NZ270390A - Spray containing buffered hydroxycarboxylic acid, citric acid and surfactant(s) to remove stains from fruit - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £70390 270390 Complete Specification Filed: ...Uew.f.:.3. Class: (6) .. &.Q!Ql/.Qta * • BOlfklj,Do Publication Date:. 2.S..AUP..M6 P.O. Journal No: IV+oT? No: 270390 Date: 24 January 1995 NEW ZEAJaWP Patents Act 1953 COMPLETE SPECIFICATION IMPROVEMENTS IN AND RELATING TO THE REMOVAL OF STAINS FROM FRVXS We, SOLEXIN INDUSTRIES LIMITED a New Zealand company of Devon Road, New Plymouth, New Zealand do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- 2703 This invention relates to modifications and improvements to the invention described and claimed in our New Zealand Patent No 225335 (the "parent patent") relating to the removal of stains from fruit and more particularly stains from kiwifruit.

Staining on the surface of kiwifruit is a well recognised problem which while usually of a cosmetic nature is indicative, to the consumer, of a second grade product. Such staining is commonly a result of water stains with the main cause believed to be water coming off necrotic plant tissues in the canopy and dripping onto the fruit causing staining down the side of the fruit. This staining is believed to be due to the leaching out of tannins, phenolic compounds and minerals from the necrotic tissue and the redeposit of these on the fruit. It is also believed that staining can be attributable to the presence of high pH or high concentrations of mineral elements such as iron in water. In addition staining can result from chemical deposits such as pesticide residues, dust in the nature of limestone and fertiliser and bird droppings.

It is known to remove or lessen such staining by spraying the kiwifruit just prior to harvest with citric acid. This can for example be achieved by using a 0.5% solution (food grade citric acid in water) together with a suitable wetting agent. While citric acid spraying 2703 has been shown to provide an effective means of removing or lessening staining it does not provide a total solution to the problem and indeed there are identified shortcomings associated with this pre-harvest treatment. For example citric acid spraying can lead to visible deposits being left on the fruit or developing after harvest. Citric acid spraying also does not prevent the development during storage of fungal contamination of the fruit.

The invention described in the parent patent relates to a spray formulation for the removal of staining from fruit, especially kiwifruit, which comprises a buffered hydroxycarboxylic acid combined with a surface active agent(s). In the preferred form described in the parent patent the spray comprises lactic acid and alkali salts of phosphoric acid with a compatible blend of surface active agents.

The invention of the parent patent overcomes the shortcomings and/or problems normally associated with known sprays such as citric acid sprays. However, with citric acid based treatments the fruit can be sprayed and picked on the same day whereas the lactic acid sprays of the parent patent ideally need to be left for two to three days after spraying before the fruit can be picked in order to maximise the reduction in staining. Therefore, the lactic acid sprays have the disadvantage that there is a greater chance that the spray will be 4 27 0 3 9 0 washed off the fruit or the fruit be restained by rainfall before the fruit is harvested.

An object of the modification or improvement in the invention of the parent patent is to provide a spray formulation for the removal of staining from fruit, especially kiwifruit, which reduces the time between spraying of fruit and harvesting thereof, while retaining the advantages of the invention of the parent patent.

Broadly there is provided a spray for the removal of staining from the surface of fruit, said spray comprising a buffered hydroxycarboxylic acid combined with citric acid and one or more surface active agents.

In a preferred form the spray comprises lactic acid, citric acid, alkali salts of phosphoric acid, and a compatible surface active agent.

The spray will be described in the following more specific disclosure with particular reference to the aforementioned preferred embodiment. This is, however, by way of example and other embodiments with.

The spray according to the modification or improvement over the spray described and claimed in the parent. person ambit stated above will be evident to 27 Q 3 9 0 patent is primarily used as a pre-harvest spray though it can be also used as a post-harvest dip. Such post-harvest treatment is, however, usually forbidden by regulation in many countries. Thus while the following disclosure will refer to the spray composition as a spray it must be remembered that it is equally useable as a dip.

According to the preferred form the buffered hydroxycarboxylic acid is lactic acid combined with citric acid which are buffered by alkali salts of phosphoric acid more particularly monosodium dihydrogen phosphate. The preferred ratio weight/weight of lactic acid to citric acid is in the range 99:1 to 1:3 but preferably is 4:1 to 1:1. The preferred weight/weight ratio of lactic acid plus citric acid to phosphoric acid equivalent is in the range of 1:1 to 10:1 but preferably is about 5:1.

The rate of application weight to volume of the spray for spray or dip treatment is between 0.01 - 2.0% lactic acid plus citric acid, and the buffer of 0.01 - 0.25% phosphoric acid equivalent as the monosodium dihydrogen salt. The preferred rate weight to volume is, however, 0.1 - 0.5% lactic acid plus citric acid, and 0.025 -0.15% phosphoric acid equivalent. >\ 17 J(JN |ggg / A 2703 Acidity of the spray is in the range of 2.0 to 3.5 pH and preferably 2.5 to 3 pH.

The surfactant chosen is a fully biodegradable alkylpolysaccharide surfactant approved for food crop use. An example of such a surfactant is ICI' s Alkadet 20 (T.M.) which has the added advantage of having a low foaming rating. The surfactant is added to the formulation at a rate between 5 - 20% to produce a stable (in the presence of high salt concentration) ready-to-use formulation.

The spray according to the modification thus provides a ready-to-use liquid concentrate formulation which/ prior to spraying or dipping is diluted with water. It does not therefore require the careful solubilising of the presently used powder form citric acid. The liquid concentrate is stable and remains fully soluble down to -15°C. It is believed that the combination of lactic acid with citric acid in the modified formulation stops the formation of insoluble citric acid salts which can be a problem when citric acid is diluted with hard water. Thus it is envisaged that the present modification will not lead to visible deposits of insoluble salts after drying or storage.

It is envisaged that another advantage of the current formulation combining lactic acid with citric acid, is the likelihood of lower occurrence of stain "reversal" 270 3 90 commonly associated with the use of straight citric acid formulations. The present state of the art is that the origin of storage stains is not well understood, but fungal organisms growing on the fruit surface have been implicated. It is understood that fungal mycelium on the fruit surface frequently results from contamination of harvested fruit by damaged fruit during harvesting and grading. Lactic acid is known to act as a preservative against fungal growth. Therefore it is believed that the present formulation will provide antimicrobial activity against mould organisms developing on the fruit in storage. By buffering the lactic acid with a phosphate, an acid state will tend to be maintained into the storage time and will inhibit the establishment of fungal growth.

The preferred formulation according to the invention may be applied at the same time or following the usual pre-harvest fungicide spray [such as Ronilan (reg. Trade Mark) and functionally similar fungicides] used to reduce rot diseases in stored fruit. In fact the preferred formulation compared with known citric acid treatment does not result in the often experienced flocculant redisposition caused by the citric acid/fungicide interaction.

The spray according to the present invention thus effectively removes stains from the surface of kiwifruit and "polishes" (eg cleans and brightens) up the surface

Claims (19)

270 so that the visual effect is that required for fruit with a high quality finish. The buffered acid takes off the staining while the surfactants clean and brighten the finished fruit to a desirable greenish brown colour. Furthermore, the fruit can be sprayed and picked on the same day thus greatly minimising the chances of bad weather interference. While the foregoing has paid particular attention to kiwifruit, it is believed the spray of the present invention will be effective with other fruits, whether the fruit be sprayed or dipped, and will exhibit substantially the same advantages and end results. 9 27 03 9 0' WHAT WE CUIM IS!-

1. A spray for the removal of staining from the surface of fruit, said spray comprising a buffered hydroxycarboxylic acid combined with citric acid and one or more surface active agents.

2. A spray as claimed in claim 1 wherein the buffered hydroxycarboxylic acid is lactic acid and alkali salts of phosphoric acid.

3. A spray as claimed in claim 2 wherein the lactic acid is buffered by monosodium dihydrogen phosphate.

4. A spray as claimed in claim 2 or 3 wherein the weight/weight ratio of lactic acid to citric acid is in the range of 99:1 to 1:3.

5. A spray as claimed in claim 4 wherein the weight/weight ratio of lactic acid to citric acid is in the range of 4:1 to 1:1.

6. A spray as claimed in claims 2 to 5 wherein the weight/weight ratio of lactic acid plus citric acid to phosphoric acid equivalent is in the range of 1:1 to 10:1. 10 27 0 3 9 0

7. A spray as claimed in claim 6 wherein the weight/weight ratio of lactic acid plus citric acid to phosphoric acid equivalent is 5:1.

8. A spray as claimed in any one of the preceding claims wherein the rate of application thereof weight to volume is between 0.01 - 2.0% lactic acid plus citric acid, and for the buffer, between 0.01 - 0.25% phosphoric acid equivalent as the monosodium dihydrogen salt.

9. A spray as claimed in claim 8 wherein the rate of application weight to volume is between 0.1 - 0.5% lactic acid plus citric acid, and between 0.025 - 0.15% phosphoric acid equivalent.

10. A spray as claimed in any one of the preceding claims wherein the acidity of the spray is in the range of 2.0 to 3.5 pH.

11. A spray as claimed in claim 10 wherein the acidity is in the range of 2.5 to 3.0 pH.

12. A spray as claimed in any one of the preceding claims wherein the surface active agent is an alkylpolysaccharide surfactant. A*"*'; 11 '27 0 & 9-0

13. A spray as claimed in claim 12 wherein the surface active agent is added to the spray at a rate of between 5 to 20% weight to volume.

14. A method for the removal of staining from the surface of fruit comprising the step of spraying the fruit with, or dipping the fruit in the spray formulation claimed in any one of the preceding claims.

15. A method as claimed in claim 14 wherein the spray formulation claimed in any one of claims 1 to 13 is provided as a liquid concentrate which is diluted with water prior to use.

16. A method as claimed in claims 14 and 15 wherein a fungicide is applied at the sane time or just prior to spraying or dipping the fruit.

17. A spray as claimed in claim 1 substantially as hereinbefore described.

18. A method as claimed in claim 14 substantially as hereinbefore described.

19. A kiwifruit spray as claimed in claim 1. s<< cm >n ' ■ SOLEXIN INDUSTRIES LIMITED 0\ By its Attorney ' % ^ DON HOPKINS & ASSOCIATES i — 4 4 17 JUN1996 y per: » .