IMPROVEMENTS IN OR RELATING TO THE STORAGE OF POTATOES

Abstract: The invention relates to potato storage arrangements and is particularly advantageous in arrangements substantially sealed against the surrounding atmosphere. In one embodiment the arrangement includes means for circulating the atmosphere in the store upwardly through the potatoes and samples of the atmosphere are examined by analytical techniques to monitor one or more volatiles in said atmosphere. When the level of the monitored volatile(s) falls below or rises above a predetermined level the potatoes are exposed to a treatment material, for example a sprout growth regulator or a pest disease treatment material, preferably a volatile treatment material released into the atmosphere to pass upwardly through the potatoes. The application of the treatment material continues until a calculated volume has been released or as the value of the monitored volatile material reaches a predetermined level. In a preferred embodiment the monitored volatile is dimethylnaphthalene and the treatment material is dimethylnaphthalene and/or diosopropylnaphthalene.

Description: "IMPROVEMENTS IN OR RELATING TO THE STORAGE OF POTATOES" This invention relates to a method of, and apparatus for, storing potatoes and has particular application to the long term storage of ware and seed potatoes. It is well known in the art to keep potatoes in long term storage dormant by maintaining the potatoes at low temperature but such storage requires purpose-built storage facilities, which are expensive to to build and equip, and such storage facilities are expensive to operate. It is also well known in the art to keep potatoes dormant by dosing the potatoes with chemicals, which may kill off the sprouting organs of the potatoes or simply delay the sprouting of the potatoes. A further problem with potatoes stored for prolonged periods is attack by pests and disease and in conventional methods for storing this threat is countered by applying pest and disease control chemicals to the stored potatoes. Such sprout control, pest control and disease control chemicals as have been used todate have been contact chemicals, applied to the potatoes as a dust, spray, or the condensates of a vapour, and which methods of application inevitably lead to localised underdosing or overdosing of the stored potatoes. Such prior art chemicals as are commercially used to- date are foreign to the potato chemistry and the residues of many of such chemicals in the potatoes have been found to be detrimental to the end user. In the event, public opinion is strengthening against the use of contact chemicals, particularly when the stored potatoes are intended for human consumption. The potato, in its natural dormant period, is now known to emit volatile materials and the present applicant became aware that the said emissions included certain alkyl naphthalenes, including dimethylnaphthalene. Experiments showed the value of dimethylnaphthalene as a sprout growth regulator and the applicant's discovery was published in European Patent Publication No.0168094. In subsequent experiments the applicant proved the value of di-isopropylnaphthalene as an effective sprout growth regulator and this discovery was published in the P.C.T. Patent Publication No.888249. In both the above identified publication the proposal was to apply the chemical to the potatoes by conventional methods. Potatoes in storage are also susceptible to attack by pests and diseases and it is known to treat the potatoes with chemical compositions to slow down or eradicate the pests or disease by one of the above contact methods. The present invention seeks to provide a method of, and apparatus for, storing potatoes. According to the present invention there is provided a method for storing potatoes comprising the steps of monitoring the level of at least one volatile in the atmosphere surrounding the potatoes and exposing said potatoes to a treatment material when the level of the monitored volatile material rises above, or falls below, a predetermined value or range of values. In a preferred embodiment the method comprises the steps of exposing said potatoes to a volatile treatment material by releasing the volatile treatment material into the atmosphere surrounding the potatoes. Preferably the method is characterised by the steps of identifying the onset of volatiles produced by the potatoes in the atmosphere surrounding the potatoes and thereafter monitordLng the level of at least one volatile in the said atmosphere and exposing said potatoes to a treatment material when the level of the monitored volatile material rises above, or falls below, a predetermined value or range of values. In one eπ±iod-Lment the method is characterised by the steps of selecting the treatment material to be a sprout growth regulator and exposing said potatoes to the said treatment material when the level of the monitored volatile material falls below a predetermined value. In another eπfoodiment the method is characterised by the steps of selecting the said treatment material to be a pest or disease control material and exposing the potatoes to said treatment material when the level of the monitored volatile material rises above a predetermined level. Preferably the method is characterised by the steps of exposing the potatoes to the treatment material or materials by any one or more of the conventional methods for applying treatment materials to potatoes in store. In one embcidiment the method is characterised by the steps of selecting the treatment material to be identical to the monitored volatile material. In another embodiment the method is characterised by the steps of exposing the potatoes simultaneously to a treatment material identical to the monitored volatile material and at least one other treatment material. Preferably the method is characterised by the steps of selecting the monitored volatile material to comprise one or more alkyl naphthalene materials and selecting the treatment material to comprise one or more of the alkyl naphthalenes. In one preferred embodiment the method is characterised by the steps of selecting the monitored volatile material to comprises dimethylnaphthalene. In another preferred ernbodimen the method is characterised by the steps of selecting the treatment material to comprises, or include, di-isopropylnaphthalene. Preferably the method is characterised by the steps of selecting the said predetermined level of the monitored volatile material at which the potatoes are to be exposed to the treatment material to be below 10 mg m~ 3 and, more preferably, below 5 mg m . In one embodiment the method is characterised by the steps of terminating the supply of treatment material to the potatoes when the level of the monitored volatile material reaches a predetermined level. In another eπibodiment the method is characterised by the steps of terminating the supply of treatment material to the potatoes when a predetermined volume of said treatment material has been released into the potatoes. In such an embodiment the method preferably includes the steps of calculating said predetermined volume of treatment material to be applied by a calculation based on the volume of the potatoes. Preferably the method is characterised by the steps of storing the potatoes in a store substantially sealed from the surrounding atmosphere, causing the atmosphere in the store to circulate upwardly through the stored potatoes and introducing the treatment material into the circulating atmosphere in the lowermost regions of said circulating atmosphere. The invention also envisages apparatus for storing potatoes characterised by monitoring means for monitoring the level of a volatile material in the atmosphere surrounding the potatoes and means for exposing the potatoes to a treatment material when the level of the monitored volatile material rises above, or falls below, a predetermined value or range of values. Preferably the apparatus comprises a potato storage facility including means for generating circulating air flows in the atmosphere surrounding the potatoes, said air flows passing upwardly through the stored potatoes. Preferably the apparatus includes means for extracting samples of the atmosphere surrounding the potatoes and supplying said samples to said monitoring apparatus. In one embodiment the apparatus is characterised in that the means for extracting samples of the atmosphere surrounding the potatoes comprises at least one aspiration tube arranged with one of its ends buried in the stored potatoes. Preferably the apparatus includes means for placing the, or each, aspiration tube under a negative pressure whereby atmosphere surrounding the potatoes is drawn into the, or each, aspiration tube at a substantially constant rate. Preferably the monitoring apparatus means comprises means for monitoring the volatile material by anylitical techniques. In one embodiment the apparatus is characterised in that said monitoring means comprises, apparatus for practising gas chromatographic analysis techniques on samples of the atmosphere surrounding the potatoes. In another eπibodiment the apparatus is characterised in that said monitoring means comprises a photofluorimetric apparatus. In a further eπώodiment the apparatus is characterised in that the said monitoring means comprises an optical sensing apparatus. The invention will now be described further by way of the example with reference to the accompanying drawings in which the single figure shows, diagraramatically, a vertical cross-section through a potato storage facility in accordance with the invention, In the eπ-boάxment illustrated in Fig. 1, a store 11, for storing potatoes 12, is substantially sealable against the atmosphere surrounding the store 11. The potatoes 12 may be stored in random heaps or in stacked containers. The store 11 includes air ducts 13 below the potatoes 12, in a custom built storage facility 11 the air ducts 13 may be below the floor level 11a of the store 11 but for some storage facilities the air ducts 11a may be formed by "A" frames or perforated plates upon which the potatoes are placed when the potatoes 12 are in random heaps, or by the containers for the stored potatoes 12 spacing the stored potatoes above the floor 11a of the store 11. The store includes a fan arrangement 14 arranged, to supply air taken from the atmosphere above the potatoes 12, to the air ducts 13, whereupon said supplied air is delivered into the lower regions of the stored potatoes 12, to circulate through the stored potatoes 12 before rising above the said stored potatoes 12. The store 11 also includes sampling means, in the form of ducts 15 entered into the stored potatoes 12 in spaced apart relationship, and extractor means 16 for extracting air from each of the ducts 15 in a predetermined order. The extractor means 16 is arranged to take a predetermined volume of air from each of the ducts 15 in the predetermined order and to pass each sample to a monitoring apparatus 17 arranged to monitor the level of a volatile material in each sample of air supplied thereto. The monitoring apparatus 17 may conveniently comprise any means capable of determining the level of the desired volatile material to be monitored from the air samples supplied from the ducts 15. By way of one example, said monitoring apparatus 17 may include means for collecting volatiles in the gas samples on an adsorbent medium for examination by gas chromatographic analysis techniques. In another method for monitoring alkyl naphthalene volatiles the monitoring apparatus includes a continuous flow cell through which the volume samples of atmosphere from the ducts 15 are passed in succession and the flow cell forms part of a photofluorimetric apparatus. By passing a predetermined wavelength through the volatile laden atmosphere passing through the flow cell the molecules of the alkyl naphthalene volatile are caused to fluoresce, and the collected wavelength can be used to determine the levels of the alkyl naphthalene in the collected samples of atmosphere. The wave length of the emitting high intensity radiation for activation of the molecules of alkyl naphthalene will be in the region of 280 m u and the fluorescence wave length will be in the region of 330 m u. The monitoring system 17 may also comprise, or include, means for detecting and monitoring the levels of volatiles resulting from attack by pests or diseases and the treatment volatile material known to be effective for the treatment of the pest or disease and capable of being volatilized. By way of example 2-amino butane is known to be effective in controlling a number of diseases and the volatile of 2 amino butane can be readily monitored by optical sensing means. Using such a technique levels of dimethylnaphthalene lower than 5 mg " ^ can be detected. The ducts 15 and the gas sample passages therefrom to the monitoring apparatus are preferably lipophobic, to prevent error by adsorption. The apparatus described above may conveniently be operated by a continuous monitoring of samples of the air extracted from the ducts 15. In another method for operation the samples of air from the ducts 15 are monitored only over prescribed periods. In practising this second method there may be relatively long periods of reduced disturbance of the air surrounding the potatoes and, as the potato will not initiate the growth cycle for some time after being placed in storage and/or whilst the temperature in the store is below a predetermined temperature, the monitoring of the atmosphere below that temperature may be unnecessary. In the event, even when the temperature and humidity of the atmosphere surrounding the potatoes is ideal to initiate the growth cycle, the potato reacts slowly to its environment and the sampling of the atmosphere once a day may be sufficient to maintain and effective monitoring of the stored potatoes 12. In one method for operating the store the monitoring apparatus 17 is arranged to monitor the level of the volatile dimethylnaphthalene in the atmosphere samples supplied thereto and, when the monitored value of the dimethylnaphthalene falls to a predetermined value, for example, below 5 mg. m~ 3 of the sample of atmosphere, and the treatment may be maintained until the monitored level reaches 20 mg m-3 when the release of the treatment volatile material is terminated. The volatile treatment material may comprise any conventional volatile dosing material known to have a sprout growth regular effect, or a volatile pest or disease control chemical, and may be applied by conventional means. IJI one method for operating the treatment volatile material may conveniently be released into the atmosphere in the store by placing a tray 18, which may include a wick or wicks (not shown), containing said volatile material in the outlet duct of the fan arrangement 14 and starting said fan 14, whereupon the air flows over the tray 18 causes vapours of the dosing volatile material to be entrained by said flows and carried along the ducts 13 to the atmosphere surrounding the potatoes and the level of the dosing volatile material in the atmosphere will be increased thereby. When the dosing material is an alkyl naphthalene and the monitoring apparatus 17 is monitoring an alkyl naphthalene the tray 18 of treatment chemical may be left in the air flow to the ducts 13 until the level of the monitored volatile material rises above a predetermined value, when the tray 18 may be removed from the air duct. In another method for operating a predetermined volume of alkyl naphthalene, for example dimethylnaphthalene or di- isopropylnaphthalene, is placed in the tray 18 and allowed to remain in the air flow until all the chemical has volatilised. The amount of dosing chemical required to be placed in the tray can be calculated as the amount of chemical required to raise the value of the monitored volatile material from the detected level to a desired level in the air volume surrounding the potatoes. In other embodiments the apparatus may include other means for dosing the air flow with the dosing volatile material and, by way of example, the apparatus may include conventional atomising means in said air flow. As stated hereinbefore, the treatment chemical can be the same material as the monitored material, or another volatile material beneficial to the storage of the potatoes. By way of example, the monitoring apparatus 17 may be arranged to monitor the level of dimethylnaphthalene in the atmosphere and the dosing material may comprise di- isopropylnaphthalene, which is now known to exhibit sprout growth control properties and pest and disease control properties. As di-isopropylnaphthalene is an alkyl naphthalene analysis of the monitored volatile material will show the sum total of alkyl naphthalenes in the monitored atmosphere. Further, the treatment volatile material may comprise more than one volatile material and may, for example, comprise the monitored material, or a substitute therefore, together with an additional volatile pest or disease control material. Whilst the monitoring apparatus 17 may not be capable of monitoring the said additional volatile material the level of the additional volatile material in the atmosphere can be readily deduced by the volumetric level of said additional material in relation to the level of the added monitored material and/or by calculation based on the volume of potatoes in the store 11 or the volume of the store 11. Further, the method is not restricted to the monitoring of a volatile material emitted from the potatoes 17, and may comprise the monitoring of any volatile material in the atmosphere in the store 11. I the event it will now be appreciated that in a preferred embodiment the method proposed by the present invention seeks to utilise the natural emissions from the stored potatoes to maximum advantage and to add dosing materials to the atmosphere surrounding the potatoes only when required, so that only a relatively small amount of dosing chemical is necessary to maintain the potatoes in good condition for prolonged periods. A further advantage of the method proposed by the invention is that the problems of overdosing and underdosing are effectively avoided, as also are the problems of undesirable residues in the potatoes. Whilst in the foregoing description the fan 14 has been described as operating only when additional volatile material is being added to the atmosphere in the store 11, the fan arrangement 14 may be operated at other times to perform other functions and may, for example, be operated simply to "stir" the atmosphere in a large store, to distribute the volatiles in the atmosphere more uniformly throughout the store 11. Further, the store may be provided with means for monitoring the ratio of carbon dioxide to oxygen levels in the store 11. With such an arrangement the fan arrangement 14 may include an inlet, selectively connectable to the atmosphere surrounding the store 11, and the store will include vents, selectively openable to the atmosphere surrounding the store 11. On detecting an undesirable carbon dioxide/oxygen ratio, the fan arrangement may be operated to blow fresh air into the store to restore the carbon dioxide/oxygen ratio to a more desirable ratio. It will be appreciated that after using such a facility the level of the monitored volatile material in the atmosphere surrounding the potatoes may fall below that level at which the dosing volatile material will be released into the atmosphere and preferably the apparatus includes means for preventing release of the treatment volatile material until the monitored volatile material has stabilized, thus to avoid unnecessary application of the dosing material.

Claims: C AIMS 1. A method for storing potatoes comprising the steps of monitoring the level of at least one volatile in the atmosphere surrounding the potatoes and exposing said potatoes to a treatment material when the level of the monitored volatile material rises above, or falls below, a predetermined value or range of values. 2. Amethod according to claim 1, comprising the steps of exposing said potatoes to a volatile treatment material by releasing the volatile treatment material into the atmosphere surrounding the potatoes. 3. A method according to claims 1 or 2, characterised by the steps of identifying the onset of volatiles produced by the potatoes in the atmosphere surrounding the potatoes and thereafter monitoring the level of at least one volatile in the said atmosphere and exposing said potatoes to a treatment material when the level of the monitored volatile material rises above, or falls below, a predetermined value or range of values. 4. A method according to claims 1, 2 or 3, characterised by the steps of selecting the treatment material to be a sprout growth regulator and exposing said potatoes to the said treatment material when the level of the monitored volatile material falls below a predetermined value. 5. A method according to claims 1, 2, 3 or 4, characterised by the steps of selecting the said treatment material to be a pest or disease control material and exposing the potatoes to said treatment material when the level of the monitored volatile material rises above a predetermined level. 6. A method according to claims 1, 2, 3, 4 or 5, characterised by the steps of exposing the potatoes to the treatment material or materials by any one or more of the conventional methods for applying treatment materials to potatoes in store. 7. A method according to any one of the preceding claims, characterised by the steps of selecting the treatment material to be identical to the monitored volatile material. 8. A method according to any one of the preceding claims, characterised by the steps of exposing the potatoes simultaneously to a treatment material identical to the monitored volatile material and at least one other treatment material. 9. A method according to any one of the preceding claims, characterised by the steps of selecting the monitored volatile material to comprise one or more alkyl naphthalene materials and selecting the treatment material to comprise one or more of the alkyl naphthalenes. 10. A method according to any one of the preceding claims, characterised by the steps of selecting the monitored volatile material to comprises dimethylnaphthalene. 11. Amethod according to any one of the preceding claims, characterised by the steps of selecting the treatment material to comprise, or include, dimethylnaphthalene. 12. A method according to any one of the claims 1 to 10 inclusive characterised by the steps of selecting the treatment material to comprises, or include, di-isopropylnaphthalene. 13. Amethod according to any one of the preceding claims, characterised by the steps of selecting the said predetermined level of the monitored volatile material at which the potatoes are to be exposed to the treatment material to be below 10 mg 14. A method according to claim 3, characterised by the steps of selecting the said predetermined level of the monitored volatile material at which the potatoes are to be exposed to the treatment material to be below 5 mg m~ 3 15. A method according to any one of the preceding claims, characterised by the steps of terminating the supply of treatment material to the potatoes when the level of the monitored volatile material reaches a predetermined level. 16. A method according to any one of claims 1 to 14, characterised by the steps of terminating the supply of treatment material to the potatoes when a predetermined volume of said treatment material has been released into the potatoes, 17. A method according to claim 16, characterised by the steps of calculating said predetermined volume of treatment material to be applied by a calculation based on the volume of the potatoes. 18. A method according to any one of the preceding claims characterised by the steps of storing the potatoes in a store substantially sealed from the surrounding atmosphere, causing the atmosphere in the store to circulate upwardly through the stored potatoes and introducing the treatment material into the circulating atmosphere in the lowermost regions of said circulating atmosphere. 19. Apparatus for storing potatoes characterised by monitoring means for monitoring the level of a volatile material in the atmosphere surrounding the potatoes and means for exposing the potatoes to a treatment material when the level of the monitored volatile material rises above, or falls below, a predetermined value or range of values. 20. Apparatus according to claim 19, characterised by a potato storage facility including means for generating circulating air flows in the atmosphere surrounding the potatoes, said air flows passing upwardly through the stored potatoes. 21. Apparatus according to the claim 20 or 21, includes means for extracting samples of the atmosphere surrounding the potatoes and supplying said samples to said monitoring apparatus. 22. Apparatus according to claim 21 characterised in that the means for extracting samples of the atmosphere surrounding the potatoes comprises at least one aspiration tube arranged with one of its ends buried in the stored potatoes. 23. Apparatus according to claim 21 characterised by means for placing the, or each, aspiration tube under a negative pressure whereby atmosphere surrounding the potatoes is drawn into the, or each, aspiration tube at a substantially constant rate. 24. Apparatus according to any one of the preceding claims characterised in that the monitoring arrangement is arranged to monitor its level of the monitored volatile by anylitical techniques. 25. Apparatus according to claim 24 characterised in that said monitoring means comprises, apparatus for practising gas chromatographic analysis techniques on samples of the atmosphere surrounding the potatoes. 26. Apparatus according to claim 24 characterised in that said monitoring means comprises a photofluorimetric apparatus. 27. Apparatus according to claim 24 characterised in that the said monitoring means comprises an optical sensing apparatus. 28. Apparatus, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Inventors: EVERST-TODD SELWYN, EVERST-TODD, SELWYN
Applicants: OULTON RICHARD JOHN, OULTON, RICHARD, JOHN
Application year: 1992
Main classification: A23B7
IPC codes: A23B7