Why humidification of fresh produce?

The evaporator of a cooling system withdraws moisture from the air by condensing water vapour on the cold surface of the evaporator. The amount of moisture is withdrawn depends on the quality of the evaporator. The higher the temperature difference (Δt) over the evaporator, the more moisture is condensed.

In a display filled with unpacked fresh produce, the effect is not directly obvious. Humidity measurements give a rather high relative humidity. This is caused by the transpiration of the fresh produce. Because of the water vapour differential pressure between the produce and the cooled air, moisture is leaves the produce into the surrounding air. Measurements taken from

an empty display show a relative humidity of about 50 % of the ambient air.

In modern supermarkets with air conditioning, or in wintertime with heating, the ambient air is very dry, sometimes >20% RV. This also causes fresh produce to dry out and lose its fresh appearance, even when displayed without cooling in the open (vegetable tables). Because of the loss of water content of the fresh produce, a number

of effects occur:

- Change in appearance

- Discoloration (meat and salad)

- Structural change (flabby salad, soft radish)

- Crust forming (dough, ready made salads)

Weight loss:

- Spring onions up to 40 % in 6 days

- Steak up to 14 % in 60 hours.


By adding humidification, the negative effects are strongly diminished with the following advantages:

Increase in turnover:

– The produce has a fresher appearance and influences buying.

– During preparation and consumption of the produce the customer appreciates the freshness and will return more often.

– It no longer necessary to reduce the price of a product because of deterioration. The product keeps its value.

– In the case of selling a product by weight, the value of the product remains constant. Some products even gain weight

because theycontinue to grow by taking in moisture in through the leaves as a natural process.

– More expensive products with a lower turnover rate can also be offered without the risk of having to throw them away after

one week (for example, exclusive mushrooms).

Reduction of loss:

– The cutting away of the dry and discoloured surface of meat becomes a thing of the past.

– It is no longer necessary to throw away the top layer of take away salads because a crust has formed.

– More than 50 % of the fruit and vegetables that are usally thrown away because they have lost their fresh appearance

can be saved.

Labour costs:

– There is no need to unload displays at the end of the day. Fresh produce may be left in the display-case overnight.

– Labour is better used as the display can be re-merchandised at the end of the day when trade is quiet requiring

less labour the following morning.

– It is no longer necessary to shrink wrap produce to prevent water loss.


Why ultrasonic humidification:

Ultrasonic humidifiers produce a fine mist of water particles of 1 micron. The water particles

evaporate and withdraw evaporation energy from the surrounding air (adiabatic effect).

Consequently the temperature of the surrounding air will drop. The products don’t get wet and don’t feel wet.

The humidifier contributes to the cooling process and uses very little energy. The humidifier reacts directly

(no warming up) and produces no noise.

Alternatives to ultrasonic humidifiers are nozzles (spraying systems) and steam. Steam needs a lot of energy to

produce (10x as much, compared to ultrasonic). The warm vapour has to be cooled again. Nozzle systems require

huge installations (compressor, high pressure pump). The nozzles are noisy. Water particles are bigger causing dripping

and wet products.


Why Contronics humidifiers:


It is absolutely necessary that no bacteria develops, and that favourable circumstances for bacteria are avoided.

Contronics has taken the following measures:

Design of the humidifier:

- The humidifiers are built of chemically polished stainless steel RVS316L, to make sure that bacteria can’t hide in the

pores of the material.

- A flushing program cleans the system on an hourly basis and refills the unit with fresh water.

- When the humidifier is switched off, no water remains behind. The reservoir is emptied by the drain.

Clean feed water:

- In combination with fresh produce, demineralised water should be used. Contronics has built an economical filter system,

based on reversed osmosis. This system prevents bacteria, and even viruses, from entering the humidifier. Also all media for

bacteria to feed on are filtered out of the water.

Clean air and system:

- In most cases it is not necessary to purify the air. In places where bacteria are likely (meat products) or in places with

high temperatures (bakeries), it makes sense to add air purification. Contronics uses Ozone generators, which are

optionally built into the humidifier. For two hours each the night, ozone gas (O3) is flushed through the humidifier and

the connected system. Ozone enters into the tiniest places and kills the bacteria. Ozone has a very short lifecycle. In a short time it converts to Oxygen (O2) without leaving a residue. In this way ozone is an efficient and safe detergent.


- Fresh, bacteria free produce is good for your health.

Ca. 50% less losses. Less good food ends up on the rubbish dump.

- Positive energy balance.

- The humidifier uses only 80 watt to nebulize 1000 gr of water.

The adiabatic cooling effect produces 700 watt of energy when evaporating 1000 gr. of water. You save 620 watt

per 1000 gr. evaporated water. For an average installation this means 16.000 KW per year, a CO2 reduction of 12 tons!

Award winning development:

The Contronics humidification system is the only system in the world especially developed for fresh produce. This innovation and its success on the world market was awarded the prestigious Eureka Lynx Award in 2002.