WO2002011548A2

WO2002011548A2 - Means for extending the shelf-life of vegetables

Info

Publication number: WO2002011548A2
Application number: PCT/EP2001/008930
Authority: WO
Inventors: Oscar Johannes Maria Goddijn; Eline Voogd
Original assignee: Syngenta Mogen Bv; Oscar Johannes Maria Goddijn; Eline Voogd
Priority date: 2000-08-09
Filing date: 2001-08-02
Publication date: 2002-02-14
Also published as: WO2002011548A8; AU2001282057A1

Abstract

A method for inhibiting sprouting and/or extending the shelf-life of root vegetable is described, comprising the substantially continuous contacting of root vegetables with at least a C1 to C6 alcohol vapour or a mixture of C1 to C6 alcohol vapours.

Description


  



  MEANS FOR EXTENDING THE SHELF-LIFE OF VEGETABLES
The present invention concerns means for extending the shelf-life of vegetables. More specifically, the present invention concerns means for extending the shelf-life of root vegetables, comprising substantially continuous contacting of the root vegetables with at least a Ci to C6 alcohol vapour or a mixture thereof.



   In order to extend the shelf-life of root vegetables, it is usually necessary that the root vegetable remains in an essentially dormant state. Various means are available for prolonging the shelf-life of root vegetables or for ensuring (albeit indirectly) that the vegetables remain in an essentially dormant state. For example, inhibition of sprouting, decreasing the rate of necrosis, inhibiting the spread and attack of pathogens all contribute to the shelf-life of root vegetables being extended.



   The following may vary depending on the particular root vegetable and the desired end use, but typically, after harvest, tubers are allowed to suberise (which involves toughening of the skin or periderm) at warm temperatures for about 10 days and are then gradually cooled to a storage temperature of about   10 C.    At least in the case of some potato cultivars, for the first 2 to 3 months after harvest, the tubers remain dormant and exhibit little inclination to sprout. However, after this period, the tubers must be treated to prevent sprouting. This often consists of a chemical treatment which can result in numerous deleterious effects on the tubers. Deleterious effects associated with sprouting include, loss of fresh weight, conversion of starch to sugars and a decrease in the quality and appearance of the tubers.

   Sprouts and the surrounding tissue also contain elevated levels of toxic   glycoalkaloids,    which are not destroyed by cooking.



   Inhibition of sprouting contributes to extension of the shelf-life of root vegetables. Conventional means for inhibition of sprouting include contacting the root vegetables, typically potatoes, with anti-sprouting agents, such as carvone or chloropropham   (CIPC    ;   l-methylethyl-3-chlorophenylcarbamate).    However, questions concerning the toxicology of CIPC have recently been raised. Other means for extending the shelf-life of vegetables include storing the vegetables in optimal storage conditions (i. e., under conditions of controlled temperature, light and humidity) or by use of antipathogenic agents.

   Lowering the temperature causes sprouting to be inhibited but has the disadvantage of inducing cold sweetening which causes the vegetable (especially potatoes) to turn an unsightly   brown/black    colour during cooking (due to the conversion of starch to sugar and the subsequent caramelising of these sugars) thereby rendering the vegetable undesirable for use. It is important to ensure that the means used for extending the shelf-life of the root vegetables does not cause significant physiological changes (which may affect the flavour or other characteristics of the vegetables) or significant morphological changes (which might have a negative bearing on consumer choice of that vegetable).



   Various means for preventing rot and sprouting of various vegetables are   known.    For example, International Patent Application WO 94/28716 describes a composition suitable for inhibiting the start of rot in potatoes and for inhibiting sprouting, which composition comprises a rape oil methyl ester in mixture with medium   and/or    long-chain alcohols and/or ethereal oil and/or sprout inhibiting agents.



   US 7723118 (Patent Number 5,129,951) discusses exposing potato tubers to aromatic aldehydes or alcohols to inhibit sprouting, loss of fresh weight, rotting and growth of fungi. The aromatic aldehydes or alcohols mentioned in the document are benzaldehyde, salicylaldehyde,   cinnamaldehyde,    hydrocinnamaldehyde, cuminaldehyde, thymol or mixtures thereof.



   Patent document DD-209378 discloses the use of mixtures of higher alcohols comprising mainly   Cg    to   Cl4    alcohols as temporary germination inhibitors for seed potatoes. The composition is applied between October and March and is effected by dispersal in the air for up to 144 hours or up to 48 hours without forced circulation.



   Furthermore, patent document DD-138731 describes the temporary inhibition of sprouting of seed potatoes by contacting the potatoes with higher alcohols, preferably nonanols and decanols.



   Patent document DD-147039 discloses a composition for temporarily inhibiting sprouting of seed potatoes, which composition comprises   Cl7    to C20 alcohols and/or C21 to C23 alcohols and isopropyl phenylcarbamate.



   Japanese patent application JP 06340502 describes a germination inhibiting process which involves contacting the pellicle of potatoes with an aqueous solution of 60 to 100% volume of ethanol (preferably 100% volume) preferably by immersing the potatoes in the ethanol. The authors report that the potatoes are preferably contacted with the ethanol twice in the germination period. An alternative inhibiting process is also described involving contacting the pellicle of the potatoes with ethanol vapour.



  Application of ethanol vapour twice during the germination period of potatoes is described in the Japanese document, i. e. non-continuous application of ethanol vapour. However, the document does not hint or suggest the continuous application of a Cl to C6 alcohol vapour nor does it provide any indication of the concentration of the alcohol vapour to be used.



   A method for delaying maturation in tomatoes which comprises exposing the tomatoes for 10 hours to ethanol vapour has been reported (Informatore Agrario Vol.



  46 (46): p. 51-53 (1989)). In this document, the maturation of the tomatoes is reported to be delayed by 3 to 4 days.



   The prior art documents discuss means for preventing sprouting and/or rotting, which means generally involve contacting root vegetables (typically potatoes) with compositions comprising various alcohols. However, the prior art does not mention means for extending the shelf-life of vegetables, inhibiting rot or inhibiting sprouting by the substantially continuous contacting of root vegetables with at least a Cl to   C6    alcohol vapour. The use of lower alcohols would generally be less toxic, less expensive and easier to handle and apply than some higher alcohols. Similarly, continuous application of an alcohol vapour via a conventional ventilation/aeration system is likely to be much more user-friendly and less cumbersome than noncontinuous application of an alcohol vapour.



   As mentioned above, disadvantages associated with methods and compositions of the prior art include various economic and toxicity-related disadvantages associated with known compositions used for extending the shelf-life of root vegetables.



   Therefore, despite the various means available for extending the shelf-life of root vegetables, there remains a need for improved means for extending the shelf-life of root vegetables. It is therefore an object of the present invention to provide improved means for extending the shelf-life of root vegetables, thereby alleviating some of the problems associated with prior art means.



   According to the present invention, there is provided a method for extending the shelf-life of root vegetables, comprising the substantially continuous contacting of root vegetables with an effective amount of at least a Ci to C6 alcohol vapour or a mixture of Cl to   C6    alcohol vapours. 



   The term shelf-life as defined herein is taken to mean the period of time the root vegetables last without significant deterioration (i. e., the length of time the vegetables remain in a state fit for consumer use).



   A root vegetable as defined herein encompasses any vegetable typically cultivated underground, more specifically, any underground vegetable comprising an edible root or stem. According to a preferred feature of the present invention, the root vegetable is selected from potato, sweet potato, yam,   sugarbeet,    swede, parsnip, beetroot, turnip or carrot.



   Preferably, the C1 to C6 alcohol is selected from methanol   (CH30H)    ; ethanol   (CH3CH20EI)    ; propyl alcohol   (CH3CH2CH20H)    ; isopropyl alcohol (CH3CH   (OH) CH3)    ; butyl alcohol   (CH3CH2CH2CH20H)    ; isobutyl alcohol (CH3CH   (CH3) CH20H)    ; sec-butyl alcohol   (CH3CH2CH    (OH) CH3) ; tert-butyl alcohol (CH3) 3COH); pentyl alcohol (CH3(CH2)3CH2OH) ; hexyl alcohol (CH3   (CH2) 4CH20H)    ; cyclopentanol, cyclohexanol and benzyl alcohol   (C6H5CH2OH).   



  Most preferably, the C1 to   C6    alcohol is cyclohexanol. The C1 to C6 alcohols have boiling points ranging from 64.7 C to   205 C    (methanol = 64.7 C, ethanol = 78.3 C, propyl alcohol = 97.2 C, isopropyl alcohol = 82.3 C, butyl alcohol = 117.7 C, isobutyl alcohol = 108.0 C, sec-butyl alcohol = 99.5 C,   tert-butyl    alcohol = 82.5 C, pentyl alcohol = 138.0 C, hexyl alcohol = 156.5 C, cyclopentanol =   140 C,    cyclohexanol = 161.5 C and benzyl alcohol =   205 C).    The C1 to   C6    alcohol is applied to the root vegetable in vapour form, at a concentration of between about 0.025 to about 2.00ml/20 litres, more preferably at a concentration of between about 0.05 to about 1.5mi/20 litres,

   further preferably at a concentration of between about 0.1 to about   l.      Oml/20    litres. Most preferably, the C1 to   C6    alcohol is applied at a concentration of at least about 0.9ml/20 litres when the C1 to C6 alcohol is ethanol; or at a concentration of at least about 0.3ml/20 litres when the C1 to C6 alcohol is   1-    propanol; or at a concentration of at least about   0.      5ml/20    litres when the Cl to   C6    alcohol is 2-propanol ; or at a concentration of at least about   0.      5ml/20    litres when the
Ci to C6 alcohol is   2-methyl-2-propanol    ;

   or at a concentration of at least about   0.      1ml/201itres    when the C1 to   C6    alcohol is 1-butanol ; or at a concentration of at least about   0.      05ml/20    litres when the C1 to   C6    alcohol is cyclohexanol.



   According to a preferred feature of the present invention, the Ci to C6 alcohol is applied via a conventional   ventilation/aeration    system. However, alternative application means may also be employed provided that concentration levels of the   C    to C6 alcohol coming into contact with the vegetables remain within the defined ranges. The concentration of alcohol may be monitored using conventional monitoring sensor/apparatus and the level of alcohol adjusted, as necessary, to maintain the concentration at a steady level.



   It is further preferred that the vegetables contacted with the C1 to C6 alcohol are stored at temperatures above   4 C,    preferably at about 7   tolO C.    Further preferably, the vegetables are stored in substantially light-free conditions and under conditions of controlled humidity.



   Additionally, the root vegetables may be further contacted (either continuously or non-continuously) with one or more agents capable of extending the shelf-life of root vegetables, such as one or more anti-sprouting agents   and/or    one or more preservatives or the   lilce      and/or    one or more antipathogenic agents and/or one or more additional alcohols selected from higher and/or lower alcohols, aromatic   and/or    aliphatic alcohols.



   Advantageously, use of the method defined by the present invention enables inhibition of sprouting, prevents rotting and growth of fungi in root vegetables, such that the shelf-life of these vegetables is extended relative to control vegetables.



   Further advantageously, contacting of root vegetables according to the method defined by the present invention does not have any effect on the ultimate germination capability of the vegetables following removal of the vegetables from storage under the continuous application of the   C1    to C6 alcohol vapour.



   Further advantageously, employing the method defined by the present invention does not adversely affect physical or physiological properties of the vegetables.



   Advantageously, the method defined by the present invention may be carried out on genetically modified root vegetables (genetically modified using recombinant
DNA technology). For example, root vegetables may be genetically modified to inhibit sprouting relative to non-genetically modified varieties or they may be genetically modified to increase levels of resistance to various pathogens relative to resistance levels of their non-genetically modified counterparts. Employing the method according to the present invention on genetically modified plants advantageously enables the shelf-life of the root vegetables to be extended relative to the shelf-life of corresponding non-genetically modified root vegetables.



   Advantageously, the method according to the present invention allows potatoes to be stored at a relatively high temperature (thereby alleviating the problem of cold sweetening) without sprouting taking place.



   Further advantageously, the shelf-life of the root vegetables can be extended for a period of at least nine months.



   Importantly, the method defined by the present invention, when applied in quantities defined by the present invention, is non-toxic to humans and animals and has no adverse effects on the vegetables themselves.



   The method according to the present invention may be carried out any time of the year. Preferably the method according to the present invention is carried out at the outset of storage (post-harvest) and preferably applied continuously thereafter until the vegetables are ready for use.



   The present invention will now be described with reference to the following figures, in which:
Figure 1 is a graphical representation of the effect of ethanol on sprouting of potato cultivar Bintje after 70 days storage at   10 C.   



   Figure 2 is a graphical representation of the effect of ethanol on sprouting of potato cultivar Desire after 70 days storage at   10 C.   



   Figure 3 is a graphical representation of the effect of 1-propanol on sprouting of potato cultivar Bintje after 70 days storage at   10 C.   



   Figure 4 is a graphical representation of the effect of 1-propanol on sprouting of potato cultivar Desire after 70 days storage at   10 C.   



   Figure 5 is a graphical representation of the effect of 2-propanol on sprouting of potato cultivar Bintje after 70 days storage at   10 C.   



   Figure 6 is a graphical representation of the effect of 2-propanol on sprouting of potato cultivar Desire after 70 days storage at   10 C.   



   Figure 7 is a graphical representation of the effect of 2-methyl-2-propanol on sprouting of potato cultivar Bintje after 70 days storage at   10 C.   



   Figure   8    is a graphical representation of the effect of 2-methyl-2-propanol on sprouting of potato cultivar Desire after 70 days storage at   10 C.    



   Figure 9 is a graphical representation of the effect of 1-butanol on sprouting of potato cultivar Bintje after 70 days storage at   10 C.   



   Figure 10 is a graphical representation of the effect of 1-butanol on sprouting of potato cultivar Desire after 70 days storage at   10 C.   



   Figure 11 is a graphical representation of the effect of cyclohexanol on sprouting of potato cultivar Bintje after 70 days storage at   10 C.   



   Figure 12 is a graphical representation of the effect of cyclohexanol on sprouting of potato cultivar Desire after 70 days storage at   10 C.   



   The present invention will now be described with reference to the following examples. The examples specifically concern potato, however, the invention is equally applicable to other root vegetables.



  EXAMPLES
Example 1
Experiments were carried out to determine the effect of ethanol on potato sprouting. Wild-type potato varieties Desiree, Kardal and Bintje were used for the experiments. Studies were carried out at two different temperatures, namely   4 C    and   10 C.    The potato varieties were stored either at   4 C    or at   10 C    in the continuous presence of ethanol applied at a rate of lml ethanol/20 litres air, 4ml ethanol/20 litres air or   16ml    ethanol/20 litres air. The ethanol was pipetted into a petri dish which was then placed at the bottom of a 20-litre container. Upon evaporation of the ethanol, the potato samples were introduced to the container and the container closed. Control samples, omitting contact with ethanol, were also set up.

   The potato samples were monitored for the presence of sprouting and monitored for changes in   starch/sugar    levels and changes in fresh weight over a 6 month time course.



   The potatoes treated with ethanol at a concentration of 4ml ethanol/20 litres air and   16ml    ethanol/20 litres air rapidly showed signs of necrosis relative to control potatoes. The potatoes treated with ethanol at a concentration of lml   ethanol/20    litres air showed no sprouting relative to potatoes stored in an ethanol-free environment, indicating that application of ethanol at that concentration was able to inhibit sprouting. Furthermore, potatoes treated with ethanol at a concentration of   1ml    ethanol/20 litres air showed comparable starch/sugar levels relative to control potatoes indicating the absence of starch breakdown in these potatoes. The fresh weight of potatoes treated with ethanol at a concentration of lml ethanol/20 litres air was also comparable to the fresh weight of control potatoes.

   In all the above cases, the potatoes stored at a temperature of   4 C    sprouted at a slower rate and showed reduced signs of necrosis relative to potatoes stored at a temperature of   10 C.   



  Table 1
Effect of ethanol vapour   (1    ml ethanol/20 litres of air applied) on the sprout growth of 3 potato cultivars during storage (239 days) at 2 different temperatures.
EMI8.1     

 storage <SEP> temperature <SEP> ( C) <SEP> 4 <SEP> 4 <SEP> 10 <SEP> 10
<tb> treatment <SEP> control <SEP> ethanol <SEP> control <SEP> ethanol
<tb>  <SEP> % <SEP> sprouted <SEP> tubers <SEP> *
<tb>  <SEP> (after <SEP> number <SEP> of <SEP> days
<tb>  <SEP> stored)
<tb> cultivar
<tb> Solara <SEP> 0 <SEP> (239) <SEP> 0 <SEP> (239) <SEP> 100 <SEP> (77) <SEP> 0 <SEP> (239
<tb> Desiree <SEP> 100 <SEP> 91 <SEP> 0 <SEP> 239 <SEP> 100 <SEP> 50 <SEP> 0 <SEP> 239
<tb> Kardal <SEP> 100 <SEP> (174) <SEP> 0 <SEP> (239) <SEP> 100 <SEP> (50) <SEP> 0 <SEP> (239)

  
<tb> * <SEP> % <SEP> potatoes <SEP> with <SEP> sprouts <SEP>  >  <SEP> 3 <SEP> I
<tb> 
Example 2
The effect of different alcohols on the sprouting of Dutch potato cultivars
Desire and Bintje was tested. Desire and Bintje tubers were cultivated and harvested as seed potatoes. Where necessary, conventional fertilizers and plant protection measures were used.



   Up to 18 tubers were placed on stainless steel trays in salable 20 litre plastic containers. C02 increase due to respiration of the tubers was reduced by placing a petri dish filled with 25g of Ca (OH) 2 in the container underneath the stainless steel trays. Sealed containers were then placed in cold storerooms at temperatures of 4  C   and 18'C.   



   Several alcohols were tested at the concentration ranges shown in Table 2 (the amount of alcohol was   corrected    according to molecular weight and density of the alcohol in question at   20  C).    The alcohol was indirectly applied to the potato tubers by placing the alcohol in petri dishes underneath the stainless steel trays. The containers were sealed allowing the potato tubers to be exposed to the alcohol vapour in the containers. The alcohol was divided equally and placed in two glass petri dishes so as to ensure a more even distribution of vapour within the container.



  Alcohol was reapplied after the first 7 days and every two weeks thereafter using clean petri dishes each time.



   Tubers in the containers were monitored visually each week for signs of sprout growth. The number of tubers and number of sprouts per tuber with sprout growth  >  2mm were counted and the weight of the sprouts for each tuber determined. At the end of the 70-day storage period, the number of sprouts per tuber and the total weight of the sprouts per tuber were determined.



   Tubers in the containers were also monitored visually each week for signs of fungal infection or necrotic decay due to phytoxicity caused by the alcohol treatments.



  Tubers that deteriorated before the end of the 70-day time course were removed.



   The results are shown in Figures 1 to 12.



  Table 2
Correction of the Alcohols
EMI9.1     


<tb>  <SEP> applied <SEP> component: <SEP> ethanol <SEP> cyclo-1-butanol <SEP> 1-propanol <SEP> 2-propanol <SEP> 2-methyl
<tb>  <SEP> hexanol <SEP> 2-propanol
<tb>  <SEP> Mol <SEP> WF <SEP> 46. <SEP> 07 <SEP> 100.16 <SEP> 74.12 <SEP> 60.1 <SEP> 60.1 <SEP> 74.12
<tb>  <SEP> d <SEP> (20) <SEP> 0.7893 <SEP> 0.962 <SEP> 0.8098 <SEP> 0.8035 <SEP> 0.7855 <SEP> 0.7887
<tb>  <SEP> mp <SEP> ( C)"-114. <SEP> 1"+25. <SEP> 4-89.8-126.1-89.5 <SEP> +25.4
<tb>  <SEP> bp <SEP> ( C) <SEP> 78. <SEP> 2 <SEP> 160. <SEP> 8 <SEP> 117.7 <SEP> 97.2 <SEP> 82. <SEP> 3 <SEP> 82.4
<tb>  <SEP> (equiv <SEP> of <SEP> EtOH)
<tb>  <SEP> applied <SEP> amounts:

   <SEP> ml <SEP> g <SEP> ml <SEP> ml <SEP> ml <SEP> g
<tb>  <SEP> (mUcontainer)
<tb>  <SEP> 0
<tb>  <SEP> 0. <SEP> 20 <SEP> 0.35 <SEP> 0.32 <SEP> 0.26 <SEP> 0.27 <SEP> 0.26
<tb>  <SEP> 0. <SEP> 40 <SEP> 0.70 <SEP> 0.64 <SEP> 0.52 <SEP> 0.53 <SEP> 0.51
<tb>  <SEP> 0. <SEP> 60 <SEP> 1.02 <SEP> 0.93 <SEP> 0.76 <SEP> 0.78 <SEP> 0.76
<tb>  <SEP> 0. <SEP> 80 <SEP> 1.37 <SEP> 1.25 <SEP> 1. <SEP> 02 <SEP> 1. <SEP> 05 <SEP> 1.01
<tb>  <SEP> 1. <SEP> 00 <SEP> 1. <SEP> 72 <SEP> 1. <SEP> 57 <SEP> 1. <SEP> 28 <SEP> 1. <SEP> 31 <SEP> 1. <SEP> 27
<tb>  <SEP> application <SEP> intervals: <SEP> day <SEP> 0,7,21,35,49,63
<tb> screening <SEP> : <SEP> every <SEP> week <SEP> number <SEP> of <SEP> tubers <SEP> with <SEP> sprouts <SEP> 2 <SEP> 2mm
<tb>

Claims

CLAIMS 1. Method for extending the shelf-life of root vegetables, comprising substantially continuous contacting of a root vegetable with at least a C1 to C6 alcohol vapour or a mixture of C1 to C6 alcohol vapours.

2. Method according to claim 1, wherein the C1 to C6 alcohol is selected from one or more of ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 1-butanol and cyclohexanol.

3. Method according to claim 1 or 2, wherein said Cl to C6 alcohol vapour is administered via a ventilation/aeration system.

4. Method according to any of claims 1 to 3, comprising further contacting, either continuous or non-continuous, of one or more of the following: one or more anti sprouting agents, one or more preservatives or the like, one or more anti pathogenic agents or one or more further alcohols selected from higher and/or lower alcohols, aliphatic and/or aromatic alcohols.

5. Method according to any of claims 1 to 4, for inhibiting sprouting in vegetables capable of producing sprouts.

6. Method according to any of claims 1 to 5, wherein said root vegetable is selected from potato, sweet potato, yam, sugarbeet, swede, parsnip, beetroot, turnip or carrot.

7. Method according to any of claims 1 to 6, wherein said root vegetable is a potato, preferably a potato cultivar selected from Bintje, Desiree or Kardal.

8. Method according to any of claims 1 to 7, wherein said Cl to C6 alcohol is administered at a concentration of between about 0.025 and about 2ml alcohol/20 litres air, more preferably at a concentration of between about 0.05 to about 1. 5ml/20 litres, further preferably at a concentration of between about 0.1 to about l. Oml/20 litres, and wherein the alcohol is corrected according to its molecular weight and density at 20 C.

9. Method according to claim 8, wherein said C, to C6 alcohol is ethanol and is administered at a concentration of at least about 0. 9ml alcohol/20 litres air.

10. Method according to claim 8, wherein said Cl to C6 alcohol is 1-propanol and is administered at a concentration of at least about 0.3ml alcohol/20 litres air, as corrected.

11. Method according to claim 8, wherein said Ci to C6 alcohol is 2-propanol and is administered at a concentration of at least about 0. 5ml alcohol/20 litres air, as corrected.

12. Method according to claim 8, wherein said Cl to C6 alcohol is 2-methyl-2 propanol and is administered at a concentration of at least about 0.5ml alcohol/20 litres air, as corrected.

13. Method according to claim 8, wherein said Cl to C6 alcohol is 1-butanol and is administered at a concentration of at least about 0. lml alcohol/20 litres air, as corrected.

14. Method according to claim 8, wherein said Cl to C6 alcohol is cyclohexanol and is administered at a concentration of at least about 0. 05m1 alcohol/20 litres air, as corrected.

15. Method according to any of claims 1 to 14, wherein said root vegetables are stored at a temperature of between about 4 to about 10 C.

16. Method according to any of claims 1 to 15, wherein said root vegetables are stored in substantially light-free conditions and preferably in conditions of controlled humidity.

17. A root vegetable treated according to the method of any of claims 1 to 16.

18. A root vegetable according to claim 17, wherein said root vegetable is genetically modified using recombinant DNA technology.

19. A root vegetable according to claim 17 or 18, wherein said genetic modification comprises modification to inhibit sprouting relative to non-genetically modified varieties and/or modification to increase levels of resistance to various pathogens as compared with resistance levels of non-genetically modified counterparts.