Abstract:
The invention provides a produce decontamination apparatus comprising a chamber  10  for accepting produce to be decontaminated and/or sterilized, and means for producing a free radical saturated atmosphere within the chamber  10  so that, in use, the free radical saturated atmosphere decontaminates and/or sterilizes the produce. Preferably, the means for producing a free radical saturated atmosphere comprises one or more first atomizing sprayheads  30   a , a supply  32  of ozonized liquid which is supplied to the first sprayheads  30   a , and means for breaking down the ozone forming part of the ozonized liquid once discharged from the first sprayheads  30   a . Preferably, the means for breaking down the ozone is in the form of one or more UV light emitting devices  48,50 . Produce decontaminated using the apparatus is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a U.S. national stage of PCT International Application No. PCT/GB2004/004636, filed on Nov. 4, 2004. 
     FIELD OF THE INVENTION 
     This invention relates to produce decontamination apparatus and, more particularly, to the decontamination of produce by free radical washing. 
     BACKGROUND OF THE INVENTION 
     Fresh produce is typically washed, post harvest, with various decontaminating solutions containing biocide, such as chlorine/chlorine dioxide, ozone, or any number of combinations of chemicals. This is intended to reduce the risk of introducing potentially damaging or pathogenic microorganisms to the consumer. 
     However, the use of chemicals within the food chain is now less acceptable, and many chemical biocides are now limited by legislation. 
     Traditional techniques of sanitisation or decontamination use vast quantities of water, which is also a valuable commodity. 
     The present invention seeks to provide a solution to these problems. 
     BRIEF SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided produce decontamination apparatus comprising a chamber for accepting produce to be decontaminated and/or sterilised, and means for producing a free radical saturated atmosphere within the chamber so that, in use, the free radical saturated atmosphere decontaminates and/or sterilises the produce. 
     Preferable and/or optional features of the invention are set forth in the claims. 
     According to a second aspect of the present invention, there is provided produce decontaminated using produce decontamination apparatus in accordance with the first aspect of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention will now be more particularly described, by way of example only, with reference to the only accompanying FIGURE. 
         FIG. 1  shows diagrammatically a cross-sectional elevation view of one embodiment of the produce decontamination apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is shown produce decontamination apparatus which comprises a substantially enclosed chamber  10  which is open to atmospheric pressure and which has a produce inlet  12 , a produce outlet  14 , an air inlet  16 , a pumped chamber exhaust  18 , and two conveyors  20  and  22 . 
     Each conveyor  20  and  22  includes a conveyor belt  24  and  26  fully housed within the chamber  10 . The conveyor belts  24  and  26  are vertically spaced apart and horizontally positioned relative to each other so that one end of the upper conveyor belt  24  overhangs the lower conveyor belt  26 . A produce flow path is thus generated horizontally along the upper conveyor belt  24 , vertically down from the upper conveyor belt  24  to the lower conveyor belt  26 , and then horizontally along the lower conveyor belt  26 , as indicated by arrows A. 
     The vertical spacing between the upper and lower conveyor belts  24  and  26  is adjustable through an adjustment mechanism (not shown). The adjustment mechanism typically allows height adjustment of the lower conveyor belt  26 , as shown in the FIGURE by the phantom lines  7  and arrows B. However, the upper conveyor belt  24  could alternatively or additionally be height adjustable. An adjusted position  28  is shown in the figure. 
     Sprayheads  30  are located within the chamber  10 , and form part of means for producing a free radical saturated atmosphere. The sprayheads  30  are provided along the full extent of the produce flow path A. More specifically, the sprayheads  30  are provided at a constant spacing directly above each conveyor belt  24  and  26  and also at the vertical spacing between the upper and lower conveyor belts  24  and  26 . Since the vertical spacing between the upper and lower conveyor belts  24  and  26  is an open space, the sprayheads  30  are provided on at least two sides. 
     The sprayheads  30  are atomising sprayheads and discharge a non-condensing mist of liquid having a droplet size of between 1 and 15 microns. The average droplet size is preferably 5 microns. 
     The sprayheads  30  are divided into ozone and ferrous sprayheads  30   a  and  30   b . The ozone sprayheads  30   a  are fluidly-connected to a first supply  32  of ozonised liquid, typically being ozonised water; and the ferrous sprayheads  30   b  are fluidly-connected to a second supply  34  of liquid, typically water, having ferrous ions. The first and second supplies  32  and  34  reside externally of the chamber  10 . 
     The first supply  32  includes a reservoir  36  and a pump  38  for supplying the liquid in the reservoir  36  to the ozone sprayheads  30   a  at the correct pressure to ensure atomisation. The liquid passing from reservoir  36  to the ozone sprayheads  30   a  is initially pumped through a venturi  40  or any other similar device by which ozone from an ozone generator  42  can be introduced. The ozone concentration is regulated at between 1 and 5 parts-per-million (ppm). 
     The second supply  34  includes a reservoir  44  and a pump  46 . The liquid in the reservoir  44  is charged with ferrous salts, such as ferrous Sulphate, typically in the concentration of 10 to 15 ppm. However, different concentrations depending on necessity can be used. 
     The ferrous sprayheads  30   b  and the second supply  34  together form means for catalysing the breakdown of hydrogen peroxide which is formed by the breakdown of ozone discharged as part of the ozonised liquid from the ozone sprayheads  30   a.    
     The ozone and ferrous sprayheads  30   a  and  30   b  are provided in alternating fashion along the produce flow path A. A ferrous sprayhead  30   b  is provided at the beginning of the flow path A. 
     Means for breaking down the ozone discharged as part of the ozonised liquid from the first sprayheads  30   a  are in the form of ultraviolet light emitting devices  48 , typically being UV fluorescent tubes. The UV light emitting devices  48  are waterproof and are mounted along the full extent of the produce flow path. Specifically, the UV light emitting devices  48  are positioned at a constant spacing directly above the upper and lower conveyor belts  24  and  26 , and at the vertical spacing between the two conveyor belts  24  and  26 . As with the sprayheads  30 , the UV light emitting devices  48  are positioned on at least two sides at the vertical spacing between the two conveyor belts  24  and  26 . 
     Further UV light emitting devices  50  are also provided in any redundant spaces within the chamber  10  to ensure full exposure of the ozonised liquid to the ultraviolet light. 
     The UV light emitting devices  48 , 50  emit ultraviolet light at wavelengths of between 185 and 253.7 nanometers. 
     To catalyse the breakdown of the ozone discharged as part of the ozonised liquid from the ozone sprayheads  30   a , the interior surfaces  52  of the chamber  10  have a coating including an ozone catalysing agent or agents. At least one of the ozone catalysing agents is titanium oxide or titanium dioxide. This coating forms ozone catalysing means, and helps to ensure that there is no build up of ozone contamination within the chamber  10 . 
     Ozone in solution breaks down rapidly when subjected to ultraviolet light to form hydrogen peroxide H 2 O 2 , which itself then breaks down to form peroxide radicals HO—OH, and finally highly reactive hydroxyl radicals OH. and OH − . The rate of conversion from hydrogen peroxide to hydroxyl radicals can be greatly enhanced by the use of ferrous ions Fe 2+ , which act as a catalyst during their conversion to ferric ions Fe 3+ . This is generally known as Fenton&#39;s Reaction, and follows the formula:
 
H 2 O 2 +Fe 2+ ═OH.+OH − +Fe 3+ 
 
     In use, a dense mist is generated in the interior of the chamber  10  through discharge of atomised ozonised liquid via the ozone sprayheads  30   a  and atomised liquid having ferrous ions via the ferrous sprayheads  30   b . The atmosphere within the interior of the chamber  10  thus becomes saturated with free radicals resulting from the catalysed breakdown of the ozone of the discharged ozonised liquid and the hydrogen peroxide. 
     To ensure that the free radical saturated atmosphere does not leak out to the general environment in which the apparatus is placed, the pumped chamber exhaust  18  generates a slight negative pressure within the chamber  10  by recirculating a portion of the free radical saturated atmosphere (arrow C) and promoting the ingress of ambient air through air inlet  16  (arrow D). 
     Produce to be decontaminated or sterilised is introduced into the chamber  10  through produce inlet  12  (arrow E). The produce is first subjected to a spray of the liquid having the ferrous ions from the ferrous sprayhead  30   b  at the beginning of the flow path A. This initially coats the surface of the produce with liquid having ferrous ions. The produce is then exposed to the ozonised liquid from the next ozone sprayhead  30   a . This ensures that free radical generation is strongest on the surface of the produce. 
     The produce travels on the upper conveyor belt  24  and moves along the rest of the flow path A through the dense free radical saturated atmosphere within the chamber  10 . Depending on the produce and the length of time needed for sufficient decontamination, the speed of the conveyor belts  24  and  26  can be adjusted. 
     The produce drops through the vertical spacing between the upper and lower conveyor belts  24  and  26 . This enables the entire exterior surface of the produce to be fully exposed to the free radical atmosphere as it passes through the vertical spacing, and also the positioning of the produce to be altered from one conveyor belt  24  to the conveyor belt  26 , thereby allowing other surfaces of the produce to be exposed to the free radical atmosphere for an extended period. 
     Again, depending on the produce, the distance of the vertical spacing between the upper and lower conveyor belts  24  and  26  will be pre-adjusted to prevent damage to the produce. 
     On reaching the end of the flow path A, the produce exits the chamber  10  through the produce outlet  14  (arrow F) and is collected by any suitable means. 
     By the generation and use of free radicals, a powerful oxidising agent and biocide can be utilised to decontaminate produce. This can be enhanced by the use of Fenton&#39;s Reaction and the incorporation of a second liquid having ferrous ions. 
     The volume of liquid necessary to produce the dense free radical saturated atmosphere within the chamber is nominal, and is preferably two to four liters per hour per sprayhead. By way of example, a chamber having twenty sprayheads therefore uses no more than eighty liters of water per hour. Such a chamber has a produce decontamination capacity of several hundred kilograms per hour. 
     It is thus possible to provide apparatus which can decontaminate or sterilise produce without the need for submersion in a chemically treated liquid. It is also possible to provide apparatus which dramatically reduces the amount of liquid required for decontaminating produce. 
     The embodiment described above is given by way of example only, and modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined by the appended claims.