Table of Contents
Moisture-proof packaging is to use moisture-proof materials and moisture-proof technology (constant temperature storage) that have the ability to block water vapor to encapsulate the product to isolate the impact of external humidity changes on the product, and at the same time make the relative humidity in the package meet the requirements of the product and protect the product. the quality of.
The moisture-proof packaging of food includes two meanings
external moisture cannot enter, and internal moisture is not easy to discharge.
When the ambient humidity of food with a certain amount of moisture exceeds its allowable critical humidity, the food will quickly absorb moisture, thereby increasing its water content, reaching or even exceeding the critical moisture value for maintaining quality, resulting in excessive water content in the food and rapid Corrosion and deterioration, especially for dried foods that are sensitive to environmental humidity, the change of environmental humidity is relatively easy to exceed the critical humidity of the food.
From the perspective of the organizational structure of food, food with loose porous or powder structure has a large surface area, a large contact area with water vapor in the air, and a fast moisture absorption rate, which can easily cause changes in the quality of the food.
For example, biscuits and bread, which are both pastries, are packaged moisture-proof. The moisture-proof packaging of biscuits is to prevent moisture from entering outside (outside the package), while bread is more to prevent the moisture in the bread body from being discharged (evaporation) in the package.
In general, moisture-proof packaging has the following purposes:
Prevent moisture-containing food, fruit, etc. from deteriorating due to dehumidification (drying); prevent food, fiber products, leather and other organic materials from mildew due to moisture;
Prevent discoloration and rust of metal and its products; prevent moisture-absorbing products, such as milk powder, biscuits, dried fruits and other foods and medicines from deliquescent deterioration.
There are many technical methods to achieve moisture-proof packaging, such as using moisture-proof packaging materials to seal the product adding an appropriate amount of desiccant to the packaging container to absorb residual moisture and penetrate the moisture through the packaging material, or vacuuming the sealed packaging container. method.
The moisture-proof function of the packaging technology form is as follows.
Sealed packaging
This is the traditional packaging method. The container is made of airtight rigid material (metal, glass, hard plastic, etc.), the product is placed in it, and then the mouth of the container is welded or closed with a screw cap, buckle cap, or plug cap, which can effectively prevent external moisture entry.
Skin packaging
Put the product itself as a mold on the bottom plate, cover it with a plastic film, heat and soften the plastic sheet, and extract the air (including water vapor) between the packaging film and the bottom plate, and the plastic film will stick to the shape of the product. Therefore, skin packaging also has a moisture-proof effect.
Vacuum and air-filled packaging
In vacuum packaging, since the air in the container has been extracted, the influence of the original residual moisture on the product is avoided. The inflatable packaging pumps out the air and moisture in the package, and then fills it with dry gas or inert gas in an appropriate amount, which also reduces the impact of moisture on the product.
Generally, gases have the property of diffusing from high-concentration to low-concentration areas, and the humidity in the air also has the property of diffusing from high-humidity areas to low-humidity areas.
To cut off the flow inside and outside the package and maintain the relative humidity required by the product in the package, moisture-proof packaging materials with certain moisture permeability requirements must be used.
The moisture permeability of packaging materials depends on the type of material, processing method and material thickness. In order to determine the moisture permeability of packaging materials, moisture permeability is generally measured. my country’s national standards have stipulated the moisture permeability of moisture-proof packaging materials and containers and the moisture permeability is measured according to GB 6981 “Test method for moisture permeability of rigid packaging containers” and GB 6982 “Test method for moisture permeability of flexible packaging containers”.
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