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{{Short description|Sterile food processing technique}}
'''Aseptic processing''' is the process by which a sterile ([[aseptic]]) product (typically [[food]] or pharmaceutical) is packaged in a sterile container in a way that maintains [[Asepsis|sterility]]. [[File:Yoohoo-boxes.jpg|thumb|right|Drink boxes]] Sterility is achieved with a flash-heating process (temperature between 195 and 295&nbsp;°F (91 to 146&nbsp;°C)),<ref name=APCQ&A>Aseptic Packaging Council. [http://www.aseptic.org/faq.html Carton Council Questions & Answers]{{dead link|date=October 2014}}.</ref> which retains more nutrients and uses less energy than conventional sterilization techniques such as [[retort]] or hot-fill [[canning]]. Pharmaceutical Sterile processing includes use of clean rooms, bacteria retaining filters, dry or steam heat. Aseptic [[food preservation]] methods allow [[food processing|processed food]] to keep for long periods of time without [[preservative]]s, as long as they are not opened. The aseptic packages are typically a mix of [[paper]] (70%), [[polyethylene]] (LDPE) (24%), and [[aluminum]] (6%), with a tight polyethylene inside layer.<ref name=APCQ&A/> Sterile pharmaceuticals are usually packaged in plastic or glass. Together these materials form a tight seal against microbiological organisms, contaminants, and degradation, eliminating the need for [[refrigeration]].
'''Aseptic processing''' is a processing technique wherein commercially thermally [[Sterilization (microbiology)|sterilized]] liquid products (typically [[food]] or [[Pharmaceutical industry|pharmaceutical]]) are packaged into previously sterilized containers under sterile conditions to produce shelf-stable products that do not need refrigeration.<ref name=":06">{{Cite book|title=Food processing technology : principles and practice|last=Fellows|first=Peter|publisher=Woodhead Publishing/Elsevier Science|year=2016|isbn=9780081005231|edition=4th|location=Kent|oclc=960758611}}</ref> Aseptic processing has almost completely replaced in-container sterilization of liquid foods,<ref>{{Cite web |date=1998-03-31 |title=Global renaming: SIG Combibloc / New regional companies / Group strategy |url=https://www.plasteurope.com/news/PKL_t18752/ |access-date=2023-11-30 |website=Plasteurope}}</ref> including [[milk]], fruit [[juice]]s and concentrates, [[cream]], [[yogurt]], [[salad dressing]], [[liquid egg]], and ice cream mix. There has been an increasing popularity for foods that contain small discrete particles, such as [[cottage cheese]], [[baby food]]s, [[tomato]] products, [[fruit]] and [[vegetable]]s, [[soup]]s, and rice desserts.<ref name=":06" />


Aseptic processing involves three primary steps: [[Sterilization (microbiology)|thermal sterilization]] of the product, sterilization of the [[Packaging and labeling|packaging]] material, and conservation of sterility during packaging.<ref name=":24">{{Cite book|title=Handbook of food safety engineering|date=2011|publisher=Wiley-Blackwell|others=Sun, Da-Wen.|isbn=978-1444333343|location=Oxford|oclc=767579357}}</ref> To ensure commercial sterility, aseptic processing facilities are required to maintain proper documentation of production operations, showing that commercially sterile conditions were achieved and maintained in all areas of the facility.<ref name=":74">{{cite web|url=https://www.fda.gov/ICECI/Inspections/InspectionGuides/ucm074946.htm|title=Aseptic Processing and Packaging for the Food Industry|last1=FDA|website=U.S. Food and Drug Administration|access-date=3 April 2018}}</ref> Any breach of a scheduled process for the processing or packaging system means that the affected product must be destroyed, reprocessed or segregated and held for further evaluation.<ref name=":74" /> In addition, the processing and packaging system must be cleaned and re-sterilized before processing and/or packaging operations can resume. Packaging equipment and packaging materials are sterilized with various media or combinations thereof (i.e., saturated [[steam]], superheated steam, [[hydrogen peroxide]] and heat and other treatments).<ref name=":74" />
The first aseptic filling plant for [[milk]] was presented in [[Switzerland]] in 1961. The [[Tetra Pak]] company later became one of the leading suppliers of processing and packaging equipment for [[dairy|dairies]]. Aseptic techniques were common in Europe and Asia before they were introduced in the United States in the 1980s.


== Historical development in foods ==
Aseptic containers may range in size from a few fluid ounces to a nearly {{convert|8|e6USgal|m3|adj=on}} aseptic tank on an ocean-going ship.<ref>[http://www.flowcontrolnetwork.com/applications/food-and-beverage/article/aseptics-ship-sets-sail Aseptic''s Ship Sets Sail]</ref> Aseptic processing makes worldwide export and import of new, economical and safe food products possible. [[Bag-In-Box]] technology is commonly used because it provides strong containers that are lightweight and easy to handle prior to being filled. Other common package types are drink boxes and pouches.
Aseptic processing was derived from [[C. Olin Ball|Olin Ball]]'s heat-cool-fill (HCF) machine that was developed in 1927.<ref name=":33">{{Cite book|title=Electron beam pasteurization and complementary food processing technologies|last1=Pillai|first1=Suresh|last2=Shayanfa|first2=Shima|publisher=Woodhead Publishing|year=2014|isbn=9781782421085|location=Cambridge|oclc=897799891}}</ref> While HCF was successful in improving the sensory quality of the processed [[chocolate milk]] as compared to [[Canning|canned]] product, the use of the equipment was hindered by its cost, maintenance, and inflexibility to process various container sizes, rendering the machine a failure.<ref name=":43">{{Cite book|title=Advances in food research Vol. 32|date=1988|publisher=Academic Press|others=Chichester, C. O., 1925–, Schweigert, B. S.|isbn=9780080567778|location=San Diego|oclc=647803601}}</ref>


In the 1940s, the Avoset process was developed by George Grindrod. Food products processed using the Avoset process were packaged under [[Ultraviolet|ultraviolet lamps]] and sterilized air inside a positive-pressurized room to keep the [[contaminants]] out of the processing room. Sterilization was achieved through the use of direct steam injection of {{convert|126|-|137|C|abbr=on|-1}} and then cooled. The food treated using this technique was described as an "excellent cream product" and 75–100 containers were produced each minute.<ref name=":43" />
In 1991, the [[Institute of Food Technologists]] rated the top 10 innovations in [[food technology]]. Aseptic processing and packaging ranked No. 1, ahead of juice concentrates, safe canning processes, [[freeze-drying]] and food fortification.<ref>[http://www.aseptic.org/Award%20Main.shtml An Award Winning Process]</ref> In 2007 Dr. [[Philip E. Nelson]] received the [[World Food Prize]] in recognition for his pioneering work in aseptic processing and bulk storage.


Later in the 1940s, the Dole Aseptic Process was developed by McKinley Martin.<ref name=":33" /> The foods processed ranged from soups to specialty sauces, fruits, and dairy products.<ref name=":43" /> This process involved four steps:<ref name=":33" /><ref name=":43" />
== Historical development ==
The first aseptic packing of foods (especially milk in metal cans) was carried out in Denmark prior to 1913 and in 1921 a patent for this process (termed aseptic conservation) was granted. In 1917, Dunkley in USA patented sterilization with saturated steam of cans and subsequent filling of pre-sterilized product. In 1923, aseptically packaged milk from South Africa reached a trade fair in London, England in perfect conditions. The American can company developed a filling machine in 1933, called the Heat-Cool-Fill (HCF) system which used saturated steam under pressure to sterilize the cans and ends. The sterile cans were filled with sterile product and the ends sealed on in a closed chamber, which was kept pressurized with steam or a mixture of steam and air. Three commercial plants were built and operated on this principle until 1945.


#Sterilization of product by heating and immediate cooling
In 1940s, Martin developed process in which empty metal cans were sterilized by treatment with superheated steam at 210°C prior to being filled with cold, sterile product. In 1950, the Dole Company bought the first commercial aseptic filling plant on the market. At the end of 1940, a dairy enterprise and machinery manufacturers in Switzerland (Alpura AG, Bern, and Sulzer AG, Winterthur) combined to develop UHT-sterilized, aseptically canned milk, which was marketed in Switzerland in 1953. However, this system was not economical mainly because of cost of the cans. Long shelf life milk packaged in this manner was first sold in Switzerland in October, 1961.
#Sterilization of containers and lids using steam
#Filling of cooled products aseptically into previously sterilized containers
#Sealing of lids at an atmosphere of saturated or super heated steam


The Dole aseptic machine overcame the hindrances that caused HCF's failure, since it was able to process various container sizes, needed less maintenance time and cost less. The quality of products processed was consistent regardless of container size, an important characteristic for heat sensitive foods, due to its short processing time. [[Pea soup|Split pea soup]] was treated using the Dole aseptic machine at the following dosage: heat time of {{convert|140|-|146|C|abbr=on|-1}} for 3.53 seconds, hold time of 8.8 seconds, and cooling to {{convert|32|C|abbr=on|-1}} in 14.0 – 17.0 seconds, compared to the normal processing time of 40–70 minutes at {{convert|115|-|121|C|abbr=on|-1}}. The lack of consumer interest drove foods that were processed in the Dole aseptic machine to be discontinued.<ref name=":43" /> [[File:Erik_Wallenberg_inventor_of_Tetra_Pak_first_package.jpg|thumb|[[Erik Wallenberg]], the inventor of the Tetra Classic packaging at [[Tetra Pak]]]]Roy Graves began sterilizing milk in the 1940s. The milk that was drawn from the cow went through a pipeline, into a vacuum tank, which was then heated to 285&nbsp;°F, then cooled to room temperature. The product, packaged in metal cans, was widely accepted by consumers lacking access to fresh milk, including the [[United States Armed Forces|U.S. military]].<ref name=":14">{{Cite book|title=Handbook of aseptic processing and packaging|last=D.|first=David, Jairus R.|date=2013|publisher=Taylor & Francis|others=Graves, Ralph H., Szemplenski, Thomas.|isbn=9781138199071|location=Boca Raton|oclc=811776682}}</ref>
==Common uses==
Aseptic processing is commonly used for the [[packaging]] of milks, fruit juices, liquid whole eggs, gravies, and tomatoes. Fresh tomatoes are aseptically processed and packaged for year-round remanufacture into various food products.


In 1959, the [[food industry]] saw the advent of the use of paper-foil-plastic laminated containers called tetrahedron. In 1962, the Swedish company [[Tetra Pak]], introduced this container to the United States market. They sold pasteurized milk and beverages in the containers. Roy Graves' company started sterilizing this container with [[chlorine]] and were able to aseptically fill and [[Hermetic seal|hermetically seal]] the container. The use of these containers was not accepted by the American consumers due to their difficulty in opening. It was widely used by the [[United States Navy|U.S. Navy]].<ref name=":14" />
== Recycling ==

Aseptic containers are recycled with a method called hydrapulping.<ref name=APCQ&A>Aseptic Packaging Council. [http://www.aseptic.org/Recycling%20&%20Aseptic%20Packaging.shtml Recycling and Aseptic Packaging]</ref>{{reliable source|date=June 2014}} Some plastics and aseptic packages have been assessed as "relatively good" in overall costs, although no packaging is always better.<ref name=SnomishCounty>Snomish County Public Works, Solid Waste Management. (1995). [ww.p2pays.org/ref/03/02942.pdf Prevent Packaging Waste]</ref> The major problem, however, is that the hydrapulping facilities are not that common, and thus the multimaterial packages are relatively difficult to recycle.<ref>Emagazine. (2002). [http://findarticles.com/p/articles/mi_m1594/is_6_13/ai_94011506 Juicing the Waste Stream: Aseptic Packages are Convenient, but Hard to Recycle]</ref> [[Tetra Pak]], a notable company in the industry, has launched an initiative to increase the recycling of aseptic containers.<ref>Recycling Today. (2007). [http://findarticles.com/p/articles/mi_m0KWH/is_7_45/ai_n19394660 Minnesota adds aseptic containers].</ref> A 1995 book on recycling notes that aseptic containers were not widely recycled.<ref>Aquino, John T. (1995). ''Waste Age/Recycling Times' Recycling Handbook''. [http://books.google.com/books?id=HZ2UDW8_c2gC&printsec=frontcover&source=gbs_summary_r&cad=0#PPA45,M1 p. 45].</ref> In 1993, aseptic packages could be recycled in 19 US states. Confusion over whether aseptic packages can be recycled led to a 1990 ban on them in Maine.<ref>''Food Processing''. (1993). [http://www.allbusiness.com/manufacturing/food-manufacturing/356816-1.html 'Set record straight' on aseptic cartons!].</ref> The ban was repealed in 1994.<ref>[http://business.highbeam.com/4420/article-1G1-16098278/maine-repeal-aseptic-ban-means-drink-boxes-return Maine's repeal of aseptic ban means drink boxes to return] Zuck, Robert A., Paper, Film & Foil Converter, June 1, 1994</ref>
In 1981, [[hydrogen peroxide]] was approved by the [[Food and Drug Administration|FDA]] to be used to sterilize containers.<ref name=":33" />

Today, ships used for continental food transport are equipped with aseptic tanks to transport fruit juices. Another means of transporting aseptically processed food is the use of aseptic bags.<ref name=":33" />

==Processing==
Aseptic processing allows for the food to be properly sterilized outside the container and then placed into a previously sterilized container, which is then sealed in a sterile environment.<ref name=":06" /> Most systems use [[Ultra-high-temperature processing|ultra-high temperature]] (UHT) sterilization to sterilize the food product before it is packaged. UHT sterilizes food at high temperatures usually above 135 C for 1–2 seconds. This is advantageous because it allows for faster processing, usually a few seconds at high temperatures (130–150&nbsp;°C) and better retention of sensory and nutritional characteristics.<ref name=":06" /> Aseptic products have a non-refrigerated shelf-life of a few months to several years.

Sterilization of aseptic packaging material is a crucial step in aseptic food processing. These containers are sterilized to kill microorganisms present on the container during forming and transport and prior to filling.<ref name=":83">{{Cite journal|last1=Ansari|first1=I.A.|last2=Datta|first2=A.K.|title=An Overview of Sterilization Methods for Packaging Materials Used in Aseptic Packaging Systems|journal=Food and Bioproducts Processing|volume=81|issue=1|pages=57–65|doi=10.1205/096030803765208670|year=2003}}</ref> There are numerous methods used to sterilize the containers, the most commonly used methods include: heat, hot water, chemical sterilants ([[hydrogen peroxide]] or [[peracetic acid]]), and [[radiation]] or a combination of methods.<ref name=":14" /><ref name=":83" />

UHT food products can be sterilized using either direct or indirect methods of heat transfer. [[Heat transfer|Direct heat transfer]] can be achieved through [[Steam injection (oil industry)|steam injection]] and [[steam infusion]]. Food products processed with a steam [[injector]] go through an injection chamber, where steam (150&nbsp;°C) is injected into the product, then the product is flash cooled to 70&nbsp;°C. Direct heat transfer is suitable for heat-sensitive foods such as milk. However, only low viscosity liquids can be processed using steam injection, and high-quality steam is required to ensure sterilization.<ref name=":06" /> Steam infused food products involves food free-falling into highly pressurized steam which heats the food to approximately 145&nbsp;°C and then its flash cooled to 65–70&nbsp;°C. [[Steam infusion]] provides processors with great control compared to steam injection and reduction of burn-on and overheating risks are reduced. It can process higher viscosity foods compared to steam injection, but risks the blockage of nozzles in machinery.<ref name=":06" /> Indirect forms of heat transfer include: plate [[heat exchanger]]s, tubular heat exchangers, or scraped-surface heat exchangers.<ref name=":14" /> [[Plate heat exchanger]]s are mostly used because they are inexpensive and allow for easy changes during production. Tubular and scraped-surface can heat viscous food with particulates or high pulp content with minimal damage.<ref name=":06" />

===Equipment and systems===
Equipment used in aseptic processing of food and beverages must be [[Sterilization (microbiology)|sterilized]] before processing and remain sterile during processing.<ref name=":06" /> When designing aseptic processing equipment there are six basic requirements to consider: the equipment must have the capability of being cleaned thoroughly, it must be able to be sterilized with steam, chemicals, or high-temperature water, sterilization media should be able to contact all surfaces of the equipment, meaning the equipment does not contain any cracks, crevices or dead spots, the equipment must be able to be kept in a sterile state, it must have the ability to be used continuously, and lastly, the equipment must comply with regulations.<ref name=":14" />

Aseptic packaging are generally placed in the following categories:<ref name=":53">{{Cite journal|last=Hersom|first=A.C.|date=2009|title=Aseptic processing and packaging of food|journal=Food Reviews International|volume=1:2|pages=215–270}}</ref> fill, erect, form, [[Thermoforming|thermoform]], [[Blow molding|blow mold]], and bulk packaging and storage systems.<ref name=":24" />

#''Fill and seal.'' The containers are filled and sealed in a sterile environment to avoid contamination.
#''[https://web.archive.org/web/20180608210126/http://www.atlantapackaging.co.uk/case-erection-filling-closing Erect, fill and seal].'' A plastic container is erected then sterilized, filled and sealed.
#''Form, fill and seal.'' In this system, a roll of film is first sterilized. After sterilization it is formed into the desired shape, filled and sealed.
#''Thermoform, fill and seal.'' A roll of film is heated and thermoform on a sterile surface or environment. It is then filled and seal, also in a sterile environment.
#''Blow mold, fill and seal.'' The process requires an extrudable material to be first blow-molded into a sterile package before filling and sealing. This process is usually used to produce bottle products like [[juice]]s and sodas.
#''Bulk packaging and storage systems.'' Packaging used for bulk storage (drums, totes, bags, etc.) are sterilized using either heat or [[disinfectant]]s. After sterilization they are able to be filled and sealed.

==Packaging material==
Aseptic packaging consists of filling and sealing a sterilized packaging material with a sterilized product. Aseptic packaging material not only has to assure sterile conditions within the package and protect the product from physical damage, but also maintain the quality of the product inside the packaging.<ref name=":83" /> To achieve this, a laminate material is formed from the following components: semi-rigid paper, [[Aluminium|aluminum]], and plastic.<ref name=":24" /> Paper (70%) provides the stiffness, strength, and the efficient brick shape to the package; potential for bacteria needs to be addressed.<ref>{{cite journal
| last =Vaisanen
| first =O M
| title =Bacteria in food packaging paper and board
| journal =Journal of Applied Bacteriology
| volume =71
| pages =130–133
| date =1991
| issue =2
| doi =10.1111/j.1365-2672.1991.tb02967.x
| pmid =1917722
| url =http://blogs.unpad.ac.id/souvia/files/2010/03/bacteria-in-paper1.pdf
| accessdate =24 March 2021
| archive-date =10 August 2017
| archive-url =https://web.archive.org/web/20170810095612/http://blogs.unpad.ac.id/souvia/files/2010/03/bacteria-in-paper1.pdf
| url-status =dead
}}</ref> [[Low-density polyethylene]] (24%), the most common plastic used for aseptic packaging, located on the innermost layer forms the seals that make the package liquid-tight. [[Aluminum]] (6%) is located on the inside of the aseptic package, forming a barrier against light and oxygen, thereby eliminating the need for refrigeration and preventing spoilage without using preservatives.<ref>{{cite book|title=Aseptic Processing and Packaging of Particulate Foods|last1=Willhoft|first1=Edward|date=1993|publisher=Blackie Academic & Professional|edition=1st|location=London|pages=1–192}}</ref> Most packaging material used in aseptic packaging is made from [[plastic]]s instead of [[metal]] or [[Container glass|glass containers]] due to the relatively low cost of producing plastic material when compared to metal and glass. Plastics are lighter than metal or glass making them cheaper and easier to transport. Plastics also required much less energy to produce than metal and glass.<ref name=":24" /> These factors have made plastic the packaging material of choice for use in aseptic processing.[[File:Tetra_Pak_packaging_portfolio_I_medium_size.jpg|thumb|Aseptic packaging material made by Tetra Pak]]

===Selection of aseptic containers===
There are a lot of factors that can influence the type of aseptic container chosen for a product. The following factors may influence the choice of packaging material for aseptically processed products: functional properties of the plastic polymer (gas and water vapor barrier properties, chemical [[Chemically inert|inert]]ness, and flavor and odor absorption or [[scalping]]), potential interactions between plastic polymer and food product, desired shelf life, economical costs, mechanical characteristics of the packaging material (molding properties, material handling characteristics, and compatibility with packaging and sterilization methods), shipping and handling conditions (toughness, compression), compliance with regulation, and targeted consumer group.<ref>{{cite book|title=Food Processing: Principles and Applications|last1=Smith|first1=J. Scott|date=2004|publisher=Blackwell Publishing|edition=1st|location=Iowa, USA}}</ref>

There are a range of different types of containers to choose from depending on the product. The table below offers a few container types and examples.<ref name=":24" />
{| class="wikitable"
|+ Selection of aseptic containers<ref name=":24" />
! Container Type
! Examples
! Container Characteristics
|-
|Rigid containers
|Metal cans, totes, glass bottles, and jars
|-Strength, rigidity, large capacity, minimum storage for final product
|-
|Paperboard Containers
|Webfed and Rollfed paper/foil/plastic cartons and preformed cartons
|-Great barrier and low cost
|-
|Semi-rigid plastic containers
|Webfed thermoformed cups, tubs, and trays
Preformed cups, tubs, trays, and bottles
|High production rates
Operation flexibility, container quality able to be checked in advance
|-
|Flexible plastic containers
|Pouches, sachets, etc.
|-Low cost, large capacity, simple equipment
|}

==Effects on food quality==
Aseptic processing preserves [[food quality]] through fast heat treatment followed by a short holding time and rapid cooling.<ref name=":06" /> Compared to [[canning]] where food products are subjected to high temperature processing, the fast heat treatment provided by aseptic processing enables heat-sensitive characteristics of the food to be better retained.<ref name=":06" />

===Flavor===
The flavor of aseptically processed food products is minimally changed.<ref name=":06" /> Dairy products could have a cooked flavor because of exposure to [[sulfhydryl]] groups. The flavor is reduced during storage as the sulfhydryl groups [[oxidize]]. Severely treated milk could have a [[Taste|bitter flavor]] because of [[proteolysis]].<ref name=":06" />

===Color===
Dairy products could have changes in color, an effect caused by [[Maillard reaction|Maillard browning]]. This depends on the amount of reducing sugar, the formation of pyralysins and [[melanoidin]]s, the severity of the treatment, and the storage temperature.<ref name=":06" />

Plant pigments, [[carotene]] and [[betanin]], are not affected, while [[chlorophyll]] and [[anthocyanin]]s are minimally reduced.<ref name=":06" />

===Texture===
Meat is less likely to toughen when aseptically processed, compared to [[Canning (food preservation method)|canned]] products.<ref name=":06" />

Fruit juice [[viscosity]] is unaffected. Processed sliced fruit and vegetable pieces are softer compared to unprocessed pieces as a result of the solubilization of pectic materials and loss of cell turgor.<ref name=":06" />

===Nutritional value===
Aseptic Processing achieves sterility through a flash-heating process with temperatures ranging from 91&nbsp;°C to 146&nbsp;°C and is minimally processed. Due to the significantly lower processing time and temperature range used in aseptic processing compared to conventional sterilization, such as canning, products that are aseptically processed are able to retain more nutrients.<ref>{{cite book|title=Nutrition: Science and Applications|last1=Smolin|first1=Lori|date=2017|publisher=Content Technologies, Inc.|edition=2nd}}</ref> [[Riboflavin]], [[pantothenic acid]], [[biotin]], [[Niacin (nutrient)|niacin]], and [[vitamin B6]] are unaffected. Approximately 10% of [[thiamine]] and [[vitamin B12]], approximately 15% of [[Folate|folic acid]] and [[pyridoxine]], and approximately 25% of [[vitamin C]] are lost during aseptic processing.<ref name=":06" />

==Advantages and limitations==
===Advantages===
Foods that are processed aseptically have better nutritional, vitamin, and natural pigment retention ([[chlorophyll]], [[anthocyanin]]s, [[betalain]]s, [[carotenoid]]s) compared to [[Canning (food preservation method)|canned]] food products because of the lower temperature the foods are subjected to upon processing.<ref name=":06" /> Aseptic processing provides flexibility in using various container sizes as well as possibility of addition of bioactive and heat-sensitive components after processing ([[probiotic]]s, [[omega-3 fatty acid]]s, conjugated [[linoleic acid]]s).<ref name=":06" />

===Limitations===
Aseptic processing costs more than canning because sterilization of the packaging materials requires different machinery and can get complex.<ref name=":06" /> In addition, maintaining air sterility in the processing room is difficult.<ref name=":06" />

==FDA inspection and regulation for aseptic processing==
Inspections of aseptic processing is one of the most complex inspection of food manufacturing operations. Process authorities are required to establish a process that ensures commercial sterility for the following:

#The product
#All equipment including the hold tube and any equipment downstream from the holding tube such as the filler
#The packaging equipment
#The packaging material.

Documentation of production operations must be maintained by the facility, showing an achievement of commercial sterile conditions in all areas of the facility.<ref name=":74" />

The general regulatory requirements for all [[Food and Drug Administration|U.S Food and Drug Administration]] (FDA) regulated foods are found in section 21 of the [[Code of Federal Regulations|U.S. Code of Federal Regulations]] (CFR) Part 117. Section 113.40 lists specific requirements for aseptic processing and packaging systems, including specifications for equipment and instrumentation. One requirement of the FDA regulations is that all thermal processing operations must be conducted under the operating supervision of an individual who has completed an FDA-approved course of instruction on control of thermal processing systems, container closures, and acidification procedures. The {{usurped|1=[https://web.archive.org/web/20170712162027/http://www.gmaonline.org/resources/science-education-foundation/better-process-control-schools/ Better Process Control School]}} provides a section on aseptic processing and packaging systems, and will meet the FDA requirement for supervisors of aseptic operations.<ref name=":63">{{cite book|url=https://books.google.com/books?id=m97VRCEDfEUC&pg=PA151|title=Principles of Aseptic Processing and Packaging|last1=Nelson|first1=Philip|date=1993|publisher=GMA Science and Education Foundation|edition=3|location=USA|isbn=978-1-55753-496-5|page=151}}</ref>

Processing authorities are responsible for aseptic systems must be aware of certain factors unique to aseptic processing and packaging operations, therefore specific knowledge in this area is essential. Neither the FDA nor other regulatory agency maintains a list of recognized processing authorities, however, certain organizations are widely recognized within government agencies and the industry as having the experience and expertise. The FDA regulations rely upon aseptic processing and packaging authorities to establish parameters for sterilization of product, packages, and equipment so that commercial sterility of the end product is assured.<ref name=":63" />

The forms presently used to file aseptic processes for low-acid foods with the FDA is Form 2541c. Processes for acidified foods that are aseptically processes and packaged are filed under 2541a. Additionally, processing plants must be registered with the FDA using Form 2541. The FDA has also developed a Low-acid Canned Food (LACF) Electronic Process Filling System that facilitates the completion and submission of the forms.<ref name=":63" />

The FDA does exert authority over the types of aseptic processing and packaging systems that can be utilized to produce foods for distribution in U.S. commerce by reviewing and either accepting or rejecting process filing forms from individual processing firms. The FDA may request sufficient technical information from the processor to evaluate adequacy of the equipment and the procedures used to produce a commercially sterile product. Until the FDA finds no further objections to a process filing, the company is prevented from distributing product produced on that system in interstate commerce.<ref name=":63" />

Final aseptic products must undergo an incubation test before the product is released into distribution. The firm must determine the time and temperature of incubation as well as how many containers are incubated.<ref name=":63" /> It is generally accepted to incubate at 20–25&nbsp;°C for a minimum of 7 days followed immediately, or after a first reading, by incubation at 30–35&nbsp;°C for a total minimum incubation time of 14 days. Other incubation schedules should be based on supporting validation data. It is important to note that prior to incubation, the containers with the microbial growth medium must be inverted to ensure all surfaces are thoroughly wetted by the medium.<ref>{{cite web|url=https://www.picscheme.org/|title=Recommendation on the Validation of Aseptic Processes|last1=Hargreaves|first1=Paul|website=Pharmaceutical Inspection Co-Operation Scheme|publisher=PIC/S|access-date=8 May 2018}}</ref>

The FDA relies on periodic inspections of processing plants to monitor compliance with its regulatory requirements. Inspection frequency for an individual plant may vary significantly depending upon products packed, occurrence of potential hazardous processing problems at the plant, and availability of FDA inspection personnel.<ref name=":63" />


==See also==
==See also==
{{portal|Food}}
{{portal|Food}}
{{div col|cols=3}}
{{div col|colwidth=22em}}
* [[Blow fill seal]]
* [[Blow fill seal]]
* [[Cosmetics]]
* [[Cosmetics]]
Line 45: Line 166:
* [[Tetra Pak]]
* [[Tetra Pak]]
{{div col end}}
{{div col end}}

== References ==
<references />

== Further reading ==

* {{Cite news|url=https://www.pharmaceuticalonline.com/doc/are-you-asking-too-much-from-your-filler-0001|title=Are You Asking Too Much From Your Filler?|last1=Bozenhardt|first1=Erich H.|date=18 October 2018|work=Pharmaceutical Online|access-date=30 October 2018|publisher=VertMarkets|last2=Bozenhardt|first2=Herman F.|type=Guest column }}


==External links==
==External links==
* {{cite web|url=http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM070342.pdf |title=Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing — Current Good Manufacturing Practice |accessdate=2009-08-15 |date=September 2004 |format=PDF |work=Pharmaceutical CGMPs |publisher=[[Food and Drug Administration (United States)|Food and Drug Administration]] | archiveurl= http://web.archive.org/web/20090827023242/http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM070342.pdf| archivedate= 27 August 2009 <!--DASHBot-->| deadurl= no}}
* {{cite web|url=https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM070342.pdf |title=Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing — Current Good Manufacturing Practice |access-date=2009-08-15 |date=September 2004 |work=Pharmaceutical CGMPs |publisher=[[Food and Drug Administration (United States)|Food and Drug Administration]] | archive-url= https://web.archive.org/web/20090827023242/https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM070342.pdf| archive-date= 27 August 2009 | url-status= live}}
* [http://www.aseptic.org/ Aseptic Packaging Council]


==References==
{{reflist}}
{{packaging}}
{{packaging}}


{{DEFAULTSORT:Aseptic Processing}}
{{DEFAULTSORT:Aseptic Processing}}
[[Category:Packaging]]
[[Category:Packaging]]
[[Category:Food science]]
[[Category:Food processing]]

Latest revision as of 22:10, 20 December 2024

Aseptic processing is a processing technique wherein commercially thermally sterilized liquid products (typically food or pharmaceutical) are packaged into previously sterilized containers under sterile conditions to produce shelf-stable products that do not need refrigeration.[1] Aseptic processing has almost completely replaced in-container sterilization of liquid foods,[2] including milk, fruit juices and concentrates, cream, yogurt, salad dressing, liquid egg, and ice cream mix. There has been an increasing popularity for foods that contain small discrete particles, such as cottage cheese, baby foods, tomato products, fruit and vegetables, soups, and rice desserts.[1]

Aseptic processing involves three primary steps: thermal sterilization of the product, sterilization of the packaging material, and conservation of sterility during packaging.[3] To ensure commercial sterility, aseptic processing facilities are required to maintain proper documentation of production operations, showing that commercially sterile conditions were achieved and maintained in all areas of the facility.[4] Any breach of a scheduled process for the processing or packaging system means that the affected product must be destroyed, reprocessed or segregated and held for further evaluation.[4] In addition, the processing and packaging system must be cleaned and re-sterilized before processing and/or packaging operations can resume. Packaging equipment and packaging materials are sterilized with various media or combinations thereof (i.e., saturated steam, superheated steam, hydrogen peroxide and heat and other treatments).[4]

Historical development in foods

[edit]

Aseptic processing was derived from Olin Ball's heat-cool-fill (HCF) machine that was developed in 1927.[5] While HCF was successful in improving the sensory quality of the processed chocolate milk as compared to canned product, the use of the equipment was hindered by its cost, maintenance, and inflexibility to process various container sizes, rendering the machine a failure.[6]

In the 1940s, the Avoset process was developed by George Grindrod. Food products processed using the Avoset process were packaged under ultraviolet lamps and sterilized air inside a positive-pressurized room to keep the contaminants out of the processing room. Sterilization was achieved through the use of direct steam injection of 126–137 °C (260–280 °F) and then cooled. The food treated using this technique was described as an "excellent cream product" and 75–100 containers were produced each minute.[6]

Later in the 1940s, the Dole Aseptic Process was developed by McKinley Martin.[5] The foods processed ranged from soups to specialty sauces, fruits, and dairy products.[6] This process involved four steps:[5][6]

  1. Sterilization of product by heating and immediate cooling
  2. Sterilization of containers and lids using steam
  3. Filling of cooled products aseptically into previously sterilized containers
  4. Sealing of lids at an atmosphere of saturated or super heated steam

The Dole aseptic machine overcame the hindrances that caused HCF's failure, since it was able to process various container sizes, needed less maintenance time and cost less. The quality of products processed was consistent regardless of container size, an important characteristic for heat sensitive foods, due to its short processing time. Split pea soup was treated using the Dole aseptic machine at the following dosage: heat time of 140–146 °C (280–290 °F) for 3.53 seconds, hold time of 8.8 seconds, and cooling to 32 °C (90 °F) in 14.0 – 17.0 seconds, compared to the normal processing time of 40–70 minutes at 115–121 °C (240–250 °F). The lack of consumer interest drove foods that were processed in the Dole aseptic machine to be discontinued.[6]

Erik Wallenberg, the inventor of the Tetra Classic packaging at Tetra Pak

Roy Graves began sterilizing milk in the 1940s. The milk that was drawn from the cow went through a pipeline, into a vacuum tank, which was then heated to 285 °F, then cooled to room temperature. The product, packaged in metal cans, was widely accepted by consumers lacking access to fresh milk, including the U.S. military.[7]

In 1959, the food industry saw the advent of the use of paper-foil-plastic laminated containers called tetrahedron. In 1962, the Swedish company Tetra Pak, introduced this container to the United States market. They sold pasteurized milk and beverages in the containers. Roy Graves' company started sterilizing this container with chlorine and were able to aseptically fill and hermetically seal the container. The use of these containers was not accepted by the American consumers due to their difficulty in opening. It was widely used by the U.S. Navy.[7]

In 1981, hydrogen peroxide was approved by the FDA to be used to sterilize containers.[5]

Today, ships used for continental food transport are equipped with aseptic tanks to transport fruit juices. Another means of transporting aseptically processed food is the use of aseptic bags.[5]

Processing

[edit]

Aseptic processing allows for the food to be properly sterilized outside the container and then placed into a previously sterilized container, which is then sealed in a sterile environment.[1] Most systems use ultra-high temperature (UHT) sterilization to sterilize the food product before it is packaged. UHT sterilizes food at high temperatures usually above 135 C for 1–2 seconds. This is advantageous because it allows for faster processing, usually a few seconds at high temperatures (130–150 °C) and better retention of sensory and nutritional characteristics.[1] Aseptic products have a non-refrigerated shelf-life of a few months to several years.

Sterilization of aseptic packaging material is a crucial step in aseptic food processing. These containers are sterilized to kill microorganisms present on the container during forming and transport and prior to filling.[8] There are numerous methods used to sterilize the containers, the most commonly used methods include: heat, hot water, chemical sterilants (hydrogen peroxide or peracetic acid), and radiation or a combination of methods.[7][8]

UHT food products can be sterilized using either direct or indirect methods of heat transfer. Direct heat transfer can be achieved through steam injection and steam infusion. Food products processed with a steam injector go through an injection chamber, where steam (150 °C) is injected into the product, then the product is flash cooled to 70 °C. Direct heat transfer is suitable for heat-sensitive foods such as milk. However, only low viscosity liquids can be processed using steam injection, and high-quality steam is required to ensure sterilization.[1] Steam infused food products involves food free-falling into highly pressurized steam which heats the food to approximately 145 °C and then its flash cooled to 65–70 °C. Steam infusion provides processors with great control compared to steam injection and reduction of burn-on and overheating risks are reduced. It can process higher viscosity foods compared to steam injection, but risks the blockage of nozzles in machinery.[1] Indirect forms of heat transfer include: plate heat exchangers, tubular heat exchangers, or scraped-surface heat exchangers.[7] Plate heat exchangers are mostly used because they are inexpensive and allow for easy changes during production. Tubular and scraped-surface can heat viscous food with particulates or high pulp content with minimal damage.[1]

Equipment and systems

[edit]

Equipment used in aseptic processing of food and beverages must be sterilized before processing and remain sterile during processing.[1] When designing aseptic processing equipment there are six basic requirements to consider: the equipment must have the capability of being cleaned thoroughly, it must be able to be sterilized with steam, chemicals, or high-temperature water, sterilization media should be able to contact all surfaces of the equipment, meaning the equipment does not contain any cracks, crevices or dead spots, the equipment must be able to be kept in a sterile state, it must have the ability to be used continuously, and lastly, the equipment must comply with regulations.[7]

Aseptic packaging are generally placed in the following categories:[9] fill, erect, form, thermoform, blow mold, and bulk packaging and storage systems.[3]

  1. Fill and seal. The containers are filled and sealed in a sterile environment to avoid contamination.
  2. Erect, fill and seal. A plastic container is erected then sterilized, filled and sealed.
  3. Form, fill and seal. In this system, a roll of film is first sterilized. After sterilization it is formed into the desired shape, filled and sealed.
  4. Thermoform, fill and seal. A roll of film is heated and thermoform on a sterile surface or environment. It is then filled and seal, also in a sterile environment.
  5. Blow mold, fill and seal. The process requires an extrudable material to be first blow-molded into a sterile package before filling and sealing. This process is usually used to produce bottle products like juices and sodas.
  6. Bulk packaging and storage systems. Packaging used for bulk storage (drums, totes, bags, etc.) are sterilized using either heat or disinfectants. After sterilization they are able to be filled and sealed.

Packaging material

[edit]

Aseptic packaging consists of filling and sealing a sterilized packaging material with a sterilized product. Aseptic packaging material not only has to assure sterile conditions within the package and protect the product from physical damage, but also maintain the quality of the product inside the packaging.[8] To achieve this, a laminate material is formed from the following components: semi-rigid paper, aluminum, and plastic.[3] Paper (70%) provides the stiffness, strength, and the efficient brick shape to the package; potential for bacteria needs to be addressed.[10] Low-density polyethylene (24%), the most common plastic used for aseptic packaging, located on the innermost layer forms the seals that make the package liquid-tight. Aluminum (6%) is located on the inside of the aseptic package, forming a barrier against light and oxygen, thereby eliminating the need for refrigeration and preventing spoilage without using preservatives.[11] Most packaging material used in aseptic packaging is made from plastics instead of metal or glass containers due to the relatively low cost of producing plastic material when compared to metal and glass. Plastics are lighter than metal or glass making them cheaper and easier to transport. Plastics also required much less energy to produce than metal and glass.[3] These factors have made plastic the packaging material of choice for use in aseptic processing.

Aseptic packaging material made by Tetra Pak

Selection of aseptic containers

[edit]

There are a lot of factors that can influence the type of aseptic container chosen for a product. The following factors may influence the choice of packaging material for aseptically processed products: functional properties of the plastic polymer (gas and water vapor barrier properties, chemical inertness, and flavor and odor absorption or scalping), potential interactions between plastic polymer and food product, desired shelf life, economical costs, mechanical characteristics of the packaging material (molding properties, material handling characteristics, and compatibility with packaging and sterilization methods), shipping and handling conditions (toughness, compression), compliance with regulation, and targeted consumer group.[12]

There are a range of different types of containers to choose from depending on the product. The table below offers a few container types and examples.[3]

Selection of aseptic containers[3]
Container Type Examples Container Characteristics
Rigid containers Metal cans, totes, glass bottles, and jars
Paperboard Containers Webfed and Rollfed paper/foil/plastic cartons and preformed cartons
Semi-rigid plastic containers Webfed thermoformed cups, tubs, and trays

Preformed cups, tubs, trays, and bottles

High production rates

Operation flexibility, container quality able to be checked in advance

Flexible plastic containers Pouches, sachets, etc.

Effects on food quality

[edit]

Aseptic processing preserves food quality through fast heat treatment followed by a short holding time and rapid cooling.[1] Compared to canning where food products are subjected to high temperature processing, the fast heat treatment provided by aseptic processing enables heat-sensitive characteristics of the food to be better retained.[1]

Flavor

[edit]

The flavor of aseptically processed food products is minimally changed.[1] Dairy products could have a cooked flavor because of exposure to sulfhydryl groups. The flavor is reduced during storage as the sulfhydryl groups oxidize. Severely treated milk could have a bitter flavor because of proteolysis.[1]

Color

[edit]

Dairy products could have changes in color, an effect caused by Maillard browning. This depends on the amount of reducing sugar, the formation of pyralysins and melanoidins, the severity of the treatment, and the storage temperature.[1]

Plant pigments, carotene and betanin, are not affected, while chlorophyll and anthocyanins are minimally reduced.[1]

Texture

[edit]

Meat is less likely to toughen when aseptically processed, compared to canned products.[1]

Fruit juice viscosity is unaffected. Processed sliced fruit and vegetable pieces are softer compared to unprocessed pieces as a result of the solubilization of pectic materials and loss of cell turgor.[1]

Nutritional value

[edit]

Aseptic Processing achieves sterility through a flash-heating process with temperatures ranging from 91 °C to 146 °C and is minimally processed. Due to the significantly lower processing time and temperature range used in aseptic processing compared to conventional sterilization, such as canning, products that are aseptically processed are able to retain more nutrients.[13] Riboflavin, pantothenic acid, biotin, niacin, and vitamin B6 are unaffected. Approximately 10% of thiamine and vitamin B12, approximately 15% of folic acid and pyridoxine, and approximately 25% of vitamin C are lost during aseptic processing.[1]

Advantages and limitations

[edit]

Advantages

[edit]

Foods that are processed aseptically have better nutritional, vitamin, and natural pigment retention (chlorophyll, anthocyanins, betalains, carotenoids) compared to canned food products because of the lower temperature the foods are subjected to upon processing.[1] Aseptic processing provides flexibility in using various container sizes as well as possibility of addition of bioactive and heat-sensitive components after processing (probiotics, omega-3 fatty acids, conjugated linoleic acids).[1]

Limitations

[edit]

Aseptic processing costs more than canning because sterilization of the packaging materials requires different machinery and can get complex.[1] In addition, maintaining air sterility in the processing room is difficult.[1]

FDA inspection and regulation for aseptic processing

[edit]

Inspections of aseptic processing is one of the most complex inspection of food manufacturing operations. Process authorities are required to establish a process that ensures commercial sterility for the following:

  1. The product
  2. All equipment including the hold tube and any equipment downstream from the holding tube such as the filler
  3. The packaging equipment
  4. The packaging material.

Documentation of production operations must be maintained by the facility, showing an achievement of commercial sterile conditions in all areas of the facility.[4]

The general regulatory requirements for all U.S Food and Drug Administration (FDA) regulated foods are found in section 21 of the U.S. Code of Federal Regulations (CFR) Part 117. Section 113.40 lists specific requirements for aseptic processing and packaging systems, including specifications for equipment and instrumentation. One requirement of the FDA regulations is that all thermal processing operations must be conducted under the operating supervision of an individual who has completed an FDA-approved course of instruction on control of thermal processing systems, container closures, and acidification procedures. The Better Process Control School[usurped] provides a section on aseptic processing and packaging systems, and will meet the FDA requirement for supervisors of aseptic operations.[14]

Processing authorities are responsible for aseptic systems must be aware of certain factors unique to aseptic processing and packaging operations, therefore specific knowledge in this area is essential. Neither the FDA nor other regulatory agency maintains a list of recognized processing authorities, however, certain organizations are widely recognized within government agencies and the industry as having the experience and expertise. The FDA regulations rely upon aseptic processing and packaging authorities to establish parameters for sterilization of product, packages, and equipment so that commercial sterility of the end product is assured.[14]

The forms presently used to file aseptic processes for low-acid foods with the FDA is Form 2541c. Processes for acidified foods that are aseptically processes and packaged are filed under 2541a. Additionally, processing plants must be registered with the FDA using Form 2541. The FDA has also developed a Low-acid Canned Food (LACF) Electronic Process Filling System that facilitates the completion and submission of the forms.[14]

The FDA does exert authority over the types of aseptic processing and packaging systems that can be utilized to produce foods for distribution in U.S. commerce by reviewing and either accepting or rejecting process filing forms from individual processing firms. The FDA may request sufficient technical information from the processor to evaluate adequacy of the equipment and the procedures used to produce a commercially sterile product. Until the FDA finds no further objections to a process filing, the company is prevented from distributing product produced on that system in interstate commerce.[14]

Final aseptic products must undergo an incubation test before the product is released into distribution. The firm must determine the time and temperature of incubation as well as how many containers are incubated.[14] It is generally accepted to incubate at 20–25 °C for a minimum of 7 days followed immediately, or after a first reading, by incubation at 30–35 °C for a total minimum incubation time of 14 days. Other incubation schedules should be based on supporting validation data. It is important to note that prior to incubation, the containers with the microbial growth medium must be inverted to ensure all surfaces are thoroughly wetted by the medium.[15]

The FDA relies on periodic inspections of processing plants to monitor compliance with its regulatory requirements. Inspection frequency for an individual plant may vary significantly depending upon products packed, occurrence of potential hazardous processing problems at the plant, and availability of FDA inspection personnel.[14]

See also

[edit]

References

[edit]
  1. ^ a b c d e f g h i j k l m n o p q r s t u Fellows, Peter (2016). Food processing technology : principles and practice (4th ed.). Kent: Woodhead Publishing/Elsevier Science. ISBN 9780081005231. OCLC 960758611.
  2. ^ "Global renaming: SIG Combibloc / New regional companies / Group strategy". Plasteurope. 1998-03-31. Retrieved 2023-11-30.
  3. ^ a b c d e f Handbook of food safety engineering. Sun, Da-Wen. Oxford: Wiley-Blackwell. 2011. ISBN 978-1444333343. OCLC 767579357.{{cite book}}: CS1 maint: others (link)
  4. ^ a b c d FDA. "Aseptic Processing and Packaging for the Food Industry". U.S. Food and Drug Administration. Retrieved 3 April 2018.
  5. ^ a b c d e Pillai, Suresh; Shayanfa, Shima (2014). Electron beam pasteurization and complementary food processing technologies. Cambridge: Woodhead Publishing. ISBN 9781782421085. OCLC 897799891.
  6. ^ a b c d e Advances in food research Vol. 32. Chichester, C. O., 1925–, Schweigert, B. S. San Diego: Academic Press. 1988. ISBN 9780080567778. OCLC 647803601.{{cite book}}: CS1 maint: others (link)
  7. ^ a b c d e D., David, Jairus R. (2013). Handbook of aseptic processing and packaging. Graves, Ralph H., Szemplenski, Thomas. Boca Raton: Taylor & Francis. ISBN 9781138199071. OCLC 811776682.{{cite book}}: CS1 maint: multiple names: authors list (link)
  8. ^ a b c Ansari, I.A.; Datta, A.K. (2003). "An Overview of Sterilization Methods for Packaging Materials Used in Aseptic Packaging Systems". Food and Bioproducts Processing. 81 (1): 57–65. doi:10.1205/096030803765208670.
  9. ^ Hersom, A.C. (2009). "Aseptic processing and packaging of food". Food Reviews International. 1:2: 215–270.
  10. ^ Vaisanen, O M (1991). "Bacteria in food packaging paper and board" (PDF). Journal of Applied Bacteriology. 71 (2): 130–133. doi:10.1111/j.1365-2672.1991.tb02967.x. PMID 1917722. Archived from the original (PDF) on 10 August 2017. Retrieved 24 March 2021.
  11. ^ Willhoft, Edward (1993). Aseptic Processing and Packaging of Particulate Foods (1st ed.). London: Blackie Academic & Professional. pp. 1–192.
  12. ^ Smith, J. Scott (2004). Food Processing: Principles and Applications (1st ed.). Iowa, USA: Blackwell Publishing.
  13. ^ Smolin, Lori (2017). Nutrition: Science and Applications (2nd ed.). Content Technologies, Inc.
  14. ^ a b c d e f Nelson, Philip (1993). Principles of Aseptic Processing and Packaging (3 ed.). USA: GMA Science and Education Foundation. p. 151. ISBN 978-1-55753-496-5.
  15. ^ Hargreaves, Paul. "Recommendation on the Validation of Aseptic Processes". Pharmaceutical Inspection Co-Operation Scheme. PIC/S. Retrieved 8 May 2018.

Further reading

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[edit]
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