Preservation and rapid ripening of fruit, vegetables and other food products in refrigerated containers by the use of modern and technologically sophisticated processes plays an important part in maintaining intact the high quality of the food items concerned.

These technological processes therefore constitute a fac¬ tor for raising income but such is their cost that their use is only economically viable for high grade products of excellent appearance and flavour.

Not only must the physical conditions (temperature, humi¬ dity, ventilation) of the air be maintained but also the level of purity which the natural atmosphere possesses when the process is commenced.

This applies both to composition of atmospheric gases ^" and also to the quantity of bacteria present.

What occurs now however is that, in certain complex meta- bolical processes, various gases and volatile substances are given off in the refrigerated compartments and these

seriously pollute the atmosphere to the extent that nega¬ tive consequences follow.

Condensation of water in particular frequently exposes the products to attack by harmful bacteria and germs which proliferate in an uncontrolled manner leading to develop¬ ment of epidemicts and to the growth of fungi. At present, therefore, various techniques and methods are adopted for cleaning and sterilizing the air inside the refrigerators . During the process of preservation permanganate of potas¬ sium is used on balls of alumina on whose surfaces oxidat ion of ethylene takes place.

To remove CO , volatile substances and unpleasant odours while ripening is in progress, ventilation either manual or automatic is provided.

Bacteria and germs are eliminated by specific chemical pro¬ ducts such as fumigants and others spread throughout the environment by nebul izat ion . Even so, use of these products leaves some problems unsolved. Regulations now in force, especially those issued by the EC, severely limit the use of such products by establishing maximum quantities and tolerances of residual chemicals remaining on fruit and on other food products. Effectiveness of many such chemical products is known to be low.

The organoleptic properties, especially of fruit and vege¬ tables, often suffer from use of these products and the presence of 'additives as well as of unpleasant odours may be clearly noted. The above invention offers great advantages compared with techniques at present in use and solves many serious prob¬ lems as will be explained below.

Subject of the invention is a process for cleaning air, particularly that in refrigerators for preserving and ripening fruit vegetables and other food, based substan¬ tially on circulation of air by means of a set of filters consisting of granules of zeolite of a macroreticula e and microporous structure.

Where preservation is concerned, the zeolite granules are activated by placing them in a bath of permanganate of potassium to remove the ethylene by oxidation and fix- ing. Associated with the zeolite filters are UV lamps whose photolithic properties sterilize and disinfect the air .

This process is put into effect using an apparatus which, in one preferred construction, consists of a wall-mounted parallelepiped structure with a grid at the top, downward inclined at 45 °. through which air enters, electric centri¬ fugal fans, a dust filter, UV lamps, zeolite filters which may or may not need to be activated by a permanganate of potassium bath, and an air outlet grid at the bottom in- clined upward at 45°.

The filters preferably lie horizontal and the granules rest on a fine net fixed onto a frame.

The UV lamps are placed parallel to the filters.

Air is drawn into the apparatus upstream of the filters and is expelled downstream of the lamps and filters.

The electric centrifugal fans are placed inside the appara¬ tus underneath the upper grid.

Air speed can be regulated by a speed variator. The filtering effect can be modified by selecting the num- ber of filters, by air speed and by intensity of the lamps, varying their number and power; a suitable programmer is

used to carry out the cycles of treatment automatically establishing operating and non-operating stages of some or all of the lamps and of some or all of the fans. Remote operation through a control panel can be used to turn the lamps and fans on and off, program cleansing of the air, vary air speed and quantity, and the intensity of radia¬ tions by keeping on, or turning off, some lamps and fans.

There are clearly many advantages to be obtained by this process . The active surface of the zeolite filters is three or four times greater than that of present filters as an ionic exchange of absorption takes place inside the pores of the granules as well as outside.

Pressure of air inside the apparatus prevents oxidation and clogging of the pores since the volatile waste products from metabolism cannot accumulate and so are not reabsorbed.

Pressure of air also inhibits growth of fungi and moulds

(spores) that develop in refrigerated compartments.

No specialized operators are needed. Sterilization of air is automatic and can be continuous.

The process can be used for all types of fruit and foodstuffs without exception since it is non-toxic, odourless and does not generate ozone.

With this system the organoleptic properties of fruit and vegetables kept in the refrigerated compartments suffer no adverse effects .

The environment and the products inside the apparatus receive uniform treatment , even in the innermost recesses, by air that circulates and recirculates under pressure through the filters and on the lamps.

As the process inhibits the ripening stage, pulp does not soften but, remaining firm, is less subject to attack by fungi.

Synergia between absorption of ethylene and s erilization of the air by UV rays makes fruit resistent in a way that would not be possible if the processes were separate. Similarly, synergic action by the UV rays and permitted chemicals or fumigators is highly effective.

The filters can be easily changed according to whether the process required is for preserving or ripening. Sterilization can be carried out in operating or storage environments throughout the voids and solids of the food- stuffs treated.

While with present systems there is always a risk of em¬ ploying quantities of additives and fumigators greater than permitted levels, both during refrigeration and in other stages of the work such as washing, sizing, drying etc. , the above method avoids any such risk.

While the process is proceeding, staff can enter the treated environment, the process being harmless as radiation is not directed outward but remains inside the apparatus. Staff can gain access at any time since doors, where needed, can open and close without impediment.

A new external contaminated area would, within a few hours, become automatically sterile after possible contamination by persons, other goods or mechanical systems. More filters containing active carbon, useful for elimina- ting other gases, especially ozone, can with advantage be associated to the zeolite filters.

The UV lamps can be situated upstream or downstream of the filters as preferred. The advantages of the apparatus may be summarised thus: less labour and chemicals are needed making the process less expensive to run and providing greater security while attain ing results, from a technological standpoint, of the highest level

Characteris ics and purposes of the invention will be made still clearer by the following example of its execution illustrated by diagrammat ica1ly drawn figures. Fig. 1 Wall-mounted apparatus for cleaning the air. Fig. 2 Control unit for working the apparatus.

The apparatus 10 consists of a metal structurel l with two chambers, an upper one 12 and a lower one 13, both closed by grids, respectively 14 and 15, inclined at about 45° and comprising two doors, 16 and 17, at the front that open on horizontal hinges, 24 and 25 respectively.

The upper chamber 12 contains the electric centrifugal fans 20 and 21 with motors 22 and 23 to draw in air from outside through the grid 14, pass it through ducts 18 and 19 inside the intermediate chamber 30 to the point of exit through the lower grid 15.

Inside the intermediate chamber 30 is a dust filter 40 above, fitted into pairs of lateral supports 41 and 42. Below said filter 40, on the pairs of lateral supports 5! and 52, is the frame 50 for two rectilinear UV lamps 53 and 54. Below said lamps 53 and 54 is a set of horizontal filters 60 sustained by pairs of lateral supports 61 and 62. Each filter 60 consists of a wooden rectangular frame 65 on which granules 70 of zeolite, of a macroreticular and microporous structure, rest on a fine net 66. For the preserving process said granules are made active by immersion in a bath of permanganate of potassium. These filters cannot therefore be regenerated. The UV lamps, by photolithic action, thoroughly disinfect and sterilize the air. The control panel 80 for remote operation is connected by a cable 81 to the apparatus 10.

Visible items of the apparatus include the programmer 82, the timer 83, amperometer 84, switch 85 for the lamps, pilot lights 86, 90 to show that the lamps are lit, fuses 87, 91, pilot lights 88, 92, to show that the motors 21 and 23 for the electric fans 20 and 21 are working, and the switch 89 for said motors, 22 and 23.

The air, drawn in by electric fans 20 and 21, passes through the upper grid 14, through the cartridge 40 and having passed by the lamps 53 and 54, carries on through the set of filters 60 to emerge again through the lower grid 15.

Speed of air passage is such as to permit removal of gaseous substances and impurities, generally present in the environ¬ ment, and which are then deposited in the filters. The UV lamps irradiate the air, sterilizing it and, by photo- lithic action ,e1iminate microorganisms, yeasts (spores) and fung In the ripening process the air leaves the apparatus steri¬ lized and cleaned since the zeolite granules hold back impu¬ rities and gaseous substances such as carbon dioxide, ammonia sulphur dioxide, hydrogen sulphide and other volatile and noxious products that develop inside the refrigerator due to the intense metabolic process during stages of ripening. Oxidation and clogging of the pores is prevented as, during ventilation, the volatile waste products , created by metabolic changes , cannot accumulate and are therefore not reabsorbed. During the process of preservation the zeolite granules of the filters, activated by the bath of permanganate of potas¬ sium, react by oxidizing and fixing the ethylene produced by the ^' fruit . In all cases the air sterilized by UV rays kills germs and inhibits certain organisms and growth of fungi.

The fungi and moulds that generally form in refrigerated containers are carried away by air thrust from the fans thus

improving the organolep ic ' properties of the products. It is clear that the apparatus and the process obtained by means of it can be used not only in refri eration but in many other places such as warehouses, storerooms for production and preservation of dried or dehydrated foods, in laboratories and in the production of pork products, cheese and bread, in vineyards and in nurseries, in pro¬ cesses for the fermentation of paper, in the milk and dairy industries, in agriculture and in transport generally