Editing Food preservation (section)

== Modern industrial techniques ==
Techniques of food preservation were developed in research laboratories for commercial applications.

===Aseptic processing===
{{main|Aseptic processing}}
Aseptic processing works by placing sterilized food (typically by heat, see [[ultra-high temperature processing]]) into sterlized packaging material under sterile conditions. The result is a sealed, sterile food product similar to canned food, but depending on the technique used, damage to food quality is typically reduced compared to canned food. A greater variety of packaging materials can be used as well.

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

=== Pasteurization ===
{{Main|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 {{cvt|70|C|F}} for 15–30 seconds to kill the bacteria present in it and cooling it quickly to {{cvt|10|C|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 people|French]] chemist, in 1862.

=== Vacuum packing ===
{{Main|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 [[nut (fruit)|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 ===
{{excerpt|only=paragraphs|Freeze drying}}

=== Preservatives ===
{{Main|Preservatives|Sulfite food and beverage additives}}
Preservative [[food additives]] can be ''[[antimicrobial]]'' – which inhibit the growth of [[bacterium|bacteria]] or [[Fungus|fungi]], including [[Mold (fungus)|mold]] – or ''[[antioxidant]]'', such as [[oxygen absorber]]s, which inhibit the [[oxidation]] of food constituents. Common antimicrobial preservatives include [[nisin]], [[sorbate]]s, [[calcium propionate]], [[sodium nitrate]]/[[sodium nitrite|nitrite]], [[sulfite]]s ([[sulfur dioxide]], [[sodium bisulfite]], [[potassium hydrogen sulfite]], etc.), [[EDTA]], [[hinokitiol]], and [[polylysine|ε-polylysine]]. [[Antioxidant]]s include [[tocopherol]]s (Vitamin E), [[butylated hydroxyanisole]] (BHA) and [[butylated hydroxytoluene]] (BHT). Other preservatives include [[ethanol]].

There is also another approach of impregnating packaging materials (plastic films or other) with antioxidants and antimicrobials.<ref>{{cite journal |last1=Yildirim |first1=Selçuk |last2=Röcker |first2=Bettina |last3=Pettersen |first3=Marit Kvalvåg |last4=Nilsen-Nygaard |first4=Julie |last5=Ayhan |first5=Zehra |last6=Rutkaite |first6=Ramune |last7=Radusin |first7=Tanja |last8=Suminska |first8=Patrycja |last9=Marcos |first9=Begonya |last10=Coma |first10=Véronique |title=Active Packaging Applications for Food: Active packaging applications for food… |journal=Comprehensive Reviews in Food Science and Food Safety |date=January 2018 |volume=17 |issue=1 |pages=165–199 |doi=10.1111/1541-4337.12322|pmid=33350066 |doi-access=free |hdl=20.500.12327/362 |hdl-access=free }}</ref><ref name=Book>{{cite book |last1=L. Brody |first1=Aaron |last2=Strupinsky |first2=E. P. |last3=Kline |first3=Lauri R. |title=Active Packaging for Food Applications |date=2001 |publisher=CRC Press |isbn=9780367397289 |edition=1}}</ref>

=== Irradiation ===
{{Main|Food irradiation}}
Irradiation of food<ref>''Food Irradation – A technique for preserving and improving the safety of food'', WHO, Geneva, 1991</ref> is the exposure of food to [[ionizing radiation]]. Multiple types of ionizing radiation can be used, including [[beta particle]]s (high-energy [[electron]]s) and [[gamma ray]]s (emitted from radioactive sources such as [[cobalt-60]] or [[cesium-137]]). Irradiation can kill bacteria, molds, and insect pests, reduce the ripening and spoiling of fruits, and at higher doses induce sterility. The technology may be compared to [[pasteurization]]; it is sometimes called "cold pasteurization", as the product is not heated. Irradiation may allow lower-quality or contaminated foods to be rendered marketable.

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.<ref name="JECFI">World Health Organization. Wholesomeness of irradiated food. Geneva, Technical Report Series No. 659, 1981</ref><ref name="JSGHDI">World Health Organization. High-Dose Irradiation: Wholesomeness of Food Irradiated With Doses Above 10 kGy. Report of a Joint FAO/IAEA/WHO Study Group. Geneva, Switzerland: World Health Organization; 1999. WHO Technical Report Series No. 890</ref> Consumers may have a negative view of irradiated food based on the misconception that such food is radioactive;<ref>Conley, S.T., What do consumers think about irradiated foods, FSIS Food Safety Review (Fall 1992), 11–15</ref> 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.<ref>Hauter, W. & Worth, M., ''Zapped! Irradiation and the Death of Food'', Food & Water Watch Press, Washington, DC, 2008</ref> International legislation on whether food may be irradiated or not varies worldwide from no regulation to a full ban.<ref>[http://nucleus.iaea.org/NUCLEUS/nucleus/Content/Applications/FICdb/FoodIrradiationClearances.jsp?module=cif NUCLEUS – Food Irradiation Clearances] {{webarchive|url=https://web.archive.org/web/20080526025627/http://nucleus.iaea.org/NUCLEUS/nucleus/Content/Applications/FICdb/FoodIrradiationClearances.jsp?module=cif |date=26 May 2008 }}</ref>

Approximately 500,000 tons of food items are irradiated per year worldwide in over 40 countries. These are mainly [[spice]]s and [[condiment]]s, with an increasing segment of fresh fruit irradiated for fruit fly quarantine.<ref>[http://www.mindfully.org/Food/Irradiation-Position-ADA.htm Food irradiation – Position of ADA J Am Diet Assoc. 2000;100:246-253] {{webarchive|url=https://web.archive.org/web/20160216174601/http://www.mindfully.org/Food/Irradiation-Position-ADA.htm |date=16 February 2016 }}</ref><ref>C.M. Deeley, M. Gao, R. Hunter, D.A.E. Ehlermann, The development of food irradiation in the Asia Pacific, the Americas and Europe; tutorial presented to the International Meeting on Radiation Processing, Kuala Lumpur, 2006. {{usurped|1=[https://web.archive.org/web/20170202002120/http://doubleia.org/index.php?sectionid=43&parentid=13&contentid=494]}}</ref>

=== Pulsed electric field electroporation ===
{{Main|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 ===
{{Main|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 ({{chem2|O2}}) concentration and increasing the [[carbon dioxide]] ({{CO2}}) concentration slows down their respiration, conserves stored energy, and therefore increases shelf life.<ref name="Brody, A.L., Zhuang, H.-2011">{{Cite book|title=Modified atmosphere packaging for fresh-cut fruits and vegetables|last=Brody, A.L., Zhuang, H.|first=Han, J.H|publisher=Blackwell Publishing Ltd|year=2011|isbn=978-0-8138-1274-8|location=West Sussex, UK|pages=57–67}}</ref> High humidity is also used to reduce water loss.<ref>{{Cite web |url=http://www.bestapples.com/facts/facts_controlled.aspx |title=Controlled Atmospheric Storage (CA) :: Washington State Apple Commission |access-date=8 August 2013 |archive-date=14 March 2012 |archive-url=https://web.archive.org/web/20120314160122/http://www.bestapples.com/facts/facts_controlled.aspx |url-status=dead }}</ref>
* Red meat, which needs high {{chem2|O2}} to reduce oxidation of [[myoglobin]] and maintain an attractive bright red color of the meat.<ref name="Djenane, D.-2018">{{Cite journal|last=Djenane, D.|first=Roncales, P.|date=2018|title=Carbon monoxide in meat and fish packaging: advantages and limits|journal=Foods|volume=7|issue=2|pages=12|doi=10.3390/foods7020012|pmid=29360803|pmc=5848116|doi-access=free}}</ref>
* Other meat and fish, which uses higher {{chem2|CO2}} to reduce oxidation and slow down some microbes.<ref name="Fellows, P.J-2017">{{Cite book|title=Food processing technology: principles and practice (4th ed)|last=Fellows, P.J|publisher=Woodhead Publishing|year=2017|isbn=978-0-08-101907-8|location=Duxford, UK|pages=992–1001}}</ref>

=== Nonthermal plasma ===
{{Main|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.<ref>NWT magazine, December 2012</ref>

=== High-pressure food preservation ===
{{Main|Pascalization}}
[[High pressure]] can be used to disable harmful microorganisms and spoilage enzymes while retaining the food's fresh appearance, flavor, texture and nutrients.  By 2005, the process was being used for products ranging from [[orange juice]] to [[guacamole]] to [[deli meat]]s and widely sold.<ref name=military>{{cite news |title=High-Pressure Processing Keeps Food Safe |url=http://www.military.com/soldiertech/0,14632,Soldiertech_Squeeze,,00.html |work=[[Military.com]] |access-date=2008-12-16 |archive-url = https://web.archive.org/web/20080202232043/http://www.military.com/soldiertech/0,14632,Soldiertech_Squeeze,,00.html |archive-date = 2008-02-02}}</ref> Depending on temperature and pressure settings, HP processing can achieve either pasteurization-equivalent [[log reduction]] or go all the way to achieve sterilization of all microbes.<ref>{{cite journal |last1=Aganovic |first1=Kemal |last2=Hertel |first2=Christian |last3=Vogel |first3=Rudi. F. |last4=Johne |first4=Reimar |last5=Schlüter |first5=Oliver |last6=Schwarzenbolz |first6=Uwe |last7=Jäger |first7=Henry |last8=Holzhauser |first8=Thomas |last9=Bergmair |first9=Johannes |last10=Roth |first10=Angelika |last11=Sevenich |first11=Robert |last12=Bandick |first12=Niels |last13=Kulling |first13=Sabine E. |last14=Knorr |first14=Dietrich |last15=Engel |first15=Karl-Heinz |last16=Heinz |first16=Volker |title=Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety |journal=Comprehensive Reviews in Food Science and Food Safety |date=July 2021 |volume=20 |issue=4 |pages=3225–3266 |doi=10.1111/1541-4337.12763|pmid=34056857 |s2cid=235256047 |url=https://mediatum.ub.tum.de/1624516 }}</ref>

=== Biopreservation ===
[[File:Nisin 1WCO.png|thumb|right|3D stick model of [[nisin]]. Some [[lactic acid bacteria]] manufacture nisin. It is a particularly effective preservative.]]
{{Main|Biopreservation}}

[[Biopreservation]] is the use of natural or controlled [[Microflora|microbiota]] or [[antimicrobial]]s as a way of preserving food and extending its [[shelf life]].<ref name="Ananou1 et al" /> Beneficial bacteria or the [[fermentation (biochemistry)|fermentation]] products produced by these bacteria are used in biopreservation to control spoilage and render [[pathogen]]s inactive in food.<ref name="Yousef&Carlstrom">Yousef AE and Carolyn Carlstrom C (2003) [https://books.google.com/books?id=aYORXplZq0wC&dq=biopreservation&pg=PA226 ''Food microbiology: a laboratory manual''] Wiley, Page 226. {{ISBN|978-0-471-39105-0}}.</ref> It is a benign ecological approach which is gaining increasing attention.<ref name="Ananou1 et al">Ananou S, Maqueda M, Martínez-Bueno M and Valdivia E (2007) [http://www.formatex.org/microbio/pdf/Pages475-486.pdf "Biopreservation, an ecological approach to improve the safety and shelf-life of foods"] {{Webarchive|url=https://web.archive.org/web/20110726061822/http://www.formatex.org/microbio/pdf/Pages475-486.pdf |date=26 July 2011 }} In: A. Méndez-Vilas (Ed.) ''Communicating Current Research and Educational Topics and Trends in Applied Microbiology'', Formatex. {{ISBN|978-84-611-9423-0}}.</ref>

[[Lactic acid bacteria]] (LAB) have antagonistic properties that make them particularly useful as biopreservatives. When LABs compete for nutrients, their [[metabolite]]s often include active antimicrobials such as lactic acid, acetic acid, hydrogen peroxide, and [[peptide]] [[bacteriocin]]s. Some LABs produce the antimicrobial [[nisin]], which is a particularly effective preservative.<ref name="FAO preservation">FAO: [http://www.fao.org/fishery/topic/12322/en Preservation techniques] Fisheries and aquaculture department, Rome. Updated 27 May 2005. Retrieved 14 March 2011.</ref><ref>Alzamora SM, Tapia MS and López-Malo A (2000) [https://books.google.com/books?id=2gTCY5Dvha4C&dq=biopreservation&pg=PA266 ''Minimally processed fruits and vegetables: fundamental aspects and applications''] Springer, p. 266. {{ISBN|978-0-8342-1672-3}}.</ref>

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]].<ref name="Ananou1 et al" />

=== Hurdle technology ===
{{Main|Hurdle technology}}

[[Hurdle technology]] is a method of ensuring that [[pathogen]]s in [[food product]]s 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.<ref name="Alasalvar" />

Hurdle technology has been defined by Leistner (2000) as an intelligent combination of hurdles that secures the [[microbial]] safety and stability as well as the [[organoleptic]] and nutritional quality and the economic viability of [[food product]]s.<ref>Leistner I (2000) [http://envismadrasuniv.org/Physiology/pdf/Basic%20aspects%20of%20food%20preservation.pdf "Basic aspects of food preservation by hurdle technology"] ''International Journal of Food Microbiology'', '''55''':181–186.</ref> 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 [[acidity]], lowering the [[water activity]] or [[redox potential]], and the presence of [[preservative]]s or [[biopreservative]]s. 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.<ref name="Alasalvar">Alasalvar C (2010) [https://books.google.com/books?id=l-APOWUVp-8C&pg=PT232&dq=%22hurdle+technology%22|%22hurdle+technologies%22&hl=en&ei=5GSFTaTGCJCSuAOj66zGCA&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDgQ6AEwAg#v=onepage&q=%22hurdle%20technology%22|%22hurdle%20technologies%22&f=false ''Seafood Quality, Safety and Health Applications''] John Wiley and Sons, Page 203. {{ISBN|978-1-4051-8070-2}}.</ref>

{| class="wikitable"
|+ Principal hurdles used for food preservation (after Leistner, 1995)<ref>Leistner L (1995) [https://books.google.com/books?id=6a_dbGRoiWIC&q=Principles+and+applications+of+hurdle+technology "Principles and applications of hurdle technology"] In Gould GW (Ed.) ''New Methods of Food Preservation'', Springer, pp. 1–21. {{ISBN|978-0-8342-1341-8}}.</ref><ref name="Lee">Lee S (2004) [http://www.internetjfs.org/articles/ijfsv4-3.pdf "Microbial Safety of Pickled Fruits and Vegetables and Hurdle Technology"] {{Webarchive|url=https://web.archive.org/web/20110901001910/http://www.internetjfs.org/articles/ijfsv4-3.pdf |date=1 September 2011 }} ''Internet Journal of Food Safety'', '''4''': 21–32.</ref>
|-
! Parameter
! Symbol
! Application
|-
| High temperature
| style="text-align:center;"| F
| Heating
|-
| Low temperature
| style="text-align:center;"| T
| [[Refrigeration|Chilling]], [[Frozen food|freezing]]
|-
| Reduced [[water activity]]
| style="text-align:center;"| a{{sub|w}}
| [[Drying]], [[Curing (food preservation)|curing]], [[Conserve (condiment)|conserving]]
|-
| Increased [[acidity]]
| style="text-align:center;"| [[pH]]
| Acid addition or formation
|-
| Reduced [[redox potential]]
| style="text-align:center;"| E{{sub|h}}
| Removal of oxygen or addition of [[ascorbate]]
|-
| [[Biopreservative]]s
|
| Competitive [[flora]] such as [[microbial]] [[Fermentation (food)|fermentation]]
|-
| Other [[preservative]]s
|
| [[Sorbate]]s, [[sulfite]]s, [[nitrite]]s
|}