Storage

To maintain good fruit quality, it is important to assess temperature, airflow, humidity and ethylene in your cool store on a regular basis. As an assessor, you need to be aware of the optimum conditions to store fruit and understand the risks by observing and measuring.

The environment in which your fruit has been transported (containers and trucks) or stored (cool stores) could affect your overall fruit quality if storage conditions are not optimal. Taking the time to assess your storage conditions to make sure they are within Zespri’s recommended specifications, will help to reduce unexpected outcomes in your inventory.

Temperature

Temperature is the most important factor in managing Zespri Kiwifruit inventory. The most certain indication of effective temperature control is to routinely measure and record flesh temperature using a calibrated temperature probe within the flesh of the fruit.

Kiwifruit soften slower when stored at 0.0°C ±0.5°C. This is the optimal flesh temperature for all of Zespri varieties under 3Kgf.

Kiwifruit will start to freeze at -1.5°C pending on how mature the fruit is.

Temperature Measurement

When monitoring temperature you are confirming and recording:

• If temperatures are within your specifications,

• Any variance between flesh and air temperature.

• If temperature variability is an issue across different locations within a coolroom.

• Track pallets with elevated temperatures to see if they have a satisfactory cooling rate. Be aware that within a pallet temperatures can be quite variable. (Pop up - resent arrivals or ripened – see below 2 graphs MB pre-cooling)

• It is important to verify the temperature in the centre of these pallets. Note different pack types will cool faster or slower.

• If temperatures are out of specification see if you can understand why this might be:

  • Airflow – refer to airflow

  • Pallet movement

  • Delivery air to return air

Should temperatures not conform to specifications, measure more temperatures to establish the size and extent of any problem using a grid sample of pallets working out from identified problem zones.

Temperature Monitoring Frequency

Manual Probe

• For cooling – monitor temperature repeatedly to ensure that fruit are coming down to storage temperature as expected.

• Stabilised Fruit temperatures – at least 3 times weekly.

• Outside specification – increase frequency and sample size of readings.

Permanent Probes

• Monitor data from permanently mounted sensors daily.

Permanently Mounted Temperature Sensors

Permanent mounted temperature sensors continually monitor and record temperature readings over time. The function of these sensors are also to provide an alert, should the refrigeration fall outside the specified alarm settings. This should be part of your assessment:

• Confirm alarm functionality and settings are set within your specifications

• Assess temperature patterns over time to see if things have been operating within expectations.

Permanent temperature sensors are ideally in locations that measure:

• Delivery air (coldest air)

• Return air (warmest air)

• Longer term flesh temperatures in different locations of the room pending on room size.

The amount of sensors will depend on room size and shape.

Note - Air temperatures fluctuate a lot more than fruit temperatures.

Air Flow

The air within a coolroom has to circulate freely along paths between pallets that permit heat removal from the product. Our main tool for influencing rates of temperature change and maintenance of temperature is airflow. Air is “lazy” in the way it flows resulting in airflow taking:

• The widest path

• The path of least resistance (e.g. the path with least corners)

• Around rather than through packaging

There are two different scenarios in where airflow is important:

• Initial cooling or heating of the fruit for ripening or bringing temperature down (precooling)

• Maintenance of fruit temperature during coolstorage

Air Spaces

The optimal positioning of pallets within the coolroom will improve airflow patterns and increase cooling effectiveness. Correct spacing will ensure there is a sufficient area for heat transfer to occur across the pallets surface.

The following minimum clear air spaces between pallets will provide for adequate return air movement and ensure access for temperature monitoring. If the coolroom is not racked, it is important to check that adequate spacing is maintained during your temperature assessment.

• 100mm (hand width) between pallets in a row

• 200mm between pallets and walls

• 400mm between the top of pallets and the coolroom ceiling

• 

Doors

• All working external doors (UNLESS Rapid Roll doors) on the cool stores should be fitted with plastic curtains to restrict air movement and limit temperature variations when the door is open.

• Check curtains/doors are being maintained and in good working order.

• Confirm doors are shut as often as possible.

• Open doors increase condensation of moisture on coils and build-up of ice. This then creates a higher amount of defrosts being required – leads to poor temperature control and high-energy use.

Relative Humidity (RH)

Relative humidity is the amount of water vapour present in air expressed as a percentage of the amount needed for saturation at the same temperature. Lack of humidity can result in water loss, which can cause fruit deterioration resulting in direct quantitative losses and also causing wilting and shrivelling, loss in texture quality (softening) and nutritional quality.

We recommend maintaining relative humidity at 92% to 95%. Keep fruit in original packaging and do not remove polyliners to avoid dehydration.

Electronic humidity sensors are simple to use and provide a helpful, approximate indication as to whether the high humidity desired in a cool store (92-95% RH) is being achieved.

Ethylene

Ethylene (C₂H₄) is a gas produced from natural and man-made sources that causes kiwifruit to ripen faster than normal, even if fruit are stored at cool store temperatures.

Check and prevent all potential sources of ethylene if possible:

If the cool store is equipped with an ethylene scrubbing unit, verify it is being used in accordance with the manufacturer's guidelines.

If you have scope to measure ethylene, follow the sampling protocol issued by your laboratory.

Containers

If you are an importer receiving containers, it is critical that you assess the storage conditions of the container as soon as possible. Early inspection, will provide crucial time-dependent indicators as to the occurrence of any temperature issues during the voyage, which could have an impact on your fruit quality.

Initial Inspection and Temperature recorders

The initial inspection of a container is very important, as it will provide you with useful information about how the fruit has performed during the voyage. Follow these guidelines at the devanning (unloading) stage to get a better understanding about how each container has performed.

1. Check overall consignment condition- Inspect pallets and packs to see if there are signs of a rough voyage. Look in the container for any signs of excessive moisture or ice content, this could indicate issues with the refrigeration unit.

2. Retrieve the temperature recorder - When the container doors are first opened you will see a temperature recorder (TempTale logger) near the base of one of the front pallets. This recorder holds temperature data from when the container first left the cool store back in New Zealand. Retrieve the logger and hold down the stop button until the stop sign As soon as possible download the TempTale’s data via ColdStream/Zespri's portal – this will let you and Zespri know if there were any temperature failures during transit. (link to TempTale images + logger handling instructions) 

3. Check container temperature – Ensure the container temperature arrived in specification by checking and recording results against container number;

   1. Container LCD display at opposite end of container door prior to opening.

   2. TempTale LCD as soon as door is opened.

   3. At least one pallet fruit temperature at time of door opening.

If temperature(s) outside specification, take additional pallet fruit temperatures against the pallet number and location that it came from within the container.

• Take fruit temperature readings - Take manual fruit temperature readings as soon as possible after opening the container doors. This will help you to quickly identify if there was any temperature issues during transit. Take temperatures from one or more pallets and record the pallet ID numbers against the temperature [link to temperature page] & [link to record pallet ID] 

• Check Container Ventilation – If you have identified that there is an issue with the container, check the vents to ensure they are clear. The vents should have been set at 15 m3 / h. 

Marine Cargo Claims - If you find your container has a significant quality issue and as a result, you need to make a marine cargo claim; notify your Zespri local representative ZGL Insurance Manager as soon as possible (within 24h). ZGL Zespri will arrange to assess the damage.