If sticking occurs during bagging of fruit preserves, do not rush to change the film. Follow the three-step process: “product sticking—film sticking—syrup entering the sealing area” to identify the issue. Most problems can be located within two rounds. Soft and sugary fruit preserves behave differently from brittle snacks in the forming tool and sealing blade: they are directly affected by temperature, syrup viscosity, and downtime. The same roll of film may perform differently in the morning shift compared to the afternoon. Below is the sequence of actions to take during on-site troubleshooting, as well as the items to check during sample making and first piece confirmation.
Key Points
- Stickiness on the bag should first determine whether it is the product adhering to the film or the film adhering to the film; the handling approaches for the two are opposite.
- The re-start section after shutdown is most prone to sticking, so it must be observed separately and the first few bags isolated.
- The inspection of sealing and opening should become a fixed procedure and not be performed only once at startup.
Why do dried fruit pieces tend to stick to the forming tool during bagging?
This text applies to the production lines of vertical packaging machines and pre-formed bag lines for fruit candy products. Adhesion occurs on the forming tool from two directions. First, the syrup exuding from the surface of the fruit candy comes into contact with the hotter surface of the forming tool, causing its viscosity to decrease and forming a thin adherent layer. Second, the inner layer of the film is heated by friction with the forming tool, changing its surface energy and making it more susceptible to wetting by the syrup. The combined effect results in increased film running resistance, distorted bag shapes, and in severe cases, wrinkling or even tearing.
The impact of downtime is often overlooked. After a short stoppage, the temperature of the forming unit remains, causing the fruit candy to stay in the same position continuously. It is easiest for the product to stick when restarting. Therefore, when troubleshooting, the number of stoppages and their duration should be recorded together, rather than just focusing on the normal operating period.
Distinguish whether the sticking bag is a single-layer film or a double-layer film.
The handling approaches for these two situations are opposite. They must be addressed separately before taking action. For product adhesion, symptoms include residue of preserved fruit being pulled out from the bag opening, sugar stains on the inner wall, and stringy pulling when opening the bag. For film adhesion, symptoms include the inner walls of empty bags sticking together, difficulty in opening, and difficulty in stretching the bag after forming. The former should be addressed by checking product temperature, syrup condition, and the inner surface of the film. The latter is mostly related to the winding tension of the film roll, storage temperature, and opening design.
| Phenomenon | More likely causes | Check what first |
|---|---|---|
| Inner wall has sugar residue, bag tears with stringy texture when opened | Product Lining | Bagging temperature of candied fruits and surface syrup condition |
| Bag inner wall adheres tightly, difficult to stretch open | Membrane mucosa | Film roll winding tension, storage temperature, opening structure |
| Hard spots at the seal, sugar crystals visible when peeled open | Syrup enters the sealing zone | Cutting position, sealing line distance from the material surface |
| Operates normally at startup, gradually deteriorates after one hour | Mold Temperature Accumulation | Cooling air volume, number of shutdowns and duration |
Handling Points for Opening and Tear Locations
Most difficulty in tearing or tearing off at an angle is not due to the film itself, but rather the design or position of the tear notch. Common causes include: the distance between the tear notch and the sealing edge being inappropriate, causing the tear line to reach the sealed edge; the tear direction not aligning with the film orientation, resulting in a skewed tear line; and insufficient or excessive notch depth, where the former makes the bag difficult to tear and the latter causes the bag to tear through the body immediately. For fruit candy bags, there is an additional issue: after the inner wall is slightly moistened by syrup, the two layers of film adhere together, requiring consumers to apply more force, which gives the sensation of “being unable to tear.”
On-site verification is straightforward: take twenty bags from continuous production, tear them according to consumer habits, and record whether the tearing is smooth, whether it deviates from the tear line, and whether there is syrup stringing. This action provides more realistic feedback than examining film samples.
What is the correct order for performing anti-sticking treatment?
The sequence of actions is more important than individual measures. First, control the product condition, then the equipment and environment, and finally consider changing the film. On the product side, confirm the temperature and surface condition of the candied fruits at the time of bagging. Candied fruits that are just out of the drying chamber and have a large temperature difference are more prone to stick. On the equipment side, check the temperature of the forming tool, the cooling air volume, and the film tension, especially paying attention to the restart phase after a machine stop. On the environmental side, confirm the range of temperature and humidity fluctuations in the workshop. After these steps are stabilized, if sticking still occurs, then discuss changing the inner layer or adjusting the opening and sealing structure.
It should be noted that the “anti-stick” property of the material is more of a relative performance and not a complete solution. The release characteristics of different inner layers do indeed vary, but the actual performance of a specific dried fruit product can only be confirmed through actual bagging and sample testing. It cannot be determined solely based on the film sample.
How to handle if syrup gets on the sealing area?
If syrup or sugar crystals become trapped in the sealing area, the sealing strength will significantly decrease, and the issue is often not visible in appearance. It usually becomes apparent only after transportation pressure. On-site handling involves two levels: first, reducing the opportunity for syrup to enter the sealing area, such as adjusting the material discharge position, increasing the distance between the sealing line and the material surface, and adding a purge step after discharge. Second, establishing a fixed inspection process, conducting regular sampling checks, rather than only checking once at startup.
In terms of testing methods, in addition to the conventional seal peel test, a rough leak check can also be performed according to the packaging integrity method. The conditions and criteria for the rough leak test can be referred to as follows: ASTM F2096The actual pressure and soaking time should be adjusted according to the specifications of the products produced in your factory before implementation.
What items should be checked during sample making and first article confirmation?
For fruit preserves products, it is recommended to use real products and actual machines for sample making, rather than relying on sample films for tactile comparison. The first-piece confirmation should cover at least the following aspects: the adhesion performance during actual bagging, including the first few bags after stopping and restarting the machine; whether the tear opening is smooth and whether it runs off track; inspection of the seal area by peeling; stability of the bag shape and position of the pattern; and the shape changes of the entire box after static storage. The sample quantity should be sufficient for transportation simulation and static observation; otherwise, only the performance of that day can be observed.
If the same machine needs to switch between brittle snacks or dried goods,Dry foods and oily foods have different material requirements.Before switching, it is recommended to check the material direction first to avoid using the same roll of film that does not match the product characteristics. For example,Blueberry dried fruit self-standing bagThere are already relatively mature bag types that can serve as a starting point, but the final confirmation still needs to be based on the factory’s products and actual bagging conditions through sample testing.
Conclusion
The three issues of sticking, tearing, and leakage in fruit jerky packaging can be addressed with the same sequence on-site: first identify the root cause, then stabilize the product and equipment status, and only then handle the material. Include the restart phase after stopping the machine in the observation process, and make checking the seal by peeling it open a standard procedure. This is usually more effective than frequently changing the film structure. When it’s necessary to reorganize the bag type and structure, proceed as follows:Agricultural Product Packaging SolutionsThe design should be determined based on this approach, and then the sample should be made for specific products to verify.
Common Questions
Can the fruit preserves stuck to the mold be resolved by replacing the inner film layer?
It depends on where the adhesion of the fruit candy packaging bag is coming from. If the syrup has already moistened the inner wall and the membrane surface has been repeatedly heated, changing the release characteristics of the contact layer can indeed be helpful. However, if the adhesion mainly comes from high mold temperature and prolonged downtime, replacing the film is often just postponing the problem. It is recommended to first conduct a comparison test using the same roll of film with “lowering the mold temperature, increasing cooling, and reducing downtime,” then determine whether it is really necessary to change the material.
When the machine stops and restarts, the bag sticking becomes more severe. What should be adjusted first?
Prioritize temperature and time adjustments over membrane replacement. Allow the forming unit to return to normal operating temperature and restore cooling airflow before restarting. After startup, isolate the first few bags separately for observation, and do not directly merge these products into the finished goods during this period. Also, record the duration of each shutdown. If the downtime exceeds a certain threshold, perform a fixed cleaning and test bag run. Standardizing the procedure is more effective than repeatedly adjusting parameters.
Where is the best position for the tear notch on fruit candy bags?
The main focus is on the available area between the sealing edge and the contents. The tear notch should be kept at a sufficient distance from the sealing edge to prevent the tear line from reaching the seal. It should also avoid the inner wall area that may be moistened by syrup, as slight adhesion between the two layers of film will significantly increase the opening force. After determining the position, test the tear by pulling on continuously produced bags according to consumer habits to check if the tear line is consistent. Then finalize the design.
Should the entire batch of bags be scrapped if syrup is found at the sealing area?
First determine the extent of contamination rather than handling the entire batch. Take samples from bags at different time points, opening and inspecting the seals. If foreign objects are found only during specific periods, it is likely an issue with the feeding or cleaning process during that interval. Isolate the bags from that period and perform integrity checks afterward. If sugar crystals are found at multiple time points, it indicates that the feeding position or the distance of the sealing line needs adjustment. In such cases, stop the machine for calibration and then resume production.