Storage

The storage environment in which you store your fruit can have a significant impact on its overall performance.

The Storage section of the sites contains storage guidelines relating to temperature, humidity and ethylene levels, in order to help you improve the storage life of your inventory.

All coolstores vary in their performance, you may need to consider your coolstore's ability to hold set temperatures when applying the guideline temperatures.

If your coolstorage is performing below requirements then it’s important to understand the reason why so you remedy the issue and mange your inventory appropriately.

Temperature Control

The margin between optimal storage temperature and freezing temperature is very small, therefore it's critical that the air leaving your heat exchanger is not lower than the freezing temperature of the kiwifruit (-1.5°C).

There must be sufficient air circulation to absorb the heat of respiration of the fruit and other heat gains without the temperature of the warmest air creating fruit temperatures above the optimum temperature.

 

Relative Humidity

In the long term storage of kiwifruit, relative humidity of the atmoshphere surrounding the fruit is very important. At zero degrees the fruit continues to be susceptable to weight loss, albeit at a reduced rate.

By maintaining a high relative humidity (92–95%) it is possible to achieve more than six months storage with acceptable weight loss figures (1% or less).

The use of polyliners enables the Zespri product to maintain a high humidity environment within the pack. If polyliners are disturbed for inspection or repacking, they should be replaced afterwards.

Coolrooms used for cooling storage or ripening of produce cannot usually maintain 100% R.H. Most operate in the 80% to 95% range and those operating below 80% should not be used for fresh produce.

Condensation

If saturation occurs over a prolonged timeframe, this can cause condensation to form on the room floor, walls and packaging. This excessive moisture greatly increases the deterioration process of the packaging.

When coolroom doors are opened, the in-rushing warm air may be cooled as it enters the room to below the dew point. This will occur commonly in hot, humid, climates. 

Another situation when condensation occurs is when the coolstore temperature is warmer than the outdoor temperature.

Ethylene Monitoring and Removal

Ethylene is a naturally occurring gas which is released by fruit such as bananas, apples, pears and kiwifurit as they ripen. The gas itself is an extremely effective ripening agent. Even at very low concentrations it has the ability to trigger the ripening of kiwifruit. In order to optimise storage life of your fruit, it is important to ensure coolstores are ethylene-free, with a concentration below 0.03ppm.

Sources of ethylene typically include ripening or rotting fruit, fumes from internal combustion engines, as well as cigarette smoke. Preventing the build-up of ethylene by keeping the sources out of the coolstore where possible.

  • Try to avoid storing kiwifruit with other ethylene producing fruit such apples, bananas, pears.

  • Remove soft fruit from pack. As kiwifruit soften there is an increase in the rate of ethylene production. This increase is very small in good quality fruit until the fruit becomes very soft. One piece of soft kiwifruit will cause the entire pack to ripen.

  • Only use electric forklifts.

(**Need to find or develop Ethylene related image**)

The accurate monitoring of ethylene requires laboratory-grade equipment. This is because the concentration of ethylene which can trigger the ripening process of kiwifruit is very small. We recommend that you assess your coolstore's ethylene levels regularly if storing kiwifruit medium to long term.

If you find the concentration is higher than 0.03ppm, there are a number of ways you can remove ethylene from your coolstores, including:

  • Use of ozone from UV lamps.

  • Various chemical absorbers and catalytic conversion.

  • Venting the store with fresh air. (Note: sometimes outside air may do more harm in heavily polluted environments.)