Packing Strawberries in Paper Boxes Designed for Chilling Storage
In an efficient cold-chain system, cold air should be well circulated within the boxes used for packaging. Moreover, boxes should not lose their shape even if they become damp. Each box should hold the right amount of fruit, and be of a proper size to minimize the cost of distribution.
Structure
Dimensions and Materials
The improved packaging consists of an external box made of corrugated fiberboard, with a capacity of 6 kg, and six internal boxes made of cardboard, each holding 1kg of fruit. The outer box is 54 cm long x 36 cm wide x 9 cm high, and it was designed to occupy 96% of the area of the base of the most commonly used pallette (1.1m x 1.1m) used for loading Fig. 1 and Fig. 2).
Ventilation Holes
To facilitate the circulation of cold air, ventilation holes were made in the sides of the box and the internal partitions. The ratio of ventilation holes to surface area in the outer box is 4.5%, while that of the internal partitions is 10.5%. The circulation of cold air through the holes shortens the pre-cooling period and makes cooling more uniform.
Furthermore, the ventilation holes are round and less than 20 mm in diameter, small enough to prevent the strawberries from being caught in the holes. The box is a folding type to avoid shape distortion, which often happens to other packaging boxes as a result of humidity. With this new box, the strawberries can be safely stored for a longer period (Fig. 3).
Performance and Effectiveness
Using this newly developed corrugated paperboard box, the cooling rate was 10.2oC/hour. This represents an improvement in cooling efficiency of about 40%, compared to the corrugated paperboard box widely used on farms in Korea, which has a cooling rate of 6.3oC/hour. The improved box gave the fruit a uniform temperature. The temperatuare difference between the warmest and coolest fruit was less than 1oC.
The freshness of fruit stored for 12 days in the newly developed box, and for the same period in the commonly used traditonal box, was compared. It was found that the new box was better at maintaining the appearance, color and flavor of the fruit, with less shape distortion and discoloration.
When the traditional cardboard box was used, the fruit began to discolor after only four days of storage. After six days of storage, the strawberries had changed their color to blackish red, and were no longer marketable. Those in the improved box were still marketable after 12 days of storage.
Index of Images
Figure 1 (Right) Diagram of Box Used for Packaging Strawberries
Figure 2 Outer Box for Strawberries Holds Six Smaller Boxes, Each Containing 1KG of Strawberries.
Figure 3 Strawberries Packed into Six Small Boxes Fitted into Strong Outer Box
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