GCS nitrogen generator for modified atmosphere packaging

Modified atmosphere/modified humidity (MA/MH) packaging is a technology used to preserve the quality of fresh produce so that it can be sold to markets far away from where it is grown, extend the marketing period, and to help suppliers reduce

food waste Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...

within the cold chain. Commercial examples of MA/MH include sea freight of Galia and cantaloupe melons from Central and South America to Europe (a 21-day journey) and North America (a 7-day journey); transport of white asparagus from fields in Peru to markets in Western Europe (a 20-day journey by land and sea); and trucking of cherries from orchards in Turkey to supermarkets in the UK (a 7-day journey).

Scientific terms

;EMAP:Equilibrium modified atmosphere packaging ;MA/MH:Modified atmosphere/modified humidity ;MAP:

Modified atmosphere Modified atmosphere packaging (MAP) is the practice of modifying the composition of the internal atmosphere of a package (commonly food packages, drugs, etc.) in order to improve the shelf life. The need for this technology for food arises from t ...

packaging ;RH:

Relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

;MVTR: Moisture vapor transmission rate

History

/modified humidity (MA/MH) packaging is a type of equilibrium modified atmosphere packaging (EMAP), which evolved due to the need for more control of humidity in the packaging. Most of the polymers that are commercially used in EMAP are polyolefin-based, characterized by low moisture vapor transmission rate (MVTR). Temperature fluctuations during the various links in the cold logistics chain are unavoidable and will result in condensation forming on the inner surface of the package. The accumulation of condensed water in packages with low MVTR is conducive for pathological and physiological disorders. Not only does excess moisture enhance fungal and bacterial decay and the formation of off odors, it also encourages leaf sprouting in topped root vegetables, regrowth of leaves and physiological disorders such as tissue discoloration and peel blemishes. Certain produce items are more sensitive to excess moisture than others. In 1995
StePac LA. Ltd.
with the assistance of th
Agricultural Research Organization – The Volcani Center
began developing plastic films with higher MVTR than most commercially available EMAP products then on the market. The aim was to provide more humidity control in EMAP products and alleviate problems associated with excess moisture. Since this original research and development work, StePac LA Ltd. has developed MA/MH films and bags for over 50 different fruits, vegetables and herbs in a product line commercially known a
Xtend

Technology

MA/MH technology is achieved by combining proprietary blends of

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

s to obtain the desired MVTR and then manipulating the

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

() and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

() transmission rates of the polymer by laser and/or mechanical microperforations. The result is a film which is tailored to provide the optimum modified atmosphere and modified humidity for the produce to be packaged. “Film composition and extent of microperforation are tailored in accordance with the respiratory activity and weight of the produce packaged, anticipated temperature fluctuations during storage and shipment, and expected physiological and pathological responses of the produce to / concentrations and humidity levels inside the package. . . . A/MHpackaging allow the formation of a desirable modified atmosphere, retarding ripening and senescence of the produce. Additional beneficial effects . . . include reduction of decay, chilling injury, leaf elongation, leaf sprouting, tissue discoloration, peel blemishes, and formation of off-odors, and inhibition of bacterial growth on the produce surface.”Aharoni, Nehemia, et al.; ''Intelligent and Active Packaging for Fruits and Vegetables''; Chapter Five: Modified atmosphere packaging for vegetable crops using high-water-vapor-permeable films;

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Benefits to fresh produce

Modifying the atmosphere inside fresh produce packaging to provide lowered levels of and elevated levels of is beneficial for many fresh produce items and “can reduce respiration, decrease ethylene production and action, retard tissue ripening and softening, retard chlorophyll degradation and biosynthesis of

carotenoids Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, co ...

and

anthocyanins Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical com ...

, reduce

enzymatic Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...

browning, alleviate physiological disorders and chilling injury, retard development of decay, and maintain nutritional quality of produce. The effect of decreased and increased on senescence and ripening process are additive and can be synergistic.” “In vegetative tissues MAP can also reduce leaf regrowth (green onion and leek), stem toughening (asparagus),and leaf sprouting and rooting in root vegetables (parsnip, radishes). The delay of ripening and senescence of fruits and vegetables also reduces their susceptibility to

pathogens In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a ger ...

.”

The importance of tightly controlled relative humidity

Maintaining high relative humidity (RH) in modified atmosphere packaging is important because it “results in reduced transpiration of water from the produce, thereby reducing wilting, shriveling, and loss of firmness. The accumulation of vapor in the packaging depends on the rate of water loss from the product, its surface area, the water vapor transmission rate (WVTR) of the film, and the external environment temperature.” “The RH in most sealed packaging is near the saturation level. Therefore, even very small fluctuations in temperature during storage or shipment may result in water condensation on the surface of both film and produce. Condensed water on the produce surface may adversely affect the gas exchange, leading to an unfavorable internal atmosphere.” Even more detrimental may be the enhancement of produce decay, and physiological processes such as regrowth. In addition, certain human pathogens may proliferate when in-pack atmosphere contains high humidity and low .

Hazards associated with MAP

Successful delivery of fresh produce in MAP is not without potential hazards due to incompatibility of MAP film to the fruit or vegetable it is intended to keep fresh and high dependence on good temperature management. Undesirable consequences of incompatible film and/or high temperatures may be “

anaerobic respiration Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain. In aerobic organisms undergoing r ...

with the accumulation of acetaldehyde,

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

ethyl acetate Ethyl acetate ( systematically ethyl ethanoate, commonly abbreviated EtOAc, ETAC or EA) is the organic compound with the formula , simplified to . This colorless liquid has a characteristic sweet smell (similar to pear drops) and is used in glues ...

, and

lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as nat ...

, all of fermentation, contributing to the development of off odors, off flavors, and disuse deterioration.” Extreme changes in and to intolerable levels often occur when fresh produce packed in improper MAP is exposed to higher than recommended temperatures during shipment and distribution. Other undesirable effects of improper MAP are initiation or aggravation of certain physiological disorders, irregular fruit ripening, and increased susceptibility to decay following physiological damage.”Kadar and Saltveit, 2003

Products

Several types of products, including retail bags, carton liners, bin bags, lidding films and flow pack have been developed from MA/MH films and are commercially available. Each product type is uniquely engineered for the specific produce type (and in some cases, the produce variety) to be packaged. This is done through a rigorous process of developing, testing, adjusting and retesting each MA\MH product both in the lab and in commercial trials. This meticulous process is repeated for each combination of produce and packaging type because of the many factors involved in developing a successful MA/MH packaging. These factors are “storage and shipment temperature, product respiration rate and quotient, response to levels of , and humidity, and product weight. Hence, film packaging that is adequate for consumer packages is not always suitable for bulk packaging and vice versa.”

Sources

References

* Fonseca, Jorge M.; High Relative Humidity
Fresh Americas
#1, 2008 Series, Master Media Worldwide Publishing * Devon Zagory, Devon Zagory & Associates, University of California, Davis,
Advances In Modified Atmosphere Packaging (MAP) of Fresh Produce
Perishables Handling Newsletter Issue No. 90, May 1997, pages 2–3 * N. Aharoni, V. Rodov, E. Fallik, R. Porat, E. Pesis and S. Lurie; Department of Postharvest Science of Fresh Produce, ARO, The Volcani Center
Humidity Improves Efficacy of Modified Atmosphere Packaging of Fruits and Vegetables
* Adel A. Kader, Dept. of Pomology University of California, Davis
Modified Atmosphere Packaging of Fresh Produce
Outlook Second Quarter, Volume 13, No. 2, 1986 * Stephen R. Harris

ttp://www.fao.org/wairdocs/X5014E/X5014e0a.htm Storage of fresh produce Bridgetown, Barbados, December 1988 {{DEFAULTSORT:Modified Atmosphere Modified Humidity Packaging Packaging Food technology