Return list

Answers to common quality problems in food packaging

Apr 23,2023

Source: Link Testing instruments co.,ltd.

Why do pickled vegetables become rancid, mildewed, and swollen?

Quality issues:

After a period of storage, some pickles and pickled vegetables often have problems such as rancidity, mildew, and bag swelling.

Cause Analysis:

(1) Packaging materials

• Poor barrier property—the permeation rate of oxygen and water vapor in the environment is relatively large, causing the growth and reproduction of residual microorganisms.

• Poor Composite Fastness Poor Composite Fastness——The peel strength of the composite film used in the packaging bag is poor, that is, the composite fastness between the single-layer films in the composite film is poor, especially in the acidic environment of pickled vegetables. The delamination phenomenon of the composite film leads to the decline of the overall barrier properties of the composite film.

(2) Finished product packaging production process

• Poor airtightness—the airtightness of the packaging bag body or the heat-sealed part is poor, and it is easy to cause slow air leakage in the finished product packaging during the long-term storage of the finished product packaging. In particular, the sealing quality of the heat-sealed part is poor. If the heat-seal strength is too low or too high, or the heat-seal strength is uneven, air leakage is more likely to cause deterioration.

• Incomplete sterilization—that is, there are still some microorganisms in the finished product packaging. These microorganisms will grow and reproduce in large quantities when encountering a suitable temperature, humidity environment and oxygen concentration, resulting in bulging bags.

Expert advice:

——Pay attention to the monitoring of main properties such as oxygen transmission rate, sealing performance (negative pressure method), heat sealing strength, and peeling strength of packaging materials.

——Select packaging materials with high barrier properties or improve the quality of existing packaging materials.

——Increase the sterilization effect and improve the sealing quality of the heat seal (that is, the heat seal effect).

Typical quality cases:

——Test sample: plastic composite film for mustard mustard packaging (the customer reported that the product was complained about the problem of bag swelling).

——Targeted testing items: oxygen transmission rate, sealing performance (negative pressure method).

——Test results: In the sealing performance (negative pressure method) test, the finished package did not leak at -89KPa, and the airtightness was good; the oxygen transmission rate of the packaging bag was 600.3419 cm3/(m2•24h•0.1MPa), far lower than Average value for quality products on the market. Therefore, the low barrier property of the packaging is an important reason for the above-mentioned problems in this product.

What properties should be focused on when inspecting the material of instant coffee packaging?

(1) Barrier property

• Oxygen and water vapor barrier properties in the environment—Verified by oxygen transmission rate and water vapor transmission rate tests to prevent packaging materials from moldy and agglomerated foods due to large permeation rate and poor barrier properties .

• Rubbing resistance - for composite films containing aluminum (such as aluminized film, aluminum foil, etc.), compare and verify the oxygen transmission rate or water vapor transmission rate test before and after rubbing. If the rubbing resistance is poor, Creases, pinholes, etc. are prone to occur, resulting in reduced barrier properties and poor sealing properties of packaging materials.

(2) Physical and mechanical properties

• Uniformity of thickness - verified by testing the thickness of the package, the uniformity of thickness is the basis for ensuring good performance of the packaging material.

• Slipperiness——Verified by the friction coefficient test to prevent the packaging material from being difficult to unwind or slip due to too large or too small friction coefficient.

(3) Hygienic performance

• Residual amount of organic solvents—Verified by solvent residual test. If there is too much residual solvent, the packaging film will have an odor, and the residual solvent will easily migrate to the packaged instant food, which will cause the instant food to have an odor and affect consumer health.

What are the common packaging forms of instant coffee?

(1) Plastic composite film: It is a packaging film composed of plastic film and plastic film, and the state of the contents can be observed. Since the barrier properties of composite films of different materials are quite different, when using such composite films, attention should be paid to their barrier properties.

(2) Aluminum-plastic composite film: a packaging film made of aluminum foil and plastic film, which has high barrier properties and good light-shielding properties. When using it, pay attention to its rubbing resistance to prevent its barrier property due to poor rubbing resistance. decrease.

(3) Aluminized composite film: a packaging film composed of aluminized film and plastic film. It has high barrier properties and good light-shielding properties. When using it, attention should be paid to its barrier properties and rub resistance.

For more details please visit

Live Chat