background:

Fruit bagging technology is a practical technique that has been promoted in China in recent years to improve the quality rate of orchards and increase pollution-free fruit cultivation techniques. This technology is based on the shape, size, and type of solid fruit, using different specifications, different colors of polyethylene film or flexible, flexible paper to make one to three layers of different sizes of bags. The mechanism is that the fruit in the bag will not be invaded by birds and will not be infected by Drosophila bacteria. It will not be scratched by the branches during the growth process, avoid direct sunlight, and more because of the air permeability of the bag itself. Sex can produce individual greenhouse effects, so that the fruit maintains the proper humidity, temperature, increase the sweetness of the fruit, improve the luster of the fruit, increase fruit production, and shorten its growth period. At the same time, since no pesticides are required during the growth process, the fruits have high quality and no pollution, reaching international standards.

 

At present, domestic fruit bagging technology has been widely popularized. Paper bagging has already had corresponding industry standards, but there is no clear standard for the polyethylene film used for protecting fruit products. Labthink has a professional testing laboratory and combines its own years of testing experience to provide companies with the following barrier performance test methods for polyethylene film bagging.

 

test instrument:

Fruit protective films are mostly made of polyethylene materials and have certain oxygen permeability and moisture permeability. In the actual test, the oxygen permeability test can use the pressure difference test equipment, and the moisture permeability test uses the weighing method equipment.

Oxygen permeability test:

Selection of Labthink VAC-V1 Gas Permeability tester, the test conditions are 23 ± 2 ℃, 50 ± 5 % RH. The film was cut into a circular specimen with a diameter of 90 mm . The specimen was laid flat on the lower chamber of the VAC-V1 tester, gently smoothed with a finger, and the upper handle was lowered by rotating the handle. Turn on the vacuum pump and start the test. At this point, the upper chamber is a flowing high-purity oxygen and the lower chamber is a vacuum. Because of the difference in pressure between the two sides of the sample, oxygen penetrates from the upper chamber through the lower chamber of the sample. The oxygen permeability of the sample can be calculated by testing the pressure in the lower chamber. The VAC-V1 Differential Pressure Gas Permeameter is computer controlled and easy to operate.

Moisture permeability test:

The moisture permeability test selects the W3/0120 water vapor transmission rate tester. During the test, the film is cut into a circular sample with a diameter of 74 mm . Before placing the sample into the moisture permeable cup, it can be placed in the support frame to avoid the sample being too soft against the water surface. Place the moisture-permeable cup with the sample in the instrument and start the test. The weight change of the permeation cup before and after the test was automatically weighed by the system to calculate the water vapor transmission rate of the sample. Select 38 °C , 90%RH for this test condition and set the test interval to 30min .

Because the fruit protective film is generally thin, about 10-20 microns in thickness , if you do not flatten the sample, it is prone to wrinkles, resulting in erroneous test results.

 

Result analysis:

Judging from the test results, the oxygen permeability of polyethylene protective film varies between 2000-70000cm3/m2.24h.0.1MPa , and the moisture permeability is between 30-40g/m2.24h .

After inspection by the Languang Laboratory, it can be seen that due to the different emphasis on the application of the protective film of the fruit, the thickness, color, and material of the protective film will be different during the production, so the oxygen permeability and moisture permeability of the protective film will be somewhat different.

 

to sum up:

The function of the fruit protective film is to prevent the fruit from being attacked by the outside, bacterial infection, and reduce the use of pesticides. Due to various factors such as the production process, material selection, and processing thickness, the oxygen permeability and moisture permeability of the fruit protection film will be very different. When purchasing it, it must be used for different purposes, and the special fruit protection film products produced by the regular enterprises should be selected to avoid The economic losses caused by poor product performance indicators.