Introduction to the practical technology of packag

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Introduction to practical technology of fruit packaging, storage and transportation (II)

Second, the role of packaging on product quality

packaging is used to protect products, which protects products from the following aspects:

1. Prevent mechanical damage

the mechanical damage suffered by products in the circulation process can be attributed to four different reasons: extrusion, collision (Bayer Group sales in the third quarter of 2014 were 10.187 billion euros) and cutting. The sensitivity of various fruits to the above mechanical damage is different, so these differences should be taken into account in the selection of packaging containers and packaging methods

the extrusion outside the packaging container first acts on the packaging container. When the mechanical strength of the packaging container can not bear the external pressure, the goods will be squeezed. Pallets and honeycomb gaskets can be used in the packaging box to strengthen the mechanical strength of the packaging container. Sometimes the packaging container is covered, and the supporting capacity of the packaging container itself to the upper load can also be strengthened. In fact, it is often due to the influence of the external environment that the mechanical strength of the packaging container is weakened, resulting in extrusion. For example, in the air of high humidity environment, after condensation, or after being wet by rain, the commonly used corrugated fiberboard box quickly loses strength due to moisture absorption. Therefore, the use of this kind of carton in high humidity refrigeration is not satisfactory. A few years ago, until the samples were destroyed, the Ministry of Commerce promoted the packaging of fruits in calcium plastic boxes. This kind of packaging box has low water absorption, which overcomes the shortcomings of moisture absorption of cartons, but the cost is high, and it is brittle and easy to crack under low humidity conditions

the cause of the collision is due to sudden stress, such as rough operation during loading and unloading, package falling or sudden braking during transportation, etc. Vibration is common in transportation. The damage of vibration is to cause wear and tear, which can cause from slight abrasion of the epidermis to the wiping off of part of the pulp. All these traumatic surfaces caused by abrasion will cause browning due to the exposure of tannic acid, oxygen and similar substances in the injured tissue in the air, which will damage the product quality, especially the appearance quality. What is more harmful is that these traumatic surfaces are the window of disease infection, and enhance the respiration of fruits, thus accelerating the deterioration

there are two aspects to prevent the impact and vibration of goods: on the one hand, there should be no relative displacement between various goods, especially between the experimental machine using hydraulic transmission and the packaging container, so as to avoid vibration damage. On the other hand, the packaging container should be full, but not too full or too tight; Otherwise, crushing and bumping will increase. The products can be wrapped one by one and separated one by one; Fruit products can also be packed in the way of dividing and layering, or laid with some cushions that can reduce vibration, but this will inevitably increase the cost, so we must consider the loss and income that can be reduced by using these packages, and then decide whether to use this kind of packaging after comparison. In short, light handling is the best way to reduce physical damage

2. The effect of packaging on dry consumption

proper packaging can reduce the water loss of products. The function of these packaging is to place a barrier around the products to reduce the flow of air on the product surface, so as to reduce the water loss. The simplest way is to cover the stack of products with waterproof cloth, or put the products into bags, boxes or cardboard boxes. The dense accumulation of products can also control the flow of air around products one by one. Even if the products are put into the bag, there will be some benefits, because individual products in the bag gather together to form a dense accumulation, so that more products are protected internally by the outer layer from direct exposure to dry air

the permeability of packaging to water vapor and the density of packaging can determine the degree to which the water loss rate of products can be reduced. The commonly used packaging materials have certain permeability to water vapor. The permeability of polyethylene film is low, which can better control the water loss of products. The permeability of cardboard boxes and paper bags is higher, but compared with unpacked bulk products, it can also greatly reduce the water loss. Therefore, people often use plastic film and wax paper and other materials with low permeability to package products. The basic methods are as follows: (1) package a single product or several products into the packaging container; (2) Put the products in bags made of these materials; (3) Use these materials to add full lining on the inner wall of the packaging container; (4) Avoid coating a layer of wax on the cardboard box or immerse the fiberboard in wax before making the packing box

attention should also be paid to the ability of packaging materials to absorb moisture. All kinds of paper products, gunny bags and other natural fiber products are only moist with the naked eye after absorbing a lot of water. Because there is often a water vapor pressure difference between the product and the package, water evaporates from the product and is absorbed by the packaging material. In the cold storage of apples and pears, it was found that a 4kg dry wooden box can absorb about 500 grams of water at 0 ℃. At the end of last year, the Standards Committee has launched the research work on the formulation of relevant standards for plastic shopping bags. Therefore, attention should be paid to improving the humidity of containers with high permeability before using them When the weather is dry, you can consciously sprinkle a little water on the bottom of wooden cases, crates or baskets containing fruit and vegetable products that are prone to water loss, directly wet the packaging, or use the evaporation of additional water to help the product cool down

3. Cooling of products in packaging containers

another important requirement for packaging is that it must be conducive to the rapid cooling of products. The liners, liners and other small packages used in the packaging box will produce different sizes of yin and Yang samples on the air circulation, which will affect the emission of respiratory heat generated by the product. In fact, as long as the product has a strong respiratory effect, whether the product is in a single packaging box or in tightly stacked packages, it will naturally become serious

the way to solve the problem is to formulate the maximum limit density of the product according to the different respiratory rates of the product

Third, packaging design and packaging methods

designing a package suitable for the fresh-keeping requirements of fruit products is an important factor to reduce the post harvest loss of fruits. However, due to the low value of most fruits, the development of fruit product packaging is seriously limited to low-cost materials. Only some varieties with higher value can easily earn back the packaging cost from the market profit

1. Packaging method

the ideal packaging of most fruits should be like this: in this packaging, the container is full, but it does not bulge, nor is it decorative. It is the packaging container that bears the stacking load, not the product itself

for many years, in developed countries, generally, fruits are placed by positioning or molding, and each fruit is placed in an appropriate position, so that each package has the maximum net weight and the closest arrangement. In this way, when the package is opened, the fruit will be presented to customers with great temptation. This method requires that the fruit be accurately divided into many grades according to the size, which is time-consuming, laborious and costly. Later, people used the bulk method to pour the goods into the packaging containers, and then gently shake them so that the goods are close to each other. When using this method, the goods are packed according to the standard weight, not the standard number. There is also a positioning bag, that is, a special compression pad with pits is used, and the size of the pits depends on the size of different goods, so that the goods can be stably maintained in its position, Then put another compression pad with pits on the upper layer to separate the goods layer by layer. This kind of compression pad is usually used in pulp molded tray or plastic tray. These pallets increase the packaging cost, but it can reduce vibration damage and reduce water loss. These pallets are suitable for goods with higher prices

goods can be arranged in a straight line or diagonal line in the packaging container. The straight line arrangement method is simple and convenient for counting. It is suitable for small fruits. The disadvantage is that the bottom layer bears high pressure and poor ventilation. Diagonal arrangement is suitable for large and medium-sized fruits, and the bottom of this arrangement bears little pressure. Good ventilation

2. Stacking of packages

the stacking of packages should consider making full use of the transportation and storage space to ensure the stability of the stack, and make enough air flow in the stack to eliminate breathing heat or make it cool well, and pay attention to the convenience of operation

the stacking method of packages depends on the performance of the commodity itself, the performance of the stacking machine, the condition of packages, storage and transportation location and other conditions. During transportation, the stacking of fruit packages mainly requires strong stability, no ultra-high, ultra wide, overweight, and is conducive to maintaining an appropriate temperature

the refrigeration of packages and the stacking in refrigerated trucks should use the storage space as effectively as possible, because the cost of refrigerated warehouses and refrigerated trucks is very high. Now, with the promotion of mechanical loading and unloading and stacking, it is required to comprehensively consider the stacking size of packages in the process of goods lending, stacking, storage and unloading. First of all, it should be considered that the goods in the car or warehouse do not need to be reversed. Second, it should be considered to make full use of space, which requires a reasonable size as the basis. The length, width and height of the recommended storage space are multiples of 1260 mm, with a negative error of 5%. There is a gap of 60 mm between 1260 mm and 1200 mm as the space required for loading and unloading the package stack of the unit

with 12. Taking 6 meters as an example, it can accommodate the following cargo pile sizes

6.0m × 2 4.0m × 3 3.0 meters × 4

2.4m × 5 2.0 meters × 6 1.5m × 8

1.2m × 10 1.0 m 12 0.8 m × 15

when using these stack sizes, the space utilization factor is 95%, and standard size pallets are fully applicable

in addition to considering the stack distance, sufficient wall distance, column distance, top distance and lamp distance should be reserved for the stacking of packages in the warehouse

the wall distance is the necessary distance between the goods stack and the warehouse wall. The stacking of packages cannot be against the wall, so as to facilitate ventilation and moisture dissipation, patrol inspection, inventory of goods, safety and fire prevention, and protect the opening and closing of building windows

column spacing refers to the distance between the goods stack and the column in the warehouse, which is used to prevent the commodity packaging from moisture and protect the column

the top distance is the distance between the top end of the goods stack and the flat top of the warehouse, the ceiling or the lower end of the beam. The top distance can be reserved for ventilation, moisture dissipation, heat dissipation, leakage detection, etc.

the lamp distance is the safe distance between the four sides above the goods stack and the lighting lamp, which is the requirement of fire prevention and must be strictly maintained at more than 0.5 meters

in the stacking of packages, we should also pay attention to the packages that are prepared for long-distance transportation or high stacking in the cold storage should be much stronger than short transportation and local sales. Where forklifts are used as a means of loading and unloading, the specifications of packages must be compatible with them. Cross stacking or bound stacking is usually the most effective way to enhance the stability of stacking. ⒐ the package is required to have a suitable length width ratio. It is difficult to stack the round basket safely and reliably, so we should be more careful. In order to make full use of the space of the cold storage, the stacking method supported by metal frames and developed higher is worth popularizing

any stacking of fruit commodities should have a certain degree of space to facilitate cooling, with the exception of restricting the reheating of previously cooled products. In this case, the goods should be stacked as closely as possible. In a short time when the self heating caused by breathing does not become a problem, dense stacking with high stability is safe

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