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Saturday, February 4, 2017

Humidity Management

The humidity level has a direct infl uence on the quality of your produce – especially as
it pertains to shelf life.

Low humidity levels cause:
  • Dehydration of produce
  • Weight loss
  • Negative changes in produce appearance

High humidity levels cause:
  • Growth of mold and bacteria
  • Fungal disorders

Relative humidity in the air that circulates in a reefer container depends on the
following key factors:
  • Rate of fresh air ventilation
  • Relative humidity of fresh air entering into the container
  • Temperature of the evaporator coil relative to the dew point of the air in the container
  • Vapor pressure defi cit, which will infl uence the rate of moisture transfer between the air and commodity
  • Carriage and produce temperature
  • Packaging
  • Type of commodity (respiration rate)
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Humidity control
In reefer containers, humidity can be infl uenced in the following ways:
  1. Top-icing for products that are not susceptible to freezing or chilling injury, e.g. broccoli
  2. Applying perforated fi lm packaging
  3. Using moisture pads (for items such as asparagus)
  4. Maintaining surface wax (for items such as apples)
It is critical to understand that cargo needs to be pre-cooled to its optimal
temperatures, because there will be a rapid loss of humidity if cargoes are warmloaded.
Large temperature differences between the cooling units and cargo will lead
to condensation on the cooling coiling, which dries the air and causes evaporation
from the produce; ultimately resulting in water loss.

Dehumidifi cation
Dehumidifi cation is a process that lowers humidity within the container to ensure
dry packing, prevent rotting and reduce the incidence of fungal development. It is
especially vital to carry out dehumidifi cation for containers carrying commodities
such as pharmaceutical products, electronic components, photographic fi lm, onions,
ginger and garlic.
www.apl.com/reefer

Most of APL’s reefer equipment comes equipped with dehumidifi cation systems
where relative humidity can be set between 60% and 95% and can be controlled
according to cargo requirements.

Bulb mode
This feature is used mainly for the transportation of fl ower bulbs. It is an extension
of dehumidifi cation mode and upon activation, the user can select:
  • Evaporator fan speed (low, high or alternate)
  • Defrost termination sensor setting
  • Lower humidity levels
Bulb mode, utilized mainly for transportation of fl ower bulbs, provides exporters
with better control of the adjustable features to accommodate the need for optimal
storage conditions, facilitating stringent temperature, ventilation and humidity
requirements for a large variety of bulbs. All APL containers are ATO certifi ed by
research institution Agrotechnology and Food Innovations (AFI).