Milk is one kind of liquid food, when we choose the packaging material for milk, there are so many factors we need to consider about. Generally speaking, PE film (milk pouch) is the first choice to pack milk.
Any Other Options of Material for Milk Pouch?
The film were seperated into 3 types according to the layer structure.
Option 1: Single Layer Films
PE and white masterbatch processed by blown film machine, the finished blown film is Non barrier structure.
This film mainly used for “ready to eat” dairy products.
The dairy products usually been processed by pasteurization and the lifetime around 3 days
Option 2: Three-layer Co-extruded Films
Made by
- LDPE、
- LLDPE、
- EVOH、
- MLLDPE
- and white or black Masterbatch.
The Outside layer is LLDPE and LDPE.
Middle layer is HDPE and LPE, the middle layer makes the barrier perfermance better.
Inner layer is LDPE +LPE and black masterbath, the black masterbatch keeps the film untransparent and easy to seal
This three-layer film totally match with the expecttion of right packaging material for milk. high temperature sterilization and Hydrogen peroxide sterilization make the lifetime of the milk more than 30days.
Option 3: Five-layer Co-extruded Films
This kind of film is different with the three-layer co-extruded film, there is a barrier layer(made from EVA、EVAL) in the middle part.
This packaging film is processed under aseptic producing line and the performance of hot seal and Oxygen resistance is excellent. These features keep the food in a long lifetime, almost 90 days under room temperature.
On another hand, this packaging film applied in various of different fields due to the low cost , low transportation cost and easy stock.
How to Choose Packaging Films for Milk Pouch?
1, Smoothness
The friction coefficient of the film should be between 0.2-0.4, this index is very important for automatic filling machine, whatever high or low will make the auto fill not very efficiently.
Generally , the producer use slip agent to keep the friction coefficient steadily.
But the printing quality and performance of hot seal will go down if there is excessive slip agent. In the meanwhile, the smell is very bad.
2, Tensile Strength
During the auto fill, the film is pulled by the machine , so we must consider the tensile strength to avoid break or out of shape.
LLDPE and HDPE show us a very good performance under this considerration.
3, Surface Tension
The surface tension of film is very close related to the quality of printing.
Generally, the surface tension should be more than 38dyne, better if more than 40dyne.
Even if the index is more than 40dyne, the nature of PE is still not friendly to printing ink compare with PVC.
4, Hot Seal
As mentioned above, the performance of hot sealing is the key factor for an packaging film, especally for the liquid packaging film.
Generally , the milk pouches are processed by the auto filling machine.
If the quality of hot sealing is not good, more problem come out during the transportation and storage.
5, Barrier
Prevent Oxgen, light, moisture and smell.
Keep the milk in a stale condition.
This is realy important for expand the lifetime of the milk food.
6, Printing Ink
Most of the packaging film is printed when they were produced.
We must choose the high quality printing ink because the whole pack will be under high tempreture or low tempreture for sterilization, even some packs will be soaked in the hydrogen peroxide.
So the high quality printing ink will not dissolve or fade
7, Stablizition Under High Tempreture
The stablizition under high tempreture is really connected to the safety and sterilizition of the milk pouch.
As we montioned above , the packaging film is laminated with different films, a lot of factors will impact the structure of the finished films, such as different tempreture or different producing procedure.
We must follow the instruction to transport and store the liquid packaging , especially in summer.
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