AU769891B2 - Post-harvest method for treating fruits and vegetables using eugenol and/or isoeugenol - Google Patents

Abstract

The invention concerns an anti-germinating method for tubers and bulbs consisting in applying on said tubers and bulbs a treatment composition based on an active principle selected among eugenol, a eugenol salt fit for human consumption, isoeugenol, an isoeugenol salt fit for human consumption and their mixtures. The invention also concerns the use of a composition based on an active principle selected among eugenol, a eugenol salt fit for human consumption, isoeugenol, an isoeugenol salt fit for human consumption and their mixtures as anti-germinating agent.

Description

WO 00/32053 PCT/FR99/03007 Process for treating fruit and vegetables after harvesting using eugenol and/or isoeugenol The invention relates to a process for treating fruit and vegetables after harvesting, by applying a treating composition based on eugenol or isoeugenol to the said fruit and vegetables.

It is important for fruit and vegetables not to loose their organoleptic quality and to conserve an appealing appearance when they are placed on sale, for rapid consumption.

However, after harvesting, fruit and vegetables are commonly stored for relatively long periods before being placed on sale.

The phenomena likely to impair the appearance and taste of fruit and vegetables are, in particular, the proliferation of fungi and bacteria on their surface. These degradations are even faster in the region of the small bruises and nicks appearing on the skin of fruit and vegetables during their storage or handling.

Many processes exist in the prior art for treating fruit and vegetable to enable the proliferation of bacteria and fungi at the surface of the fruit and vegetables to be slowed down and/or partially or totally prevented.

The active principles used in most of these processes are synthetic products, which present high risks of toxicity for the consumer, as a result of which the permitted doses are always low. Consequently, research efforts have essentially been directed towards the development of ever more effective products.

The development of these treating agents is very expensive, to the detriment of the economic viability of the treatment.

To overcome these drawbacks, processes using natural products have been proposed.

2 Thus, patent application FR 95/05157 is directed towards an antifungal treatment process for fruit and vegetables which consists in applying a terpene-based composition to the said fruit and vegetables. The example in that document more specifically illustrates a treating composition based on L-carvone. More generally, that document makes reference to the use of monooxygenated terpenes such as terpineol, menthol, menthone, cineol (or eucalyptol) and citronellal.

However, these natural products are less effective than many of the synthetic products developed to date.

The invention is based on the discovery of the unexpected efficacy of two dioxygenated terpenes, i.e.

eugenol and isoeugenol, of formulae: OH

OH

OCH3 X OCH 3

CH

2

-CH=CH

2

CH=CH-CH

3 Eugenol Isoeugenol in protecting fruit and vegetables against bacteria and fungi.

One of the particularly advantageous characteristics of eugenol and isoeugenol is their broad spectrum of activity: in fact, the superiority of these substances over other terpenes is manifested in the case of very varied bacterial strains and in the case of very varied species of fungi.

Amongst the bacterial strains are, for example, Erwinia carotovora or Escherichia coli.

Examples of fungal species which may be mentioned are Fusarium oxysporum, Geotrichum candidum, Gloeosporium fructigenum, Penicillium digitatum, Penicillium expansum and Phytophthora parasitica.

3 The invention thus relates to a process for treating fruit and vegetables after harvesting, characterized in that it comprises the steps consisting in: a bringing a treating composition to a temperature of 400C to 60 0

C,

b subjecting the said fruit and vegetables to a treatment, for not more than 10 minutes, by spraying them with the said treating composition or by immersing them in the said treating composition, and doing so before storing the fruit and vegetables, the said treating composition comprising, as percentages by weight: from 10% to 40% of an active principle chosen from eugenol, a nutritionally acceptable eugenol salt, isoeugenol, a nutritionally acceptable isoeugenol salt, and mixtures thereof; from 0% to 90% of a nonionic surfactant; and from 0% to 90% of a solvent chosen from aliphatic alcohols, glycols, water and alkyl esters of carboxylic acids, and mixtures thereof; the treatment of tubers and bulbs being excluded.

In step the temperature to which the treating composition is heated is adjusted depending on the nature of the product treated. In fact, it is important not to cause the fruit and vegetables to cook or degrade. Only the surface of* the fruit and vegetables should be heated by placing in contact with the treating composition. According to one preferred embodiment, the surface should reach at least 350C, better still at least 400C, for example between 450C and 50 0

C.

In general, the treating composition is brought to a temperature of between 40'C and 60'C and the contact time is adjusted in parallel so as to reach the desired temperature at the surface of the fruit and vegetables.

4 The treating composition is preferably brought to between 45 0 C and 550C, better still between 480C and 52 0 C, for example 50 0

C.

In step the contact time is very short and in all cases less than 10 minutes. It generally ranges between 30 seconds and 10 minutes, advantageously between 30 seconds and 5 minutes. A contact time of 2 to 3 minutes is usually sufficient.

When the duration of treatment with the hot composition has passed, the application is stopped by any known means, in particular by simply stopping the sprinkling or spraying.

In one advantageous variant, in particular in the case of heat-sensitive fruit and vegetables, the process can comprise a further step consisting in rapidly cooling the fruit or vegetables which have been placed in contact with the hot treating composition, cooling them down to a temperature below or equal to ambient temperature.

This cooling can be carried out by circulation of air or by contact with water (in particular immersion or spraying), the temperature of which is below or equal to ambient temperature.

In the case of fruit and vegetables that are particularly heat-sensitive, such as peaches, apricots, tomatoes and pears, it is recommended to cool them before carrying out the hot treatment with the said treating composition. The cooling should take effect down to the very core of the fruit ahd vegetables. The fruit and vegetables are, for example, subjected to a treatment by hydrocooling. This can be carried out by spraying them with an aqueous cooling composition or by immersing them in an aqueous cooling composition.

The temperature of the aqueous cooling composition is generally between 000C and 150C.

The temperature and time of pretreatment with the cooling composition are adjusted so as to cool the treated fruit or vegetables entirely rather than just their outer layer. These parameters depend mainly on 5 the nature of the fruit and vegetables. As a guide, it will be noted that the temperature of the cooling composition is less than or equal to the conventional storage temperature recommended in the art.

According to one preferred embodiment, the aqueous cooling composition has a temperature of from 0 0 C to 10 0 C, better still from 0oC to 5-60C. The duration of the pretreatment with the aqueous cooling composition is generally between 2 minutes and 2 hours, usually between 2 minutes and 60 minutes, for example between 4 minutes and 30 minutes.

This variant is described more specifically in patent applications FR 96/03100 and FR 98/08995.

The active principle can comprise a nutritionally acceptable eugenol or isoeugenol salt.

Salts that are particularly preferred include, in particular, alkali metal salts such as the sodium salts, lithium salts and potassium salts.

According to a first embodiment of the invention, the active principle is preferably a nutritionally acceptable salt or a mixture of such salts. Specifically, in this case, lower volatility of the active principle is observed. In this way, the duration of protection of the fruit and vegetables after the treating composition has been applied is prolonged. The active principle advantageously comprises one or more nutritionally acceptable eugenol salts.

According to a second embodiment of the invention, the active principle is chosen from eugenol, nutritionally acceptable eugenol salts, and mixtures thereof.

It should be understood that the treating composition can comprise, in addition to the active principle of eugenol or isoeugenol type, another active principle which counteracts the growth of bacteria and fungi and/or which inhibits the germination of potatoes and onions.

6 Examples of nonionic surfactants which can be used according to the invention include, in particular: the product of condensation of an aliphatic fatty alcohol, which is preferably C8-C22, with a C2-C3 alkylene oxide. The C2-C3 alkylene oxide can be ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide in any proportion. An example of such surfactants is the product of condensation of lauryl alcohol (or n-dodecyl alcohol) with 30 mol of ethylene oxide; the product of condensation of an alkylphenol in which the alkyl chain is C8-C22 with a C2-C3 alkylene oxide. In this case also, the products of condensation with ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide in any proportion are also advantageous. As an example of such surfactants, mention may be made of the product of condensation of n-nonylphenol with 10 mol of ethylene oxide; the product of condensation of a fatty acid, which is preferably C 8

-C

22 with a C2-C3 alkylene oxide, for example ethylene oxide or propylene oxide or a mixture of ethylene oxide and propylene oxide in any proportion. These condensation products have an alkoxylated chain on the hydroxyl function of the carboxylic group. Preferred surfactants of this group are the condensation products obtained from ricinoleic acid with 10 mol of ethylene oxide.

It should be understood that "the surfactant can consist of several nonionic surfactants.

When the treating composition comprises active substances in the form of salts, the presence of a surfactant is optional. This surfactant is then generally present in the treating composition in a proportion of from 0% to 20% by weight, for example from 10% to 20% by weight.

When the treating composition comprises only salified active substances, the surfactant can represent from 10% to 90% by weight and preferably from 7 to 85% by weight of the composition, for example from 10% to 20% by weight.

Examples of preferred aliphatic alcohols include CI-C 12 alkanols.

In the context of the invention, glycols denote alkylene glycols and polyalkylene glycols.

The term "alkylene glycol" means dihydroxylated alcohols derived from aliphatic hydrocarbons by replacing two hydrogen atoms with two hydroxyl groups.

(C

2

-C

6 )alkylene glycols such as ethylene glycol and propylene glycol are preferred.

The term "polyalkylene glycol" means the compounds of formula HO-(CpH 2 pO)n-H in which p and n are integers between 2 and 6.

By way of example, mention may be made of dipropylene glycol.

According to the invention, the group CpH 2 pO is linear or branched. The preferred polyalkylene glycol according to the invention is dipropylene glycol.

The preferred alkyl esters of carboxylic acids are the (C 1

-C

6 )alkyl esters of (C 1

-C

6 )alkanoic acid, such as butyl acetate.

Water is a preferred solvent.

It should be understood that the solvent can consist of a mixture of solvents.

When the treating composition comprises active substances in the form of salts, the presence of a solvent is highly desirable. The solvent will preferably represent from 40% to 90% by weight of the composition, for example from 50% to 85% by weight, better still from 50% to 80% by weight and generally from 60% to 80% by weight. The solvent in this case is advantageously water.

When the treating composition does not comprise only salified active substances, the amount of solvent may be smaller. It may advantageously range between 0% and 80% by weight, better still between 0% and 50% by weight, for example between 0% and 20% by weight.

8 According to another preferred embodiment, one or more agents for reducing the evaporation of the active principle are added to the treating composition.

Such agents are known in the art.

By way of example, mention may be made of water-dispersible polyterpenes; glycerol esters of pine resin; gum lacquers; lecithins; drying oils; polyvinyl alcohol; polyvinylpyrrolidone; alkali metal polyacrylates; and gum arabic.

Isoprene polymers and natural rubber are polyterpenes which can be used in the context of the invention.

The glycerol esters of pine resin are abietic acid esters.

The gum lacquers can be used in their natural form or in purified form, such as shellac resin.

The lecithins are mixtures of combinations of oleic, stearic and palmitic acid esters with glycerophosphoric acid and choline.

The polyvinyl alcohol, polyvinylpyrrolidone, alkali metal polyacrylates and gum arabic are watersoluble synthetic resins which also function as agents for reducing the evaporation of the active principle.

However, it should be understood that the invention is not in any way limited to the use of these specific water-soluble resins, but that any other type of water-soluble resin may also be suitable provided that it is capable of reducing the evaporation of the active principle.

Preferred examples of drying oils are glyceryl linoleate, linoleic acid and linolenic acid.

When it is present, the evaporation-reducing agent represents from 0% to 10% by weight and preferably between 1% and 10% by weight of the treating composition.

One preferred formulation of the treating composition is as follows: 15% to 30% by weight of active principle, better still from 15% to 25% by weight; 9 0% to 20% by weight of a nonionic surfactant, better still from 10% to 20% by weight; 40% to 90% by weight of a solvent (preferably water), better still from 50% to 80% by weight.

In this case, it is advantageous to use active principles in the form of salts.

Another preferred formulation is as follows: from 15% to 30% by weight of active principle, better still from 15% to 25% by weight; from 10% to 85% by weight of nonionic surfactant, better still from 15% to 85% by weight; from 0% to 50% by weight of solvent, better still from 0% to 20% by weight.

In this case, it is advantageous to use nonsalified active principles.

The treating composition is prepared in a conventional manner per se by simply mixing its constituents together.

When the treating composition comprises a nutritionally acceptable salt, this salt may be introduced into the composition, during its preparation, in salt form or else in neutral form; in the latter case, the salt is formed in situ by addition of a suitable base such as an alkali metal hydroxide (sodium hydroxide or potassium hydroxide) The amount of treating composition which needs to be applied to the fruit and vegetables depends on the nature of the fruit and vegetables concerned and on the application method selected.

The residual amount of active principle remaining on the fruit and vegetables after application generally varies after each application between 0.4 g and 20 g per tonne of fruit or vegetables treated.

More generally, the amount of active principle applied will be adjusted as a function of the duration of storage. Since eugenol and isoeugenol are odoriferous products, it is in fact preferable that, at the end of storage, most of the active principle should have evaporated off so as not to adversely affect the 10 commercial value of the fruit and vegetables when they are placed on sale. The amount of active principle which needs to be applied thus depends on the volatility of the active principle and on the duration of storage.

The process of the invention is particularly advantageous since it uses an active principle which is particularly effective as a bactericide and fungicide.

The implementation variants specifically described above are themselves also particularly advantageous since they contribute towards improving the efficacy of the active principle: by increasing the penetration of the active principle into the surface layer of the fruit and vegetables; due to the introduction into the treating composition of agents which reduce the volatility of the active principle; due to the use of a nutritionally acceptable salt of eugenol and/or isoeugenol.

The treatment of tubers (and, for example, of potato tubers) and that of bulbs (such as onion bulbs) is excluded from the context of the invention.

The examples which follow further illustrate the invention.

EXAMPLE 1 This example illustrates aqueous compositions which can be used in unmodified form in the process of the invention. The active principle in these aqueous compositions is eugenol in the form of its sodium salt.

Table 1 gives the formulation of compositions 1.1 to 1.3.

11 TABLE 1 EXAMPLE SURFACTANT EUGENOL NaOH Water 1.1 0 15 8 77 1.2 15 16 4 1.3 0 14 2.4 83.6 Table 1 gives the weight percentages of the various constituents.

EXAMPLE 2 The fungicidal activity of eugenol and isoeugenol was demonstrated in vitro and compared with that of other terpenes.

The cristomalt medium used to evaluate the fungicidal activities contains 0.1% cristomalt (malt extract) and 0.2% agar agar.

After sterilization, this culture medium is brought to 55°C. The terpene compound tested is then introduced in pure form into the hot culture medium.

Immediately after stirring, the medium supplemented with the terpene product is poured into Petri dishes (9 cm diameter, filled with 20 ml of medium). The agar medium solidifies on cooling. The Petri dishes are then inoculated with explantates (plugs) 6 mm in diameter taken from the edge of a culture of the test fungus obtained on cristomalt medium.

The inoculation is carried out at 220C.

The mycelial growth was determined periodically to 15 days depending on the species of fungus).

The results are expressed in Table 3 below in terms of MIC, which is the content (in uig/ml) which gives total inhibition of mycelial growth.

It will be noted that ranges of variation of the MIC values are indicated in Table 2. In fact, each experiment was carried out several times such that, for each terpene and for each species of fungus, a minimum value and a maximum value were obtained.

12 TABLE 2 CARVONE EUCALYPTOL EUGENOL ISOEUGENOL TERPINEOL SAFROL AA 40-80 >1280 20-40 20-40 40-80 80-160 BC 20-40 640-1280 20-40 20-40 40-80 80-160 FO 40-80 640-1280 20-40 20-40 40-80 80-160 GC 80-160 320-640 10-20 10-20 80-160 160-230 GR 40-80 320-640 20-40 20-40 40-80 40-80 PD 40-80 >1280 20-40 20-40 40-80 160-230 PE 80-160 >1280 20-40 20-40 40-80 640-1280 PV 80-160 160-320 40-80 20-40 40-80 80-160 PhP 40-80 320-640 20-40 20-40 20-40 40-80 Throughout the text of the present description, the meanings of the abbreviations used in Table 2 are as follows: AA Alternaria alternata BC Botrytis cinerea FO Fusarium oxysporum GC Geotrichum candidum GR Gliocladium roseum PD Penicillium digitatum PE Penicillium expansum PV Phlyctaena vagabonda ("Gloeosporium") PhP Phytophthora parasitica The analysis of the results obtained is carried out simply by using the assessment scale illustrated in Table 3: 13 TABLE 3 MIC included in the range Grades of inhibition delimited by the two values indicated in ppm (ig/ml) 10-20 8 (strong inhibition) 20-40 7 40-80 6 80-160 160-320 4 320-640 3 640-1280 2 >1280 1 (weak inhibition) In Table 4, the results obtained have been expressed using the scale from Table 3.

TABLE 4 CARVONE EUCALYPTOL EUGENOL ISOEUGENOL TERPINEOL SAFROL AA 6 1 7 7 6 BC 7 2 7 7 6 FO 6 2 7 7 6 GC 5 3 8 8 5 4 GR 6 3 7 7 6 6 PD 6 1 7 7 6 4 PE 5 1 7 7 6 2 PV 5 4 6 7 6 PhP 6 3 7 7 7 6 Total of the 52 20 63 64 54 42 degrees of inhibition 0 It emerges clearly from Table 4 that eugenol and isoeugenol are markedly more active than the other terpenes.

14 EXAMPLE 3 The activity of eugenol and isoeugenol on spore germination was evaluated in vitro and compared with that of other terpenes.

The procedure of Example 2 was used to do this, except that the concentration of eugenol and isoeugenol was set at x pg/ml in the culture media used and that il of a spore suspension adjusted to 100,000 spores/ml are placed in each Petri dish.

The same experiment was carried out starting with a terpene-free culture medium (control test).

The results were evaluated using the following assessment criteria: spore germination comparable to that of the control considerable reduction in the level of spores germinated 0 no spores germinated.

Tables 5, 6 and 7 show the results obtained for 3 different concentrations of terpenes in the culture medium, i.e. 40 pig/ml, 80 ug/ml and 1280 p.g/ml.

TABLE 5 (x 40 ig/ml) CARVONE EUCALYPTOL EUGENOL ISOEUGENOL TERPINEOL SAFROL AA 0 0 BC 0 FO 0 0 GC 0 0 PD 0 0 PE 0 0 PV 0 0 PhP 0 0 0 0 15 TABLE 6 (x 80 ig/ml) CARVONE EUCALYPTOL EUGENOL ISOEUGENOL TERPINEOL SAFROL AA 0 0 0 0 BC 0 0 0 0 0 FO 0 0 0 0 GC 0 0 0 PD 0 0 0 0 PE 0 0 0 PV 0 0 0 0 PhP 0 0 0 0 0 TABLE 7 (x 1280 jig/ml) CARVONE EUCALYPTOL EUGENOL ISOEUGENOL TERPINEOL SAFROL AA 0 0 0 0 0 0 BC 0 0 0 0 0 0 FO 0 0 0 0 0 0 GC 0 0 0 0 0 0 PD 0 0 0 0 0 PE 0 0 0 0 PV 0 0 0 0 0 0 PhP 0 0 0 0 0 0 It results clearly from these various tables that the activity of eugenol and isoeugenol is far superior to that of the other terpenes. A concentration of 40 pg/ml is sufficient to inhibit spore germination.

EXAMPLE 4 The bactericidal activity of eugenol and isoeugenol was evaluated in vitro and compared with that of other terpenes.

The culture medium used is the following LB medium: Bactotryptone: Yeast extract: 1% by weight 0.5% by weight 16 NaCI: 0.5% by weight Agar agar: 1.2% by weight A bacterial suspension containing 106 CFU/ml was prepared in sterilized water using the LB medium.

200 pl of this bacterial suspension were added to 20 ml of presterilized LB culture medium and brought to 550C.

The terpene tested is then added to the culture medium.

After stirring, the medium is immediately distributed in Petri dishes. The medium solidifies on cooling.

The incubation is carried out at 280C when the bacterium is Erwinia carotovora and at 370C when the bacterium is Escherichia coli.

The growth of the bacterial cloud in the culture medium is observed. The same experiment is carried out in the absence of terpene (control experiment).

The results are evaluated using the following assessment scale: bacterial cloud identical to that of the control bacterial cloud present with a marked reduction in growth relative to the control total absence of growth.

Table 8 summarizes the results obtained for 3 different concentrations, i.e. 20, 80 and 320 tg/ml in the case of the bacterium Erwinia carotovora.

TABLE 8 Concentration CARVONE EUCALYPTOL EUGENOL ISOEUGENOL TERPINEOL SAFROL in Ig/ml 320 In another series of experiments, the concentration of terpene required for total inhibition of the growth of the bacteria (MIC) was determined. The P:\Opcr\Mal2003\232030 9 331.doc-27/11/03 -17procedure used is that described above.

obtained are given in Table 9 below.

The results Table 9 MIC in CARVONE EUCALYPTOL EUGENOL ISOEUGENOL TERPINEOL SAFROL Pg/ml Erwinia 80-160 320-640 20-40 20-40 80-160 320-640 sp.

Esche- 320-640 >640 40-80 40-80 160-320 >640 richia sp.

On the two bacteria, eugenol and isoeugenol are found to be the most active.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (11)

1. 2. Treatment process according to Claim 1, characterized in that, before treating the fruit and vegetables with the said treating composition, they are cooled to the core by spraying with an aqueous cooling composition or by immersion in an aqueous cooling composition, the said aqueous cooling composition o having a temperature of greater than or equal to OOC and less than or equal to 15 0 C.
2. 3. Treatment process according to either of the preceding claims, characterized in that the said active principle is a salt acceptable in foodstuffs or a mixture of such salts. 19
3. 4. Process according to any one of the preceding claims, characterized in that the active principle is eugenol, a salt of eugenol which is acceptable in foodstuffs or a mixture thereof.
4. 5. Process according to any one of the preceding claims, characterized in that the said treating composition also comprises one or more agents for reducing the evaporation of the said active principle.
5. 6. Process according to claim characterized in that the evaporation-reducing agents are chosen from water-dispersible polyterpenes; glycerol esters of pine resin; lacs; lecithins; drying oils; polyvinyl alcohol; polyvinylpyrrolidone; alkali metal polyacrylates; and gum arabic.
6. 7. Process according to either of Claims 5 and 6, characterized in that the said treating composition comprises from 1% to 10% by weight of one or more evaporation-reducing agents.
7. 8. Process according to any one of the preceding claims, characterized in that the said treating composition is brought to a temperature of 45 0 C to 50 0 C in step
8. 9. Process according to any one of the preceding claims, characterized in that the said treating 25 composition essentially comprises: o*e* from 15% to 30% by weight of active principle; from 0% to 20% by weight of nonionic surfactant; from 40% to 90% by weight of a solvent. Process according to Claim 9, characterized in that the solvent is water and the active principle is a salt or a mixture of salts.
9. 11. Process according to any one of Claims 1 to 8, characterized in that the treating composition essentially comprises: from 15% to 30% by weight of active principle; from 15% to 85% by weight of nonionic surfactant; from 0% to 50% by weight of solvent.
10. 12. Process according to claim 11, characterized in that the active principle is chosen from eugenol and isoeugenol, and mixtures thereof.
11. 13. Process according to any one of claims 1 to 12 substantially as hereinbefore described with reference to the examples. DATED this 3 rd day of November, 2003 Xeda International By DAVIES COLLISON CAVE Patent Attorneys for the Applicants o *oo