to remain active in the food. The right combination of hurdles can ensure all pathogens are eliminated or rendered harmless in the final product.[25]

Hurdle technology has been defined by Leistner (2000) as an intelligent combination of hurdles that secures the&nbsp;microbial&nbsp;safety and stability as well as theorganoleptic&nbsp;and nutritional quality and the economic viability of&nbsp;food products.[26]&nbsp;The organoleptic quality of the food refers to its sensory properties, that is its look, taste, smell, and texture.

Examples of hurdles in a food system are high temperature during processing, low temperature during storage, increasing the&nbsp;acidity, lowering the&nbsp;water activity&nbsp;or&nbsp;redox potential, and the presence of&nbsp;preservatives&nbsp;or&nbsp;biopreservatives. According to the type of pathogens and how risky they are, the intensity of the hurdles can be adjusted individually to meet consumer preferences in an economical way, without sacrificing the safety of the product.[25]


Principal hurdles used for food preservation (after Leistner, 1995)[27][28]
ParameterSymbolApplication
High temperatureFHeating
Low temperatureTChilling,&nbsp;freezing
Reduced&nbsp;water activityawDrying,&nbsp;curing,&nbsp;conserving
Increased&nbsp;aciditypHAcid addition or formation
Reduced&nbsp;redox potentialEhRemoval of oxygen or addition of&nbsp;ascorbate
BiopreservativesCompetitive&nbsp;flora&nbsp;such as&nbsp;microbial&nbsp;fermentation
Other&nbsp;preservativesSorbates,&nbsp;sulfites,&nbsp;nitrites



See also[edit]


Food portal




Blast chilling
Food engineering
Food microbiology
Food packaging
Food rheology
Food science
Food spoilage
Freeze-drying
Fresherized
List of dried foods
List of pickled foods
List of smoked foods
Refrigerate after opening
Shelf-life