Why humidification of fresh produce?
The evaporator of a cooling system withdraws moist from the air, by condensing water vapour on the cold surface of the evaporator. The amount of moist that is withdrawn depends on the quality of the evaporator. The higher the temperature difference (Δt) over the evaporator, the more moist 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 transpiration of the fresh produce. Because of the water vapour differential pressure between the produce and the cooled air, moisture is leaving 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 airconditoning or in wintertime with heating, the ambient air is very dry,
sometimes >20% RV. This also causes the fresh produce to dry out an loose its good 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
- Discolorations (meat and salad)
- Structural change (flabby salad, soft radish)
- Crust forming (dough, ready made salads)
- Spring-onions up till 40 % in 6 days
- Steak up till 14 % in 60 hours.
By adding humidification the negative effects are strongly diminished with the following advantages:
Increase of turnover:
– The produce has a fresher appearance and influences the buying
– During preparing and consuming of the produce the customer appreciates the freshness and will return more often.
– It is not necessary, to reduce the price of a product when it does not look so well anymore. The product keeps its value.
– In the case of selling the product by weight, the value of the product stays constant. Some products even gain weight
because they keep on growing by taking in moisture through the leaves, as a natural process.
– More expensive products with a lower turnover-rate, may 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 is past time.
– It is not necessary anymore to throw away the top layer of take away salads because it had formed a crust.
– More than 50 % of the vegetables and fruit that usually are thrown away because they have lost their fresh appearance
can be saved.
– It is not necessary 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 not necessary any more to wrap up 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 become 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 costs a lot of energy to
produce (10x as much, compared to ultrasonic). The warm vapour has to be cooled again. Nozzle systems require a
huge installation (compressor, highpressure pump). The nozzles are noisy. Water particles are bigger causing dripping
and wet products.
Why Contronics humidifiers:
It is absolutely necessary that no bacteria are added, and that favourable circumstances for bacteria are avoided.
Contronics took 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 fills the unit again 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 builds an economical filter system,
based on reversed osmosis. This system prevents bacteria and even viruses to enter 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-in in the humidifier. During two hours in the night, ozone gas (O3) is flushed through the humidifier and
the connected system. Ozone enters in the tiniest places and kills the bacteria. Ozone has a very short lifecycle. In a short time it converts to normal 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 with the prestigious Eureka Lynx Award in 2002.