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Common food packaging quality problems (2-5)

Nov 28,2021

Source: Link Testing Instruments Co., Ltd

What are the reasons for the slippage or deviation of puffed food packaging during bag making?

Quality issues:

The packaging film used in some puffed foods is prone to slipping and deviation during the unrolling and bag making process on the production line.

Cause Analysis:

(1) Packaging materials

• The friction coefficient is low or uneven-when the friction coefficient between the inner surface and the outer surface of the packaging film of potato chips and other puffed food is low or uneven (or the inner surface of the packaging film is in direct contact with the metal reel of a good production equipment The coefficient of friction between them is low or uneven). When unrolling the bag, under the same drag force, it is easy to slip or run off.

(2) Production equipment

• The surface of the unwinding reel is not smooth-the surface of the reel on which the roll film is placed on the production equipment is not smooth, resulting in uneven friction coefficient with the inner surface of the roll film, which is prone to deviation.

Expert advice:

——Pay attention to the in-factory monitoring of the coefficient of friction of packaging materials.

——Reasonably adjust the amount of additives such as slip agent and anti-blocking agent in the packaging materials, and check the equipment regularly.

Typical quality case:

——Test sample: Popcorn packaging——plastic composite film (customers report that the packaging film is easy to slip during bag making).

—— Targeted test items: friction coefficient (friction between the inner surface and the outer surface of the film).

——Test results: The friction coefficient of the packaging film is relatively low. The average dynamic friction coefficient is 0.13, which is much lower than the average value of similar high-quality products on the market (the dynamic friction coefficient is about 0.25). This low friction coefficient is caused The main reason for roll film slipping during unwinding.

COF Tester from Link Testing
COF Tester

Why does the puffed food packaging leak and deflate?

Quality issues:

Potato chips or other puffed foods often appear in flat bags during the sales process.

Cause Analysis:

(1) Packaging materials

• Poor barrier properties-high permeability of the packaging material from the inside of the package, that is, large gas permeability and poor barrier properties, such as internal air, nitrogen, etc.

• Poor rub resistance-for composite film packaging containing aluminum structures (such as aluminized film, aluminum foil), the handling and sales process will be rubbed by external forces, and potato chip packaging bags with poor rub resistance are prone to creases, pinholes, etc. Defects, resulting in poor barrier properties, and internal gas permeates out of the packaging bag.

(2) Finished product packaging process

• Poor airtightness-the bag body or heat-sealed part of the soft plastic package is prone to air leakage under certain pressure or long-term storage, especially the sealing quality of the heat-sealed part is poor, such as the heat-sealing strength is too low or too high , If the heat sealing strength is not uniform, air leakage and bag collapse are more likely to occur.

Expert advice:

——Pay attention to the daily monitoring of the barrier properties such as the nitrogen permeability and air permeability of the package, the nitrogen permeability after kneading, the air permeability after kneading, etc., the daily monitoring of the barrier performance after kneading, the sealing performance (negative pressure method), and the heat sealing strength. .

——Adjust the parameters of the heat-sealing machine to improve the quality of the heat-sealed parts; choose packaging materials with high barrier properties and good rubbing resistance or improve the quality of existing packaging materials.

Typical quality case:

——Test sample: potato chip packaging bag—aluminum-plated composite film composed of aluminized film and plastic film (the manufacturer reported that the product had a relatively high percentage of bag collapse during the sales process).

—— Targeted testing items: nitrogen permeation volume, nitrogen permeation volume after kneading, sealing performance (negative pressure method).

——Test result: The nitrogen permeation rate of the aluminum-plated composite film before being rubbed is 2.0819 cm3/(m2•24h•0.1MPa), and the nitrogen permeation rate rises to 150.2877 cm3/(m2•24h•0.1MPa) after rubbing, packaging The barrier properties of the bag are significantly reduced, which makes the internal nitrogen gas permeate slowly; in the sealing performance (negative pressure method) test, the heat-sealed leakage occurs when the finished product is packaged at -34KPa. Therefore, the serious decrease in barrier properties caused by the inability of the packaging material to be rubbed and the poor sealing of the heat seal are the main reasons for the deflated bag problem of the product.

Leak Tester LTY-01

Which properties should be paid attention to in the packaging of finished milk powder?

The sealing strength of the heat seal is verified by the heat seal strength test. If the heat seal strength is improper, problems such as air leakage and bag breakage are likely to occur.

② Tightness-through the sealing performance (negative pressure method) test to verify, you can find out the parts of the finished package that are prone to air leakage and leakage.

③ Resistance to impact of contents—verified by burst pressure test. Fill the package with gas to test whether the finished package is broken under the pressure impact of the internal gas, and used to find the location where the package is prone to rupture and the compressive strength.

④ The gas composition inside the package is verified by the headspace gas analysis test, which can monitor the proportion of oxygen, carbon dioxide, and nitrogen in the finished product package, so as to determine the tightness of the finished product package and ensure that the internal gas proportion meets the quality of the milk powder need.

⑤ Pressure resistance performance-to further verify whether the finished product package is broken during the stacking process or when it is squeezed by external force through related tests of pressure resistance performance.

⑥ Drop resistance performance-through the drop resistance test to further verify whether the bag breaks when the finished package falls within a certain height.

What should I do if there is a peculiar smell in the plastic packaging during use?

Quality issues:

Before using some plastic packaging bags, the packaging itself has a pungent peculiar smell, and even the packaged food has a similar peculiar smell.

Cause Analysis:

--Packaging Materials

• Improper control of the printing process-the organic solvents (alcohols, ketones, esters, benzene and other solvents) that dissolve printing inks are not sufficiently volatilized. The solvent residue test can be used to test the total amount of residual solvents and verify whether they contain harmful Benzene substances;

• Improper control of the compounding process-As a result, when the packaging compound film used is compounded with an adhesive, the organic solvent that dissolves the adhesive is not fully volatilized;

• Poor quality of raw materials-the resin raw materials used to produce the packaging materials themselves or the small molecules with peculiar smells added to them contain more;

• Adhesives are of poor quality-the adhesives used to laminate each layer of film produce harmful substances such as toluene diamine at high temperatures.

Expert advice:

——Pay attention to the monitoring of sanitary performance indicators such as solvent residues, evaporation residues, toluene diamine content, and potassium permanganate consumption in packaging.

——Choose appropriate inks (such as solvent-free inks) and adhesives, and adjust the volatilization and drying process parameters during printing and compounding.

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