By water cooling we mean the use of refrigerated mains water to counteract rising temperatures in food processes. This allows the control of fermentation, the proliferation of micro-organisms and the guarantee of food safety in the production of products (bakery, meat preparations, etc.).
Post-harvest treatments are also applied in order to obtain a food product with the best organoleptic qualities. Techniques such as hydrocooling help to maintain these qualities during storage and transport. This technique stands out for its capacity to slow down the ripening of the fruit by pre-cooling it quickly and efficiently by cooling it with water. In addition to reducing the thermal load in the chambers, this also helps to reduce one of the great problems of post-harvest: discards.
In addition to water cooling for ice production, tap water cooling is applied in order to control temperatures during the production process. This allows to control the growth of micro-organisms, or to perform a thermal shock by mixing it with chilled water, highlighting the following stages of food processes:
In addition to temperature control, water quality control must also be carried out. There are parameters that must be controlled by sensory analysis (such as odour, taste, colour and turbidity) and other physicochemical parameters (such as pH, conductivity, ammonium, bacteria, free residual chlorine and some metals).
In these systems, the use of removable food-grade plate heat exchangers stands out, which, thanks to their design, facilitate cleaning and thus the efficiency of energy transfer and water quality.
Temperature is the most relevant factor affecting the deterioration of harvested fresh produce, directly affecting its respiration rate and the release of ethylene that promotes its ripening. Temperature lowering is one of the most efficient post-harvest techniques to maintain the quality of fruit and vegetables and extend their marketing period. This technique is based on the need to reduce the temperature quickly to the minimum safe value. In addition, water pre-cooling reduces the thermal load in cold storage and transport systems.
Water pre-cooling is a service increasingly demanded by the most demanding consumers. This technique makes it easier to obtain a product of the highest quality by making it possible to harvest at the optimum point of harvesting, and to increase the shelf life of fresh produce.
This reduces moisture loss, allows for higher sugar content, greater firmness and texture and limits the increase in fibre content.
The use of other harvesting techniques, such as harvesting at the ripe green stage, results in fruit without the organoleptic characteristics that are currently in demand by consumers. Another aspect to highlight is the commercial opportunity for crops of early varieties that are harvested in summer or early autumn, by allowing the reduction of high environmental temperatures and the heat coming from the field.
Pre-cooling techniques for rapid removal of heat from the field include:
Hydrocooling consists of the application of cold water in the temperature range of 1 to 5 ºC, in order to carry out a rapid cooling of the product thanks to the high thermal exchange capacity of the water. This system reduces the typical dehydration generated by air cooling in the refrigeration chambers, and allows obtaining a product of greater firmness and texture, reducing the losses during post-harvest.
The hydrocooling technique can be applied by different equipment designs and application methods such as: cold shower, water basin, immersion, drencher, washing machine, etc.
At the moment, it is being implemented in:
The high heat transfer capacity of the water increases the energy efficiency of the system to lower the high reception temperatures of the fruit coming from the field (from 30 to 2 ºC) in order to reduce fruit respiration and increase storage time without deterioration. This allows harvesting at its optimum point, obtaining the best organoleptic properties. The time the product needs to cool is related to the size, the skin and the flow rate of the cooled water. The benefits of hydrocooling include:
Its application, in addition to the benefits obtained thanks to the rapid pre-cooling and reduction of product respiration, enables cleaning and disinfection after arrival from the field, allowing the elimination of phytosanitary products, pest control and pathogenic microorganisms such as insects, bacteria or fungi (Penicillium sp., Botrytis sp., Rhyzopus sp., Alternaria sp., Monilina sp., etc.), soluble solids in suspension and larger solids (dust, branches, leaves, etc.) that would negatively affect its sale and consumption, thus providing food safety to the product. This is why they require a water treatment system, by means of chemical disinfectants applied to refrigerated water such as sodium hypochlorite or ozone, or other non-chemical systems for pathogen control (such as UV-C light, ultrasound, etc.) and suspension of soluble solids (such as mechanical filtration).
There are two main types of hydrocooling:
Static | Dynamic |
Productions up to 2,500 kg/h | All types of productions |
Lower initial investment cost | Lower labour costs |
Requires less equipment power | Better adaptability to food safety principles |
Monitoring of the time spent inside the equipment | Adjusting the travel speed and length of the equipment |
INTARCON, thanks to its experience in the refrigeration sector, proposes different solutions for temperature control:
A schematic diagram of the principle of mains water cooling is shown below.
The application of chilled water excels in its ability to control process temperatures quickly and efficiently, whether it be:
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