Air cooling, conventional cool stores .....continued

The conventional cool store is ideal as buffer storage to prevent produce reheating after cooling. This is essential for the maintenance of the cool chain.
Cooling times - depend very much on the way the stores are used. Soft fruit can be cooled in less than 2½ hours if positive ventilation is used, while Brussels sprouts or cauliflowers can take 24 hours or even longer.

Prepacks and large volumes of produce are difficult to cool. Open stacking, where possible, will improve cooling rates.
Frequent access to the store during warm weather results in an increased demand on cooling plant and higher running costs.

Wet-air cooling with positive ventilation
Produce is held in bins through which cooling air is blown. In this system the air is cooled by close contact with  water which is cooled either by melting ice or by a bank of refrigerated tubes. In the ice bank systems the            refrigeration plant is used to make the ice which acts as a buffer between the varying cooling requirement of the produce and the 'constant' capacity of the refrigerator.
Most crops can be cooled by this method, dry bulb onions are an exception.

Cooling times - Soft fruit and salads can be cooled in 2 to 8 hours. Brassicas and other vegetables are cooled in 10 to 17 hours. Shorter cooling times can be achieved by using higher air flow rates.

Costs
Capital and running costs will vary according to an individual's circumstances and requirements. Therefore a direct comparison of total cost per package cooled can only be made for a specific case. Table 2 sets out typical gross capital and running costs, together with a guide throughput based on an eight hour working day.
The efficiency of the cooling and packing operation depends on close liaison between the buyer and his supplier, as in addition to the daily requirement, a reserve of cooled produce must be available for peak demands during the week.

In the field
The success of the cooling operation depends to a large extent on the way the crop has been handled in the field and the time taken to reach the cooling facility. Most crops should be cooled as soon and as quickly as possible  after harvest, otherwise shelf-life will be reduced.