METHOD FOR THE STORAGE OF POTATO COMPRISING TREATMENT BY ETHYLENE AND 1-METHYLCYCLOPROPENE

Abstract

A method of storing potatoes includes providing a plurality of dormant potatoes, wherein the potatoes have been cured after harvesting; in a first treatment step, treating the potatoes with 1-methylcyclopropene by exposing the potatoes, which are at a first treatment temperature within the range of from 10 to 30° C., to 1-methylcyclopropene; storing the potatoes at a second storage temperature within the range of from 4 to 15° C.; and in a subsequent second treatment step during the storing step, treating the potatoes with ethylene by exposing the potatoes, which are at the second storage temperature, to ethylene.

Claims

1. A method of storing potatoes comprising the steps of: i. providing a plurality of dormant potatoes, wherein the potatoes have been cured after harvesting; ii. in a first treatment step, treating the potatoes with 1-methylcyclopropene exposing the potatoes, which are at a first treatment temperature within the range of from 10 to 30° C., to 1-methylcyclopropene; iii. storing the potatoes at a second storage temperature within the range of from 4 to 15° C.; and iv. in a subsequent second treatment step during the storing step, treating the potatoes with ethylene by exposing the potatoes, which are at the second storage temperature, to ethylene.

2. The method according to claim 1 wherein prior to the first treatment step ii, the cured dormant potatoes provided in step i have been maintained at a temperature of at least 10° C.

3. The method according to claim 1 wherein prior to the first treatment step ii, the cured dormant potatoes have not been subjected to a temperature pulldown to the second storage temperature.

4. The method according to claim 1 wherein the first treatment step ii is carried out for a first treatment period of at least 12 hours.

5. The method according to claim 1 wherein during the first treatment step ii the potatoes are stored in a store having a store volume, and the 1-methylcyclopropene is applied at a concentration of from 0.5 to 5 μL/L, wherein the concentration in μL/L is the ratio of the volume of 1-methylcyclopropene to the store volume.

6. The method according to claim 1 wherein the first treatment temperature is within the range of from 12 to 25° C., optionally within the range of from 12 to 22° C.

7. The method according to claim 1 wherein second storage temperature is within the range of from 8 to 13° C.

8. The method according to claim 1 wherein in the second treatment step iv the potatoes are treated continuously with ethylene so that, after initiation of the second treatment step iv, the potatoes are subsequently stored in an ethylene-containing atmosphere during the storing step iii.

9. The method according to claim 1 wherein during the storing step iii, and the second treatment step iv, the potatoes are stored in a store having a store volume, and the ethylene is applied at a concentration of from 5 to 20 μL/L, wherein the concentration in μL/L is the ratio of the volume of ethylene gas, measured under the pressure and temperature conditions of the storage step iii, to the store volume.

10. The method according to claim 1 wherein (a) the second treatment step iv is initiated after eye movement in at least one control potato stored in atmospheric air, of a plurality of control potatoes stored in atmospheric air, or (b) the second treatment step iv is initiated after eye movement in at least one of the potatoes.

11. The method according to claim 1 wherein the second treatment step iv is initiated at least 4 weeks after the first treatment step ii.

12. The method according to claim 1 wherein in the storing step iii the potatoes are stored in atmospheric air at atmospheric pressure.

13. The method according to claim 1 wherein, before the first treatment step ii, the potatoes have been cured after harvesting by storing the potatoes at a temperature range of from 10 to 20° C. for a period of from 3 to 14 days, optionally at a relative humidity of from 90 to 95%, in atmospheric air at atmospheric pressure.

14. The method according to claim 1 wherein prior to the first treatment step the potatoes have not been pre-treated with a sprout suppressant.

15. The method according to claim 1 wherein prior to the first treatment step ii the potatoes are pre-treated with a chlorpropham (CIPC) sprout suppressant.

16. The method of storing potatoes, the method comprising the steps of: providing a plurality of dormant potatoes, wherein the potatoes have been cured after harvesting; storing the potatoes at a storage temperature within the range of from 4 to 15° C. in atmospheric air at atmospheric pressure; monitoring the dormancy of the stored potatoes or of control potatoes stored in atmospheric air; in response to initiation of eye movement of at least one of the stored potatoes or of at least one control potato stored in atmospheric air, treating the stored potatoes with ethylene by exposing the stored potatoes, which are at the storage temperature, to ethylene which is added to the atmospheric air, and wherein the method further comprises step A, prior to or during the storing step ii and before the treating step iv, treating the cured dormant potatoes with 1-methylcyclopropene by exposing the potatoes to 1-methylcyclopropene at a temperature of at least 8° C., and wherein before treatment step A the cured potatoes have not been cooled below a temperature of 8° C.

17. The method according to claim 16 wherein the treatment with 1-methylcyclopropene is carried out at a temperature within the range of 8 to 30° C.

18. The method according to claim 16 wherein prior to the treatment step A, the cured dormant potatoes have not been subjected to a temperature pulldown to the storage temperature.

19. The method according to claim 16 wherein before treatment step A the cured potatoes have not been cooled below a temperature of 10° C.

20. The method according to claim 16 wherein the treatment with 1-methylcyclopropene is carried out for a treatment period of at least 12 hours.

21. The method according to claim 16 wherein during the treatment with 1-methylcyclopropene the potatoes are stored in a store having a store volume, and the 1-methylcyclopropene is applied at a concentration of from 0.5 to 5 μL/L, wherein the concentration in μL/L is the ratio of the volume of 1-methylcyclopropene powder to the store volume.

22. The method according to claim 16 wherein the treatment step iv is initiated at least 4 weeks after the treatment step A.

23. The method according to claim 16 wherein during the treatment with ethylene the potatoes are treated continuously with ethylene so that, after initiation of the second treatment step, the potatoes are stored in an ethylene-containing atmosphere, during the storing step iii.

24. The method according to claim 16 wherein during the storing step, and the treatment with ethylene, the potatoes are stored in a store having a store volume, and the ethylene is applied at a concentration of from 5 to 20 μL/L, wherein the concentration in μL/L is the ratio of the volume of ethylene gas, measured under the pressure and temperature conditions of the storage step iv, to the store volume.

25. The method according to claim 16 wherein (a) the second treatment step is initiated after eye movement in at least one control potato stored in atmospheric air of a plurality of control potatoes stored in atmospheric air, or (b) the second treatment step is initiated after eye movement in at least one of the potatoes, optionally after eye movement in from 1 to 10% by number of the potatoes.

26. The method according to claim 16 wherein second storage temperature is within the range of from 8 to 13° C.

27. The method according to claim 16 wherein the potatoes provided in step i have been cured after harvesting by storing the potatoes at a temperature range of from 10 to 20° C. for a period of from 3 to 14 days, optionally at a relative humidity of from 90 to 95%, in atmospheric air at atmospheric pressure.

28. The method according to claim 16 wherein prior to the first treatment step ii the potatoes have not been pre-treated with a sprout suppressant.

29. The method according to claim 16 wherein prior to the first treatment step ii the potatoes are pre-treated with a chlorpropham (CIPC) sprout suppressant.

30. The method according to claim 15 wherein the pre-treatment with the chlorpropham (CIPC) sprout suppressant comprises: a. a first pretreatment step which exposes the potatoes to the chlorpropham (CIPC) sprout suppressant at a chlorpropham (CIPC) concentration of from 10 to less than 18 grams per tonne of potatoes after curing and within a period of less than 4 weeks from harvesting; and optionally b. a second pretreatment step which exposes the potatoes to the chlorpropham (CIPC) sprout suppressant at a chlorpropham (CIPC) concentration of from 10 to less than 18 grams per tonne of potatoes within a period of from 2 to 8 weeks after the first pretreatment step.

31. The method according to claim 30 wherein in the first pretreatment step the chlorpropham (CIPC) concentration is from 12 to 15 grams per tonne of potatoes and in the optional second pretreatment step the chlorpropham (CIPC) concentration is from 12 to 15 grams per tonne of potatoes.

32. The method according to claim 30 wherein the second pretreatment step is carried out from 3 to 5 weeks after the first pretreatment step.

33. The method according to claim 16 wherein in step i the potatoes are endodormant.

Description

[0054] Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:

[0055] FIG. 1 shows the relationship between the fructose level and the storage period for potatoes stored in Examples according to the invention and Comparative Examples;

[0056] FIG. 2 shows the relationship between the fructose level and the storage period for potatoes stored in Examples according to the invention and Comparative Examples;

[0057] FIG. 3 shows the relationship, disclosed in a paper which is part of the state of the art, between the fructose level and the storage period for potatoes stored by a method not in accordance with the present invention;

[0058] FIG. 4 shows the relationship between the fructose level and the storage period for potatoes stored in Examples according to the invention and Comparative Examples;

[0059] FIG. 5 shows the relationship between the mean value of the b* colour coordinate of a fried potato chip produced from the stored potatoes and the storage period for potatoes stored in Examples according to the invention and Comparative Examples;

[0060] FIG. 6 shows the relationship between the mean value of weight loss and the storage period for potatoes stored in Examples according to the invention and Comparative Examples;

[0061] FIG. 7 shows the relationship between the fructose level and the storage period for potatoes stored in Examples according to the invention and Comparative Examples;

[0062] FIG. 8 shows the relationship between the mean number of tubers with eye movement and the storage period for potatoes stored in Examples according to the invention and Comparative Examples; and

[0063] FIG. 9 shows the sprouting behaviour disclosed in a paper which is part of the state of the art, of potatoes stored by three different methods each not in accordance with the present invention.

[0064] The present invention relates to a method of storing potatoes. The method comprises the initial step of providing a plurality of dormant potatoes. The dormant potatoes preferably include at least some potatoes that are endodormant. However, the plurality of dormant potatoes may include at least one or more ecodormant potatoes, and so the plurality of dormant potatoes may comprise endodormant potatoes, ecodormant potatoes or a combination of ecodormant and endodormant potatoes.

[0065] As is well known to those skilled in the art of potato production and storage, curing, also known in the art as suberization, is an important element of modern potato production. Curing heals wounds in the potato surface that are formed during harvesting by promoting suberin formation below damaged cells, and also dries the crop to reduce disease development. Curing can be achieved in the field or artificially in store.

[0066] In the methods of the present invention, the potatoes have been cured after harvesting; for example, before the first treatment step ii, the potatoes have been cured after harvesting by storing the potatoes at a temperature within a temperature range of typically from 10 to 20° C. for a period of from 3 to 14 days, preferably at a relative humidity of from 90 to 95%, in atmospheric air at atmospheric pressure. The curing temperature is typically the harvest temperature. The harvest temperature may vary between different potato growing regions around the world. The curing is conventionally carried out after harvesting in order to allow a protective layer of cells to form an outer skin on the tubers and to allow at least partial healing of wounds caused by the harvesting process.

[0067] After curing, the potatoes may, or may not, be pre-treated with a sprout suppressant, for example chlorpropham (CIPC).

[0068] In some embodiments of the present invention the cured potatoes have not been pre-treated with a sprout suppressant.

[0069] In other embodiments of the present invention the potatoes have been pre-treated with a sprout suppressant, such as chlorpropham (CIPC), but the present invention can utilize lower concentrations of the chlorpropham (CIPC) sprout suppressant than are currently conventionally used in commercial potato storage, because if CIPC is optionally used, it is typically only used in a single treatment, rather than used in plural sequential CIPC treatments that are used in the commercial potato storage regimes of the prior art. CIPC treatment of potatoes is well known to those skilled in the art of potato production and storage. For example, as is well known in the art, CIPC can be applied as a fog using a petrol or electro fogger. Multiple fog formulations are commercially available (i.e. solid or liquid). Tubers can also be dipped into a CIPC liquid formulation.

[0070] Typically, the pre-treatment with the chlorpropham (CIPC) sprout suppressant comprises: a first pretreatment step which exposes the potatoes to the chlorpropham (CIPC) sprout suppressant at a chlorpropham (CIPC) concentration of from 10 to less than 18 grams per tonne of potatoes after curing and within a period of less than 4 weeks from harvesting. Optionally, the pre-treatment may further comprise a second pretreatment step which exposes the potatoes to the chlorpropham (CIPC) sprout suppressant at a chlorpropham (CIPC) concentration of from 10 to less than 18 grams per tonne of potatoes within a period of from 2 to 8 weeks, optionally from 3 to 5 weeks, after the first pretreatment step. In each of the first and second pretreatment steps the chlorpropham (CIPC) concentration may be from 12 to 15 grams per tonne of potatoes. In one example, the first CIPC pretreatment is carried out within 2 weeks of harvesting and the second CIPC pretreatment is carried out within about 4 to 5 weeks after the first CIPC pretreatment. Preferably, the second pretreatment step is not employed, but is omitted, so that the total CIPC concentration, if CIPC is used in embodiments of the present invention, is from 10 to less than 18 grams per tonne of potatoes, such as from 12 to 15 grams per tonne of potatoes. However, as described above preferably a CIPC sprout suppressant pre-treatment is not used in the preferred embodiments of the present invention.

[0071] Preferably, the potatoes are endodormant prior to their subsequent treatment and storage, as described below.

[0072] The cured, and optionally CIPC pretreated, potatoes are then treated chemically by a first treatment step of treating the potatoes with 1-methylcyclopropene (1-MCP). The 1-MCP can be applied before or after the CIPC treatment. Prior to the 1-MCP treatment step, the cured dormant potatoes have not been subjected to a temperature pulldown to the storage temperature.

[0073] Therefore the treatment protocol according to embodiments of the preset invention may comprise the following sequences:

i. Cure harvested potatoes; treat with 1-MCP; treat with CIPC; temperature pulldown to storage temperature; store at storage temperature and monitor dormancy; treat with ethylene after dormancy break or preset time period;
ii. Cure harvested potatoes; treat with CIPC; treat with 1-MCP; temperature pulldown to storage temperature; store at storage temperature and monitor dormancy; treat with ethylene after dormancy break or preset time period; or
iii. Cure harvested potatoes; treat with 1-MCP; temperature pulldown to storage temperature; store at storage temperature and monitor dormancy; treat with ethylene after dormancy break or preset time period.

[0074] Preferably, the time period between curing and temperature pulldown should be as short as possible, but allowing for a 24 h 1-MCP treatment followed by 24 h ventilation period in air, and, if employed, a 6 h CIPC treatment.

[0075] The first treatment step of treating the potatoes with 1-methylcyclopropene is carried out either (a) prior to chilling the potatoes, and in particular prior to chilling the potatoes to a chilled temperature at which they are to be stored in a long term (i.e. a period of at least one month) potato storage facility, or (b) without any subsequent chilling of the potatoes prior to and during long term storage.

[0076] In some embodiments the stored potatoes may not be chilled as compared to the preceding 1-MCP treatment temperature. For example the 1-MCP treatment temperature may be within the range of from 8 to 30° C., for example from 10 to 30° C., and the storage temperature may be within a partially overlapping storage temperature range of from 8 to 13° C. Alternatively, the 1-MCP treatment temperature is a value that is within the range of from 8 to 30° C., for example from 10 to 30° C. but above a storage temperature that is within the range of from 8 to 13° C.

[0077] In other embodiments, the potatoes are chilled as compared to the 1-MCP treatment temperature. For example, the 1-MCP treatment temperature is a value that is within the range of from 8 to 30° C., for example from 10 to 30° C., and the 1-MCP treatment temperature is above a chilled storage temperature that is within the range of from 4 to less than 13° C. This chilled storage temperature range includes a lower sub-range of from 4 to less than 8° C. for potatoes to be sold for use as table potatoes, i.e. for domestic use, and a higher sub-range of from 8 to less than 13° C. for potatoes to be sold to be processed commercially, for example to manufacture potato chips or crisps.

[0078] Such cooling of potatoes to a chilled storage temperature range, for example within the range of from 4 to less than 13° C., is typically known to those skilled in the art of potato storage as “pulldown”—in “pulldown” the potato tubers are subjected to a controlled cooling regime from an initial temperature, typically the temperature at which the potatoes were transported and delivered to the potato storage facility, to a lower storage temperature. For example, a typical controlled cooling regime cools the potatoes from a delivery temperature of about 10 to 20° C. to a storage temperature of from 4 to less than 13° C., for example about 6° C., at a controlled chilling rate selected to minimize chilling stresses in the potatoes and allow time for any further wound healing in addition to any wound healing previously occurring during the curing process. A typical cooling rate is a 0.5° C. reduction in temperature per day at ambient relative humidity.

[0079] The chemical treatment comprises a first treatment step of treating the potatoes with 1-methylcyclopropene, and preferably, prior to the first treatment step, the cured dormant potatoes have been maintained, post curing, at a temperature of at least 8° C. or at least 10° C.

[0080] The first treatment step comprises exposing the potatoes to 1-methylcyclopropene. Prior to the 1-MCP treatment step, the cured dormant potatoes have not been subjected to a temperature pulldown to the storage temperature. Typically, during the first treatment step the potatoes are at a first treatment temperature within the range of from 8 to 30° C., for example from 10 to 30° C., more typically from 12 to 25° C., for example from 12 to 22° C. Specific typical treatment temperatures are 13° C. and 21.5° C.

[0081] Typically, the first treatment step is carried out for a first treatment period of at least 12 hours, optionally from 12 to 36 hours, further optionally from 18 to 30 hours, yet further optionally about 24 hours.

[0082] Typically, during the first treatment step the potatoes are stored in a store (which may be the same store used for subsequent long term storage) having a store volume, and the 1-methylcyclopropene is applied at a concentration of from 0.5 to 5 μL/L, optionally from 0.5 to 2 μL/L, further optionally from 0.75 to 1.25 μL/L, yet further optionally about 1 μL/L, wherein the concentration in μL/L is the ratio of the volume of 1-methylcyclopropene to the store volume.

[0083] The 1-methylcyclopropene is typically in a commercially available powder form in which the 1-MCP is bound with cyclodextrin, which is treated to generate 1-methylcyclopropene in gaseous form from the 1-methylcyclopropene powder. The 1-MCP was applied by adding the powdered 1-MCP (e.g. the product sold under the trade mark Smartfresh sold by Rohm and Haas, PA, USA) to warm water (50° C.) to release the gas, as disclosed in section 2.2.1 of the Foukaraki et al paper entitled “Impact of ethylene and 1-MCP on sprouting and sugar accumulation in stored potatoes” as discussed above. For example, to generate 1-MCP at a concentration of 1 μL/L in air, a dose of 1.8 g of Smartfresh (comprising 0.14 wt % 1-MCP) is added to a conical flask, then 20 mL of warm water at 50° C. was added to release the gaseous 1-MCP. The concentration of the 1-MCP may be measured and checked using calibrated gas chromatography.

[0084] Therefore, prior to the subjecting of the potatoes to the storage temperature, the cured dormant potatoes are treated with 1-methylcyclopropene by exposing the potatoes to 1-methylcyclopropene.

[0085] After the first treatment step of 1-methylcyclopropene, the potatoes are then stored at the second storage temperature. Typically, for processing potatoes the second storage temperature is within the range of from 8 to less than 13° C., whereas for table or domestic potatoes the storage temperature may be from 4 to less than 8° C.

[0086] Preferably, the potatoes are stored in atmospheric air at atmospheric pressure. However, the gaseous environment may alternatively comprise atmospheric air to which additional carbon dioxide has been added (the carbon dioxide displacing other gases present in air), and the added carbon dioxide may at least in part be provided by respiratory carbon dioxide emitted from the stored potatoes.

[0087] The stored potatoes, or control potatoes, are monitored for an indicator of dormancy break, at which the endodormant potatoes become ecodormant potatoes, and require further environmental treatment or control to suppress sprout growth. As described above, the term “eye movement” refers to the early visible stages of growth of tuber meristems which if not suppressed will go on to form sprouts, and in this specification “eye movement” as an indicator of dormancy break means that the tuber meristems have grown to a length of at least 1 mm, and the detected eye movement may be present anywhere on the outer surface of the potato tuber.

[0088] In the present invention, the eye movement as an indicator of dormancy break is defined as meaning that any tuber meristems have grown to a length of at least 1 mm. Such eye movement is visible to the naked eye. The tuber meristems, if not suppressed, would continue to grow and form sprouts in the potatoes.

[0089] Therefore, preferably the present invention includes the step of monitoring the dormancy of the stored potatoes or of control potatoes stored in atmospheric air. In response to initiation of eye movement of at least one of the stored potatoes or of at least one control potato stored in atmospheric air, the stored potatoes are treated with ethylene, the treatment comprising exposing the stored potatoes, which are at the storage temperature, to ethylene which is added to the atmospheric air.

[0090] Therefore, when eye movement has been detected, the stored potatoes are subjected to a second chemical treatment, which is preferably carried out while stored potatoes remain in the same storage facility and at the same second storage temperature. In other words, the second chemical treatment chemically treats the potatoes during the long term storage regime either (a) when the storage is at a temperature (typically at least 10° C.) which is sufficiently high that there has been no chilling or “pulldown” of the potatoes, or (b) after “pulldown” when the storage is at a temperature which is sufficiently low that there has been chilling of the potatoes prior to storage.

[0091] In the subsequent second treatment step during the storing step, the potatoes are treated with ethylene. The treatment comprises exposing the stored potatoes, which are at the second storage temperature, to ethylene. Typically, in the second treatment step the potatoes are treated continuously with ethylene so that, after initiation of the second treatment step, the potatoes are stored in an ethylene-containing atmosphere, during the storing step.

[0092] The treatment of stored potato tubers by ethylene is well known in the art, and is disclosed in various prior art documents as summarized hereinabove. Ethylene can be applied using any of the various known methods as long as the desired concentration is achieved and maintained. Known ethylene treatments include the commercially-available Restrain ethylene generator which converts ethanol to ethylene (https://www.restrain.eu.com/equipment/) or the commercially-available BioFresh system (http://www.bio-fresh.com/ethylene-management-system/ ) which uses ethylene gas canisters.

[0093] During the storing step, and the second treatment step, the potatoes are stored in a store having a store volume. Preferably, the ethylene is applied at a concentration of from 5 to 20 μL/L, optionally from 5 to 15 μL/L, further optionally from 7.5 to 12.5 μL/L, yet further optionally about 10 μL/L, wherein the concentration in μL/L is the ratio of the volume of ethylene gas, measured under the pressure and temperature conditions of the storage step, to the store volume.

[0094] The initiation of the application of the ethylene is determined by monitoring the nature of the dormancy of the potatoes.

[0095] In the preferred embodiments of the present invention, the second treatment step is initiated after eye movement in at least one control potato stored in atmospheric air, optionally in from 1 to 10%, by number of potatoes, of a plurality of control potatoes stored in atmospheric air.

[0096] In alternative embodiments of the present invention, the second treatment step is initiated after eye movement in at least one of the stored potatoes, optionally after eye movement in from 1 to 10% by number of the stored potatoes.

[0097] Accordingly, in the method of storing potatoes according to preferred embodiments of the invention, the dormancy of the dormant potatoes, treated by 1-MCP, is monitored and in response to eye movement of at least one of the stored potatoes or of at least one control potato, the potatoes are treated with ethylene.

[0098] The present invention is illustrated further with reference to the following non-limiting Examples.

EXAMPLE 1

[0099] Potato tubers of the commercially available cultivar Lady Rosetta which had been harvested in the summer of 2013 and had been initially treated with 12 grams/tonne CIPC (chlorpropham) growth suppressant were provided. The tubers were dormant and had been cured conventionally. Upon arrival at the laboratory testing facility in October 2013, two batches of the potatoes were prepared. For each batch, the tubers were placed in stackable trays and stored in an air tight storage box of at least 100 litres capacity which was sealed with water.

[0100] The first batch of potatoes was immediately exposed to 1-MCP at a concentration of 1 μL/L based on the volume of the storage box for a period of 24 hours, with the exposed potatoes being at an ambient temperature of about 21.5° C. There was no temperature pulldown to the storage temperature before the 1-MCP treatment. Hereinafter, this treatment protocol is called “early 1-MCP”. The potatoes were then stored at a storage temperature of 10° C. The treated potatoes were not subjected to a temperature pulldown to a temperature of below 10° C. before the 1-MCP treatment.

[0101] In January 2014, the treated potatoes of the first batch were subjected to an ethylene treatment in which the potatoes were exposed to ethylene added to the atmospheric air at a concentration of 10 μL/L based on the volume of the storage box. The ethylene was applied continuously. The exposed potatoes were at the storage temperature of 10° C. Thereafter, the treated potatoes were continued to be stored at the storage temperature of 10° C.

[0102] The second batch of potatoes was treated with ethylene and 1-MCP as described above, but in the reverse order.

[0103] Accordingly, in October 2013 the potatoes of the second batch were subjected to an ethylene treatment in which the potatoes were exposed to ethylene added to the atmospheric air at a concentration of 10 μL/L based on the volume of the storage box. The ethylene was applied continuously. The exposed potatoes were at the storage temperature of 10° C. Thereafter, the treated potatoes were continued to be stored at the storage temperature of 10° C.

[0104] In January 2014, the treated potatoes of the second batch were exposed to 1-MCP at a concentration of 1 μL/L based on the volume of the storage box for a period of 24 hours, with the exposed potatoes being at the storage temperature of 10° C. Hereinafter, this treatment protocol is called “late 1-MCP”. The potatoes were then again stored at the storage temperature of 10° C.

[0105] The fructose concentration of the potatoes of both the first and second batches was measured on a monthly basis, and the results are shown in FIG. 1. The plot of the first batch is identified as “Early 1-MCP/late ethylene” and the plot of the second batch is identified as “Early ethylene/late 1-MCP”. As a further comparison, plots of (i) a comparative batch of potatoes stored in air is identified as “Air”, and (ii) a comparative batch of potatoes continuously stored in ethylene (at the same dose in atmospheric air as used for the first and second batches) is identified as “Continuous ethylene”.

[0106] It may be seen that for the “Early ethylene/late 1-MCP” plot and the “Continuous ethylene” plot, the fructose concentration of the stored potatoes rapidly increased after February 2014, to a value of 12 mg/g DM (dry mass) in April 2014. In contrast, the plots for “Early 1-MCP/late ethylene” and “Air” had reduced fructose concentrations over the storage period to April 2014. Thus the “Early ethylene/late 1-MCP” and “Continuous ethylene” plots show that the fructose concentration of the stored potatoes rapidly increases when the ethylene is continuously applied during storage, either in the absence of any prior 1-MCP treatment or after a late 1-MCP treatment.

[0107] This experimental data shows that the order of 1-MCP and ethylene treatment is important for the maintenance of low reducing sugar levels in the stored potatoes. Using an “Early 1-MCP/late ethylene” protocol can maintain low levels of reducing sugars, whereas the reverse treatment protocol of “Early ethylene/late 1-MCP” leads to unacceptable increased levels of reducing sugars in the stored potatoes.

[0108] However, the treatment protocol should achieve the combination of (a) reduced sprout suppression and (b) reduced fructose concentration over the storage period.

[0109] The plot for “Air” was associated with reduced sprout suppression, because of the absence of ethylene as a sprout suppressant. Thus, the plot for “Air” is not associated with achieving the combination of (a) reduced sprout suppression and (b) reduced fructose concentration over the storage period.

[0110] The plot for “Early 1-MCP/late ethylene” was however associated not only with reduced sprout suppression, but also with reduced fructose concentration over the storage period, because both the 1-MCP and the ethylene function as sprout suppressants, and also the 1-MCP functions to reduce the formation of reducing sugars such as fructose which otherwise is formed as a result of the potato being exposed to ethylene over the storage period.

[0111] It may be seen particularly from the plot for “Early 1-MCP/late ethylene” that the fructose concentration in June 2014 was a maximum of about 4 mg/g DW.

[0112] This Example shows that the method of the present invention can achieve low sugar concentration without advancing eye movement or sprout suppression, and this can be achieved using early applied 1-MCP and late applied ethylene, after eye movement, and relatively high storage temperatures.

EXAMPLE 2

[0113] Potato tubers of the commercially available cultivar Saturna which had been harvested in the summer of 2013 and had not been initially treated with CIPC (chlorpropham) sprout suppressant were provided. The tubers were dormant and had been cured conventionally. Upon arrival at the laboratory testing facility in October 2013, two batches of the potatoes were prepared. For each batch, the tubers were placed in stackable trays and stored in an air tight storage box of at least 100 litres capacity which was sealed with water.

[0114] The first batch of potatoes was immediately exposed to 1-MCP at a concentration of 1 μL/L based on the volume of the storage box for a period of 24 hours, with the exposed potatoes being at an ambient temperature of about 21.5° C. There was no temperature pulldown to the storage temperature before the 1-MCP treatment. The potatoes were then stored at a storage temperature of 10° C. The treated potatoes were not subjected to a temperature pulldown to a temperature of below 10° C. before the 1-MCP treatment.

[0115] In January 2014, the treated potatoes of the first batch were subjected to an ethylene treatment in which the potatoes were exposed to ethylene added to the atmospheric air at a concentration of 10 μL/L based on the volume of the storage box. The ethylene was applied continuously. The exposed potatoes were at the storage temperature of 10° C. Thereafter, the treated potatoes were continued to be stored at the storage temperature of 10° C.

[0116] The fructose concentration of the potatoes of the first batch was measured on a monthly basis, and the results are shown in FIG. 2. The plot of the first batch is identified as “Early 1-MCP/late ethylene”. As a comparison, plots of (i) a comparative batch of potatoes stored in air is identified as “Air”, and (ii) a comparative batch of potatoes continuously stored in ethylene (at the same dose in atmospheric air as used for the first batch) is identified as “Continuous ethylene”.

[0117] It may be seen that for the “Continuous ethylene” plot, the fructose concentration of the stored potatoes rapidly increased after January 2014, to a value of 10 mg/g DM (dry mass) in June 2014. In contrast, the plots for “Early 1-MCP/late ethylene” and “Air” had reduced fructose concentrations over the storage period. Thus the “Continuous ethylene” plot shows that the fructose concentration of the stored potatoes rapidly increases when the ethylene is continuously applied during storage and in the absence of any prior 1-MCP treatment.

[0118] However, the plot for “Air” was also associated with reduced sprout suppression, because of the absence or reduction of ethylene as a sprout suppressant. Thus, the plot for “Air” is not associated with achieving the combination of (a) reduced sprout suppression and (b) reduced fructose concentration over the storage period.

[0119] The plot for “Early 1-MCP/late ethylene” was however associated not only with reduced sprout suppression, but also with reduced fructose concentration over the storage period, because both the 1-MCP and the ethylene function as sprout suppressants, and also the 1-MCP functions to reduce the formation of reducing sugars such as fructose which otherwise is formed as a result of the potato being exposed to ethylene over the storage period.

[0120] It may be seen particularly from the plot for “Early 1-MCP/late ethylene” that the fructose concentration in June 2014 was a maximum of 3 mg/g DM.

[0121] This Example shows that the method of the present invention can achieve low sugar concentration without advancing eye movement, and this can be achieved using early applied 1-MCP and late applied ethylene, after eye movement, and relatively high storage temperatures.

[0122] Similar results, with regard to sugar reduction, were found for other potato cultivars that had not been pre-treated with CIPC, in particular the cultivars Lady Rosetta, VR808, Shelford and Lady Claire.

Comparative Example 1

[0123] This Comparative Example is taken from the paper by Sofia G. Foukaraki, Katherine Cools, Gemma A. Chope and Leon A. Terry, entitled” Impact of ethylene and 1-MCP on sprouting and sugar accumulation in stored potatoes”, Postharvest Biology and Technology 114 (2016) 95-103.

[0124] In this Comparative Example, a number of potato cultivars were tested. In particular, the potato cultivar Saturna was tested. This being the same cultivar as tested in Example 2. In this Comparative Example, no sprout suppressant (such as CIPC), had been applied to the potatoes after a conventional curing regime. The potato tubers underwent a controlled “temperature pulldown” cooling regime from 15° C. (arrival temperature), at a rate of 0.5° C. reduction per day at ambient relative humidity (RH), to a holding temperature of 6° C., in order to minimize chilling stress and allow time for wound healing.

[0125] After reaching 6° C., three batches of the tubers were treated differently.

[0126] After a period of 1 week a first batch was exposed to 1 μL 1-MCP per L for 24 h at 6° C., and then after a further period of 4 weeks (i.e. at a total of 5 weeks) stored under continuous 10 μL ethylene per L of air, which in this Comparative Example is called a “late ethylene” treatment.

[0127] A second batch was not treated with 1-MCP and after a total period of 3 weeks was stored under continuous 10 μL ethylene per L of air, which in this Comparative Example is called a “continuous ethylene” treatment.

[0128] A third batch was stored in air, which in this Comparative Example is called an “air” treatment.

[0129] As for Examples 1 and 2, the fructose content of the potatoes was measured intermittently. The results are shown in FIG. 3.

[0130] The graph of FIG. 3 shows the result when the Saturna potatoes were treated with 1-MCP after pulldown to 6° C.

[0131] As for FIGS. 1 and 2, the use of an early 1-MCP treatment with subsequent late ethylene treatment, by transfer from air to ethylene, provides significantly lower levels of reducing sugars as compared to storage in continuous ethylene, and substantially similar levels of reducing sugars as compared to storage in air, although storage in air would not achieve acceptable sprout suppression.

[0132] However a comparison of FIGS. 2 and 3 shows the technical effect of early 1-MCP treatment before pulldown, in accordance with the present invention, as compared to early 1-MCP treatment after pulldown, in accordance with the disclosure of the Foukaraki et al. paper identified above in this Comparative Example.

[0133] FIG. 3 shows that the use of 1-MCP after pulldown substantially eliminated an ethylene induced sugar peak. Also, at least in the middle of the 30 week storage period, the fructose levels in the stored potatoes were lower using the 1-MCP than the control treatment of storage in air without using 1-MCP.

[0134] However, whether or not 1-MCP was used, the fructose level across the entire testing period greater than about 5 weeks remained above the concentration value of 5 mg/g fructose DW (dry weight).

[0135] The same potato cultivar Saturna was used in Example 2 and Comparative Example 1, and the 1-MCP and ethylene dosage concentrations were the same, and the late ethylene, if not continuous, was added at substantially the same eye movement trigger. The essential difference between the experimental parameters of Example 2 and Comparative Example 1 is that in Example 2 the 1-MCP was applied before temperature pulldown whereas in Comparative Example 1 the 1-MCP was applied after temperature pulldown. This parameter difference unexpectedly results in a reduction in the fructose concentration during the storage phase.

[0136] A comparison between the results of Example 2 and Comparative Example 1 shows that the timing of 1-MCP application before the potato temperature has been reduced by temperature pulldown, or example to a temperature of below 10° C. or below 8° C., can cause an even further reduction of the sugar content of stored potatoes when stored in long term storage. This technical effect can be achieved without the use of conventional spout suppressants, such as CIPC.

EXAMPLE 3

[0137] Potato tubers of two commercially available potato cultivars, Arsenal and Shelford, which had been harvested in the summer of 2016 and had not been initially treated with CIPC (chlorpropham) sprout suppressant were provided. The tubers were dormant and had been cured conventionally. Upon arrival at the pilot testing facility in October 2016 the tubers were placed in 1 tonne wooden boxes and stored in a pilot plant potato storage unit having a positive air flow plenum.

[0138] For each cultivar, a first batch of the potatoes was immediately exposed to 1-MCP at a concentration of 1 μL/L based on the volume of the potato storage unit for a period of 24 hours, with the exposed potatoes being at a temperature of about 13° C., and a second batch was not exposed to 1-MCP. There was no temperature pulldown to the storage temperature before the 1-MCP treatment. The potatoes of the first and second batches were then stored at a storage temperature of 8.5° C. The potatoes of the first and second batches were not subjected to a temperature pulldown, i.e. to a temperature reduction to a storage temperature before the 1-MCP treatment.

[0139] In early November 2016, the potatoes of the first and second batches were subjected to an ethylene treatment in which the potatoes were exposed to ethylene added to the atmospheric air at a concentration of 10 μL/L based on the volume of the potato storage unit. The ethylene was applied continuously. The exposed potatoes were at the storage temperature of 8.5° C. Thereafter, the potatoes of the first and second batches were continued to be stored at the storage temperature of 8.5° C.

[0140] The fructose concentration of the potatoes of the first and second batches was periodically measured, and the results are shown in FIG. 4. For each cultivar, in FIG. 4 the first batch is indicated with the letters “1-MCP” whereas the reference second batch is not; for example for the Arsenal cultivar, the first batch is indicated as Arsenal+MCP and the second batch is indicated as Arsenal.

[0141] It may be seen that for each cultivar the addition of ethylene to potatoes of the second batch which had not been treated with 1-MCP was generally associated with an increase in the fructose concentration. In contrast, for each cultivar the first batch which had been treated with 1-MCP was generally associated with a lower or minimal increase in the fructose concentration. The addition of ethylene to potatoes of the second batch for each cultivar which had not been treated with 1-MCP was generally associated with an increase in the fructose.

EXAMPLE 4

[0142] The pilot scale testing of Example 3 was also carried out on the same potato cultivars starting in October 2017 using the same temperature conditions. Potato tubers of the same two commercially available cultivars Arsenal and Shelford which had been harvested in the summer of 2017 and had not been initially treated with CIPC (chlorpropham) sprout suppressant were provided. The tubers were dormant and had been cured conventionally. Upon arrival at the pilot testing facility in October 2017 the tubers were placed in 1 tonne wooden boxes and stored in a pilot plant potato storage unit having a positive air flow plenum.

[0143] For each cultivar, a first batch of the potatoes was immediately exposed to 1-MCP at a concentration of 1 μL/L based on the volume of the potato storage unit for a period of 24 hours, with the exposed potatoes being at a temperature of about 13° C., and a second batch was not exposed to 1-MCP. There was no temperature pulldown to the storage temperature before the 1-MCP treatment. The potatoes of the first and second batches were then stored at a storage temperature of 8.5° C. The potatoes of the first and second batches were not subjected to a temperature pulldown to a storage temperature before the 1-MCP treatment.

[0144] On 10 Nov. 2017, the potatoes of the first and second batches were subjected to an ethylene treatment in which the potatoes were exposed to ethylene added to the atmospheric air at a concentration of 10 μL/L based on the volume of the potato storage unit. The ethylene was applied continuously. The exposed potatoes were at the storage temperature of 8.5° C. Thereafter, the potatoes of the first and second batches were continued to be stored at the storage temperature of 8.5° C.

[0145] The potatoes of the first and second batches were periodically tested by producing fried potato chips from the potatoes, and measuring the coloration, expressed as the mean value of the b* colour coordinate of the CIELAB colour space. The b* colour coordinate, when positive, is associated with a yellow colour, and in the context of the testing of potato chips is associated with increased browning. The results are shown in FIG. 5. For each cultivar, in FIG. 5 the first batch is indicated with the letters “+MCP” whereas the reference second batch is not; for example for the Arsenal cultivar, the first batch is indicated as Arsenal+MCP and the second batch is indicated as Arsenal.

[0146] It may be seen that for each cultivar the addition of ethylene to potatoes of the second batch which had not been treated with 1-MCP was generally associated with a high value of the b* colour coordinate of a fried potato chip produced from the potato. In contrast, for each cultivar the first batch which had been treated with 1-MCP was generally associated with a lower value of the b* colour coordinate of a fried potato chip produced from the potato.

EXAMPLE 5

[0147] The pilot scale testing of Example 3 was also carried out on the same potato cultivars starting in October 2016 using the same temperature conditions. Potato tubers of the same two commercially available cultivars Arsenal and Shelford which had been harvested in the summer of 2016 and had not been initially treated with CIPC (chlorpropham) growth suppressant were provided. The tubers were dormant and had been cured conventionally. Upon arrival at the pilot testing facility in October 2016 the tubers were placed in 1 tonne wooden boxes and stored in a pilot plant potato storage unit having a positive air flow plenum. The carbon dioxide concentration of the atmosphere in the pilot plant potato storage unit was restricted to a maximum of 700 μL/L by operation of a fan in the storage unit.

[0148] For each cultivar, a first batch of the potatoes was immediately exposed to 1-MCP at a concentration of 1 μL/L based on the volume of the potato storage unit for a period of 24 hours, with the exposed potatoes being at a temperature of about 13° C., and a second batch was not exposed to 1-MCP. There was no temperature pulldown to the storage temperature before the 1-MCP treatment. The potatoes of the first and second batches were then stored at a storage temperature of 8.5° C. The potatoes of the first and second batches were not subjected to a temperature pulldown to the storage temperature before the 1-MCP treatment.

[0149] On 21 Nov. 2016, the potatoes of the first and second batches were subjected to an ethylene treatment in which the potatoes were exposed to ethylene added to the atmospheric air at a concentration of 10 μL/L based on the volume of the potato storage unit. The ethylene was applied continuously. The exposed potatoes were at the storage temperature of 8.5° C. Thereafter, the potatoes of the first and second batches were continued to be stored at the storage temperature of 8.5° C.

[0150] The potatoes of the first and second batches were periodically tested by measuring the mean weight loss of the potatoes. The results are shown in FIG. 6. For each cultivar, in FIG. 6 the first batch is indicated with the letters “+MCP” whereas the reference second batch is not; for example for the Arsenal cultivar, the first batch is indicated as Arsenal+MCP and the second batch is indicated as Arsenal.

[0151] It may be seen that for each cultivar the addition of ethylene to potatoes of the second batch which had not been treated with 1-MCP was generally associated with an increased weight loss as compared to the potato for each cultivar of the first batch which had been treated with 1-MCP.

EXAMPLE 6

[0152] Example 3 was generally repeated and carried out on potatoes that had previously been treated with CIPC. Potato tubers of two commercially available cultivars Shelford and VR808 which had been harvested in October 2016 were provided. The tubers were dormant and had been cured conventionally. Upon arrival at the pilot testing facility in October 2016 the tubers were placed in 1 tonne wooden boxes and stored in a pilot plant potato storage unit having a positive air flow plenum. Therefore this example was a pilot test of a commercial scale process whereas the previous examples were laboratory scale tests.

[0153] For each cultivar, a first batch of the potatoes was immediately exposed to 1-MCP at a concentration of 1 μL/L based on the volume of the potato storage unit for a period of 24 hours, with the exposed potatoes being at a temperature of about 13° C., and a second batch was not exposed to 1-MCP. There was no temperature pulldown to the storage temperature before the 1-MCP treatment.

[0154] These potatoes were then treated with CIPC (chlorpropham) sprout suppressant 48 hours after the 1-MCP treatment commenced. A single CIPC dose of 12 g/tonne of potatoes was applied (using a fog) for a period of 6 hours in October 2016. Then, during the following day after the CIPC treatment, the potatoes were subjected to temperature pulldown to a storage temperature of 10° C. In other words, the treatment protocol was as follows: treat with 1-MCP for a period of 24 hours, ventilate in air for a period of 24 hours, treat with CIPC for a period of 6 hours, and finally subject to temperature pulldown to a storage temperature of 10° C. the day after the CIPC treatment.

[0155] The potatoes of the first and second batches were then stored at a storage temperature of 10° C. The potatoes of the first and second batches were not subjected to a temperature pulldown to the storage temperature before the 1-MCP treatment.

[0156] In November 2016, the potatoes of the first and second batches were subjected to an ethylene treatment in which the potatoes were exposed to ethylene added to the atmospheric air at a concentration of 10 μL/L based on the volume of the potato storage unit. The ethylene was applied continuously. The exposed potatoes were at the storage temperature of 8.5° C. Thereafter, the potatoes of the first and second batches were continued to be stored at the storage temperature of 10° C.

[0157] The fructose concentration of the potatoes of the first and second batches was periodically measured, and the results are shown in FIG. 7. For each cultivar, in FIG. 7 the first batch is indicated with the letters “+1-MCP” whereas the reference second batch is not; for example for the Shelford cultivar, the first batch is indicated as Shelford+1-MCP and the second batch is indicated as Shelford.

[0158] It may be seen that for each cultivar the addition of ethylene to potatoes of the second batch which had not been treated with 1-MCP was generally associated with an increase in the fructose concentration. In contrast, for each cultivar the first batch which had been treated with 1-MCP was generally associated with a lower or minimal increase in the fructose concentration after addition of ethylene. The addition of ethylene to potatoes of the second batch for each cultivar which had not been treated with 1-MCP was generally associated with an increase in the fructose concentration.

[0159] This Example shows that the technical effect of reduced sugar concentration by treatment with 1-MCP and subsequent ethylene treatment at or before eye movement is achieved even when using a conventional sprouting suppressant such as CIPC.

EXAMPLE 7

[0160] In Example 2, FIG. 2 shows the relationship between the fructose concentration and the storage time period for potato tubers of the cultivar Saturna which had not been treated with CIPC. As explained in Example 2, the 1-MCP and ethylene chemical components used in the treatment protocols function as sprout suppressants.

[0161] The sprout suppression function is shown in FIG. 8. In FIG. 8 there are three plots of the relationship between the number of tubers with eye movement and the storage time period for potato tubers of the cultivar Saturna which had not been treated with CIPC. The three plots correspond to the three treatments described above in Example 2.

[0162] The first plot corresponds to the present invention, in which the potato tubers were subjected to an early 1-MCP treatment, as indicated by the left-hand dashed line in FIG. 8, and a subsequent late ethylene treatment, as indicated by the right-hand dashed line in FIG. 8. There was no temperature pulldown to the storage temperature before the 1-MCP treatment. It can be seen that the numbers of tubers with eye movement was low even after a storage period of about 3 months. The 1-MCP and ethylene function as sprout suppressants, and the fact that ethylene was applied “late”, after the 1-MCP treatment, did not prevent effective sprout suppression.

[0163] The second plot corresponds to a comparison with the present invention, in which the potato tubers were subjected to continuous ethylene treatment throughout the entire storage period, without any 1-MCP treatment. It can be seen that the numbers of tubers with eye movement was initially low, but after a storage period of about 2 months, the numbers of tubers with eye movement increased significantly. The first and second plots show that by combining an initial 1-MCP treatment and a subsequent later ethylene treatment, sprout suppression can be enhanced as compared to the use of continuous ethylene treatment. Thus an initial 1-MCP treatment, over a short treatment period, for example about 1 day, prior to a later ethylene treatment can provide improved sprout suppression in combination with significantly reduced ethylene consumption over the storage period.

[0164] The third plot corresponds to a comparison with the present invention, in which the potato tubers were stored in air throughout the entire storage period and were not subjected to any 1-MCP or ethylene treatment. Again, it can be seen that the numbers of tubers with eye movement was initially low, but after a storage period of about 2 months, the numbers of tubers with eye movement increased significantly. The second and third plots show that a continuous ethylene treatment, did not provide significantly improved sprout suppression as compared to the use of atmospheric air.

[0165] In FIG. 8, the eye movement/sprouting data was measured at each sampling time point, and so represents the time to dormancy break.

Comparative Example 2

[0166] In the Foukaraki et al paper discussed in Comparative Example 1, the results being illustrated in FIG. 3 discussed above, potato tubers, of cultivar Saturna which had not been subjected to any CIPC treatment, were subjected to three different storage protocol treatments of (i) 1-MCP and late ethylene, and the 1-MCP was applied after pulldown to a storage temperature below 8° C.; (ii) continuous ethylene and (iii) air.

[0167] In Foukaraki et al, sprout growth was measured at the end of the storage period of the experiments, after sprouts had developed. Therefore Example 7 of the present invention described above measured eye movement during the storage period, which represents the time to dormancy break, whereas in contrast Foukaraki et al measured sprout length at the end of the storage period.

[0168] The results of the Foukaraki et al sprout growth measurements are shown in FIG. 9. This data shows no significant difference between the three treatments, since the sprouts were measured at an advanced stage, after a storage period of 30 weeks, rather than throughout the storage period. The Foukaraki et al data shows that there is no added benefit on sprout suppression of combining a 1-MCP treatment, applied after temperature pulldown, and a subsequent ethylene treatment.

[0169] In contrast, the data of Example 7 shows that there is an added benefit on sprout suppression of combining a 1-MCP treatment, applied before any temperature pulldown, and a subsequent ethylene treatment.

[0170] Various modifications to the present invention will be readily apparent to those skilled in the art and are encompassed within the scope of the present invention as defined in the appended claims.