GB2509499A

GB2509499A - Cleaning root crops using reduced pressure

Info

Publication number: GB2509499A
Application number: GB201300048A
Authority: GB
Inventors: Charles Tong
Original assignee: TONG ENGINEERING Ltd
Current assignee: TONG ENGINEERING Ltd
Priority date: 2013-01-03
Filing date: 2013-01-03
Publication date: 2014-07-09
Also published as: GB201300048D0

Abstract

A method of cleaning root crops having adhering soil comprises placing the crops 7 in a pressure vessel 1, covering the crops with water, sealing the vessel, reducing the pressure in an air space above the water, and maintaining the reduced pressure until the soil becomes detached from the root crops. Preferably the pressure is reduced to 20kPa for three minutes. The invention further provides apparatus for cleaning root crops having adhering soil, comprising a pressure vessel 1 connected to a means for reducing pressure 3, an inlet 10 for introducing clean water into the vessel and an outlet 8 for removing contaminated water from the vessel, and water treatment means 9 between the inlet and the outlet for separating entrained soil from the water. The pressure may be reduced by moving two relatively-movable sealed parts of the pressure vessel rapidly so as to increase the volume within the vessel. Alternatively, the pressure may be reduced using a vacuum pump.

Description

METHOD OF AND APPARATUS FOR CLEANING ROOT CROPS

Field of the Invention

This invention relates to a method of cleaning root crops and the like, and apparatus for cleaning root crops.

Background to the Invention

Potatoes and other root crops are typically subjected to mechanical cleaning treatments, for example using roller tables or vibrating screens, to re-move entrained soil and stones. While this is very effective for crops grown on lighter soils, it cannot remove the adhering soil typically resulting from growing in heavier soils, or harvesting in wet conditions. This has traditionally limited the growing of root crops to areas of the country with lighter soils, and harvesting in dry conditions.

However, with the cost of transporting crops after harvest becoming an ever-increasing factor, it would be desirable to be able to grow in other types of is soil. The transport costs have to be offset against the cost of cleaning the crops for sale, and for some types of soils, it can be very difficult to remove adhering soil without risking damaging the crops in the process. Furthermore, in some seasons harvesting in dry conditions may not be possible, and crops harvested in the wet, particularly potatoes, will have adhering soil. Crops with adhering soil will typically have a lower value than clean crops.

Summary of the Invention

The present invention provides a method of cleaning root crops having adhering soil, comprising placing the crops in a pressure vessel, covering the crops with water, sealing the vessel, reducing the pressure in an air space above the water, and maintaining the reduced pressure until the soil becomes detached from the root crops.

A pressure reduction below atmospheric of around O.SBar (i.e. down to an absolute pressure of around 2OkPa) has been found to be effective, while removal of stubbornly adhering mud from potatoes has been found to occur within around 3 minutes' treatment period at reduced pressure.

It has been found that rapid reduction of pressure is more effective in re-leasing adhering mud. Vegetables have a certain amount of air contained in their cells. As the pressure is reduced in the washing chamber, any air that is in there expands. This includes the free air in the washing chamber, the air that is in the water and most important the air that is inside the vegetable. As the air expands on the outer edges of the potato, it forms into bubbles. These bubbles then release any soil that is built up on the skin of the potato. The rapid reduc-tion in pressure causes this process to happen quickly. This creates lots of air bubbles which in turn creates a cleaning and agitation effect in the washing chamber.

Some rinsing of the crop may subsequently be required, but the resulting crop is free from adhering soil, and thus represents a higher value crop than could be achieved for the untreated crop. No adverse effect on the quality or shelf life of the crops is experienced after treatment in accordance with the in-vention.

In one embodiment, ultrasonic vibrations are also applied to the crops is while in the pressure vessel to further enhance detachment of adhering soil.

The invention further provides apparatus for cleaning root crops having adhering soil, comprising a pressure vessel having means for reducing the pressure therein, for example an external vacuum pump, an inlet for introducing clean water into the vessel and an outlet for removing contaminated water from the vessel, and water treatment means between the inlet and the outlet for sep-arating entrained soil from the water.

The apparatus may further comprise an ultrasonic actuator for vibrating the crops when in the pressure vessel.

As an alternative to the use of a vacuum pump, the pressure vessel may be configured such that relative movement of two pressure-sealed parts of the vessel causes reduction of the pressure within the vessel by increasing the in-ternal volume. This arrangement may facilitate rapid pressure reduction.

Brief Description of the Drawings

The drawing illustrates diagrammatically apparatus according to an ex-emplary embodiment of the invention.

Detailed Description of the Illustrated Embodiment

The apparatus comprises a pressure vessel 1 having a sealable lid 2 at-tached through a pivot 2a, the lid 2 being connected to a vacuum pump 3. The vessel may be formed with a sump 4 to accumulate soil detached from the root crops, the sump being separated from the remainder of the vessel by a grid support 5, on which may be received a steel or other basket 6 containing the root crops 7, e.g. potatoes with adhering soil. The lid 2 is pivoted open to per-mit introduction of the crops into the vessel and their removal after treatment.

The sump 4 is connected through an outlet valve 8 at the end of the treatment to a water treatment unit 9 which separates the soil from the water, permitting it to be returned to the vessel through an inlet valve 10 when required for the next processing batch. It will, of course, be necessary to top up the wa-ter to make up for losses during water treatment and also water entrained with the root crops when removed from the vessel.

The vacuum pump is operated to reduce the pressure in the sealed ves- sel above the water to around 0.2Bar (2OkPa absolute, O.8Bar below atmos-pheric pressure), and the reduced pressure is maintained for a period sufficient to detach the adhering soil, typically around 3 minutes.

Claims

CLAIMS1. A method of cleaning root crops having adhering soil, comprising placing the crops in a pressure vessel, covering the crops with water, sealing the vessel, reducing the pressure in an air space above the water, and main-taming the reduced pressure until the soil becomes detached from the root crops.
2. A method according to Claim 1, comprising reducing the pressure to approximately 2OkPa.
3. A method according to Claim 1 or 2, comprising maintaining the reduced pressure for 3 minutes.
4. A method according to Claim 1, 2 or 3, comprising reducing the pressure rapidly.
5. A method according to any preceding claim, comprising subse-quently rinsing the root crops.
6. A method according to any preceding claim, further comprising applying ultrasonic vibrations to the crops within the vessel.
7. Apparatus for cleaning root crops having adhering soil, comprising a pressure vessel having means for reducing the pressure therein, an inlet for introducing clean water into the vessel and an outlet for removing contaminated water from the vessel, and water treatment means between the inlet and the outlet for separating entrained soil from the water.
8. Apparatus according to Claim 7, further comprising means for generating ultrasonic vibrations within the vessel.
9. Apparatus according to Claim 7 or 8, wherein the means for re-ducing pressure comprises an external vacuum pump.
10. Apparatus according to Claim 7 or 8, wherein the pressure vessel comprises two relatively-movable sealed parts, and means for moving the parts rapidly so as to increase the volume within the vessel, thereby reducing the pressure.
11. Apparatus for cleaning root crops having adhering soil, substan-tially as described with reference to, and/or as shown in, the drawings.