WO1999020119A1

WO1999020119A1 - Method and apparatus for the post-harvest treatment of fresh fruit and vegetables

Info

Publication number: WO1999020119A1
Application number: PCT/NZ1998/000155
Authority: WO
Inventors: Geoff Lewis
Original assignee: The Tender Tips Company Limited
Priority date: 1997-10-16
Filing date: 1998-10-15
Publication date: 1999-04-29
Also published as: AU9767498A

Abstract

A process and apparatus are provided for the treatment of past-harvest produce. The process includes the steps of: submerging the said produce in warm water held at a temperature maintained within a predetermined temperature range; keeping the said produce submerged for a period of time falling within a predetermined range of time; and aerating the water in which the produce is submerged. In a preferred option the produce is rapidly cooled to about 1 °C to 5 °C after treatment, and may optionally be cooled by submerging in cold water prior to the rapid cooling. Apparatus comprising one or two containers of water for treatment and subsequent cooling is provided, with means for the controlled rate entry and exit of produce from the water in the containers. Means for regulating temperature of the water, and aerating the water are also provided. The preferred post-harvest produce is asparagus.

Description

METHOD AND APPARATUS FOR THE POST-HARVEST TREATMENT OF FRESH FRUIT AND VEGETABLES

FIELD OF THE INVENTION

This invention relates to a method and apparatus for treating fruit, vegetables and floricultural crops, and in particular to a method of and/or apparatus for organic post- harvest treatment of temperate vegetables, especially asparagus.

BACKGROUND

Fresh produce such as fruit and vegetables, is often treated after harvesting in order to prepare it for both local and export markets. Depending on the nature of the produce, the treatment may be for the purposes of cleaning, deinfestation of pests, the improvement of appearance or other similar reasons. Exported produce is often required to meet specific criteria, and frequently, on importation, the produce is further treated to ensure these criteria are met. This adds to the cost of the produce, and it would be most advantageous if this further treatment was not required because adequate treatment had been effected in the country of origin.

One method of treatment of produce, for the purposes of deinfestation or killing of any pests residual on it, is by way of fumigation. Gases such as HORTIGAS are known to be used for this purpose. However, there are problems with the use of this method. Chemical treatment of produce for human consumption is now regarded as undesirable and there is consumer resistance to purchasing produce which has been treated with any chemicals. Treatment by fumigation is often only partially successful as a means of deinfestation of produce as often the insects or other pests to be killed and/or removed, reside within the structure of the fruit or vegetables and the gas is only effective in killing pests on the surface. Consequently many of the pests may not be killed. Fumigation, furthermore, is not effective in removing the pests (whether dead or alive) from the produce. There can sometimes be difficulties in obtaining the gases required for fumigation, and if the deinfestation is dependent on a certain gas, which subsequently, for a number of possible reasons, becomes unavailable, the supplier is then unable to effect the deinfestation. Shelf life and appearance of produce can be adversely affected by fumigation or other chemical treatments.

OBJECT It is an object of this invention to provide a novel process for the post-harvest treatment of fresh produce, such as fruit, vegetables and floricultural crops, which will obviate or minimise the foregoing disadvantages, or at least provide the public with a useful choice.

STATEMENT OF INVENTION

In a first aspect the invention consists of a process for treating post-harvest produce such as fruit, vegetables and floricultural crops, which includes the steps of:

submerging said produce in warm water held at a temperature maintained within a predetermined temperature range;

keeping said produce submerged for a period of time falling within a predetermined range of time; and

aerating the said water.

Preferably, the said produce is rapidly cooled subsequent to being removed from the water.

Preferably a second container of cold water is provided, and the treated produce, on removal from the warm water, is immersed in this container for a predetermined period of time prior to any rapid cooling.

Optionally the warm water in which the produce is treated contains an additive, such as a surfactant, organic cleansing agent, or other substance. Preferably the produce is a vegetable such as corn, broccoli or asparagus and in a most preferred aspect the vegetable is asparagus. In a most preferred option the asparagus has been stored for one to two days prior to treatment.

Preferably the temperature range for the water temperature is between 36° C and 44°C. In a most preferred aspect the temperature is 38.5° C to 40°C.

Preferably the time for which the produce is submerged is between 2 minutes and 32 minutes. The most preferred range is between 8 minutes and 20 minutes and in a most preferred aspect the produce is submerged for 15 minutes.

Preferably the temperature range for the cold water in the second container is between 12°C and 16°C, and the produce is submerged for about 10 minutes.

In a further aspect the invention consists of apparatus for the post-harvest treatment of fresh produce, such as fruit, vegetables or floricultural crops, comprising:

a first container to hold a body of warm water for the immersion of the said produce;

means to effect entry into and removal from said water of said produce such that said produce remains submerged for a predetermined period of time;

means to maintain said water within a predetermined temperature range; and

means for aeration of said water.

Preferably the apparatus comprises means for the subsequent rapid cooling of the produce after it has been removed from the water.

Preferably the apparatus includes a second container provided to hold a body of cold water for cooling said produce subsequent to the treatment in the first container of warm water, and prior to any rapid cooling of the produce. Preferably the cold water in the second container is aerated.

Optionally the apparatus comprises means for moving or stirring the water in either or both containers. Preferably water pressure is used to constantly circulate the water within either or both containers.

Optionally the apparatus comprises means for introducing and mixing an additive into the water of either or both containers.

It is envisaged as within the scope of the invention that any suitable method may be employed to effect the submerging of the produce for the required length of time. One suitable method is by way of a batch process, whereby the produce, either loose or held within containers, is placed into a suitable holding means which can then be lowered or otherwise moved so that the holding means and produce contained therein are all submerged in the water. After the required period of time has elapsed the holding means are then moved again so that the holding means and said produce are removed from the water. Another suitable method is by way of a continuous flow process, whereby the produce, either loose or held within containers, is moved through the water bath by way of a conveying means, the speed of which is regulated so that the said produce emerges from the water after a predetermined period of time has elapsed.

On removal from the water the temperature of the produce may be rapidly reduced by any suitable means. A number of suitable methods are well known in the art, such as hydro-cooling using chilled water, or forced air cooling.

A second cooling container of cold water may be positioned adjacent the first treatment container, and the produce may be immersed in the second tank for a fixed period of time using means similar to those used to submerge the produce in the first treatment tank. The water in this tank may also be aerated. Preferably the water in the second container is held between 12°C and 16°C, and the produce is immersed in this water for at least 10 minutes. Produce removed from this cooling container is then further rapidly cooled to preferably 1°C to 4°C by hydrocooling using chilled water, or forced air cooling or any other suitable methods.

The water in the initial water bath may be aerated by forcing bubbles of air through it. The air bubbles act as an abrasive which is useful for removing both dirt and dead insects or pests from the produce. The movement of the air bubbles through the water also ensures that the water is constantly in motion, thus assisting in keeping the temperature of the water constant throughout its volume.

While it is envisaged that any means may be employed to aerate the water in the treatment and cooling tanks, a preferred method is to deliver the air by way of a fan. Preferably the fan is capable of delivering high volumes of air that will displace water to a depth of 500mm. The air is pumped into the water by way of sparge pipes which run along the base of the tanks.

The inclusion of additives to the water, such as surfactants or cleaning agents, can assist in the cleansing of the produce and may further assist in improving the appearance of the produce.

Constant movement of the water in the container is desirable to ensure uniformity of water temperature throughout. It is envisaged as within the scope of the invention that this may be achieved by constantly circulating the water under pressure, or by using a mechanical stirring means.

It has been found that treatment of fresh produce by the process as described provides several benefits.

As a first benefit, it has been found that, in the case of asparagus for example, the process is extremely effective in killing and removing the pests, in particular thrips and aphids, with trial data showing 100% mortality in some instances. Unlike the fumigation process referred to earlier, where only pests on the surface of the produce tend to be killed, pests which are located within the produce itself are killed as the water and heat penetrate the produce to reach them. Furthermore the abrasive effects of aeration and water movement assist in removing the dead pests (and other dirt or undesirable material) from the produce.

While the process was initially developed for the purposes of deinfestation of the produce, it has been further found that it is also effective in enhancing the cleanliness of the produce over and above the cleanliness achieved by previous cleaning methods.

The appearance and shelf life of the produce can also be improved. In the case of asparagus the treatment by the method of the process has been found to extend asparagus spear life by more than a day over the untreated spears, which is a major advantage for a crop that normally only lasts in good condition for four or five days on arrival at its export destination, such as Japan. Furthermore, the appearance of the asparagus is improved in terms of the greenness and intensity of colour.

The process is further particularly desirable from both the consumers' and importers' point of view in that it is a non-chemical method of treatment. There is a consumer resistance to chemically treated food products, and produce treated without the use of chemicals is therefore found to be preferable.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred form of the invention will now be described in more detail, and by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is a perspective view of one embodiment of the apparatus, suitable for a continuous flow process;

FIGURE 2 is a perspective view of one embodiment of the apparatus, suitable for a batch process. FIGURE 3 is a cross-sectional view of the apparatus of Figure 4, taken along the cutting plane 3-3.

FIGURE 4 is a plan view of the apparatus where both treatment and cooling containers are employed.

FIGURE 1

The apparatus of Figure 1 is suitable for a continuous flow process for the movement of the produce through the water to ensure that the produce remains submerged for the required period of time.

The apparatus 1 , for the post-harvest treatment of produce provides an entry means 2, whereby the produce, either held within containers, or in loose form, enters the apparatus. It is envisaged that in a preferred form of the apparatus only one entry means for the produce is made available, to ensure that all produce remains submerged for exactly the required, pre-determined period of time. Container 3 is adapted to hold a volume of water 4, such that the container 3 is filled to a predetermined fill height. An internal, immersed, conveyor system 5 conveys or moves the submerged produce through the water and in this embodiment of the invention the rate of movement of the conveyor belt is regulated so that, on reaching the point of exit, 6, the produce has been submerged for the required, pre-determined length of time. A drive unit, 7 moves the conveyor system at the required speed. A temperature management system 8, is housed within the apparatus to regulate both the heating and temperature control of the water held within the container. A drainage area 9 is provided to allow excess water to run off the produce. Optionally the produce then enters a temperature reduction area where it is rapidly cooled.

FIGURE 2 The apparatus of Figure 2 is suitable for the batch process whereby the produce, either loose or held in containers, is placed into a holding means which is removed from the water after the required period of time has elapsed. The apparatus provides a holding means 1 1, and a water bath 12, containing water to a level 15. The water bath is supplied with heating elements 14, and has provision for air delivery into the water 13. The holding means 1 1 , is preferably a cage made of mesh so that water and air can circulate through it. The produce is placed into the holding means 11, either loose or in containers, and said holding means is then placed into the water bath and held there for the required length of time.

EXAMPLES The process of the invention will now be described in detail with reference to the following examples. It will be appreciated however that widely differing embodiments or applications of the invention may be employed without departing from the scope of the invention.

EXAMPLE 1

Fresh asparagus is placed in containers of various sizes. The containers are placed on a conveyor system designed to carry them through a thermostatically regulated volume of water within a water bath. The conveyor systems moves the containers of asparagus through the water at a regulated speed so that as the containers exit the bath the asparagus will have been submerged for 15 minutes. The water in the water bath is heated to and held at a temperature of between 38.5°C and 40°C by a temperature management system, and uniformity of temperature throughout the water is maintained by the movement of the water due to air being forced through the volume of water, or by mechanical means. As the asparagus passes through the water, pests residual on it are killed and subsequently removed by the abrasive effects of air bubbles and water movement. Dirt and other undesirable materials are also removed. On exiting the water bath the containers of asparagus are rapidly cooled to a temperature of about 1-4°C.

EXAMPLE 2

Containers of asparagus, as described in Example 1 , are placed into a holding means which can be lowered or otherwise moved so as to enter a water bath containing a volume of water heated to and maintained at between 38.5°C and 40°C. The holding means is moved into a position so that the containers of asparagus are submerged in the water, and held there for 15 minutes. The water may contain an organic cleansing agent (eg. VEGGIWASH) or a surfactant, dissolved to produce a solution of approximately 0.2-1%. The asparagus is kept submerged for a period of 15 minutes, after which the holding means is elevated to remove the asparagus from the water. After draining the asparagus is rapidly cooled to a temperature of about 1-4° C.

The quantities of asparagus processed at any given time may vary. Commercial quantities can typically be from 50kg to 10 tonnes, although it is envisaged that the apparatus can be varied to handle whatever quantities of produce may be required.

EXAMPLE 3 In this embodiment of the invention two containers are incorporated as part of the process prior to the rapid cooling of the produce. The first container (21) is the treatment container and contains water at 39.5°C, while the second container (22) contains cold water at between 12°C and 16°C. Asparagus which had been picked, and stored for 2 days, is placed into asparagus containers which are placed on a conveyor belt (5). The conveyor belt is moved by a drive unit (7), so that the speed of the conveyor belt is such that the asparagus container spends 15 minutes submerged in the treatment container, by which time the asparagus container is elevated to the top of the conveyor belt, and transferred to the cooling container by means of the inter-container transfer conveyor (23). A suitably positioned conveyor belt in the cooling container receives the asparagus container, and is driven by another drive unit (7) at a speed which ensures that the asparagus container and produce is submerged in the cold water for about 10 minutes. The conveyor belt then elevates the asparagus container to the drainage area (9). The water in both the warm water and cold water containers is aerated by means of sparge pipes (13) running along the base of each container. The warm water in the treatment container is maintained at the temperature of between38.5°C and 40°C by the combined workings of the temperature sensors (24) and the heating elements (25), while the cold water is maintained at between 12°C and 16°C by an automated system which drains water from the tank when it reaches 16°C and allows fresh cold water to enter the container. The drained asparagus is then rapidly cooled to 1-4°C by forced air cooling.

The following trial data summarises the results of considerable trial and experiment to establish the suitable temperature range for the water and the effective periods of time to submerge the produce. The effectiveness in pest removal is further illustrated in the trial data included herewith.

TRIAL DATA There have been two major lines of investigation undertaken, over a period of two years, to develop a successful vegetable deinfestation process, and in particular an organic deinfestation process for asparagus.

The first line of reseach involved the use of warm, controlled atmospheres. While a degree of success was achieved in trials, difficulties in applying the conditions to commercial quantities have lead to this method being left in the meantime.

The second line involved the use of warm water, and is the subject of this application. It was known that some success had been achieved when similar treatments were applied to tropical fruits and floriculture crops, but not to temperate vegetables, fruits or floriculture crops. It was not initially expected that this method would produce a valid deinfestation treatment.

In the 1995 season treatment temperature, immersion time and cooling regimes were explored.

From the first experiments it was found that good insect mortality could be attained (100%) with 4-32 minutes immersion in 40°C or 42.5°C. Two minutes immersion did not give acceptable mortality. The rate that the asparagus was subsequently cooled did not affect insect mortality or asparagus shelf life significantly. Residual shelf-life of the asparagus declined rapidly at a treatment temperature of 45°C. Residual shelf- life of asparagus spears was greatest with treatment in warm water for 2, 4, and 8 minutes, declining sharply after 16 and 32 minutes treatment. Further experiments showed that to attain good control of New Zealand flower thrips took 8 minutes treatment in 40°C water.

In 1996 this research was scaled up to take commercial size lots in a tank that holds 3,800 litres of water heated by a PLC (Programmable Logic Controller) that was calibrated to hold water temperature at 40°C. In this type of research it is always expected that the larger scale system will require more treatment than was required in the laboratory research. Tests were therefore made for 10, 15 and 20 minutes exposure to find the level of treatment duration needed to maximise spear quality and insect mortality. It was found that 15 minutes treatment gave that outcome.

An analysis of bacterial populations showed that the cool store bacterial numbers were as low as the entry numbers before the produce was treated. There is, therefore, no increase in bacterial risk associated with the treatment of the invention.

The novelty of this treatment is that it has not previously been achieved for temperate crops. Furthermore, it has been found that the treatment extends asparagus spear life by more than a day over untreated spears (which is a major advantage for a perishable crop that normally only lasts in good condition for around 4-5 days once it arrives in Japan).

INDUSTRIAL APPLICABLILITY

The process of this invention can be readily applied to post-harvest produce, and is especially suited to asparagus. The ability to clean and deinfest the produce without the use of chemicals is both effective, and appealing to the consumer. The potential to eliminate the requirement for fumigation or further treatment on importation of produce into countries such as Japan may significantly reduce the cost of the produce. The benefits of improvement in shelf life and appearance of the produce, which may be achieved through the application of this process, further illustrate the potential value of it. The word "comprising" and other forms of the word "comprising" used in this description and in the claims does not limit the invention to exclude any variations or additions which are obvious to the person skilled in the art and which do not have a material effect upon the invention.

Claims

1. A process for treating post-harvest produce which includes the steps of : submerging said produce in warm water held at a temperature maintained within a predetermined temperature range; keeping said produce submerged for a period of time falling within a predetermined range of time; and aerating the said water.

2. A process according to claim 1 wherein the said produce is rapidly cooled after treatment.

3. A process according to claim 1 wherein said produce is immersed in cold water after treatment.

4. A process according to claim 3 wherein said cold water is held between 12┬░C and 16┬░C, and said produce is submerged for at least 10 minutes.

5. A process according to either of claims 3 or 4, wherein said produce is rapidly cooled after emerging from said cold water.

6. A process according to any one of the claims 2 to 5 wherein said rapid cooling is by means of a cold water spray, hydrochilling or forced air cooling to between 1┬░C and 5┬░C.

7. A process according to any one of the preceding claims wherein the temperature of the warm water in which said produce is treated is between 36┬░C and 44┬░C.

8. A process according to claim 7 wherein said temperature is between 38.5┬░C and 40┬░C.

. A process according to any one of the preceding claims wherein said produce is held in said warm water for between 2 minutes and 32 minutes.

10. A process according to claim 9 wherein said produce is held in said warm water for between 8 minutes and 20 minutes.

1 1. A process accoring to claim 10 wherein said produce is held in said warm water for 15 minutes.

12. A process according to any one of the preceding claims wherein said warm water is continually circulated.

13. A process according to any one of the preceding claims wherein said warm water is circulated by means of a recirculating pump.

14. A process according to any one of the preceding claims wherein said warm water contains any additives such as surfactants, cleaning agents or other.

15. A process according to any one of the preceding claims wherein said produce to be treated is asparagus.

16. Apparatus for treating post-harvest produce comprising: a first container to hold a body of warm water for immersion of said produce; means to effect entry into and removal from said water of said produce such that said produce remains submerged for a predetermined period of time; means to maintain said water within a predetermined temperature range; and means for aeration of said water.

17. Apparatus as claimed in claim 16 which further includes means for rapidly cooling said produce after treatment.

18. Apparatus as claimed in either claim 16 or 17 wherein a second container is provided to hold a body of cold water for cooling said produce subsequent to treatment in said warm water and prior to any rapid cooling.

19. Apparatus as claimed in claim 18 wherein said second container is provided with means to effect entry into and removal from said water of said produce such that said produce remains submerged for a predetermined period of time; means to maintain said water within a predetermined temperature range; and means for aeration of said water.

20. Apparatus as claimed in any one of claims 16 to 19 wherein the means for effecting entry and removal from said water of said produce from any of said containers is a conveyor belt.

21. Apparatus as claimed in any one of claims 16 to 19 wherein the means for effecting entry and removal from said water of said produce from either or both of said containers is a holding means for holding said produce which may be inserted into and removed from the said containers of water.

22. Apparatus as claimed in any one of claims 16 to 21 in which the water in either or both of the said containers is aerated by means of a fan and sparge pipes.

23. Apparatus as claimed in any one of claims 16 to 22 wherein the water in either or both of the said containers is circulated by means of a recirculating pump.

24. A process for the treating of post-harvest produce substantially as herein described with reference to the accompanying drawings.

25. Apparatus for treating post-harvest produce substantially as herein described with reference to the accompanying drawings.