Most producers use a solid two-piece box where fruit is packed into a modified atmosphere (MA) bag within a 1, 2 or 5kg sized cardboard base.
Box design (cont from last issue)
Aussie cherry boxes
The bag is then sealed and a cardboard lid is placed over the top with these boxes then placed inside a larger cardboard outer (Figure 1).
Inability to cool packaged fruit
The issue with this style of packaging is the inability to cool fruit once it has been packaged and palletised.
Even vented boxes under passive cooling conditions have been shown to maintain current fruit temperatures for at least 20 hours.
It is most unlikely that sealed, unvented boxes stacked in sealed, unvented outers will show any decrease in fruit temperature once palletised at all in the same period of time.
For Tasmanian cherry producers to achieve a lower pulp temperature, boxes and outers will need to be redesigned to feature vents, allowing for FA cooling. This may well have some implications in regard to specified protocols of importing trade partners but currently it represents the best feasible option to extend shelf life.
Modified Atmosphere (MA) packaging
Cherries maintain quality in storage longer when oxygen levels are low, and carbon dioxide levels are high, lowering the respiration rate of the fruit.
The optimum ratio of gasses can be achieved through controlled atmosphere storage, or most commonly through using modified atmosphere (MA) packaging.
This practice involves packing cherries into polyethylene plastic bags with specific film permeability to allow carbon dioxide and oxygen gasses to reach a desired equilibrium.
There are several different bags used globally, with each designed to be used under certain temperatures, and with a specific volume of fruit.
CO2 levels
Usually, the high level of carbon dioxide in these bags is generated by the natural respiration of the cherries. This is referred to as ‘passive MA packaging’ and it can take several days or even over a week in storage until gasses have reached required equilibrium.
Alternatively, the bag can be directly filled with desired concentration of gasses before being sealed. This is termed ‘active MA packaging’ and allows the benefits of MA to be applied immediately.
Benefits of MA packaging (cont next issue)
See this article in Tree Fruit July 2022
