What is vacuum cooling?
The technology is based on the phenomenon that as the vapour pressure on a liquid reduces, its boiling point reduces. The boiling point of a liquid is defined as the temperature at which the vapour pressure of the liquid is equal to the external pressure. When the pressure above a liquid is reduced, the vapour pressure needed to induce boiling is also reduced, and the boiling point of the liquid decreases. By reducing pressure we can even boil off water at lower temperatures. This rapid evaporation of moisture from the surface and within the products due to the low surrounding pressure, absorbs the necessary latent heat for phase change from the product itself. This latent heat required for evaporation is obtained mostly from the sensible heat of the product and as a consequence of this evaporation the temperature of the product falls and the product can be cooled down to its desired storage temperature.
ICL Vacuum coolers serve the following sectors
- Fruits and vegetables
Benefits of pre-cooler vacuum cooling include
- Very quick cooling time 15-25 minutes to reach 3 deg
- Longer shelf life of product
- Quality stays fresh for longer
- Product can travel further because of increased shelf life (new avenues to market)
- Most energy efficient method of pre-cooling for reaching optimum temperature
- Product enters cold storage at optimum temperature relieving duty on cold store/ transport refrigeration
Research and development studies
Please take a look at the study undertaken comparing vacuum cooling to other methods of pre cooling. Below is the abstract and conclusion. (click for link)
The aim of the present study was to pre-cool cauliflower using forced-air, vacuum and high and low ow hydro cooling methods. e weight of the pre-cooled cauliflower heads (5000±5 g) was measured before they were placed in standard plastic crates. Cauliflower heads, whose initial temperature was 23.5 ± 0.5 °C, were cooled until the temperature reached at 1 °C. During the pre-cooling process, time-dependent temperature and energy consumption were measured, and during vacuum pre-cooling, the decreasing pressure values were recorded, and a curve of time-dependent pressure decrease (vacuum) was built. e most suitable cooling method to pre-cool cauliflower in terms of cooling time and energy consumption was vacuum, followed by the high and low ow hydro and forced-air pre-cooling methods, respectively. e highest weight loss was observed in the vacuum pre-cooling method, followed by the forced-air method. However, there was an increase in the weight of the cauliflower heads in the high and low ow hydro pre-cooling method. e best colour and hardness values were found in the vacuum pre-cooling method. Among all methods tested, the most suitable method to pre-cool cauliflower in terms of cooling and quality parameters was the vacuum pre-cooling method.
In the present study, cauliflower heads were cooled using the forced-air, vacuum, high and low ow hydro pre-cooling methods. Vacuum pre-cooling had the lowest cooling time and the lowest energy consumption, followed by high and low ow hydro and forced air pre-cooling methods. During the pre-cooling process, weight gain was observed in the cauliflower heads pre-cooled with the low and high ow hydro method, while those pre-cooled with forced-air and vacuum methods exhibited weight loss. e cooling methods used were compared in terms of power requirement; the vacuum pre-cooling method had the maximum power requirement, followed by the low and high ow hydro and forced-air pre-cooling methods, respectively. Regression coe cients (R2) were between 99.89% and 99.19%. In terms of brightness (L), the value indicating the brightness and white colour (colour value closest to the fresh product) was found in the cauliflower heads pre cooled with the vacuum method. Among all of the pre cooling methods used, vacuum is the most suitable method in terms of energy consumption, cooling time, colour, and hardness.
Please click this link for full text: Vacuum Cooling Study Colifl
*Storage life will vary