It is known that vegetable foodstuffs, i. e. vegetable foodstuffs such as fruit, vegetable, leafy vegetables (lettuce), grains or the like are often treated once or even several times with plant protection sprays prior to harvesting them in order to ward off certain pests or diseases. These sprays having insecticide, pesticide, fungicide or herbicide effects should, as a general rule, be removed at least partly before consumption.

It is also known to apply a thin layer of wax on particular types of fruit, and here in particular apples, after the harvest in order to improve their preservability.

Moreover there is frequently the problem that harvested vegetable foodstuffs, besides spray residues, also present adhered dirt in the form of sand, soil, peat, straw etc. The like impurities must be removed prior to preparation or ingestion.

Nearly complete removal of spray residues and even mere cleansing of vegetable foodstuffs does, however, present difficulties for the following reasons, or involves the following problems in normal households:

Plant protection sprays are generally adjusted to be hydrophobic, i. e. water-repellent, to thereby prevent freshly applied sprays from being washed off again by precipitations. This fact and the frequently irregular or rough surface structure of particular vegetable foodstuffs, where not entirely precluding the removal of spray residues by mere rinsing in water, at least causes the removal to be very incomplete because owing to the hydrophobic properties of the sprays and/or a rough surface the spray residues can only be removed most incompletely. Although the cleaning effect of a water bath may be aided by additionally rubbing the vegetable foodstuffs by hand, i. e. by genuinely "washing"them, this is nevertheless only practicable or possible for certain types of vegetable foodstuffs but is not acceptable in a large number of cases, particularly where the type and texture of the plant product in question does not allow for such additional manual surface treatment. As examples for this type, leafy vegetables such as lettuce, spinach, as well as delicate small fruits such as raspberries or strawberries may be named.

This problem, i. e. the hydrophobic properties of the coating, is manifest in the same manner in the case of waxed apples and the like.

The cleansing or removal of other types of impurities, e. g. soil or sand, is problematic whenever the surface property of the plant product in question ensures good adhesion of such impurities, rendering easy rinsing off impossible. Examples for this are again small fruits, for instance raspberries or strawberries having a sensitive surface structure, or

vegetables having a particularly rugged surface structure, such as broccoli or cauliflower.

Adhesion of spray residues or wax resulting from their hydrophobic properties can to some extent be counteracted by adding to the cleaning water an auxiliary cleaning agent or cleaning substance, for instance a surfactant, which reduces the surface tension of the water and thus ensures a better cleaning effect. The problems related to the circumstance that certain vegetable foodstuffs are not capable of withstanding a manually performed washing or cleaning process, or only while suffering certain damage and thus losses of quality in the process, however, are thereby not eliminated.

From Chinese Patent Application No. 80 20 1393 a device relying on vibration for cleaning sensitive objects, for example fruit or the like, has become known. This known device comprises an elongate conveyor trough, at one end of which a charging hopper is provided and at the other end of which a removal opening is provided. The conveyor trough can be vibrated by means of vibration generators mounted on the conveyor trough in such a way that the goods present in the conveyor trough are moved along its longitudinal direction from the charging end to the removal end. Above the conveyor trough a plurality of spraying nozzles are arranged which downwardly spray water including an admixture of cleaning agent in a first section of the conveyor trough and, in a second section, downwardly spray pure water as the rinsing fluid. Underneath the floor of the conveyor trough, which has the form of a perforated plate, a number of

flat receiving trays is arranged so that water arriving from the spraying nozzles initially wets the objects located on the conveyor trough, i. e. for example fruit or vegetables, then passes through the perforated bottom plate of the conveyor trough and enters into the receiving trays positioned underneath. Owing to the vibrations, the fluid located in the trays is also excited to perform oscillations such that this fluid will again splash upward, with the objects located on the conveyor trough being wetted or showered as a result not only from above but also sprinkled by the water splashing up from the receiving bowls located underneath. In the course of their passage from the charging end to the removal end, the objects are thus shaken or jolted by the vibrations, are in the process also imparted with a component of movement towards the discharge end, and are on all sides showered by cleaning fluid and subsequently by rinsing fluid.

This known device initially presents the drawback that, because of its very dimensions and stationary construction, it is utterly unsuited for use in the household; it rather represents an industrial-use cleaning device. Moreover only comparatively robust vegetable foodstuffs can be cleaned with it as those having a sensitive peel or surface (for example: strawberries, raspberries, kiwis, grapes and the like) would suffer damage.

In contrast, it is the object of the present invention to furnish a method for cleansing vegetable foodstuffs whereby smaller amounts of delicate vegetable foodstuffs, i.. e. in the household, may also be cleaned gently and yet thoroughly.

In order to attain this object, the present invention suggests to initially place the vegetable foodstuffs in a fluid, in particular in water, as is generally known per se up to this point. Moreover, in accordance with the teaching of the present invention, the fluid is agitated in such a way as to be permeated by oscillations which act on the outer surfaces of the vegetable foodstuffs, with the fluid being agitated by means of a device having the form of a fluid-tight housing which is immersed in the fluid together with the vegetable foodstuffs and is made to vibrate by means of a drive mechanism arranged inside the housing.

It was very surprisingly found that, as a result of the measures according to the present invention, i. e. by introducing into the fluid, together with the vegetable foodstuffs, a housing which is capable of being made to vibrate in such a way that the oscillations emanating from the housing are transmitted to the surrounding fluid, the fluid thus stimulated into oscillations gently as well as thoroughly acts on the outer surface of the vegetable foodstuffs, with adhering impurities being detached gently and yet very thoroughly. Owing to the integral structure having the form of the fluid-tight housing, it is also possible with the device to readily implement the method according to the invention for smaller batches, i. e. particularly in the household. It is sufficient to place the vegetable foodstuffs presenting impurities, together with the housing, into a suitable container filled with the fluid, for instance a sink, a plastic bowl or the like. Cleansing of the vegetable foodstuffs is obtained by the oscillations emanating from the

housing without any additional manual exertions on the part of the user, with these oscillations imitating cleaning motions applied by hand, however at a far higher frequency but lower intensity, whereby the cleaning process is rendered particularly gentle and yet thorough.

Advantageous developments of the invention constitute the subject matters of the appended claims.

The vibrations are preferably generated by means of an unbalance weight driven by an electromotor, said electromotor and unbalance weight being positioned inside the housing. This means that the housing accommodates the vibration or oscillation generator together with the associated drive means, such that the method according to the invention may be implemented by means of a compact apparatus which is essentially closed to the outside and easy to transport.

The vibrations are in a range of approx. 30-150 Hz, more precisely in the range of approx. 40-100 Hz, and in particular at approx. 50 Hz. Vibrations of less than approximately 30 Hz produce only an extremely weak cleaning effect or no cleaning effect at all, whereas oscillations or vibrations in excess of 150 Hz may already tend to attack and damage particularly sensitive vegetable foodstuffs.

Energy supply for generation of oscillations or vibrations is preferably achieved by means of a plurality of accumulators.

Switching on the energy supply is preferably effected in a contactless manner upon immersion of the housing into the washing liquid. This is achieved e. g. by two neighboring contact electrodes being located in close vicinity of each other on the outer surface of the housing which is exposed to the washing liquid, with these electrodes applying the load current to the consumer (s) via an amplifying circuit connected in series whenever an identical potential is provided between them on account of the surrounding washing liquid. It is therefore not necessary to provide a manually operable switch inside the housing.

Particularly whenever the impurities adhering to the vegetable foodstuffs must be expected to be hydrophobic, such as spray residues, wax or the like, it is moreover possible to add a suitable auxiliary cleaning agent such as, for instance, a surfactant to the water.

The surfactant may either be apportioned directly into the water, or a receiving chamber for the surfactant or the like adapted to cleaning vegetable foodstuffs may be provided in the housing.

The cleaning program may unfold in accordance with a memory chip incorporated into the housing, in particular one having the form of a ROM (read only memory).

Further details, aspects and advantages of the present invention will become apparent from the following description of. an embodiment by referring to the drawing, wherein:.

The single figure of the drawing shows a sectional view of an embodiment of a device which may be used for implementing the method according to the invention.

The device represented in the drawing and described herebelow is described in detail in PCT publication W095/27573. In view thereof, the content of its disclosure is herewith fully incorporated by way of reference.

A device according to the invention generally shown in the drawing under 2, whereby in the framework of the method of the invention vegetable foodstuffs are cleansed, comprises a housing 8 formed by an upper shell 4 and a lower shell 6, with the two shells 4 and 6 being connected to each other in the area of the equatorial plane by means of a watertight screw connection 10 or any other watertight connection which is capable of being released in a given case. Inside the inner space of the housing 8 defined by the shells 4 and 6, apart from an electromotor 12 a number of energy supply units, for example two batteries or accumulators 14 and 16 are provided, whereby the electromotor 12 is supplied with electrical energy.

Positional fixation of electromotor 12, energy supply units 14 and 16 and other associated components is achieved by supporting webs and ribs present in the lower shell 6, some of which are designated by reference numerals 18 to 22.

When the upper shell 4 has been removed from the lower shell 6, the inner space of the housing 8 is accessible whenever necessary, for example in order to

replace exhausted batteries with fresh ones, or in order to remove re-chargeable accumulators if these are used instead of the batteries, or to re-charge them in situ via a charging socket provided on the side of the housing. When the upper shell 4 has been removed, an electrical switch may furthermore be actuated in order to switch the electromotor 12 on and off.

Instead of a switch present inside the housing 8 for switching the electromotor 12 on and off, a switch controlled by potential and having the form of two contact surfaces arranged at a distance from each other may be provided on the outside of the housing 8, for example on the outer circumference wall of the lower shell 6, with a contact between the two contact surfaces being established by the more or less conductive washing water upon submersion of the device 2 into the washing water, and the electromotor 12 starting to operate automatically, as it were. When the housing 8 of the device 2 is subsequently removed from the washing water, the electromotor 12 automatically switches off. This embodiment is particularly preffered for practical use.

Charging the accumulators 14 and 16 may also be undertaken from the outside without having to open the housing 8, for example via inductive transmission of charging current.

On an output shaft 24 of the electromotor 12 a cam 26 is positioned. The free lower end of the output shaft 24 in Fig. 1 is held in a suitably configured support bearing 28. Upon a rotation of the electromotor 12 and thus of the output shaft 24, the cam 26 arranged

thereon in a rotationally fixed manner generates shaking or vibrating movements which are imparted to the surrounding water by the housing 8. The agitation or vibration waves propagate omnidirectionally in the water and effect corresponding vibrating motions at the dirt particles or impurities on the outside or peel of the vegetable foodstuffs. It was surprisingly found that these shaking or vibrating movements are capable of removing the dirt particles or impurities in an extremely gentle manner to the vegetable foodstuffs on the one hand, but very thoroughly on the other hand.

The motor speed is in a range of approximately 1,800 to 9,000 revolutions per minute, more precisely of approximately 2,400 to 6,000, in particular in a range of approximately 3, GG0 revolutions per minute. By means of the speeds indicated above, vibration frequencies of the cam 26 of approximately 30 to 150 Hz can be achieved. Frequencies of less than 30 Hz and in excess of 150 Hz produced no cleaning effects at all or only very inferior ones, whereas vibration frequencies of approximately 40 to 100 Hz and in particular of approximately 50 Hz achieved the best results.

A receiving chamber 30 may be formed in the housing 8 for an auxiliary cleaning agent which then, via a corresponding bore 32 in the wall of the housing 8, by and by leaves the receiving chamber 30 and passes into the water. An example for a like auxiliary agent is a surfactant which is specially adapted to cleaning vegetable foodstuffs and whereby in particular residues of hydrophobic sprays, wax and the like may be detached. Instead of being dispensed from the receiving chamber, the surfactant may also be apportioned

directly into the water. Concerning the selection of the auxiliary substance or agent, it is evident to the person having skill in the field of cleaning chemistry that such substances or agents may be fittingly selected for a respective purpose of use. Instead of, or in addition to a surfactant and the like it is, for example, also possible to use agents which not only detach but moreover neutralise the adhering spray residues. In any case, commercially available cleaning agents adapted to cleaning vegetable foodstuffs may be utilised without limitations in the method according to the invention.

The cleaning program may unfold in accordance with a memory chip incorporated in the housing, in particular one having the form of a ROM (read only memory) e. g. limiting the operation of the electromotor to a specific period of time.

The method according to the invention is carried out by proceeding in the following manner: A suitable vessel or a suitable container, for example a bowl, the kitchen sink or the like, is filled with water-which may have been slightly heated-with the possibility of adding a suitable surfactant or other auxiliary cleaning agent in accordance with need.

Suitable surfactants in particular for cleaning vegetable foodstuffs are commonly known so that a detailed discussion thereof may be omitted. The addition of a suitable surfactant in the adequate dosage is recommendable in particular when spray residues adhering to the, vegetable foodstuffs are to be removed inasmuch as their hydrophobic properties

frequently prevent obtention of the desired cleansing effect by water only. Where merely adhered impurities having the form of soil, sand or the like are to be removed from the vegetable foodstuffs, the addition of a surfactant may as a rule be omitted. The surfactant can possibly also be filled into the receiving chamber 30 to be disensed via the opening 32.

After placing the vegetable foodstuffs into the water, the housing with the drive mechanism located therein is added. Depending on the specific embodiment, either the drive mechanism must be actuated manually beforehand, or automatic actuation of the drive mechanism takes place as a result of the mechanism explained above. The drive mechanism actuates the vibration generator contained in the housing, i. e. the unbalance weight 26 located on the output shaft 24 of the motor 12 in the case of the represented embodiment, so that the housing is caused to vibrate or begins to oscillate. These vibrations or oscillations are imparted to the surrounding fluid-i. e. the water-by the housing wall, with these oscillations propagating virtually omnidirectionally in the water and acting on the surrounding vegetable foodstuffs or their surfaces, respectively. Owing to their inherent energy, the vibrations or oscillations impinging or acting on the soiled surfaces imitate manual washing or cleaning motions, i. e. rubbing or wiping motions, however at a considerably higher frequency while at the same time more gently, so that in the case of impurities adhering to the plant product surface, e. g. soil or sand, these impurities are detached gently, with impurities lodged in furrows or wrinkles also being reached and eliminated by the impinging vibrations or oscillations.

This is particularly advantageous in the case of vegetable foodstuffs having highly rugged or rough surfaces, such as broccoli, cauliflower or the like, which in the case of manual cleaning by mere rubbing motions are not cleaned to the same extent as with the method according to the invention in which the vibrations or oscillations can also reach impurities lodged in wrinkles or clefts. In the case of spray residues clinging to the vegetable foodstuffs, their thorough and moreover gentle removal is achieved in particular with the aid of a suitable surfactant.

Following a time period deemed adequate, or after termination of the internal program determined by the memory chip, the device is removed from the water, after which the cleansed vegetable foodstuffs- possibly following a rinsing process-may be further used.

Tests performed in the framework of the present invention have shown that even delicate fruit or vegetables can be cleaned extremely thoroughly and yet very gently by the method according to the invention.

The following table, in which test results have been recorded, shows this very clearly. Weight Weight with Weight of Weight % (wt.) Kind Initial after applied insecticide after cleansing weight initial insecticide cleaning cleaning 37. 402g 37. 402g 38. 493g 1. 091 g 38. 449g 96% Grape 43. 173g 43. 172g 43. 340g 0. 168g 43. 171 g 100% 45. 555g 45. 552g 45. 751g 0. 199g 45. 745g 97% 32.352g 32. 350g 32. 461 g 0. 111 g 33. 446g 99% Straw-28. 986g28. 986g-29. 172g0. 186g28. 951g 118% berry 24. 287g 24. 286g 25. 936g 0. 165g 24. 286g 100% 9. 772g 9.711g 10. 13lg 0. 360g 10. 109g 94% Lettuce 7. 819g 7.816g 8. 232g 0. 417g 7. 808g 101 % 10.358g 10.358g 10687g 0.329g 10.673g 96% 7. 15g 7.125g 7. 288g 0. 1 64g 7. 285g 98% Spinach 4.678g 4.685g 4.928g 0.243g 4.675g 104% 6. 809g 6.807g 7. 135g 0. 328g 7. 137g 101 % 2.047g 2.046g 2.278g 0.232g 2.046g 100% Parsley 1.562g 1.562g 1.858g 0.296g 1.569g 98% 1.701g 1.701g 1.892g 0.191g 1.895g 102% 180.356g 180.455g 0.099g 180.279g 177% Orange 176.561g 177.375g 0.814g 176.385g 122% 1 27. 754g 128. 711 g 0. 957g 127. 699g 106% 69. 201 g 70. 477g 1. 276g 69. 344g 88. 8% Kiwi 69.608g 70.433g 0.825g 69.652g 94.7% 72. 754g 74. 756g 2. 002g 72. 809g 97. 3% Tin foii 15. 895g 16. 291 g 0. 396g 15. 906g 98% test 15.917g 16.236g 0.319g 15.917g 100% strip 15.895g 16.434g 0.539g 15.895g 100%

The named kinds were at first subjected to initial cleaning with water where it was found that practically no cleansing effect was obtained (comparison between initial weight and weight after initial cleaning). Then an insecticide was applied by spraying, resulting in a weight increase between 2.002 g and 0.099 g.

Subsequently the respective vegetable foodstuffs were cleaned for 5 minutes in accordance with the method of the invention, wherein the water had received the addition of a surfactant designated"Juice Wash". This was followed by confirmational weight measurement in order to determine the weight proportion of the substances removed by cleansing. The above table clearly reveals that the cleaning effect due to the method according to the invention is quite considerable; in some cases (strawberries, lettuce, spinach, oranges and parsley) more than 100% (wt.) were removed by cleansing, thus demonstrating that the vibrations or oscillations penetrated even into minute recesses, wrinkles, pores etc. of the surface of the respective fruit or vegetable to there remove, besides the insecticide applied by spraying, even impurities which had not been grasped by the initial cleaning.