METHOD FOR PACKAGING AGRICULTURAL PRODUCE

FIELD OF INVENTION

The present invention relates to a method for packaging agricultural produce.

More particularly, the present invention relates to a method for packaging agricultural produce that is susceptible to spoilage and thus has a relatively limited shelf life.

BACKGROUND TO INVENTION

Agricultural produce, especially high acid food products such as fruit or acidified vegetables, that is packaged into containers is normally immersed in a liquid to assist heat transfer and reduce the gas content within the container and the subsequent oxidation and spoiling of the produce. Such containers have a residual gaseous headspace which should preferably have a low volume to reduce oxidation of the produce within the container. There are various methods employed to reduce the gas volume in the headspace prior to sealing the container, for example steam injection or inert gas injection.

However, various types of agricultural produce also contain different levels of residual gasses, including oxygen, entrained or dissolved within the flesh of the produce, i.e. in and around the cells of the produce. During time these entrained gasses can also lead to oxidation and consequently to a reduced shelf life of the agricultural produce.

Furthermore, during pasteurisation of the agricultural produce, the gasses in the headspace and the residual gasses in the produce expand substantially and therefore can result in deformation or damage to certain types of containers, such as semi-rigid containers. Thus agricultural produce in such semi-rigid containers normally needs to be pasteurised in an over pressure retort to counteract the internal pressure that is developed within the container due to gas expansion. This leads to higher capital and production costs.

It is an object of the invention to suggest a method of packaging agricultural produce, which will assist in overcoming these problems.

SUMMARY OF INVENTION

According to the invention, a method of packaging agricultural produce includes the step of subjecting the agricultural produce to a vacuum to degas the agricultural produce prior to sealing the agricultural produce inside a container.

The agricultural produce may be fresh fruit or fresh vegetables.

The agricultural produce may be high acid food products such as fruit or acidified vegetables.

The vacuum may extract residual entrained or dissolved gasses present within the agricultural produce.

The vacuum may be applied for at least 2 minutes at greater than 0.2 bar (20 kPa) below atmospheric pressure.

The vacuum may be applied for at least 30 minutes at about 0.7 bar (70 kPa) below atmospheric pressure.

The vacuum may be applied for less than 10 minutes at greater than 0.8 bar (80 kPa) below atmospheric pressure.

The vacuum pressure and time duration may be regulated to prevent cell damage to the agricultural produce formed by escaping residual gasses.

Also according to the invention, a food product includes a container; and agricultural produce sealed within the container, wherein the agricultural produce has been subjected to a vacuum to degas the agricultural produce prior to being sealed inside the container.

The container may be made of plastics material.

The container may be a multi-layer, high barrier, semi-rigid container.

The container may be sealed with a flexible film of plastics material.

The flexible film may be a multi-layer, high barrier flexible film.

The agricultural produce may be fresh fruit or fresh vegetables.

The agricultural produce may be high acid food products such as fruit or acidified vegetables.

The agricultural produce may be adapted to be subjected to a vacuum to extract residual entrained or dissolved gasses present within the agricultural produce.

The agricultural produce may be adapted to be subjected to a vacuum for at least 2 minutes at greater than 0.2 bar (20 kPa) below atmospheric pressure.

The agricultural produce may be adapted to be subjected to a vacuum for at least 30 minutes at about 0.7 bar (70 kPa) below atmospheric pressure.

The agricultural produce may be adapted to be subjected to a vacuum for less than 10 minutes at greater than 0.8 bar (80 kPa) below atmospheric pressure.

The agricultural produce may be adapted to be subjected to a vacuum pressure for a time duration regulated to prevent cell damage to the agricultural produce formed by escaping residual gasses.

BRIEF DESCRIPTION OF DRAWING

The invention will now be described by way of example with reference to the accompanying schematic drawing.

In the drawing there is shown a flow diagram of a method of packaging agricultural produce according to the invention.

DETAILED DESCRIPTION OF DRAWING

Referring to the drawing, a method of packaging agricultural produce in accordance with the invention, generally indicated by reference numeral 10, is shown. The agricultural produce can be high acid food products such as fresh fruit or acidified vegetables.

The agricultural produce is subjected to de-aeration / degassing for a period of at least 2 minutes and under a vacuum pressure of greater 0.2 bar (20 kPa) below atmospheric pressure. Thus for example, peaches are degassed at a pressure of

70 kPa below atmospheric pressure for a time period of about 30 minutes, while

pineapples are degassed at a pressure of 70 kPa below atmospheric pressure for a time period of about 40 minutes.

The vacuum pressure and time are able to be varied to allow faster degassing at higher vacuum pressures or slower degassing at lower vacuum pressures. In all cases the vacuum pressure and time duration are regulated to prevent cell damage to the agricultural produce caused by the escaping of the residual gasses.

After degassing, the volume of the agricultural produce is reduced due to a slight shrinkage thereof resulting from the extracted gasses. This allows the same mass of agricultural produce to be inserted into a smaller container than is conventionally used or alternatively placing more product into a conventional container, e.g a tin container.

The containers into which the agricultural produce is to be placed, are often made of plastics material and can be a multi-layer, high barrier, semi-rigid container. Such a container is pre-filled with a liquid to about 25% of the container volume. Thereafter the degassed agricultural produce is inserted into the container up to a desired weight and the container is topped up with further liquid until a headspace of about 3 mm is obtained.

The container is sealed with a sealing film, such as a multi-layer, high barrier flexible plastics film. The sealing film is heat sealed to the container, for example at a temperature of between 190 ⁰ C and 205 ⁰ C for a time of 0.8 to 1.2 seconds under a force of 250 kg.

The sealed container is subsequently heated to pasteurise the agricultural produce. Due to the lower volume of residual gasses in the sealed container, less expansion takes place and thus normal atmospheric pasteurisation can be conducted without the need for an over pressure retort. This reduces capital and production costs as a continuous atmospheric pasteurisation process can be utilised.

The lower gas volumes within the container has the further advantage in that less stretching of the sealing film (resulting in less damage to the barrier properties of the film) is experienced during pasteurisation due to the expansion of the gases inside the container.

Also, as less air is present in the container when it is sealed, there is likely to be less panelling of the container when at ambient temperature.

Furthermore, the lower volumes of gasses (oxygen) in the container lead to less/slower oxidation of the agricultural produce and consequently to an increased shelf life of the agricultural produce in the container.