GB2074437A - Treatment of plant matter - Google Patents

Abstract

A wound in plant matter (such as a wound in freshly cut fruit or vegetables or in living plants) is treated by applying to the wound a porous absorbent sheet material impregnated or coated with an intimate mixture of a biostat and/or biocide and, preferably a fungicide, with a latex coagulant such as aluminium sulphate. When the intimate mixture is in the form of a coating, the latter preferably also contains a water-soluble adhesive polymer; in this embodiment the coagulant may be absent. When the method is used for the treatment of freshly harvested banana hands, crown rot and latex staining is substantially reduced.

Description

SPECIFICATION Treatment of plant matter The present invention is concerned with a method of treating wounds in plant matter (such as fruit or vegetables) and a sheet material for use in such a method.

When certain fruit and vegetables are harvested, it is necessary to cut them from the plant. For example, when bananas are harvested, a large hand (or bunch) is cut from the plant stem leaving a wound on the hand at the cushion and a corresponding wound on the stem. These wounds tend to bleed juices, latex and other plant fluids, which can spoil the appearance of the bananas, eventually rendering them unsaleable. The wound on the hand also acts as a point of attack for pathogenic organisms (such as Fusarium semitectum, which is associated with crown rot decay of bananas).

A similar problem arises on harvesting most other fruit and vegetables, such as pineapples, capsicums, cucumbers and lettuce, and also when cutting a living tree or bush as, for example, when pruning, trimming or shaping or when tapping a rubber tree or palm tree for latex, or any other tree for sap.

The conventional method of treating such wounds in bananas is by washing complete hands in running water to remove latex therefrom, followed by applying to the wound (for example, by spraying or dipping) a solution of fungicide of low mammalian toxicity, such as Thiobendazole or Benlate. This method has the disadvantage that large vats are needed to contain the hands during washing, and several operational steps are required.

A recent proposal is to dip the crowns of the banana hands into a solution of aluminium sulphate (which acts as a coagulant for latex bleeding from the hands) before washing. However, this method does not satisfactorily staunch the flow of latex, so that washing must still be carried out thoroughly.

We have now developed an improved method of treating a wound in plant matter, which comprises applying to the wound a porous absorbent sheet material having, at least on a surface thereof, an intimate mixture of a biologically active material (that is, a biostat, such as a fungistat and/or a bacteriostat, or a biocide, such as a fungicide and/or a bactericide) and a latex coagulant.

The porous sheet material may be coated or impregnated with the intimate mixture; when it is impregnated therewith, it may be produced by dipping a porous absorbent web into a liquid (a suspension or solution) containing the biologically active material and the coagulant, placing the resulting impregnated web over the wound and drying in the air.

The wound in the plant matter being treated in the method according to the invention may be present in freshly cut fruit or vegetables, such as bananas, pineapples, capsicums, cucumbers and lettuce, or it may be present in a cut living tree, bush or other plant. When harvesting certain fruit and vegetables, such as, for example, pineapples, a wound on the material being harvested and a wound on the plant may both be treated according to the invention.

In order to avoid the need to prepare and handle a liquid containing a biologically active material on site, it is preferred to use a porous sheet material which has previously been provided with a coating comprising the above-mentioned intimate mixture.

In this case, a water-soluble adhesive polymer is preferably mixed with the intimate mixture of coagulant and biologically active material and applied to at least one surface of a porous liquid-absorbent web.

The present invention also comprises a coated porous absorbent web, which has been produced as described above and is suitable for use in the method according to the invention. According to a modification of this aspect of the invention, a coagulant need not be present in the coating, when the coated web is suitable for treating plant wounds which do not bleed liquids in the form of latex.

Certain coated webs according to the invention, namely those in which the biologically active mater ial is a bacteriostat and/or bactericide and the coagul ant (when present) is pharmacologically acceptable, may be suitable for use as medical dressings when supplied in sterile form.

The water-soluble adhesive polymer present in the coating on the web may be, for example, a polyox yethylene having a molecular weight of 1000 to 5000000, an acrylic polymer (such as a polymer of acrylic acid or acrylamide which, in the latter case, may be hydrolysed or a hydrolysed polymer of acrylonitrile), a cellulosic derivative, such as cellul ose ether (for example, hydroxyethyl cellulose or carboxymethyl cellulose), polyvinyl alcohoi, a natural polymer, such as starch, dextrin or gelatin, polyvinyl pyrrolidone, or a vinyl pyrrolidone/vinyl acetate copolymer.

For ease of application of the polymer to the web, it is preferred that the polymer has a distinct melting point or range, as this enables the polymer to be readilytackified during application of the coating.

For these and other reasons, preferred polymers for use in the coating are polyoxymethylenes and acrylic polymers.

When only one surface of the web is coated, means for identifying the surface bearing the coating are preferably provided. Such means may be in the form of indicia on one or other surface or a dye over the surface (preferably the surface bearing the coat ing containing the above-mentioned water-soluble adhesive polymer). Another possible means for identifying the coated surface is a peel-back sheet material releasably bonded to the coated surface.

The coating is preferably applied to the web in the form of a powder blend of the respective ingredients (which may be produced by grinding the ingredients together or by blending previously formed pow ders). The powder blend generally has a particle size of up to 600 microns, preferably 100 to 300 microns.

Such a fine particle size enables the coated web to retain its porosity and absorbency.

The powder blend is preferably dispensed on to the web by means of a scattering machine or vibrating plate, the dispensing being controlled such that a uniform distribution of powder is obtained on the web. The polymer in the powder is then softened, by the application of heat and/or water (which may be in the form of steam), such that the polymer effec tively binds the coating to the web.

Other possible ways of applying the coating to the sheet web include wet screen printing or gravu re dot printing (using the polymer as a thickening agent for the printing composition) or spraying as an aqueous solution or a solution in an organic solvent.

The coated porous absorbent web according to the invention is generallyfibrous and may be, for example, of paper, woven fabric or (preferably) a non-woven fabric such as, for example, non-woven cotton wadding. The coated web may have an absorption capacity for liquids of about six times its own weight, or more.

The coated web may be in the form of a rnIl,with transverse perforations at regular intervals so that a suitable length of coated web can be readily torn from the roll or, alternatively, the coated web maybe in the form of discrete lengths of a suitable size, the discrete lengths being preferably interleaved for easy dispensing from a dispensing package.

The biologically active material used in the method according to the invention should have low mammalian toxicity when used for treating fruit or vegetables for consumption. Suitable such materiars include Sigma, Mildathane, Delsene, Ben late (Registered Trade Mark), Thiobendazole (all fungicides), Dichlorophen (a fungicide and bactericide), Tego 51 (a bactericide), quaternary ammonium bactericides and sodium chloride.

The latex coagulant used in the method according to the invention should, like the biologically active material, have low mammalian toxicity. The coagulant may be any of the materials conventionally used for coagulating latices, such as, for example, a salt of a polyvalent metal. The polyvalent metal may be, for example, aluminium: a typical preferred coagulant is aluminium sulphate.

It is preferred that both the biologically active material and the coagulant are water-soluble or water emulsifiable.

In order that the present invention may be more fully understood, the following Examples are given by way of illustration only.

EXAMPLE 1 The following chemicals were mixed in a dry blending machine:- 50 Kilos Polyethylene glycol (molecular weight 12000) 5 Kilos "Benlate" 50% Benomyl (Methyl -1 (butylcarbamoyl) -2 - benzimidazolecarbamate) 50% Inert Filler 17.5 Kilos Aluminium sulphate 750 gms Green Vegetable Dye The ingredients were g round togeth er to produce a particle size distribution of between 0 and 300 Microns.

The ground product was curtain-coated onto a continuously moving web of a pure cellulose nonwoven fabric at a weight of 20 gms per square metre (the weight of the fabric itself was 85 gms per square metre and its absorption capacity for liquids was eight times its own weight).

The coated base fabric was then passed into an oven where the polyethylene glycol was melted; the web then continued through cold crushing rollers where the coated ingredients were crushed onto the web, and the molten polyethylene glycol solidified so as to bind all the other ingredients to the base fabric.

A sample of the coated web was then; cut into ss small areas (e.g. 4" x 3" rectangles), forlsanana i treatmertand a further sample was cut into 3" wide rolls perforated at right angles at 4" interval's so that 4" x 3" rectangles could be removed from the rolls for application to a banana hand.

Other shapes couldrof course, be cut from the main web depending on crop treatment require > - ments, i.e. small circular shapes for pineapples and capsicums To each of 169 banana hands was applied one of the resulting 4" x 3" rectangular pads; the hands were then assessed for crown rot and latex staining after a sea journey from the West Indies (St. Lucia) to Britain. The results are given in the following tables.

Crown Rot No. ofhands Rot absent 153 (90.5%) Very slight rot 11 (6.5%) 25% affected 4 (2.4%) More than 25% affected 1 (0.6%) Severe crown rot 0 (0.0%) Latex staining No. ofhands Latex absent 155 (91.7%) Veryslightstaining 12 (7.1%) 3 of all fingers affected 2 (1.2%) 1/2 or more of all fingers affected 0 (0.0%) EXAMPLE 2 A non-woven cellulose web as used in Example 1 was dipped in a solution containing Benlate and aluminium sulphate in a ratio by weight of 0.49 to 1.

Samples of the resulting impregnated web were applied to each of 124 banana hands which were then assessed for crown rot and latex staining as in Example 1. The results are given in the following tables.

Crown Rot No. ofhands Rot absent 96 (77.4%) Very slight rot 16 (12.9%) 25% affected 8 (6.5%) More than 25% affected 1 (0.8%) Severe crown rot 3 (2.4%) Latex staining No. ofhands Latex absent 116 (93.6% Veryslightstaining 2 (1.6%) 3 of altfingers affected 5 (4.0 C6) 1/2 of all fingers affected 1 (0.8%) - Severe latex staining 0 (0.0%) When, by way of comparison, banana hands were treated in the conventional manner, by washing the complete hands in running water and then dipping in a solution of a fungicide, the banana hands suf fered far more crown rot and latex staining than banana hands treated according to Example 1 or 2 after a similar sea journey. In each case (including Examples 1 and 2), assessment for crown rot and latex staining was effected approximately 16 days after harvesting the bananas.

In a prolonged evaluation over 24 shipments, banana hands were (i) treated with pads as described in Example 1; (ii) treated with an impregnated web as described in Example 2; or (iii) treated in the conventional manner, as described above.

2.9% of the hands treated according to method (i) had severe crown rot and 0% had severe latex staining; in method (ii), the corresponding figures were 6.3% (severe crown rot) and 0.5% (severe latex staining); while in method (iii), the corresponding figures were 8.75% (severe crown rot) and 2.81% (severe latex staining). These percentages are based on the total number of hands and not (as in Examples 1 and 2) based on the number of fingers.

Claims (10)

1. A method of treating a wound in plant matter, which comprises applying to the wound a porous absorbent sheet material having, at least on a surface thereof, an intimate mixture of biologically active material and a latex coagulant.

2. A porous absorbent sheet material which comprises a porous web having a dry coating on one or both surfaces, said coating comprising an intimate mixture of a water-soluble adhesive polymer, a biologically active material and a latex coagulant.

3. A sheet material according to claim 2 in which the polymer has a distinct melting point or range.

4. A sheet material according to claim 1 or 3, in which the coating is applied in the form of a powder blend of the respective ingredients.

5. A sheet material according to any of claims 2 to 4, in which the porous web comprises a nonwoven fabric having an absorption capacity for liquids of at least six times its own weight.

6. A sheet material according to any of claims 2 to 5, in which the biologically active material and the coagulant are pharmacologically acceptable and the sheet material is packaged in sterile form.

7. A modification of the sheet material claimed in any of claims 2 to 6, in which the coagulant is absent.

8. A package containing sheet material according to any of claims 2 to 7, in which the sheet material is in the form of a roll with transverse perforations at regular intervals or in the form of an interleaved stack of discrete lengths of the material.

9. A method according to claim 1, in which the sheet material is as claimed in any of claims 2 to 6.

10. A method according to claim 1 or 9, in which the wound is present in freshly cut fruit or vegetables.