IE65404B1

IE65404B1 - A process for preserving perishable foodstuffs

Info

Publication number: IE65404B1
Application number: IE283991A
Authority: IE
Inventors: William Dowling
Original assignee: William Dowling
Priority date: 1991-08-12
Filing date: 1991-08-12
Publication date: 1995-10-18
Also published as: GB9125101D0; GB2258993B; GB2258993A; BE1003599A6; IE912839A1

Abstract

The invention discloses a process for preservation of a vegetable by initially chilling it by immersion in water at a temperature in the range of 0 to 5 DEG C, immediately draining the water by centrifuging the vegetable, and packing the chilled vegetable in a wrapper which is permeable to gas. in particular, the wrapper is more permeable to carbon dioxide than to oxygen. While being stored, carbon dioxide is released by the vegetable and a substantial portion of this is stored in the wrapper, while at the same time there is a limited access of oxygen to the vegetable. An environment is induced wherein there is a relatively high carbon dioxide and a low oxygen level so that multiplication of microorganisms and anaerobic degradation of the vegetable is slowed down considerably.

Description

The invention relates to the preservation of foodstuffs and in particular to those which are of plant origin, namely, vegetables and fruit. For clarity, vegetables and fruit are hereinafter referred to generally as vegetables.

It is well known that vegetables degrade quite quickly, and in particular if they have been cut because this increases the surface area in contact with oxygen. To overcome this problem, processes such as that described in French Patent Specification No. FR2564701 have been devised which involve generating a forced modified atmosphere in an impermeable enclosure in which oxygen has been extracted and carbon dioxide and nitrogen have been injected. Generally, there is approximately 10% carbon dioxide and 90% nitrogen. While this process is effective, it is extremely expensive to carry out because specialised equipment for creation of the forced modified atmosphere and sealing of bags is required.

The invention is directed towards providing a process for * preservation of vegetables which is less expensive and simpler to carry out.

According to the invention, there is provided a process for preservation of a fresh vegetable as hereinbefore described, the process comprising the steps of:cutting the vegetable with a sharp blade; within 30 seconds, chilling the vegetable by immersion in water at a temperature in the range of 0°C to 5°C; within 30 seconds, carrying out forced draining of water from the vegetable by centrifugation; and within 3 minutes, packing the chilled vegetable by 10 enclosing it in a wrapper which is permeable to gas and is more permeable to carbon dioxide than to oxygen.

The duration of immersion in water is preferably in the range of 30 to 60 seconds.

In one embodiment, the water includes ice particles to 15 maintain stability of temperature.

The water may include 10-150ppm chlorine.

Ideally, the packed vegetable is maintained at a temperature below 3°C.

The invention will be more clearly understood from the following description of a preferred embodiment thereof, given by way of example only as follows.

In one example, lettuce is to be preserved in the shredded state for use in a restaurant.

The process involves shredding of the lettuce in a conventional manner using a sharp blade and immediately (within 30 seconds) immersing the shredded lettuce in water containing ice at a temperature in the range of 1°C to 5°C and preferably just above freezing point (1°C-2°C). The duration of immersion is 30 - 60 seconds as this is sufficient to cause chilling of the lettuce to the desired temperature.

When the lettuce is removed from the water, it is within 30 seconds centrifuged to drain water from it and it is immediately (within 3 minutes) packed in a bag of low density copolymer material and the bag is sealed. Thereafter the bag is stored in an environment at a temperature below 3°C. In this embodiment, the wrapper is of low density copolymer material comprising polyethylene having about 4% ethylene vinyl acetate having the following characteristics:Gas permeability : 0z-250-840/cc/0.001/ins (0.025/mm) thickness/100/ins2 (0.0625mz) area/24 hours C02-495-5000/cc/0.001/ins (0.025/mm) thickness/100/insz (0.0625mz) area/24 hours at 73°F (22.8°C) and 0% relative humidity outside of the ' bag. 4 Thickness : 0.0015 - 0.0035 ins (0.0375 - 0.0875 mm) Where, c.c. means cubic centimetres, and ins means inches The shredded lettuce which is stored in the bag breathes and releases water vapour which increases the relative humidity of the atmosphere within the bag. The carbon dioxide content gradually increases from an ambient level of approximately 0.3% to a level of approximately 12% because of the limited permeability of the wrapper. Further, a certain amount of oxygen permeates into the bag so that the atmosphere within the bag is not starved of oxygen completely, however, the amount is kept relatively low. It will be noted that the bag has a greater permeability to carbon dioxide than to oxygen, and thus it tends to shrink to some extent around the lettuce, because a greater volume of carbon dioxide escapes than oxygen enters. Because of the high carbon dioxide content, multiplication of micro-organisms does not occur and at the same time anaerobic degradation of the vegetable which may occur in atmospheres starved of oxygen does not occur. Thus, a gas equilibrium atmosphere is induced in which the relatively low oxygen and relatively high carbon dioxide content within the bag prevents multiplication of microorganisms and thus allows a long shelf life of up to 10 days ? for shredded lettuce. Multiplication of micro-organisms is > also significantly reduced by immediately chilling after cutting.

The time periods given above for carrying out the steps are very important because it is essential that the vegetable be packed as soon as possible after cutting to prevent microorganism action.

What the invention achieves is the induction of a suitable atmosphere which keeps the vegetable fresh for a longer period. There is no need for forcing a modified atmosphere and the consequent expense. It will also be appreciated that the invention provides a process for preservation of vegetables which is simple to carry out and does not require expensive or complicated machines.

The invention is not limited to the embodiments hereinbefore described, but may be varied in construction and detail.

Claims

1. A process for preservation of a fresh vegetable as hereinbefore described, the process comprising the steps of: 5 cutting the vegetable with a sharp blade, within 30 seconds, chilling the vegetable by immersion in water at a temperature in the range of 0°C to 5°C; within 30 seconds, carrying out forced draining of 10 water from the vegetable by centrifugation; and within 3 minutes, packing the chilled vegetable by enclosing it in a wrapper which is permeable to gas, and is more permeable to carbon dioxide than to oxygen. 15

2. A process as claimed in claim 1, wherein the duration of immersion in water is in the range of 30 to 60 seconds.

3. A process as claimed in claims 1 or 2, wherein the chilling water contains ice particles to maintain stability of temperature.

4. A process as claimed in any preceding claim, wherein the chilling water includes 10-150ppm of chlorine. K I i 5. A process as claimed in any preceding claim, wherein the packed vegetable is maintained at a temperature below 3°C.

5

6. A process substantially as hereinbefore described with reference to the examples.