Packaging Methods and Requirements for Transporting Fruits

1. Selection of Outer Packaging Materials

Most of the earliest packaging containers were made from plant materials, such as leaves, reeds, and straw woven together, and were designed in forms convenient for people to carry. Later, people used livestock for transport, and the size of packages increased accordingly, while the packaging materials used also became more diverse.

At present, many external packaging materials are used for fruit in China, and they can mainly be divided into the following five types:

Baskets: Baskets woven from natural plant materials such as bamboo and vitex twigs are traditional packaging containers in China. The main advantages of this material are that it is cheap, lightweight, locally sourced, and can be woven into containers of almost any shape and size. The disadvantages are that the shapes are irregular and often not very solid, so they are not sufficient to prevent damage; they are relatively large, and manual loading and unloading easily causes fatigue; the shape is usually large at the top and small at the bottom. Although this can reduce the pressure on the fruit in the lower layers, it is difficult to stack effectively during transport and storage.

Wooden boxes: Wooden boxes are better than containers made from other natural plant materials. Their advantage is that they are sturdy, can be made into uniform shapes of various specifications, and are stronger than other materials in preventing physical damage. However, wooden boxes themselves are relatively heavy, making handling and transportation more laborious.

Cardboard boxes: Corrugated cardboard boxes are a product of Western technology. They are lightweight and inexpensive, so as substitutes for wooden boxes, they have appeared in large numbers in the fruit distribution sector. Another advantage of cardboard boxes is that their appearance is smoother, making it easier to use printed labels and promotional materials. The biggest disadvantage of cardboard boxes is that they cannot be reused; once eroded by water or handled roughly, they are easily damaged.

Plastic boxes: Plastic boxes can be made from a variety of synthetic materials, but they are mainly made from the following two materials: the harder high-density polyethylene type and the softer low-density polystyrene type. High-density polyethylene boxes are sturdy and high-strength, easily withstanding the various pressures generally encountered in distribution, and can be stacked to a certain height; at the same time, because such boxes can be easily manufactured in uniform specifications, they can maximize the use of storage space. They have high strength and greater flexibility in design; handles, ventilation holes, and the like can also be added to the box walls without weakening the box's mechanical strength. In addition, they are easy to clean, have smooth surfaces, and can be made in a variety of bright colors. If the boxes are designed to nest into one another, the space occupied by empty boxes is only about one-third or less of that of full boxes.

These plastic boxes are considered to have relatively ideal technical characteristics for meeting the distribution requirements of fresh fruits and vegetables, so they are regarded as substitutes for traditional packaging containers in any packaging development project. However, polyethylene material is very expensive. Only when recycling can be effectively organized and the boxes can be reused multiple times is the use of such boxes economically feasible.

Polystyrene is sturdy, low in density, lightweight, and has good thermal insulation, so it can be used to transport pre-cooled goods at ambient temperatures. In addition, this material has a good ability to cushion impacts. Its main disadvantage is that excessive sudden force will cause it to break or crush. At the same time, because it is inconvenient to clean and its surface deforms on first use, containers made of this material cannot be used a second time, resulting in excessively high usage costs.

2. Inner Packaging Materials

The above five packaging materials are mainly used to make packaging containers to resist external damage, and belong to external packaging of goods. Inside the packaging container, individual goods may collide with one another or goods may collide with the container; this movement can also cause physical damage to the products. Adding inner packaging inside the packaging container can prevent damage caused by such collisions. The materials used for inner packaging mainly include:

Plant materials: Plant materials such as leaves are the cheapest inner packaging in rural areas. They are mainly used as padding and are very effective in protecting goods. In many places in China, leaves are used as inner packaging for goods packed in baskets. However, plant materials are biological tissues and therefore respire. Their respiration can affect the goods, increase heat accumulation in the packaging container, and increase microbial contamination.

Paper: Paper is very commonly used as an inner packaging material; the cheapest is old newspaper. The role played by paper is basically the same as that of plant leaves, but in addition to being used as cushioning, paper can also be used to wrap goods. Compared with plant materials, paper is not necessarily more effective in protecting goods, but it will not have any adverse interaction with the product, and it can noticeably improve the visual appearance of goods in the market.

There are many types of inner packaging paper, including wrapping paper, paper trays, corrugated insert boards, etc. Wrapping paper can be used to protect individual goods and can also serve as a carrier for postharvest chemical treatments. Paper trays and inserts can be used to separate rows of products or as additional padding for separating containers. Insert paper can also be made into troughs or compartments within the packaging container to completely isolate each individual product.

Plastic: The method of using plastic inner packaging is the same as that of paper, and there are many types. It is more attractive than paper packaging and has significant advantages in controlling product water loss and respiration, but the cost is higher. People also use soft wood shavings, foam plastic, or fiber surface layers as inner packaging.

3. How Packaging Protects Product Quality

Packaging is used to protect products, and it plays this role in the following aspects:

1. Preventing Mechanical Damage

Mechanical damage suffered by products during circulation can be attributed to four different causes: compression, impact, friction, and cutting. Different fruits have varying sensitivity to these mechanical damages, so these differences should be considered when selecting packaging containers and methods.

External compression on the packaging container first acts on the container itself. When the mechanical strength of the container cannot withstand external pressure, the product will be compressed. The mechanical strength of the packaging container can be enhanced by using trays, honeycomb pads, etc., inside the box. Sometimes adding a lid can also improve the container's ability to support the load from above. In practice, it is often the influence of the external environment that weakens the mechanical strength of the container, causing compression. For example, in high-humidity environments, after condensation occurs, or after being soaked by rain, commonly used corrugated fiberboard boxes quickly lose strength due to moisture absorption. Therefore, such cardboard boxes are not entirely satisfactory for use in high-humidity cold storage. Calcium-plastic boxes, promoted for fruit packaging in earlier years, have low water absorption, overcoming the drawback of moisture absorption in cardboard boxes. However, they are costly and become brittle and prone to cracking in low-humidity conditions.

Impact is caused by sudden forces, such as rough handling during loading and unloading, dropping of packages during transport, or sudden braking. Vibration is common during transportation. The damage from vibration lies in causing abrasion, which can range from light surface scuffing to scraping off part of the fruit flesh. All these injuries caused by abrasion can lead to browning due to the exposure of tannins and similar substances in the damaged tissue to air, harming product quality, especially appearance. More harmful is that these injured surfaces become windows for disease infection and increase the respiration rate of the fruit, thereby accelerating spoilage.

2. Reducing Impact and Vibration Damage

On one hand, there should be no relative displacement between individual products, and between the products and the packaging container, to avoid vibration damage. On the other hand, the packaging container should be filled, but not overfilled or too tight; otherwise, compression and bruising will increase. Products can be individually wrapped and separated, or fruit products can be packaged in grids and layers, with cushioning materials placed to reduce vibration. However, this inevitably increases costs, so the reduction in losses and the increase in benefits achieved by using such packaging must be compared to decide whether such packaging is needed. In short, handling with care is the best way to reduce physical damage.

4. Weighing Packaging Cost

The choice of packaging is limited by the cost of the fruit and vegetable products themselves. Factors such as product value, packaging cost, the role in protecting product quality, and selling price need to be considered. The cheapest material for fruit and vegetable packaging is baskets and bags made from locally grown plant materials. However, actual situations tell us that using this type of packaging results in considerable physical damage to the products. For example, bamboo baskets have many limitations. First, they are large in volume, making it difficult to handle them with care; second, they are often overfilled, putting great pressure on the products. In addition, they are not conducive to stacking during transportation and storage. Therefore, some experts argue that such materials are unsuitable for packaging and should be phased out in favor of other packaging materials. Based on China's actual situation, bamboo and similar natural materials have low costs. As long as the packaging containers are made smaller, have lids, and handling operations are properly improved, bamboo basket-type packaging can still be used.

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