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The use of UV light on fresh fruit and vegetables Submitted by Ozone Purification Technology , article by Carlos Ribeiro , João Canada and Bartolomeu Alvarenga
Fresh fruits and vegetables are an important part of a healthy diet . Each provides a unique blend of vitamins , minerals , fibre , phytochemicals and other nutrients required to meet the needs of the human body .
Occasionally , fresh fruits and vegetables are contaminated with harmful viruses such as Hepatitis A or bacteria such as E . coli , Listeria , or Salmonellae . These pathogens may be in the soil or water where produce grows , or the produce may become contaminated after it is harvested , such as during preparation or storage . Using safe methods of storing , washing , and preparing produce can help to produce a healthy harvest .
UV light has been used as a germicidal agent in water treatment and surfaces disinfection because of its capacity to affect DNA of microorganisms . On the other hand , low doses of UV-C irradiation can trigger some favourable reactions in biological organs , such as fruits and vegetables , which can lead to various beneficial effects , such as improvement of their shelf-life or an increase in the content of health promoting components .
The objective of what is covered in this paper is to review the results of some works on the UV application on post-harvested fruits and vegetables , taking into account both its direct germicidal activity and its hormectic effects . After the presentation of the hormesis concept , the application of UV to ready-to-use fruit and vegetables and , specifically , to various fruits and vegetables , is discussed . The use of UV radiation strictly for hormectic purposes at commercial scale still needs to be further investigated .
INTRODUCTION Although the use of ultra-violet light ( UV ) is well established for water treatment , air disinfection , and surface decontamination , its use is still limited in food treatment and in postharvest technology in particular . UV treatment has a potential for commercial use as a surface treatment of fresh-cut fruits .
The ability of UV light to sanitise and retard microbial growth on the surface of fresh-cut fruits without causing undesirable quality changes has been recognised . Irradiation with UV light may be a more effective germicidal treatment than chlorine , hydrogen peroxide , or ozone . Advances in the science and engineering of UV-light irradiation have demonstrated that UV treatment holds considerable promise for shelf-life extension of fresh fruits and vegetables .
Considering its importance , surprisingly little is known about the interaction of UV light with matter , especially with a complex food matrix . The objective of this review is by no means to describe exhaustively and in detail all the work done on the effects of UV radiation on vegetables and fruits , but only to report some of the results that can lead to the use
Scott Warman | Unsplash of UV light for post-harvest treatment of fruits and vegetables .
UV light is just one portion of the electromagnetic spectrum which covers a broad range from radio waves with wavelength of a meter or more , down to x-rays with wavelength of less than a billionth of a meter . Typically , the wavelength for UV processing ranges from 100 to 400 nm ( Koutchma et al ., 2009 ). This range may be further subdivided into UV-A ( 315 – 400 nm ), normally responsible for changes in human skin called tanning ; UV-B ( 280 – 315 nm ), which can cause skin burning and eventually lead to skin cancer ; UV-C ( 200 – 280nm ), called the germicidal range , since it effectively inactivates bacteria and viruses ; and the vacuum UV range ( 100 – 200 nm ), which can be absorbed by almost all substances and thus can be transmitted only in a vacuum ( Koutchma et al ., 2009 ).
Short UV-C is almost completely absorbed in air within a few hundred meters . When UV-C photons collide with oxygen atoms , the energy exchange causes the formation of ozone . UV-C is almost never observed in nature , since it is absorbed so quickly . Koutchma et al . reviewed the full range of commercially available UV sources , such as low- and medium-pressure mercury lamps , mercury-free amalgam lamps , and discussed the advantages of the pulsed UVlight sources currently under development .
THE CONCEPT OF HORMESIS UV-C irradiation at low doses ( 0.25 – 8.0 kJ / m 2 ) affects the DNA of microorganisms ( Terry and Joyce , 2004 ). For this reason , UV-C treatment has been used as a germicidal or mutagenic agent . In addition to this direct germicidal activity , UV-C irradiation can modulate induced defence in plants . So ,
Engin Akyurt | Unsplash
Considering its importance , surprisingly little is known about the interaction of UV light with matter , especially with a complex food matrix .
Combined treatment of fumaric acid / UV-C reduced the initial populations of total aerobic bacteria and yeast and molds in strawberries that were tested .
UV-C irradiation can be applied at lethal and sublethal doses .
UV-C can also produce a detrimental effect on plant tissues which includes tissue structural damage , changes in cytomorphology and water permeability of inner epidermal cells ( Lichtscheidl-Schultz , 1985 ). Nevertheless , low doses of UV-C irradiation stimulated beneficial reactions in biological organs , a phenomenon known as hormesis ( Shama , 2007 ).
Hormesis is defined as the stimulation by low doses of any potentially harmful agent ( Luckey , 1980 ). The agents capable of bringing about these stimulatory effects may be either chemical or physical ones . Included among the latter are various portions of the electromagnetic spectrum . Luckey ( 1980 ) conducted an extensive survey of hormetic effects induced by both ionising radiation and UV light . Hormesis involves stimulation of a beneficial plant response by low or sub-lethal doses of an elicitor / agent , such as a chemical inducer or a physical stress ( Terry and Joyce , 2004 ). Non-ionising radiation has real potential among physical methods for controlling post-harvest diseases ( Wilson et al ., 1997 ).
UV-C irradiation can trigger some favourable reactions in biological organs , such as fruits and vegetables .
According to Shama ( 2007 ), hormesis involves the use of small doses of potentially harmful agents directed against a living organism or living tissue in order to elicit a beneficial or protective response . Hormetic UV treatment is distinguished from conventional UV treatment . In conventional treatment the UV is directed at microorganisms present on the surfaces of an object , whereas in hormetic UV treatment the object itself is the target of the incident UV . The objective of the treatment is to elicit an antimicrobial response in the fruit and vegetable tissue .
Both types of UV treatment employ the same wavelengths , but for hermetic treatments only low UV doses are required . Low doses of short-wave ultra-violet light ( UVC , 190 – 280 nm wavelengths ) can control many storage rots of fruit and vegetables . It has been reported that hormetic doses
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