FEATURE
INCORPORATING COLD CHAIN
Humidity control for
perishable goods , another essential By Benjamin Brits
When one thinks of cold or cooling , linking that function with humidity seems disjointed , however in many instances humidity control is critical in several aspects of the supply chain to support quality products and process consistency .
Beth Thomas | Pixabay Reinhard Thrainer | Pixabay
In the modern age , the thought of preservation of perishable goods has widely focused on items that should be in a fridge , however the heating and refrigeration engineering sector is in fact responsible for a far greater impact on the world ’ s supply chains that involve items classed as “ perishable ”.
The definition linked to this term is often stated as : any item with a limited shelf life that is likely to decay , spoil , go bad or die - outright or in an accelerated timeframe - if not kept under ideal conditions – such as refrigeration or in a controlled environment . Most often these items are classed into foodstuffs , beverages , and biologicals .
Taking a more detailed look into preservation of perishables will show that the role of engineering has far-reaching arms and the need for humidity control
Blueberries have an optimal storage RH of 90-95 %.
Barrel halls are one location where humidity control is essential .
extends to many more functions to supply quality and consistency to the consumer - from everyday fresh fruit and vegetables to items that have a longer shelf life but are still classed as perishable , and even to the production of your favourite beverages , and more .
The history surrounding the understanding of humidity as well as the mechanical devices and techniques used in measurement - the hygrometer ( humidity measure ) and other devices influencing humidity such as the barometer ( pressure ) and anemometer ( air flow / speed ) date back many centuries and involve some wellknown people of history such as Leonardo da Vinci , Francesco Folli , Sir John Leslie , Robert Hooke and Sir Isaac Newton – a subject matter clearly followed attentively around the world .
Natural humidity conditions vary quite broadly depending largely on geographic location and it can be an engineering challenge to implement the correct solutions while not breaking the bank in terms of energy consumption , although , some humidification solutions are amongst the cheapest and simplest forms of ‘ environment conditioning ’.
Around the world ( and even within South Africa ), environments can be drastically different from one another . This not only includes inland or coastal factors but differing weather cycles depending on regions . This could include the extremes of any of the earth ’ s elements – permanent high humidity levels because of continual rain , or low levels due to habitats where relative humidity ( RH ) can be as low as a couple of percent such as in the South Australian desert .
Relative humidity ( RH ) as a simple explanation is a measure of the water vapor content of air . More technically , it is the amount of water vapor present in air expressed as a percentage (% RH ) of the amount needed to achieve saturation at a particular temperature and pressure .
Humidity control throughout the cold chain has always been regarded as “ notoriously difficult ”, owing to the fact that most ‘ cold spaces ’ are constructed and sealed to maximise the efficiency of the cooling system . With no / limited ventilation or mechanical systems , water ( as vapour ) has no way to ‘ move freely ’ which creates the difficult condition of regulation of the humidity levels . Therefore , depending on the product and process , humidification or dehumidification equipment would be required . Humidity conditions in the cold chain also have to take into account that fresh produce harvested may be coming out of the field where conditions can vary between 30 and 45 degrees Celsius .
Most commonly , humidity control ( humidification and de-humidification ) is applied where close control conditions are required to meet operational set points . An example of the need for simultaneous control is within indoor growing [ organic ] facilities where the transpiration rate varies during the growth stages , but relative humidity must be maintained to optimise plant growth . Alternatively , either humidification or de-humidification would be required if conditions outside of a desired range would have a negative impact – such as an item or product drying out or creating an environment for bacterial growth . The ideal gas law describes the relationship between pressure , volume , and temperature in air . The reason why
Humiditas | UTE humidity control is required comes down to the nature of the expansion and contraction that occurs due to changing conditions . Expansion and contraction thus create differences in RH and the difference in RH creates various impacts for products that could be extremely sensitive to changes . Here examples could be pharmaceutical products that could experience altered characteristics while in storage , or water losses ( shrivel ) with fresh fruits , and even products that may experience a change in taste or aroma .
Optimal conditions vary according to the specific type of product , be this fruit , vegetables , flowers or other perishables – fresh or being stored . Incorrect humidity ( most often ) leads to product water loss which could be as high as 20 % - cells then become less full or swollen , affecting the appearance , quality and shelf-life of the produce , which then in turn will result in a reduction in the value of the stock , or in worst case scenarios - a total loss . Fresh commodities as an example can be considered as ‘ unique packages of liquid ’. In fact , what the consumer perceives as ‘ freshness ’ is directly linked to that liquid / moisture content , and of course freshness is what is rewarded with the highest marketability and thus rates . A picture that anyone can associate with is a punnet of berries that is shrivelled up , a box of bananas that are all brown , or wilted spinach that looks like it has been in the sun all day – all of which could still be consumed but would not be appealing to the consumer . It is critically important to be able to control the RH to a highly specific point as warm air can hold more RH , for example ,
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