CUT FLOWER COOLING
Cut flowers and foliage are highly perishable items. Field heat should be removed as soon as possible after picking. Product need to be kept as cool as possible throughout the supply chain. Any temperature fluctuation may result in condensation, promoting disease development as well as reducing postharvest life. This page outlines the cooling methods commonly used in the cut flower industry.Plant material should be cooled as soon as possible after harvest to minimise deterioration. Cooling does this by reducing:
The simplest method of cooling cut flowers is to stand them in buckets of preservative solution in a cold room. If circulation of cold air around the blooms is adequate, they cool quickly. The main disadvantage with this method is that it is not space efficient. If packaged flowers are being stored in the same area, the fluctuations in temperature are not ideal, but generally not a problem unless the storage is long-term (that is, weeks rather than days). If the flowers are packed in sleeves or cartons while still warm, room cooling is not very effective through poor air circulation. More sophisticated cooling techniques are needed. Room-cooled flowers that re-warm during packaging may also benefit from subsequent cooling within the carton.
This is the best cooling method for everyday use by larger growers/exporters and requires a dedicated coolroom. The pictures below show the components of the system. The coolroom is designed with twin walls or plenums and baffles on both sides, and a gap at the top to allow air circulation. Boxes of flowers are brought into the coolroom on a conveyor belt and stacked against the wall as shown in Figure 1. Along the top of each cold wall is a row of tarpaulins on rollers. These are attached to the wall just above the air gap. When pulled out over the top of each stack of cartons they help direct the airflow back into the plenum.
Vacuum cooling is the most effective precooling method for fresh cut flowers compare with tradtinal cooling ways . Vacuum cooling speed is fast (usually only 20-30 minutes), high efficiency, uniform cooling, not affected by packaging ,which makes them more cost-effective and more suitable for the rapid precooling of flowers. Vacuum cooling is the only realistic way to cool flowers at the airport when they are transported by air (both at departure and arrival), and direct and rapid precooling after harvest can also be of great benefit..The beneficial of vacuum cooling for cut flowers:
The technique involves drawing a stream of cold air through the cartons of flowers. The movement of air through the boxes must be unrestricted. At least 6% of the area of each face through which air enters or leaves the cartons should be holes or preferably slots (to minimise the risk of blockages). The pathway for airflow in the box should not be obstructed by carton liners, packaging material or flowers packed too tightly. Ideally, after cooling and before unrefrigerated handling, the ventilation slots should be closed by folding down fibreboard flaps or by applying stickers. A fan is used to draw cold room air through the cartons. By arranging flower cartons on the cold room floor in two rows with a space of about 60 centimetres between them, then placing a fan at one end of the space and a plastic tarpaulin over the top of the space and resting on the cartons, a simple pressure cooling system is produced. Flower cartons, being relatively long, are placed only one wide in each of the two rows. Reinforcing battens are sewn into the tarpaulin at about half-metre intervals to prevent the cover from caving in when the fan is running. When the fan is on, it sucks air out of the central space (plenum), drawing cool air through the cartons via the vents at both ends of the cartons.