When to vacuum cool your flowers?
“Temperature is the single most important factor that affects flower value. Therefore, keeping flowers in low temperatures from the farm to the final destination is vital. A well known and an increasingly more used tool to achieve this is the use of Vacuum Cooling systems. These systems are known to be the quickest and most energy efficient way to cool leafy and other perishables. However, it is of utmost importance in which stage of the cold chain it is incorporated.” This is explained by Mauricio Gleiser of Vacuum Cooling Colombia, a vacuum cooling system and services supplier.
Vacuum cooler for 2 jet pallets (2.5 wide x 3.2 long x 3.0 m high each) per cycle. “Process takes 30 minutes to cool down flowers from 12ºC to 1ºC,” says Gleiser.
According to Gleiser, using vacuum cooling systems has some major advantages compared to conventional cooling. “The main advantage of vacuum cooling systems is the fact that the flowers remain cooler during transportation and have a higher quality when they arrive at their destination. The process reduces the undesired free moisture, which when timely done, not only precludes the occurrence of botrytis, but also enables the boxes to recover their mechanical strength. Besides that, it is the fastest method, capable of handling large volumes in short periods of time and reduced spaces,” he says.
When to apply it?
A proper cold chain is highly important for maintaining high quality flowers. The use of a vacuum cooling system can increase these quality standards, however, only when timely incorporated in the cold chain. When deciding to start using a vacuum cooling system, one has to take into account when and where they will make use of the system. According to Gleiser, vacuum cooling at the origin is the most effective way to use this system. “Research revealed that using vacuum cooling only at the origin (airport at Bogota in this case) increases the vase life of flowers by 54%, compared to 5% when using vacuum cooling at the destination (Miami airport) only,” says Gleiser. He refers to a study which has been conducted some years ago, where they compared the vase life of charlotte roses when using only room cooling (*enough to reach 4ºC= 39F), only vacuum cooling or both systems at the origin (Bogota) and destination (Miami). In the table below, the results of this study are listed:
|Origin (Bogota)||Destination (Miami)||Vase Life (days)|
|Vacuum cooling||Vacuum cooling||14.3|
|Vacuum cooling||Room cooling*||12.9|
|Room cooling*||Vacuum cooling||8.9|
|Room cooling*||Room cooling*||8.4|
“So, from this research, it can be concluded that vacuum cooling at the origin is the most effective means. Interesting to note is that vacuum cooling at the destination (Miami) only did little on its own,” says Gleiser
Why is cooling at origin more effective?
According to Gleiser, the reason why the vacuum cooling, at the destination only, was not as effective is that it was done too late. “When recooling the flowers in destination, flowers have already been exposed to very high temperatures, free moisture /high ethylene levels and for a long transit time, which can go up to 36 hours(to Europe). In this time, botrytis has been allowed to develop and there is no way back. When vacuum cooled at the origin, the flowers have only been some 4-6 hours out of the grower’s coolers and usually not exposed to an average over 11 degrees Celsius.”