Source：Link Testing instruments Co.,Ltd.
What properties should be paid attention to in the packaging of finished milk powder in bags?
(1) Sealing performance-prevent the finished package from leaking that due to poor sealing performance. It can be verified by sealing performance (negative pressure method) test.
(2) The sealing strength of the heat-seal—to prevent leakage and bag breakage of the finished product package due to the leakage of the heat-sealing or excessive heat-sealing. It can be verified by heat seal strength test.
(3) The performance of resistance to internal gas impact-prevent the package from breaking due to poor gas impact resistance. It can be verified by burst pressure test, and a series of tests can find out the parts with poor pressure resistance of the package.
(4) Drop resistance performance-to prevent bag breakage when the package is dropped. It is verified by drop resistance test.
(5) Pressure resistance-prevent the package from being broken when stacked or squeezed by external force. It is verified by pressure resistance test.
(6) The content of gas components in the package-for nitrogen-filled or modified atmosphere packaging, the proportion of gas components in the package has an important impact on the quality of milk powder. It can be verified by headspace gas analysis test.
How to test the sealing performance of metal milk powder cans?
At present, China does not have a test method for the tightness of metal cans of packaged milk powder, and SN/T 0400.4-2005 "Import and Export Canned Food Inspection Regulations Part 4 Containers" and GB/T 4789.26-2003 "Food Hygiene Microbiological Examination of Canned Food "Commercial Sterility Inspection" Appendix B specifies the test method for the tightness of tinplate cans, which can be used as a reference for the test of the tightness of metal cans for milk powder.
• Pressure leak test method: seal the empty can and open a hole in the can body, immerse the can in water, and inject air into the can from the opening. When the pressure in the can reaches 68 KPa or 70 KPa , Keep it for 2 minutes, and check whether there are continuous bubbles on the outside of the tank.
• Decompression leak test method: inject 80% ~ 90% of the cooked water solution into the empty tank, seal the empty tank with a glass plate with a sealing ring, and vacuum the inside of the tank. When the pressure reaches 68 KPa, keep it 1 min, check whether there are continuous bubbles inside the tank.
The above method is for empty metal cans. If it is necessary to test the tightness of the nutrient powder product cans, a certain amount of nitrogen or carbon dioxide may be filled in the packaging of the finished product, so the specific test pressure can be adjusted according to the actual situation.
What properties should be paid attention to when the soft plastic packaging used for milk powder enters the factory?
• Uniformity of thickness——The uniformity of thickness is the basis for the uniformity and goodness of other properties of packaging materials. It is verified by thickness test.
• Flexibility-to prevent the bag from broken when the bag is dropped or stacked. It is verified through horizontal and vertical tensile, elongation, elastic modulus, pendulum impact energy and other tests.
• Smoothness-to prevent problems such as slippage, deviation, and poor rolling during the bag making process. It is verified by friction coefficient test.
What should we do if the soft plastic packaging has slipped and deviated during filling and bag making?
Quality problems: In the process of product bag making and packaging, there are often problems such as slippage and deviation of the roll film.
(1) Packaging materials
• Inappropriate friction coefficient-during the unwinding and bag making process, the unsuitable friction coefficients between the inner and outer surfaces of the film, and between the inner and outer surfaces and the rollers will adversely affect the unwinding process. . If the friction coefficient is too low, problems such as slippage and deviation will occur; if the friction coefficient is too high, it will cause non-smooth unwinding and even stretch the film.
(2) Production equipment
• non-smooth rolls of the rolling bag making — If the rolls that contact the packaging material are uneven and smooth when unrolling the bag, it will also affect the rolling effect.
——Pay attention to the monitoring of the performance indicators of the friction coefficient of the packaging.
——Smoothing agent, opening agent and other small molecule substances should be added in an appropriate amount; regularly check and repair the rolling bag making equipment.
Typical quality case:
——Test sample: a roll film for packaging of a health care product (customers reported that the roll film is prone to slippage).
——Targeted test items: friction coefficient.
——Test results: The maximum static friction coefficient of the roll film is 0.201, the minimum is 0.115, the maximum dynamic friction coefficient is 0.103, and the minimum is 0.074. The friction coefficient is small and uneven. Therefore, the low and uneven friction coefficient of the rolled film is the main cause of slippage.
Why does the packaging of milk powder and other finished products appear to be deflated?
Quality problems: After a certain amount of gas filled with nutritional powder and other finished products in the package are stored for a period of time, the package collapses.
Finished product packaging process
• Poor airtightness-If the heat-sealing effect of the finished product package is poor or the airtightness of the bag surface is poor, the problem of bag collapse will occur during the process of mutual extrusion and stacking of products.
——Pay attention to the main performance of packaging nitrogen permeability, carbon dioxide permeability, oxygen permeability, oxygen permeability after kneading or nitrogen permeability after kneading or carbon dioxide permeability after kneading, heat sealing strength, sealing performance (negative pressure method), etc. monitor.
——Improve the heat sealing process and improve the heat sealing effect; improve the quality of existing packaging, or choose packaging materials with high barrier properties and good rubbing resistance.
Typical quality case:
——Test sample: aluminum-plastic composite packaging bag for protein powder packaging (customers report that the amount of gas inside the package is significantly reduced after the product has been stored for a period of time).
—— Targeted testing items: heat sealing strength, sealing performance (negative pressure method).
——Test results: The heat-seal strength is 36 N/15mm, and the heat-seal strength is relatively high; in the sealing performance (negative pressure method) test, air leakage occurs at the crease of the bag body at -40.5 KPa for about 3 minutes. Therefore, the packaging has poor resistance to rubbing, resulting in poor sealing of the packaging, which is the main reason for the reduction of gas in the packaging.
Why do nutrient powders or granules such as canned protein powders agglomerate and taste bad?
Quality problems: Health-care nutritional powders or granules such as canned protein powders often have quality problems such as agglomeration and "hala" taste during the shelf life.
Finished product packaging process
• Poor sealing performance-If the performance of the packaging tank is poor, the gas in the external environment will gradually penetrate from the weak seal to the inside of the packaging, causing the product to agglomerate and taste bad.
——Pay attention to the monitoring of the main performance of packaging materials such as sealing performance.
——Choose tank materials with good barrier properties to improve the sealing effect of finished tanks.
Typical quality case:
——Test sample: protein powder packaging (the can body is made of paper-aluminum-plastic composite sheet, and the bottom and lid of the can are tinplate and aluminum foil respectively. Customers report that the product has a bad taste).
—— Targeted testing items: oxygen permeability, sealing performance (negative pressure method).
——Test results: The oxygen transmission rate is 0.0153 cm3/(m2∙24h∙0.1MPa), which can meet the quality requirements of protein powder; in the test of sealing performance (negative pressure method), the finished product of protein powder is packaged at about -30 KPa3 Air leakage occurs within 3 minutes, indicating that the packaging tank has poor sealing. Therefore, poor sealing is the main reason for the off-flavor of the protein powder.
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